Aggregator

Issued at 200 PM MST Thu Sep 04 2025 750 WTPZ32 KNHC 042033 TCPEP2 BULLETIN Tropical Storm Lorena Advisory Number 12 NWS National Hurricane Center Miami FL EP122025 200 PM MST Thu Sep 04 2025 ...RISK OF LIFE-THREATENING FLASH FLOODING CONTINUES FOR BAJA CALIFORNIA SUR AND SOUTHWESTERN SONORA... SUMMARY OF 200 PM MST...2100 UTC...INFORMATION ---------------------------------------------- LOCATION...24.6N 114.8W ABOUT 155 MI...255 KM W OF CABO SAN LAZARO MEXICO MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H PRESENT MOVEMENT...NW OR 305 DEGREES AT 7 MPH...11 KM/H MINIMUM CENTRAL PRESSURE...996 MB...29.42 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: The government of Mexico has discontinued all warnings. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: There are no coastal watches or warnings in effect. Interests on the Baja California peninsula and in northwestern Mexico should monitor the progress of Lorena. DISCUSSION AND OUTLOOK ---------------------- At 200 PM MST (2100 UTC), the center of Tropical Storm Lorena was located near latitude 24.6 North, longitude 114.8 West. Lorena is moving toward the northwest near 7 mph (11 km/h). A turn toward the north and a decrease in forward speed are expected tonight. On the forecast track, the center of Lorena is expected to move generally parallel to the west coast of the Baja California peninsula while it weakens on Friday. Recent satellite-derived wind data and data from an Air Force Reserve reconnaissance aircraft indicate that maximum sustained winds have decreased to near 50 mph (85 km/h) with higher gusts. Lorena is expected to quickly weaken for the next couple of days, and it is forecast to degenerate into a remnant low on Friday over water, to the west of the Baja California peninsula. Tropical-storm-force winds extend outward up to 60 miles (95 km) from the center. The minimum central pressure, based on data from Air Force Reserve reconnaissance aircraft is 996 mb (29.42 inches). HAZARDS AFFECTING LAND ---------------------- Key messages for Lorena can be found in the Tropical Cyclone Discussion under AWIPS header MIATCDEP2 and WMO header WTPZ42 KNHC. RAINFALL: Bands of heavy rainfall will continue to impact Baja California Sur and Sonora Mexico through Friday. Additional rainfall totals of 4 to 8 inches, with maximum storm total amounts of 15 inches, are possible across portions of Baja California Sur, far southeast Baja California and southwestern Sonora into Friday. This will bring the risk of life-threatening flash floods and mudslides, especially in areas of higher terrain. Elsewhere across Mexico, 2 to 4 inches of rain, with isolated totals up to 6 inches, are expected across the remainder of Sonora and northern Sinaloa. These amounts will lead to isolated to scattered instances of flash flooding. Across the southwestern United States, 1 to 2 inches of rain, with isolated totals up to 4 inches, are expected across portions of Arizona and New Mexico through Saturday, bringing the potential for isolated to scattered flash flooding. For a complete depiction of forecast rainfall and flash flooding associated with Lorena, please see the National Weather Service Storm Total Rainfall Graphic, available at hurricanes.gov/graphics_ep2.shtml?rainqpf SURF: Swells generated by Lorena will continue affecting portions of the south and west coasts of Baja California Sur through Friday. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office. NEXT ADVISORY ------------- Next complete advisory at 800 PM MST. $$ Forecaster Hagen

...RISK OF LIFE-THREATENING FLASH FLOODING CONTINUES FOR BAJA CALIFORNIA SUR AND SOUTHWESTERN SONORA... As of 2:00 PM MST Thu Sep 04 the center of Lorena was located near 24.6, -114.8 with movement NW at 7 mph. The minimum central pressure was 996 mb with maximum sustained winds of about 50 mph.

5-Day Uncertainty Track last updated Thu, 04 Sep 2025 17:42:52 GMT


Wind Speed Probabilities last updated Thu, 04 Sep 2025 15:27:22 GMT

MD 2032 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PARTS OF MIDDLE/EASTERN TENNESSEE
Mesoscale Discussion 2032 NWS Storm Prediction Center Norman OK 0119 PM CDT Thu Sep 04 2025 Areas affected...parts of middle/eastern Tennessee Concerning...Severe potential...Watch unlikely Valid 041819Z - 042045Z Probability of Watch Issuance...20 percent SUMMARY...Occasional intensification of thunderstorms posing a risk for severe hail and localized damaging wind gusts may continue through late afternoon. Although the severe threat still appears mostly marginal in nature, and severe weather watch unlikely to be required, trends are continuing to be monitored. DISCUSSION...An initial surface cold front has stalled roughly along the I-40 corridor of middle/eastern Tennessee, near the southern periphery of the stronger cyclonic mid/upper flow associated with the amplified eastern U.S. troughing. Although it appears that an area of better mid/upper forcing for ascent is now shifting to the east of the southern Appalachians, lift aided by low-level warm advection along the frontal zone is maintaining renewed thunderstorm development, as a relatively moist boundary layer characterized by mid/upper 60s surface dew points destabilizes. Aided by modestly steep/steepening lower tropospheric lapse rates, mixed-layer CAPE appears to be peaking around 1500-2000 J/kg. In the presence of weak to modest clockwise curved low-level hodographs, beneath 30-35 kt westerly 500 mb flow, the environment may remain conducive to the occasional development and intensification of supercell structures posing a risk for severe hail and localized damaging wind gusts through the remainder of the afternoon. ..Kerr/Gleason.. 09/04/2025 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...GSP...MRX...OHX... LAT...LON 36478574 36548410 36568358 36318281 36038281 35258357 35368478 35448663 36048656 36478574 MOST PROBABLE PEAK WIND GUST...55-70 MPH MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0259 PM CDT Thu Sep 04 2025 Valid 042000Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF NEW YORK...TO THE MID ATLANTIC...SOUTHERN APPALACHIANS AND MID MISSOURI VALLEY... ...SUMMARY... Isolated damaging gusts remain possible across parts of New York to the Mid-Atlantic and Southern Appalachians through early this evening. Isolated severe gusts are also possible across parts of the mid Missouri Valley late this afternoon and early evening. ...20z Update Mid Atlantic and southern Appalachians... Several clusters of strong to severe thunderstorms have matured and are expected to continue through early this evening along and ahead of the slow-moving cold front from the Mid Atlantic southward. Despite poor mid-level lapse rates, heating of the modestly moist air mass is supporting around 500-1000 J/kg of MLCAPE, sufficient for a few stronger updrafts. As convection gradually increases in coverage through the remainder of this afternoon, clustering and 30-40 kt of mid-level flow will continue to support isolated damaging gust potential into early this evening. Some hail remains possible with the more cellular elements, especially father southwest over the eastern TN Valley where storm coverage should remain more isolated. The primary change was to align the western edge of the MRGL and severe probabilities with current frontal position, and shift them slightly east for ongoing storms on the border of NC and southern VA. ...New York... As the line of showers and weak thunderstorms continues eastward along the front, occasional damaging gusts remain possible owing to mixing of stronger mid-level flow downward this afternoon. Some heating, but marginal surface moisture should keep buoyancy and the resulting updrafts weak. With MLCAPE generally less than 500 J/kg, showers and storms should steadily weaken with the loss of diurnal heating. The MRGL risk area has been trimmed behind the ongoing line. Otherwise, the prior outlook remains unchanged, see the previous discussion. ..Lyons.. 