Severe Storms

WW 546 TORNADO FL CW 280855Z - 282100Z
URGENT - IMMEDIATE BROADCAST REQUESTED Tornado Watch Number 546 NWS Storm Prediction Center Norman OK 455 AM EDT Wed Sep 28 2022 The NWS Storm Prediction Center has issued a * Tornado Watch for portions of Central and South Florida Coastal Waters * Effective this Wednesday morning and afternoon from 455 AM until 500 PM EDT. * Primary threats include... Several tornadoes likely SUMMARY...As Hurricane Ian continues to approach the west coast of Florida, a strong eastern-peripheral wind field and a very moist air mass will support the potential for supercells and a related tornado risk. This tornado potential will initially be focused across the southern Peninsula early today, but is likely to further increase and spread northward into the central Florida Peninsula by late morning and afternoon. The tornado watch area is approximately along and 70 statute miles east and west of a line from 45 miles southwest of Miami FL to 15 miles east northeast of Orlando FL. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU6). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Tornado Watch means conditions are favorable for tornadoes and severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. && OTHER WATCH INFORMATION...CONTINUE...WW 545... AVIATION...Tornadoes and a few severe thunderstorms with hail surface and aloft to 0 inches. Extreme turbulence and surface wind gusts to 50 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 15030. ...Guyer Read more

No Mesoscale Discussions are in effect as of Tue Sep 27 17:56:16 UTC 2022.

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Tue Sep 27 2022 Valid 281200Z - 291200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE FLORIDA PENINSULA... ...SUMMARY... A few tornadoes will be possible across the Florida Peninsula on Wednesday, in association with Hurricane Ian. ...Synopsis... A highly amplified upper trough will continue moving slowly eastward across eastern NOAM Wednesday, while a second trough -- initially over the northeastern Pacific -- shifts inland across southern British Columbia and the Pacific Northwest during the second half of the period. In between, ridging will prevail across the U.S. Great Plains and Canadian Prairies. At the surface, a cold front is forecast to move slowly across the Pacific Northwest, while high pressure prevails over the central and much of the eastern portions of the country. The main exception will be over the Southeast, where a quasistationary front will become more ill-defined, as Hurricane Ian shifts out of the eastern Gulf and into Florida through the end of the period. ...Florida Peninsula... While track uncertainties with respect to Ian (see the latest forecasts from the National Hurricane Center) persist, risk for a few tornadoes remains evident as the storm approaches -- and eventually moves into -- the Florida Peninsula. As low-level flow intensifies with time, shear in the eastern half of the circulation will support rotating updrafts within banded convection. As such, brief tornadoes will be possible for an extended period of time. At this time, with the storm track continuing to trend more eastward, future adjustments to northern fringes of the risk area will likely be required. ..Goss.. 09/27/2022 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1126 AM CDT Tue Sep 27 2022 Valid 271630Z - 281200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THROUGH TONIGHT ACROSS THE KEYS AND SOUTH FL INTO PARTS OF CENTRAL FL... ...SUMMARY... Tornadoes are possible across the Florida Keys and south Florida today, and may spread into parts of central Florida overnight with Hurricane Ian. ...South FL and the Keys through tonight... Major Hurricane Ian will move northward or north-northeastward through tonight across the extreme southeast Gulf of Mexico, as rain bands east-through-northeast of the center continue to overspread south FL and the Keys. Some expansion of the stronger wind field, and resultant stronger vertical shear (effective SRH of 200-400 m2/s2), will occur through tonight as Ian continues to deepen (see latest NHC advisories for additional information). Widespread rain across south FL has held surface temperatures in the mid 70s through the morning with minimal surface-based buoyancy. However, some cloud breaks and modest surface heating is underway across the Keys, and should develop slowly inland from the southeast FL coast through the afternoon. Likewise, slightly higher boundary-layer dewpoints (>76 F) will spread inland, with sufficient destabilization to support supercells moving inland. Thus, the threat for tornadoes is expected to gradually increase from south-to-north later this afternoon/evening, and persist into the overnight hours. Please see SPC MD 1833 for additional details. ..Thompson/Weinman.. 09/27/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1048 AM CDT Tue Sep 27 2022 Valid 271700Z - 281200Z The forecast remains on track with only minor adjustments needed for both the Gulf Coast and southern Oregon regions. Morning water vapor imagery shows broad subsidence across the Southeast, which will maintain warm, dry conditions today as RH values continue to fall into the 20-30% range. Sustained winds near 15 mph are expected by early afternoon, and gusts up to 20-25 mph will support periods of critical fire weather conditions. Across northern CA/southern OR, GOES Derived Winds is estimating mid-level winds near 20-25 mph, which is in line with latest guidance and supports the ongoing forecast (see previous discussion below). ...Southwest to Central Oklahoma... A few surface stations are reporting elevated fire weather conditions across western OK ahead of a weak surface trough/cold front. Boundary layer winds are expected to weaken through the day across the region, which will limit the overall fire weather potential despite receptive fuels. However, periods of patchy elevated conditions are possible during the 16-21 UTC period roughly across the Altus, OK to Watonga, OK region. ..Moore.. 09/27/2022 .PREV DISCUSSION... /ISSUED 0126 AM CDT Tue Sep 27 2022/ ...Synopsis... An amplified pattern aloft featuring a broad trough in the east, a large ridge over the central U.S., and a shortwave trough over the Northwest will be in place today. At the surface, a trough will develop in the lee of the Cascades while a surface high will build into the upper Midwest. The approach of Hurricane Ian along the western Florida coast will strengthen the surface pressure gradient for the central Gulf Coast states. ...South-central Oregon... Afternoon winds will reach 15-20 mph as the surface trough deepens in the Columbia Basin. Some increase in high cloud cover is possible and may impact RH reductions in parts of the region. However, at least some areas of 15-20% appear possible during the afternoon. ...Central Gulf Coast Vicinity... The region will be situated in a dry, post-frontal airmass. The combinations of a building surface high to the north and the approach of Ian to the southeast should promote a modest increase in surface winds. In general, winds around 15 mph are expected with locally higher sustained speeds and gusts. Dry fuels and RH that will likely fall to near 25% or lower will support an increase in fire weather concerns during the afternoon. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