09/04/2025 .PREV DISCUSSION... /ISSUED 1124 AM CDT Thu Sep 04 2025/ ...New York into the Mid-Atlantic and Tennessee Valley... A closed mid/upper-level low will remain centered over Ontario today. Multiple mid-level perturbations will rotate around this feature through the period, including a shortwave trough forecast to advance generally east-northeastward across parts of the central Appalachians/Mid-Atlantic into the Northeast. Showers and thunderstorms are ongoing mainly ahead of a surface cold front from parts of western NY southward to the TN Valley in a low/mid-level moisture plume. Generally clear skies ahead of this activity should allow for ample daytime heating of a modestly moistened low-level airmass. Even so, 12Z observed soundings from BUF, IAD, and RNK/GSO show rather poor mid-level lapse rates, which will likely hinder updraft strength even as weak instability develops this afternoon with continued diurnal heating. Modestly enhanced southwesterly low/mid-level flow should still aid in some thunderstorm organization even with the apparent thermodynamic limitations, with multicells the dominant convective mode. Wherever low-level lapse rates can become steepened, a risk for at least isolated damaging winds remains apparent. Some hail may also occur with the strongest cores across parts of the TN Valley/southern Appalachians where locally greater instability should be present this afternoon. The Marginal Risk has been adjusted for ongoing trends, but the potential for a more focused corridor of scattered severe/damaging winds remains unclear. ...Mid Missouri Valley... A mid-level shortwave trough and attendant strong speed maximum will move quickly southeastward today from central Canada and the northern Plains towards the mid MO Valley and vicinity. Pronounced ascent associated with this jet should encourage convection to develop by late this afternoon across parts of eastern SD and vicinity. While low-level moisture and MLCAPE are both expected to remain very limited, enhanced low/mid-level northwesterly flow may still support some risk for severe gusts with any low-topped convection that can develop and spread quickly southeastward before weakening this evening with the loss of daytime heating. ...Kansas... A sharp cold front will sweep southward across the central Plains tonight. Elevated convection should form to the cool side of this boundary late tonight through early Friday morning given sufficient MUCAPE. Locally strong surface gusts and small hail may accompany this activity amid robust low-level northerlies, but the overall severe potential should remain fairly low given the tendency for convection to be mostly elevated. ...Arizona/Lower Colorado River Valley... Thunderstorms should develop again today across parts of central/southern AZ and the lower CO River Valley, beneath weak mid-level flow and on the periphery of increasing mid-level moisture associated with Tropical Storm Lorena. Weak shear should keep thunderstorms mostly disorganized, but occasional strong/gusty winds may occur where low-level lapse rates can become steepened. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0259 PM CDT Thu Sep 04 2025 Valid 042000Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF NEW YORK...TO THE MID ATLANTIC...SOUTHERN APPALACHIANS AND MID MISSOURI VALLEY... ...SUMMARY... Isolated damaging gusts remain possible across parts of New York to the Mid-Atlantic and Southern Appalachians through early this evening. Isolated severe gusts are also possible across parts of the mid Missouri Valley late this afternoon and early evening. ...20z Update Mid Atlantic and southern Appalachians... Several clusters of strong to severe thunderstorms have matured and are expected to continue through early this evening along and ahead of the slow-moving cold front from the Mid Atlantic southward. Despite poor mid-level lapse rates, heating of the modestly moist air mass is supporting around 500-1000 J/kg of MLCAPE, sufficient for a few stronger updrafts. As convection gradually increases in coverage through the remainder of this afternoon, clustering and 30-40 kt of mid-level flow will continue to support isolated damaging gust potential into early this evening. Some hail remains possible with the more cellular elements, especially father southwest over the eastern TN Valley where storm coverage should remain more isolated. The primary change was to align the western edge of the MRGL and severe probabilities with current frontal position, and shift them slightly east for ongoing storms on the border of NC and southern VA. ...New York... As the line of showers and weak thunderstorms continues eastward along the front, occasional damaging gusts remain possible owing to mixing of stronger mid-level flow downward this afternoon. Some heating, but marginal surface moisture should keep buoyancy and the resulting updrafts weak. With MLCAPE generally less than 500 J/kg, showers and storms should steadily weaken with the loss of diurnal heating. The MRGL risk area has been trimmed behind the ongoing line. Otherwise, the prior outlook remains unchanged, see the previous discussion. ..Lyons.. 09/04/2025 .PREV DISCUSSION... /ISSUED 1124 AM CDT Thu Sep 04 2025/ ...New York into the Mid-Atlantic and Tennessee Valley... A closed mid/upper-level low will remain centered over Ontario today. Multiple mid-level perturbations will rotate around this feature through the period, including a shortwave trough forecast to advance generally east-northeastward across parts of the central Appalachians/Mid-Atlantic into the Northeast. Showers and thunderstorms are ongoing mainly ahead of a surface cold front from parts of western NY southward to the TN Valley in a low/mid-level moisture plume. Generally clear skies ahead of this activity should allow for ample daytime heating of a modestly moistened low-level airmass. Even so, 12Z observed soundings from BUF, IAD, and RNK/GSO show rather poor mid-level lapse rates, which will likely hinder updraft strength even as weak instability develops this afternoon with continued diurnal heating. Modestly enhanced southwesterly low/mid-level flow should still aid in some thunderstorm organization even with the apparent thermodynamic limitations, with multicells the dominant convective mode. Wherever low-level lapse rates can become steepened, a risk for at least isolated damaging winds remains apparent. Some hail may also occur with the strongest cores across parts of the TN Valley/southern Appalachians where locally greater instability should be present this afternoon. The Marginal Risk has been adjusted for ongoing trends, but the potential for a more focused corridor of scattered severe/damaging winds remains unclear. ...Mid Missouri Valley... A mid-level shortwave trough and attendant strong speed maximum will move quickly southeastward today from central Canada and the northern Plains towards the mid MO Valley and vicinity. Pronounced ascent associated with this jet should encourage convection to develop by late this afternoon across parts of eastern SD and vicinity. While low-level moisture and MLCAPE are both expected to remain very limited, enhanced low/mid-level northwesterly flow may still support some risk for severe gusts with any low-topped convection that can develop and spread quickly southeastward before weakening this evening with the loss of daytime heating. ...Kansas... A sharp cold front will sweep southward across the central Plains tonight. Elevated convection should form to the cool side of this boundary late tonight through early Friday morning given sufficient MUCAPE. Locally strong surface gusts and small hail may accompany this activity amid robust low-level northerlies, but the overall severe potential should remain fairly low given the tendency for convection to be mostly elevated. ...Arizona/Lower Colorado River Valley... Thunderstorms should develop again today across parts of central/southern AZ and the lower CO River Valley, beneath weak mid-level flow and on the periphery of increasing mid-level moisture associated with Tropical Storm Lorena. Weak shear should keep thunderstorms mostly disorganized, but occasional strong/gusty winds may occur where low-level lapse rates can become steepened. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0259 PM CDT Thu Sep 04 2025 Valid 042000Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF NEW YORK...TO THE MID ATLANTIC...SOUTHERN APPALACHIANS AND MID MISSOURI VALLEY... ...SUMMARY... Isolated damaging gusts remain possible across parts of New York to the Mid-Atlantic and Southern Appalachians through early this evening. Isolated severe gusts are also possible across parts of the mid Missouri Valley late this afternoon and early evening. ...20z Update Mid Atlantic and southern Appalachians... Several clusters of strong to severe thunderstorms have matured and are expected to continue through early this evening along and ahead of the slow-moving cold front from the Mid Atlantic southward. Despite poor mid-level lapse rates, heating of the modestly moist air mass is supporting around 500-1000 J/kg of MLCAPE, sufficient for a few stronger updrafts. As convection gradually increases in coverage through the remainder of this afternoon, clustering and 30-40 kt of mid-level flow will continue to support isolated damaging gust potential into early this evening. Some hail remains possible with the more cellular elements, especially father southwest over the eastern TN Valley where storm coverage should remain more isolated. The primary change was to align the western edge of the MRGL and severe probabilities with current frontal position, and shift them slightly east for ongoing storms on the border of NC and southern VA. ...New York... As the line of showers and weak thunderstorms continues eastward along the front, occasional damaging gusts remain possible owing to mixing of stronger mid-level flow downward this afternoon. Some heating, but marginal surface moisture should keep buoyancy and the resulting updrafts weak. With MLCAPE generally less than 500 J/kg, showers and storms should steadily weaken with the loss of diurnal heating. The MRGL risk area has been trimmed behind the ongoing line. Otherwise, the prior outlook remains unchanged, see the previous discussion. ..Lyons.. 09/04/2025 .PREV DISCUSSION... /ISSUED 1124 AM CDT Thu Sep 04 2025/ ...New York into the Mid-Atlantic and Tennessee Valley... A closed mid/upper-level low will remain centered over Ontario today. Multiple mid-level perturbations will rotate around this feature through the period, including a shortwave trough forecast to advance generally east-northeastward across parts of the central Appalachians/Mid-Atlantic into the Northeast. Showers and thunderstorms are ongoing mainly ahead of a surface cold front from parts of western NY southward to the TN Valley in a low/mid-level moisture plume. Generally clear skies ahead of this activity should allow for ample daytime heating of a modestly moistened low-level airmass. Even so, 12Z observed soundings from BUF, IAD, and RNK/GSO show rather poor mid-level lapse rates, which will likely hinder updraft strength even as weak instability develops this afternoon with continued diurnal heating. Modestly enhanced southwesterly low/mid-level flow should still aid in some thunderstorm organization even with the apparent thermodynamic limitations, with multicells the dominant convective mode. Wherever low-level lapse rates can become steepened, a risk for at least isolated damaging winds remains apparent. Some hail may also occur with the strongest cores across parts of the TN Valley/southern Appalachians where locally greater instability should be present this afternoon. The Marginal Risk has been adjusted for ongoing trends, but the potential for a more focused corridor of scattered severe/damaging winds remains unclear. ...Mid Missouri Valley... A mid-level shortwave trough and attendant strong speed maximum will move quickly southeastward today from central Canada and the northern Plains towards the mid MO Valley and vicinity. Pronounced ascent associated with this jet should encourage convection to develop by late this afternoon across parts of eastern SD and vicinity. While low-level moisture and MLCAPE are both expected to remain very limited, enhanced low/mid-level northwesterly flow may still support some risk for severe gusts with any low-topped convection that can develop and spread quickly southeastward before weakening this evening with the loss of daytime heating. ...Kansas... A sharp cold front will sweep southward across the central Plains tonight. Elevated convection should form to the cool side of this boundary late tonight through early Friday morning given sufficient MUCAPE. Locally strong surface gusts and small hail may accompany this activity amid robust low-level northerlies, but the overall severe potential should remain fairly low given the tendency for convection to be mostly elevated. ...Arizona/Lower Colorado River Valley... Thunderstorms should develop again today across parts of central/southern AZ and the lower CO River Valley, beneath weak mid-level flow and on the periphery of increasing mid-level moisture associated with Tropical Storm Lorena. Weak shear should keep thunderstorms mostly disorganized, but occasional strong/gusty winds may occur where low-level lapse rates can become steepened. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0259 PM CDT Thu Sep 04 2025 Valid 042000Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF NEW YORK...TO THE MID ATLANTIC...SOUTHERN APPALACHIANS AND MID MISSOURI VALLEY... ...SUMMARY... Isolated damaging gusts remain possible across parts of New York to the Mid-Atlantic and Southern Appalachians through early this evening. Isolated severe gusts are also possible across parts of the mid Missouri Valley late this afternoon and early evening. ...20z Update Mid Atlantic and southern Appalachians... Several clusters of strong to severe thunderstorms have matured and are expected to continue through early this evening along and ahead of the slow-moving cold front from the Mid Atlantic southward. Despite poor mid-level lapse rates, heating of the modestly moist air mass is supporting around 500-1000 J/kg of MLCAPE, sufficient for a few stronger updrafts. As convection gradually increases in coverage through the remainder of this afternoon, clustering and 30-40 kt of mid-level flow will continue to support isolated damaging gust potential into early this evening. Some hail remains possible with the more cellular elements, especially father southwest over the eastern TN Valley where storm coverage should remain more isolated. The primary change was to align the western edge of the MRGL and severe probabilities with current frontal position, and shift them slightly east for ongoing storms on the border of NC and southern VA. ...New York... As the line of showers and weak thunderstorms continues eastward along the front, occasional damaging gusts remain possible owing to mixing of stronger mid-level flow downward this afternoon. Some heating, but marginal surface moisture should keep buoyancy and the resulting updrafts weak. With MLCAPE generally less than 500 J/kg, showers and storms should steadily weaken with the loss of diurnal heating. The MRGL risk area has been trimmed behind the ongoing line. Otherwise, the prior outlook remains unchanged, see the previous discussion. ..Lyons.. 09/04/2025 .PREV DISCUSSION... /ISSUED 1124 AM CDT Thu Sep 04 2025/ ...New York into the Mid-Atlantic and Tennessee Valley... A closed mid/upper-level low will remain centered over Ontario today. Multiple mid-level perturbations will rotate around this feature through the period, including a shortwave trough forecast to advance generally east-northeastward across parts of the central Appalachians/Mid-Atlantic into the Northeast. Showers and thunderstorms are ongoing mainly ahead of a surface cold front from parts of western NY southward to the TN Valley in a low/mid-level moisture plume. Generally clear skies ahead of this activity should allow for ample daytime heating of a modestly moistened low-level airmass. Even so, 12Z observed soundings from BUF, IAD, and RNK/GSO show rather poor mid-level lapse rates, which will likely hinder updraft strength even as weak instability develops this afternoon with continued diurnal heating. Modestly enhanced southwesterly low/mid-level flow should still aid in some thunderstorm organization even with the apparent thermodynamic limitations, with multicells the dominant convective mode. Wherever low-level lapse rates can become steepened, a risk for at least isolated damaging winds remains apparent. Some hail may also occur with the strongest cores across parts of the TN Valley/southern Appalachians where locally greater instability should be present this afternoon. The Marginal Risk has been adjusted for ongoing trends, but the potential for a more focused corridor of scattered severe/damaging winds remains unclear. ...Mid Missouri Valley... A mid-level shortwave trough and attendant strong speed maximum will move quickly southeastward today from central Canada and the northern Plains towards the mid MO Valley and vicinity. Pronounced ascent associated with this jet should encourage convection to develop by late this afternoon across parts of eastern SD and vicinity. While low-level moisture and MLCAPE are both expected to remain very limited, enhanced low/mid-level northwesterly flow may still support some risk for severe gusts with any low-topped convection that can develop and spread quickly southeastward before weakening this evening with the loss of daytime heating. ...Kansas... A sharp cold front will sweep southward across the central Plains tonight. Elevated convection should form to the cool side of this boundary late tonight through early Friday morning given sufficient MUCAPE. Locally strong surface gusts and small hail may accompany this activity amid robust low-level northerlies, but the overall severe potential should remain fairly low given the tendency for convection to be mostly elevated. ...Arizona/Lower Colorado River Valley... Thunderstorms should develop again today across parts of central/southern AZ and the lower CO River Valley, beneath weak mid-level flow and on the periphery of increasing mid-level moisture associated with Tropical Storm Lorena. Weak shear should keep thunderstorms mostly disorganized, but occasional strong/gusty winds may occur where low-level lapse rates can become steepened. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0259 PM CDT Thu Sep 04 2025 Valid 042000Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF NEW YORK...TO THE MID ATLANTIC...SOUTHERN APPALACHIANS AND MID MISSOURI VALLEY... ...SUMMARY... Isolated damaging gusts remain possible across parts of New York to the Mid-Atlantic and Southern Appalachians through early this evening. Isolated severe gusts are also possible across parts of the mid Missouri Valley late this afternoon and early evening. ...20z Update Mid Atlantic and southern Appalachians... Several clusters of strong to severe thunderstorms have matured and are expected to continue through early this evening along and ahead of the slow-moving cold front from the Mid Atlantic southward. Despite poor mid-level lapse rates, heating of the modestly moist air mass is supporting around 500-1000 J/kg of MLCAPE, sufficient for a few stronger updrafts. As convection gradually increases in coverage through the remainder of this afternoon, clustering and 30-40 kt of mid-level flow will continue to support isolated damaging gust potential into early this evening. Some hail remains possible with the more cellular elements, especially father southwest over the eastern TN Valley where storm coverage should remain more isolated. The primary change was to align the western edge of the MRGL and severe probabilities with current frontal position, and shift them slightly east for ongoing storms on the border of NC and southern VA. ...New York... As the line of showers and weak thunderstorms continues eastward along the front, occasional damaging gusts remain possible owing to mixing of stronger mid-level flow downward this afternoon. Some heating, but marginal surface moisture should keep buoyancy and the resulting updrafts weak. With MLCAPE generally less than 500 J/kg, showers and storms should steadily weaken with the loss of diurnal heating. The MRGL risk area has been trimmed behind the ongoing line. Otherwise, the prior outlook remains unchanged, see the previous discussion. ..Lyons.. 09/04/2025 .PREV DISCUSSION... /ISSUED 1124 AM CDT Thu Sep 04 2025/ ...New York into the Mid-Atlantic and Tennessee Valley... A closed mid/upper-level low will remain centered over Ontario today. Multiple mid-level perturbations will rotate around this feature through the period, including a shortwave trough forecast to advance generally east-northeastward across parts of the central Appalachians/Mid-Atlantic into the Northeast. Showers and thunderstorms are ongoing mainly ahead of a surface cold front from parts of western NY southward to the TN Valley in a low/mid-level moisture plume. Generally clear skies ahead of this activity should allow for ample daytime heating of a modestly moistened low-level airmass. Even so, 12Z observed soundings from BUF, IAD, and RNK/GSO show rather poor mid-level lapse rates, which will likely hinder updraft strength even as weak instability develops this afternoon with continued diurnal heating. Modestly enhanced southwesterly low/mid-level flow should still aid in some thunderstorm organization even with the apparent thermodynamic limitations, with multicells the dominant convective mode. Wherever low-level lapse rates can become steepened, a risk for at least isolated damaging winds remains apparent. Some hail may also occur with the strongest cores across parts of the TN Valley/southern Appalachians where locally greater instability should be present this afternoon. The Marginal Risk has been adjusted for ongoing trends, but the potential for a more focused corridor of scattered severe/damaging winds remains unclear. ...Mid Missouri Valley... A mid-level shortwave trough and attendant strong speed maximum will move quickly southeastward today from central Canada and the northern Plains towards the mid MO Valley and vicinity. Pronounced ascent associated with this jet should encourage convection to develop by late this afternoon across parts of eastern SD and vicinity. While low-level moisture and MLCAPE are both expected to remain very limited, enhanced low/mid-level northwesterly flow may still support some risk for severe gusts with any low-topped convection that can develop and spread quickly southeastward before weakening this evening with the loss of daytime heating. ...Kansas... A sharp cold front will sweep southward across the central Plains tonight. Elevated convection should form to the cool side of this boundary late tonight through early Friday morning given sufficient MUCAPE. Locally strong surface gusts and small hail may accompany this activity amid robust low-level northerlies, but the overall severe potential should remain fairly low given the tendency for convection to be mostly elevated. ...Arizona/Lower Colorado River Valley... Thunderstorms should develop again today across parts of central/southern AZ and the lower CO River Valley, beneath weak mid-level flow and on the periphery of increasing mid-level moisture associated with Tropical Storm Lorena. Weak shear should keep thunderstorms mostly disorganized, but occasional strong/gusty winds may occur where low-level lapse rates can become steepened. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0259 PM CDT Thu Sep 04 2025 Valid 042000Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF NEW YORK...TO THE MID ATLANTIC...SOUTHERN APPALACHIANS AND MID MISSOURI VALLEY... ...SUMMARY... Isolated damaging gusts remain possible across parts of New York to the Mid-Atlantic and Southern Appalachians through early this evening. Isolated severe gusts are also possible across parts of the mid Missouri Valley late this afternoon and early evening. ...20z Update Mid Atlantic and southern Appalachians... Several clusters of strong to severe thunderstorms have matured and are expected to continue through early this evening along and ahead of the slow-moving cold front from the Mid Atlantic southward. Despite poor mid-level lapse rates, heating of the modestly moist air mass is supporting around 500-1000 J/kg of MLCAPE, sufficient for a few stronger updrafts. As convection gradually increases in coverage through the remainder of this afternoon, clustering and 30-40 kt of mid-level flow will continue to support isolated damaging gust potential into early this evening. Some hail remains possible with the more cellular elements, especially father southwest over the eastern TN Valley where storm coverage should remain more isolated. The primary change was to align the western edge of the MRGL and severe probabilities with current frontal position, and shift them slightly east for ongoing storms on the border of NC and southern VA. ...New York... As the line of showers and weak thunderstorms continues eastward along the front, occasional damaging gusts remain possible owing to mixing of stronger mid-level flow downward this afternoon. Some heating, but marginal surface moisture should keep buoyancy and the resulting updrafts weak. With MLCAPE generally less than 500 J/kg, showers and storms should steadily weaken with the loss of diurnal heating. The MRGL risk area has been trimmed behind the ongoing line. Otherwise, the prior outlook remains unchanged, see the previous discussion. ..Lyons.. 09/04/2025 .PREV DISCUSSION... /ISSUED 1124 AM CDT Thu Sep 04 2025/ ...New York into the Mid-Atlantic and Tennessee Valley... A closed mid/upper-level low will remain centered over Ontario today. Multiple mid-level perturbations will rotate around this feature through the period, including a shortwave trough forecast to advance generally east-northeastward across parts of the central Appalachians/Mid-Atlantic into the Northeast. Showers and thunderstorms are ongoing mainly ahead of a surface cold front from parts of western NY southward to the TN Valley in a low/mid-level moisture plume. Generally clear skies ahead of this activity should allow for ample daytime heating of a modestly moistened low-level airmass. Even so, 12Z observed soundings from BUF, IAD, and RNK/GSO show rather poor mid-level lapse rates, which will likely hinder updraft strength even as weak instability develops this afternoon with continued diurnal heating. Modestly enhanced southwesterly low/mid-level flow should still aid in some thunderstorm organization even with the apparent thermodynamic limitations, with multicells the dominant convective mode. Wherever low-level lapse rates can become steepened, a risk for at least isolated damaging winds remains apparent. Some hail may also occur with the strongest cores across parts of the TN Valley/southern Appalachians where locally greater instability should be present this afternoon. The Marginal Risk has been adjusted for ongoing trends, but the potential for a more focused corridor of scattered severe/damaging winds remains unclear. ...Mid Missouri Valley... A mid-level shortwave trough and attendant strong speed maximum will move quickly southeastward today from central Canada and the northern Plains towards the mid MO Valley and vicinity. Pronounced ascent associated with this jet should encourage convection to develop by late this afternoon across parts of eastern SD and vicinity. While low-level moisture and MLCAPE are both expected to remain very limited, enhanced low/mid-level northwesterly flow may still support some risk for severe gusts with any low-topped convection that can develop and spread quickly southeastward before weakening this evening with the loss of daytime heating. ...Kansas... A sharp cold front will sweep southward across the central Plains tonight. Elevated convection should form to the cool side of this boundary late tonight through early Friday morning given sufficient MUCAPE. Locally strong surface gusts and small hail may accompany this activity amid robust low-level northerlies, but the overall severe potential should remain fairly low given the tendency for convection to be mostly elevated. ...Arizona/Lower Colorado River Valley... Thunderstorms should develop again today across parts of central/southern AZ and the lower CO River Valley, beneath weak mid-level flow and on the periphery of increasing mid-level moisture associated with Tropical Storm Lorena. Weak shear should keep thunderstorms mostly disorganized, but occasional strong/gusty winds may occur where low-level lapse rates can become steepened. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0259 PM CDT Thu Sep 04 2025 Valid 042000Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF NEW YORK...TO THE MID ATLANTIC...SOUTHERN APPALACHIANS AND MID MISSOURI VALLEY... ...SUMMARY... Isolated damaging gusts remain possible across parts of New York to the Mid-Atlantic and Southern Appalachians through early this evening. Isolated severe gusts are also possible across parts of the mid Missouri Valley late this afternoon and early evening. ...20z Update Mid Atlantic and southern Appalachians... Several clusters of strong to severe thunderstorms have matured and are expected to continue through early this evening along and ahead of the slow-moving cold front from the Mid Atlantic southward. Despite poor mid-level lapse rates, heating of the modestly moist air mass is supporting around 500-1000 J/kg of MLCAPE, sufficient for a few stronger updrafts. As convection gradually increases in coverage through the remainder of this afternoon, clustering and 30-40 kt of mid-level flow will continue to support isolated damaging gust potential into early this evening. Some hail remains possible with the more cellular elements, especially father southwest over the eastern TN Valley where storm coverage should remain more isolated. The primary change was to align the western edge of the MRGL and severe probabilities with current frontal position, and shift them slightly east for ongoing storms on the border of NC and southern VA. ...New York... As the line of showers and weak thunderstorms continues eastward along the front, occasional damaging gusts remain possible owing to mixing of stronger mid-level flow downward this afternoon. Some heating, but marginal surface moisture should keep buoyancy and the resulting updrafts weak. With MLCAPE generally less than 500 J/kg, showers and storms should steadily weaken with the loss of diurnal heating. The MRGL risk area has been trimmed behind the ongoing line. Otherwise, the prior outlook remains unchanged, see the previous discussion. ..Lyons.. 09/04/2025 .PREV DISCUSSION... /ISSUED 1124 AM CDT Thu Sep 04 2025/ ...New York into the Mid-Atlantic and Tennessee Valley... A closed mid/upper-level low will remain centered over Ontario today. Multiple mid-level perturbations will rotate around this feature through the period, including a shortwave trough forecast to advance generally east-northeastward across parts of the central Appalachians/Mid-Atlantic into the Northeast. Showers and thunderstorms are ongoing mainly ahead of a surface cold front from parts of western NY southward to the TN Valley in a low/mid-level moisture plume. Generally clear skies ahead of this activity should allow for ample daytime heating of a modestly moistened low-level airmass. Even so, 12Z observed soundings from BUF, IAD, and RNK/GSO show rather poor mid-level lapse rates, which will likely hinder updraft strength even as weak instability develops this afternoon with continued diurnal heating. Modestly enhanced southwesterly low/mid-level flow should still aid in some thunderstorm organization even with the apparent thermodynamic limitations, with multicells the dominant convective mode. Wherever low-level lapse rates can become steepened, a risk for at least isolated damaging winds remains apparent. Some hail may also occur with the strongest cores across parts of the TN Valley/southern Appalachians where locally greater instability should be present this afternoon. The Marginal Risk has been adjusted for ongoing trends, but the potential for a more focused corridor of scattered severe/damaging winds remains unclear. ...Mid Missouri Valley... A mid-level shortwave trough and attendant strong speed maximum will move quickly southeastward today from central Canada and the northern Plains towards the mid MO Valley and vicinity. Pronounced ascent associated with this jet should encourage convection to develop by late this afternoon across parts of eastern SD and vicinity. While low-level moisture and MLCAPE are both expected to remain very limited, enhanced low/mid-level northwesterly flow may still support some risk for severe gusts with any low-topped convection that can develop and spread quickly southeastward before weakening this evening with the loss of daytime heating. ...Kansas... A sharp cold front will sweep southward across the central Plains tonight. Elevated convection should form to the cool side of this boundary late tonight through early Friday morning given sufficient MUCAPE. Locally strong surface gusts and small hail may accompany this activity amid robust low-level northerlies, but the overall severe potential should remain fairly low given the tendency for convection to be mostly elevated. ...Arizona/Lower Colorado River Valley... Thunderstorms should develop again today across parts of central/southern AZ and the lower CO River Valley, beneath weak mid-level flow and on the periphery of increasing mid-level moisture associated with Tropical Storm Lorena. Weak shear should keep thunderstorms mostly disorganized, but occasional strong/gusty winds may occur where low-level lapse rates can become steepened. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0259 PM CDT Thu Sep 04 2025 Valid 042000Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF NEW YORK...TO THE MID ATLANTIC...SOUTHERN APPALACHIANS AND MID MISSOURI VALLEY... ...SUMMARY... Isolated damaging gusts remain possible across parts of New York to the Mid-Atlantic and Southern Appalachians through early this evening. Isolated severe gusts are also possible across parts of the mid Missouri Valley late this afternoon and early evening. ...20z Update Mid Atlantic and southern Appalachians... Several clusters of strong to severe thunderstorms have matured and are expected to continue through early this evening along and ahead of the slow-moving cold front from the Mid Atlantic southward. Despite poor mid-level lapse rates, heating of the modestly moist air mass is supporting around 500-1000 J/kg of MLCAPE, sufficient for a few stronger updrafts. As convection gradually increases in coverage through the remainder of this afternoon, clustering and 30-40 kt of mid-level flow will continue to support isolated damaging gust potential into early this evening. Some hail remains possible with the more cellular elements, especially father southwest over the eastern TN Valley where storm coverage should remain more isolated. The primary change was to align the western edge of the MRGL and severe probabilities with current frontal position, and shift them slightly east for ongoing storms on the border of NC and southern VA. ...New York... As the line of showers and weak thunderstorms continues eastward along the front, occasional damaging gusts remain possible owing to mixing of stronger mid-level flow downward this afternoon. Some heating, but marginal surface moisture should keep buoyancy and the resulting updrafts weak. With MLCAPE generally less than 500 J/kg, showers and storms should steadily weaken with the loss of diurnal heating. The MRGL risk area has been trimmed behind the ongoing line. Otherwise, the prior outlook remains unchanged, see the previous discussion. ..Lyons.. 09/04/2025 .PREV DISCUSSION... /ISSUED 1124 AM CDT Thu Sep 04 2025/ ...New York into the Mid-Atlantic and Tennessee Valley... A closed mid/upper-level low will remain centered over Ontario today. Multiple mid-level perturbations will rotate around this feature through the period, including a shortwave trough forecast to advance generally east-northeastward across parts of the central Appalachians/Mid-Atlantic into the Northeast. Showers and thunderstorms are ongoing mainly ahead of a surface cold front from parts of western NY southward to the TN Valley in a low/mid-level moisture plume. Generally clear skies ahead of this activity should allow for ample daytime heating of a modestly moistened low-level airmass. Even so, 12Z observed soundings from BUF, IAD, and RNK/GSO show rather poor mid-level lapse rates, which will likely hinder updraft strength even as weak instability develops this afternoon with continued diurnal heating. Modestly enhanced southwesterly low/mid-level flow should still aid in some thunderstorm organization even with the apparent thermodynamic limitations, with multicells the dominant convective mode. Wherever low-level lapse rates can become steepened, a risk for at least isolated damaging winds remains apparent. Some hail may also occur with the strongest cores across parts of the TN Valley/southern Appalachians where locally greater instability should be present this afternoon. The Marginal Risk has been adjusted for ongoing trends, but the potential for a more focused corridor of scattered severe/damaging winds remains unclear. ...Mid Missouri Valley... A mid-level shortwave trough and attendant strong speed maximum will move quickly southeastward today from central Canada and the northern Plains towards the mid MO Valley and vicinity. Pronounced ascent associated with this jet should encourage convection to develop by late this afternoon across parts of eastern SD and vicinity. While low-level moisture and MLCAPE are both expected to remain very limited, enhanced low/mid-level northwesterly flow may still support some risk for severe gusts with any low-topped convection that can develop and spread quickly southeastward before weakening this evening with the loss of daytime heating. ...Kansas... A sharp cold front will sweep southward across the central Plains tonight. Elevated convection should form to the cool side of this boundary late tonight through early Friday morning given sufficient MUCAPE. Locally strong surface gusts and small hail may accompany this activity amid robust low-level northerlies, but the overall severe potential should remain fairly low given the tendency for convection to be mostly elevated. ...Arizona/Lower Colorado River Valley... Thunderstorms should develop again today across parts of central/southern AZ and the lower CO River Valley, beneath weak mid-level flow and on the periphery of increasing mid-level moisture associated with Tropical Storm Lorena. Weak shear should keep thunderstorms mostly disorganized, but occasional strong/gusty winds may occur where low-level lapse rates can become steepened. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0259 PM CDT Thu Sep 04 2025 Valid 042000Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF NEW YORK...TO THE MID ATLANTIC...SOUTHERN APPALACHIANS AND MID MISSOURI VALLEY... ...SUMMARY... Isolated damaging gusts remain possible across parts of New York to the Mid-Atlantic and Southern Appalachians through early this evening. Isolated severe gusts are also possible across parts of the mid Missouri Valley late this afternoon and early evening. ...20z Update Mid Atlantic and southern Appalachians... Several clusters of strong to severe thunderstorms have matured and are expected to continue through early this evening along and ahead of the slow-moving cold front from the Mid Atlantic southward. Despite poor mid-level lapse rates, heating of the modestly moist air mass is supporting around 500-1000 J/kg of MLCAPE, sufficient for a few stronger updrafts. As convection gradually increases in coverage through the remainder of this afternoon, clustering and 30-40 kt of mid-level flow will continue to support isolated damaging gust potential into early this evening. Some hail remains possible with the more cellular elements, especially father southwest over the eastern TN Valley where storm coverage should remain more isolated. The primary change was to align the western edge of the MRGL and severe probabilities with current frontal position, and shift them slightly east for ongoing storms on the border of NC and southern VA. ...New York... As the line of showers and weak thunderstorms continues eastward along the front, occasional damaging gusts remain possible owing to mixing of stronger mid-level flow downward this afternoon. Some heating, but marginal surface moisture should keep buoyancy and the resulting updrafts weak. With MLCAPE generally less than 500 J/kg, showers and storms should steadily weaken with the loss of diurnal heating. The MRGL risk area has been trimmed behind the ongoing line. Otherwise, the prior outlook remains unchanged, see the previous discussion. ..Lyons.. 09/04/2025 .PREV DISCUSSION... /ISSUED 1124 AM CDT Thu Sep 04 2025/ ...New York into the Mid-Atlantic and Tennessee Valley... A closed mid/upper-level low will remain centered over Ontario today. Multiple mid-level perturbations will rotate around this feature through the period, including a shortwave trough forecast to advance generally east-northeastward across parts of the central Appalachians/Mid-Atlantic into the Northeast. Showers and thunderstorms are ongoing mainly ahead of a surface cold front from parts of western NY southward to the TN Valley in a low/mid-level moisture plume. Generally clear skies ahead of this activity should allow for ample daytime heating of a modestly moistened low-level airmass. Even so, 12Z observed soundings from BUF, IAD, and RNK/GSO show rather poor mid-level lapse rates, which will likely hinder updraft strength even as weak instability develops this afternoon with continued diurnal heating. Modestly enhanced southwesterly low/mid-level flow should still aid in some thunderstorm organization even with the apparent thermodynamic limitations, with multicells the dominant convective mode. Wherever low-level lapse rates can become steepened, a risk for at least isolated damaging winds remains apparent. Some hail may also occur with the strongest cores across parts of the TN Valley/southern Appalachians where locally greater instability should be present this afternoon. The Marginal Risk has been adjusted for ongoing trends, but the potential for a more focused corridor of scattered severe/damaging winds remains unclear. ...Mid Missouri Valley... A mid-level shortwave trough and attendant strong speed maximum will move quickly southeastward today from central Canada and the northern Plains towards the mid MO Valley and vicinity. Pronounced ascent associated with this jet should encourage convection to develop by late this afternoon across parts of eastern SD and vicinity. While low-level moisture and MLCAPE are both expected to remain very limited, enhanced low/mid-level northwesterly flow may still support some risk for severe gusts with any low-topped convection that can develop and spread quickly southeastward before weakening this evening with the loss of daytime heating. ...Kansas... A sharp cold front will sweep southward across the central Plains tonight. Elevated convection should form to the cool side of this boundary late tonight through early Friday morning given sufficient MUCAPE. Locally strong surface gusts and small hail may accompany this activity amid robust low-level northerlies, but the overall severe potential should remain fairly low given the tendency for convection to be mostly elevated. ...Arizona/Lower Colorado River Valley... Thunderstorms should develop again today across parts of central/southern AZ and the lower CO River Valley, beneath weak mid-level flow and on the periphery of increasing mid-level moisture associated with Tropical Storm Lorena. Weak shear should keep thunderstorms mostly disorganized, but occasional strong/gusty winds may occur where low-level lapse rates can become steepened. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0259 PM CDT Thu Sep 04 2025 Valid 042000Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF NEW YORK...TO THE MID ATLANTIC...SOUTHERN APPALACHIANS AND MID MISSOURI VALLEY... ...SUMMARY... Isolated damaging gusts remain possible across parts of New York to the Mid-Atlantic and Southern Appalachians through early this evening. Isolated severe gusts are also possible across parts of the mid Missouri Valley late this afternoon and early evening. ...20z Update Mid Atlantic and southern Appalachians... Several clusters of strong to severe thunderstorms have matured and are expected to continue through early this evening along and ahead of the slow-moving cold front from the Mid Atlantic southward. Despite poor mid-level lapse rates, heating of the modestly moist air mass is supporting around 500-1000 J/kg of MLCAPE, sufficient for a few stronger updrafts. As convection gradually increases in coverage through the remainder of this afternoon, clustering and 30-40 kt of mid-level flow will continue to support isolated damaging gust potential into early this evening. Some hail remains possible with the more cellular elements, especially father southwest over the eastern TN Valley where storm coverage should remain more isolated. The primary change was to align the western edge of the MRGL and severe probabilities with current frontal position, and shift them slightly east for ongoing storms on the border of NC and southern VA. ...New York... As the line of showers and weak thunderstorms continues eastward along the front, occasional damaging gusts remain possible owing to mixing of stronger mid-level flow downward this afternoon. Some heating, but marginal surface moisture should keep buoyancy and the resulting updrafts weak. With MLCAPE generally less than 500 J/kg, showers and storms should steadily weaken with the loss of diurnal heating. The MRGL risk area has been trimmed behind the ongoing line. Otherwise, the prior outlook remains unchanged, see the previous discussion. ..Lyons.. 