WW 544 TORNADO FL CW 271255Z - 272100Z
URGENT - IMMEDIATE BROADCAST REQUESTED Tornado Watch Number 544 NWS Storm Prediction Center Norman OK 855 AM EDT Tue Sep 27 2022 The NWS Storm Prediction Center has issued a * Tornado Watch for portions of South Florida Coastal Waters * Effective this Tuesday morning and afternoon from 855 AM until 500 PM EDT. * Primary threats include... A few tornadoes possible SUMMARY...Hurricane Ian will continue to move north-northeastward and likely further intensify as per the National Hurricane Center. A very moist airmass and strengthening low-level shear will support an increasing tornado potential from the Florida Keys across the southern Peninsula through the afternoon. The tornado watch area is approximately along and 80 statute miles north and south of a line from 70 miles west northwest of Key West FL to 20 miles east southeast of Miami FL. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU4). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Tornado Watch means conditions are favorable for tornadoes and severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. && AVIATION...Tornadoes and a few severe thunderstorms with hail surface and aloft to 0 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 14020. ...Guyer Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Mon Sep 26 2022 Valid 271200Z - 281200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS WEST-CENTRAL AND SOUTHWESTERN FLORIDA... ...SUMMARY... A few tornadoes will be possible across parts of Florida Tuesday into Tuesday night, in association with Hurricane Ian. ...Synopsis... Large-scale upper troughing will continue over eastern NOAM Tuesday, while a second low/trough over the northeastern Pacific gradually approaches the Pacific Northwest. In between, expansive ridging will extend from Texas and the Desert Southwest northward across the Rockies and into the Canadian Prairie Provinces. At the surface, a cold front will remain roughly in place from the southeastern U.S. Atlantic Coast, west-southwestward along the Gulf Coast vicinity. To the south, Hurricane Ian is progged to be shifting slowly northward into/across the eastern Gulf of Mexico through the period. Please refer to the latest forecasts regarding Ian from the National Hurricane Center. ...Florida Peninsula... As Ian moves slowly northward, the low-level flow across the Florida Peninsula south of the aforementioned cold front -- particularly across west-central and southwestern Florida -- will increase with time. Widespread convection surrounding Ian will overspread the area from south to north, with embedded cellular convection within bands surrounding the center of circulation. As the inland wind field gradually strengthens, potential for rotating cells will likewise increase, along with associated tornado potential. This risk may increase through the afternoon, and continue into the overnight hours as the storm gradually shifts northward. ..Goss.. 09/26/2022 Read more

No watches are valid as of Mon Sep 26 17:35:02 UTC 2022.