09/04/2025 .PREV DISCUSSION... /ISSUED 1124 AM CDT Thu Sep 04 2025/ ...New York into the Mid-Atlantic and Tennessee Valley... A closed mid/upper-level low will remain centered over Ontario today. Multiple mid-level perturbations will rotate around this feature through the period, including a shortwave trough forecast to advance generally east-northeastward across parts of the central Appalachians/Mid-Atlantic into the Northeast. Showers and thunderstorms are ongoing mainly ahead of a surface cold front from parts of western NY southward to the TN Valley in a low/mid-level moisture plume. Generally clear skies ahead of this activity should allow for ample daytime heating of a modestly moistened low-level airmass. Even so, 12Z observed soundings from BUF, IAD, and RNK/GSO show rather poor mid-level lapse rates, which will likely hinder updraft strength even as weak instability develops this afternoon with continued diurnal heating. Modestly enhanced southwesterly low/mid-level flow should still aid in some thunderstorm organization even with the apparent thermodynamic limitations, with multicells the dominant convective mode. Wherever low-level lapse rates can become steepened, a risk for at least isolated damaging winds remains apparent. Some hail may also occur with the strongest cores across parts of the TN Valley/southern Appalachians where locally greater instability should be present this afternoon. The Marginal Risk has been adjusted for ongoing trends, but the potential for a more focused corridor of scattered severe/damaging winds remains unclear. ...Mid Missouri Valley... A mid-level shortwave trough and attendant strong speed maximum will move quickly southeastward today from central Canada and the northern Plains towards the mid MO Valley and vicinity. Pronounced ascent associated with this jet should encourage convection to develop by late this afternoon across parts of eastern SD and vicinity. While low-level moisture and MLCAPE are both expected to remain very limited, enhanced low/mid-level northwesterly flow may still support some risk for severe gusts with any low-topped convection that can develop and spread quickly southeastward before weakening this evening with the loss of daytime heating. ...Kansas... A sharp cold front will sweep southward across the central Plains tonight. Elevated convection should form to the cool side of this boundary late tonight through early Friday morning given sufficient MUCAPE. Locally strong surface gusts and small hail may accompany this activity amid robust low-level northerlies, but the overall severe potential should remain fairly low given the tendency for convection to be mostly elevated. ...Arizona/Lower Colorado River Valley... Thunderstorms should develop again today across parts of central/southern AZ and the lower CO River Valley, beneath weak mid-level flow and on the periphery of increasing mid-level moisture associated with Tropical Storm Lorena. Weak shear should keep thunderstorms mostly disorganized, but occasional strong/gusty winds may occur where low-level lapse rates can become steepened. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0259 PM CDT Thu Sep 04 2025 Valid 042000Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF NEW YORK...TO THE MID ATLANTIC...SOUTHERN APPALACHIANS AND MID MISSOURI VALLEY... ...SUMMARY... Isolated damaging gusts remain possible across parts of New York to the Mid-Atlantic and Southern Appalachians through early this evening. Isolated severe gusts are also possible across parts of the mid Missouri Valley late this afternoon and early evening. ...20z Update Mid Atlantic and southern Appalachians... Several clusters of strong to severe thunderstorms have matured and are expected to continue through early this evening along and ahead of the slow-moving cold front from the Mid Atlantic southward. Despite poor mid-level lapse rates, heating of the modestly moist air mass is supporting around 500-1000 J/kg of MLCAPE, sufficient for a few stronger updrafts. As convection gradually increases in coverage through the remainder of this afternoon, clustering and 30-40 kt of mid-level flow will continue to support isolated damaging gust potential into early this evening. Some hail remains possible with the more cellular elements, especially father southwest over the eastern TN Valley where storm coverage should remain more isolated. The primary change was to align the western edge of the MRGL and severe probabilities with current frontal position, and shift them slightly east for ongoing storms on the border of NC and southern VA. ...New York... As the line of showers and weak thunderstorms continues eastward along the front, occasional damaging gusts remain possible owing to mixing of stronger mid-level flow downward this afternoon. Some heating, but marginal surface moisture should keep buoyancy and the resulting updrafts weak. With MLCAPE generally less than 500 J/kg, showers and storms should steadily weaken with the loss of diurnal heating. The MRGL risk area has been trimmed behind the ongoing line. Otherwise, the prior outlook remains unchanged, see the previous discussion. ..Lyons.. 09/04/2025 .PREV DISCUSSION... /ISSUED 1124 AM CDT Thu Sep 04 2025/ ...New York into the Mid-Atlantic and Tennessee Valley... A closed mid/upper-level low will remain centered over Ontario today. Multiple mid-level perturbations will rotate around this feature through the period, including a shortwave trough forecast to advance generally east-northeastward across parts of the central Appalachians/Mid-Atlantic into the Northeast. Showers and thunderstorms are ongoing mainly ahead of a surface cold front from parts of western NY southward to the TN Valley in a low/mid-level moisture plume. Generally clear skies ahead of this activity should allow for ample daytime heating of a modestly moistened low-level airmass. Even so, 12Z observed soundings from BUF, IAD, and RNK/GSO show rather poor mid-level lapse rates, which will likely hinder updraft strength even as weak instability develops this afternoon with continued diurnal heating. Modestly enhanced southwesterly low/mid-level flow should still aid in some thunderstorm organization even with the apparent thermodynamic limitations, with multicells the dominant convective mode. Wherever low-level lapse rates can become steepened, a risk for at least isolated damaging winds remains apparent. Some hail may also occur with the strongest cores across parts of the TN Valley/southern Appalachians where locally greater instability should be present this afternoon. The Marginal Risk has been adjusted for ongoing trends, but the potential for a more focused corridor of scattered severe/damaging winds remains unclear. ...Mid Missouri Valley... A mid-level shortwave trough and attendant strong speed maximum will move quickly southeastward today from central Canada and the northern Plains towards the mid MO Valley and vicinity. Pronounced ascent associated with this jet should encourage convection to develop by late this afternoon across parts of eastern SD and vicinity. While low-level moisture and MLCAPE are both expected to remain very limited, enhanced low/mid-level northwesterly flow may still support some risk for severe gusts with any low-topped convection that can develop and spread quickly southeastward before weakening this evening with the loss of daytime heating. ...Kansas... A sharp cold front will sweep southward across the central Plains tonight. Elevated convection should form to the cool side of this boundary late tonight through early Friday morning given sufficient MUCAPE. Locally strong surface gusts and small hail may accompany this activity amid robust low-level northerlies, but the overall severe potential should remain fairly low given the tendency for convection to be mostly elevated. ...Arizona/Lower Colorado River Valley... Thunderstorms should develop again today across parts of central/southern AZ and the lower CO River Valley, beneath weak mid-level flow and on the periphery of increasing mid-level moisture associated with Tropical Storm Lorena. Weak shear should keep thunderstorms mostly disorganized, but occasional strong/gusty winds may occur where low-level lapse rates can become steepened. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0259 PM CDT Thu Sep 04 2025 Valid 042000Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF NEW YORK...TO THE MID ATLANTIC...SOUTHERN APPALACHIANS AND MID MISSOURI VALLEY... ...SUMMARY... Isolated damaging gusts remain possible across parts of New York to the Mid-Atlantic and Southern Appalachians through early this evening. Isolated severe gusts are also possible across parts of the mid Missouri Valley late this afternoon and early evening. ...20z Update Mid Atlantic and southern Appalachians... Several clusters of strong to severe thunderstorms have matured and are expected to continue through early this evening along and ahead of the slow-moving cold front from the Mid Atlantic southward. Despite poor mid-level lapse rates, heating of the modestly moist air mass is supporting around 500-1000 J/kg of MLCAPE, sufficient for a few stronger updrafts. As convection gradually increases in coverage through the remainder of this afternoon, clustering and 30-40 kt of mid-level flow will continue to support isolated damaging gust potential into early this evening. Some hail remains possible with the more cellular elements, especially father southwest over the eastern TN Valley where storm coverage should remain more isolated. The primary change was to align the western edge of the MRGL and severe probabilities with current frontal position, and shift them slightly east for ongoing storms on the border of NC and southern VA. ...New York... As the line of showers and weak thunderstorms continues eastward along the front, occasional damaging gusts remain possible owing to mixing of stronger mid-level flow downward this afternoon. Some heating, but marginal surface moisture should keep buoyancy and the resulting updrafts weak. With MLCAPE generally less than 500 J/kg, showers and storms should steadily weaken with the loss of diurnal heating. The MRGL risk area has been trimmed behind the ongoing line. Otherwise, the prior outlook remains unchanged, see the previous discussion. ..Lyons.. 09/04/2025 .PREV DISCUSSION... /ISSUED 1124 AM CDT Thu Sep 04 2025/ ...New York into the Mid-Atlantic and Tennessee Valley... A closed mid/upper-level low will remain centered over Ontario today. Multiple mid-level perturbations will rotate around this feature through the period, including a shortwave trough forecast to advance generally east-northeastward across parts of the central Appalachians/Mid-Atlantic into the Northeast. Showers and thunderstorms are ongoing mainly ahead of a surface cold front from parts of western NY southward to the TN Valley in a low/mid-level moisture plume. Generally clear skies ahead of this activity should allow for ample daytime heating of a modestly moistened low-level airmass. Even so, 12Z observed soundings from BUF, IAD, and RNK/GSO show rather poor mid-level lapse rates, which will likely hinder updraft strength even as weak instability develops this afternoon with continued diurnal heating. Modestly enhanced southwesterly low/mid-level flow should still aid in some thunderstorm organization even with the apparent thermodynamic limitations, with multicells the dominant convective mode. Wherever low-level lapse rates can become steepened, a risk for at least isolated damaging winds remains apparent. Some hail may also occur with the strongest cores across parts of the TN Valley/southern Appalachians where locally greater instability should be present this afternoon. The Marginal Risk has been adjusted for ongoing trends, but the potential for a more focused corridor of scattered severe/damaging winds remains unclear. ...Mid Missouri Valley... A mid-level shortwave trough and attendant strong speed maximum will move quickly southeastward today from central Canada and the northern Plains towards the mid MO Valley and vicinity. Pronounced ascent associated with this jet should encourage convection to develop by late this afternoon across parts of eastern SD and vicinity. While low-level moisture and MLCAPE are both expected to remain very limited, enhanced low/mid-level northwesterly flow may still support some risk for severe gusts with any low-topped convection that can develop and spread quickly southeastward before weakening this evening with the loss of daytime heating. ...Kansas... A sharp cold front will sweep southward across the central Plains tonight. Elevated convection should form to the cool side of this boundary late tonight through early Friday morning given sufficient MUCAPE. Locally strong surface gusts and small hail may accompany this activity amid robust low-level northerlies, but the overall severe potential should remain fairly low given the tendency for convection to be mostly elevated. ...Arizona/Lower Colorado River Valley... Thunderstorms should develop again today across parts of central/southern AZ and the lower CO River Valley, beneath weak mid-level flow and on the periphery of increasing mid-level moisture associated with Tropical Storm Lorena. Weak shear should keep thunderstorms mostly disorganized, but occasional strong/gusty winds may occur where low-level lapse rates can become steepened. Read more

5-Day Uncertainty Track last updated Thu, 04 Sep 2025 17:42:52 GMT


Wind Speed Probabilities last updated Thu, 04 Sep 2025 15:27:22 GMT

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0229 PM CDT Thu Sep 04 2025 Valid 061200Z - 071200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE MID-ATLANTIC INTO THE NORTHEAST... ...SUMMARY... Widely scattered thunderstorms will pose a risk of damaging wind gusts across parts of the Mid-Atlantic into the Northeast on Saturday. ...Synopsis... A broad/amplified mid/upper-level trough encompassing much of the eastern CONUS will shift slightly eastward through the forecast period, while an accompanying strong upper-level jet advances northeastward across Quebec. In the low-levels, a related north-south-oriented cold front will move eastward across the Northeast and Mid-Atlantic region through the afternoon. ...Northeast into the Mid-Atlantic... Ahead of the eastward-moving cold front, diurnal heating/ destabilization of a moist boundary layer (middle/upper 60s to lower 70s dewpoints) will contribute to a corridor of moderate surface-based buoyancy (1000-2000 J/kg MLCAPE) from the Mid-Atlantic into the Northeast -- despite poor midlevel lapse rates. Diurnal heating and related buoyancy may be limited with northward extent owing to increased cloud coverage near the right-entrance region of the upper-level jet. As the front intercepts the destabilizing/uncapped pre-convective air mass, widely scattered thunderstorms should develop along/immediately ahead of the front during the afternoon. Around 35-45 kt of front-parallel effective shear will support a mix of loosely organized convective bands and clusters. Given the enhanced deep-layer unidirectional flow and steepening low-level lapse rates, damaging wind gusts will be possible with the stronger storms into the evening. Depending on the degree of destabilization over parts of the Mid-Atlantic into the Northeast, an eventual upgrade may be warranted. ..Weinman.. 09/04/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0229 PM CDT Thu Sep 04 2025 Valid 061200Z - 071200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE MID-ATLANTIC INTO THE NORTHEAST... ...SUMMARY... Widely scattered thunderstorms will pose a risk of damaging wind gusts across parts of the Mid-Atlantic into the Northeast on Saturday. ...Synopsis... A broad/amplified mid/upper-level trough encompassing much of the eastern CONUS will shift slightly eastward through the forecast period, while an accompanying strong upper-level jet advances northeastward across Quebec. In the low-levels, a related north-south-oriented cold front will move eastward across the Northeast and Mid-Atlantic region through the afternoon. ...Northeast into the Mid-Atlantic... Ahead of the eastward-moving cold front, diurnal heating/ destabilization of a moist boundary layer (middle/upper 60s to lower 70s dewpoints) will contribute to a corridor of moderate surface-based buoyancy (1000-2000 J/kg MLCAPE) from the Mid-Atlantic into the Northeast -- despite poor midlevel lapse rates. Diurnal heating and related buoyancy may be limited with northward extent owing to increased cloud coverage near the right-entrance region of the upper-level jet. As the front intercepts the destabilizing/uncapped pre-convective air mass, widely scattered thunderstorms should develop along/immediately ahead of the front during the afternoon. Around 35-45 kt of front-parallel effective shear will support a mix of loosely organized convective bands and clusters. Given the enhanced deep-layer unidirectional flow and steepening low-level lapse rates, damaging wind gusts will be possible with the stronger storms into the evening. Depending on the degree of destabilization over parts of the Mid-Atlantic into the Northeast, an eventual upgrade may be warranted. ..Weinman.. 09/04/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0229 PM CDT Thu Sep 04 2025 Valid 061200Z - 071200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE MID-ATLANTIC INTO THE NORTHEAST... ...SUMMARY... Widely scattered thunderstorms will pose a risk of damaging wind gusts across parts of the Mid-Atlantic into the Northeast on Saturday. ...Synopsis... A broad/amplified mid/upper-level trough encompassing much of the eastern CONUS will shift slightly eastward through the forecast period, while an accompanying strong upper-level jet advances northeastward across Quebec. In the low-levels, a related north-south-oriented cold front will move eastward across the Northeast and Mid-Atlantic region through the afternoon. ...Northeast into the Mid-Atlantic... Ahead of the eastward-moving cold front, diurnal heating/ destabilization of a moist boundary layer (middle/upper 60s to lower 70s dewpoints) will contribute to a corridor of moderate surface-based buoyancy (1000-2000 J/kg MLCAPE) from the Mid-Atlantic into the Northeast -- despite poor midlevel lapse rates. Diurnal heating and related buoyancy may be limited with northward extent owing to increased cloud coverage near the right-entrance region of the upper-level jet. As the front intercepts the destabilizing/uncapped pre-convective air mass, widely scattered thunderstorms should develop along/immediately ahead of the front during the afternoon. Around 35-45 kt of front-parallel effective shear will support a mix of loosely organized convective bands and clusters. Given the enhanced deep-layer unidirectional flow and steepening low-level lapse rates, damaging wind gusts will be possible with the stronger storms into the evening. Depending on the degree of destabilization over parts of the Mid-Atlantic into the Northeast, an eventual upgrade may be warranted. ..Weinman.. 09/04/2025 Read more