MD 1830 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PARTS OF EASTERN NY...VT...AND NH
Mesoscale Discussion 1830 NWS Storm Prediction Center Norman OK 1216 PM CDT Mon Sep 26 2022 Areas affected...Parts of eastern NY...VT...and NH Concerning...Severe potential...Watch unlikely Valid 261716Z - 262015Z Probability of Watch Issuance...5 percent SUMMARY...The risk of strong to locally damaging gusts will increase this afternoon (around 18-22Z) as storms spread eastward from eastern NY across New England. DISCUSSION...Latest water vapor loops reveal the nose of a southwesterly mid/upper-level jet streak impinging on NY, where regional VWP data shows 40-50 kt of midlevel flow. As the left exit region of this jet streak continues overspreading eastern NY and New England -- in conjunction with strengthening DCVA downstream of the midlevel trough -- convection will gradually increase in coverage as it spreads eastward along a weak low-level confluence axis this afternoon. Within the pre-convective environment, filtered diurnal heating amid middle 50s boundary-layer dewpoints, coupled with midlevel adiabatic cooling/steepening midlevel lapse rates, will contribute to weakly unstable surface-based inflow. Deep/enhanced south-southwesterly flow will yield a long/straight hodograph (35-45 kt of effective shear), supportive of loosely organized bands or clusters of storms -- especially in the 18-22Z time frame. The primary concern with this activity will be strong to locally damaging gusts with the more organized bands/clusters, and small hail will also be possible. ..Weinman/Thompson.. 09/26/2022 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...GYX...BOX...BTV...ALY... LAT...LON 42667450 43537493 44177493 44617479 44847454 45077395 45057237 45037156 44707139 43857140 43197169 42897218 42727306 42457386 42667450 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1126 AM CDT Mon Sep 26 2022 Valid 261630Z - 271200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON FROM NY INTO NORTHERN NEW ENGLAND...AND OVERNIGHT IN THE FL KEYS... ...SUMMARY... Isolated wind damage will be possible this afternoon from central/northern New York into northern New England. The potential for a tornado or two will increase by late tonight/early Tuesday across the Florida Keys in association with Hurricane Ian. ...Central/northern NY to northern New England this afternoon... Within a deep midlevel trough over the Great Lakes, an embedded speed max will eject quickly northeastward from western NY toward northern New England by late afternoon/evening. A band of ascent, coincident with a reinforcing cold frontal surge, will help focus low-topped thunderstorms early this afternoon in central/northern NY and continuing through this evening across northern New England. Weak surface-based buoyancy will result from surface heating in cloud breaks and residual boundary-layer dewpoints in the low-mid 50s, in an environment with 40-50 kt south-southwesterly midlevel flow and straight hodographs. The net result will be the potential for strong gusts and isolated wind damage with downward momentum transfer in the stronger storms this afternoon/evening. ...FL Keys tonight through early Tuesday... Hurricane Ian is expected to undergo rapid intensification and reach the western tip of Cuba as a major hurricane by early Tuesday morning (please refer to the latest updates from NHC). The deepening cyclone, expanding wind field, and increasingly banded convective structures will result in a gradual increase in the threat for supercells and a tornado or two across the Keys overnight and into Tuesday morning. ..Thompson/Weinman.. 09/26/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1029 AM CDT Mon Sep 26 2022 Valid 261700Z - 271200Z ...NO CRITICAL AREAS... Fire weather concerns remain limited for today. Periodic elevated conditions remain possible across parts of eastern OK/TX and the Southeast, as well as across portions of the Midwest where winds may gust up to 30 mph with RH values near 30%. However, marginal fuel status will modulate the overall fire weather potential. ..Moore.. 09/26/2022 .PREV DISCUSSION... /ISSUED 1139 PM CDT Sun Sep 25 2022/ ...Synopsis... A fairly amplified upper-level pattern will exist across the CONUS today. Large-scale ridging in the west will slowly shift eastward as a broad trough in the east makes similar eastward progress. At the surface, the cold front will move offshore into the Gulf and the Atlantic. A dry airmass will reside within much of the central and western U.S. A diminishing surface pressure gradient will lead to weak winds over a broad area. However, locally elevated conditions are possible. The most likely areas for these conditions will be eastern OK/TX into parts of the Southeast. Rainfall has been minimal, particularly in OK/TX, and fuels will support fire spread. RH of 20-30% is possible, though winds may struggle to reach 15 mph. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

WW 0543 Status Updates
STATUS REPORT ON WW 543 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 20 W SHD TO 5 N HGR TO 30 WSW ABE. ..MOSIER..09/25/22 ATTN...WFO...LWX...CTP... STATUS REPORT FOR WS 543 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS DCC001-251940- DC . DISTRICT OF COLUMBIA COUNTIES INCLUDED ARE DISTRICT OF COLUMBIA MDC003-005-009-013-015-017-021-025-027-031-033-037-510-251940- MD . MARYLAND COUNTIES INCLUDED ARE ANNE ARUNDEL BALTIMORE CALVERT CARROLL CECIL CHARLES FREDERICK HARFORD HOWARD MONTGOMERY PRINCE GEORGES ST. MARYS MARYLAND INDEPENDENT CITIES INCLUDED ARE BALTIMORE CITY Read more

WW 543 SEVERE TSTM DC MD PA VA WV CW 251540Z - 252300Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 543 NWS Storm Prediction Center Norman OK 1140 AM EDT Sun Sep 25 2022 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of District Of Columbia Maryland South central Pennsylvania Northern Virginia The eastern West Virginia Panhandle Coastal Waters * Effective this Sunday morning and evening from 1140 AM until 700 PM EDT. * Primary threats include... Scattered damaging wind gusts to 70 mph possible Isolated large hail events to 1.5 inches in diameter possible A tornado or two possible SUMMARY...Scattered thunderstorms will likely persist through the afternoon, with some additional storm development expected. The storm environment favors a mix of supercells and line segments with attendant threats of damaging winds and large hail. An isolated tornado or two may also occur. The severe thunderstorm watch area is approximately along and 60 statute miles east and west of a line from 15 miles north northwest of Harrisburg PA to 40 miles east of Staunton VA. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU3). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. Severe thunderstorms can and occasionally do produce tornadoes. && AVIATION...A few severe thunderstorms with hail surface and aloft to 1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 450. Mean storm motion vector 27045. ...Thompson Read more

WW 543 SEVERE TSTM DC MD PA VA WV CW 251540Z - 252300Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 543 NWS Storm Prediction Center Norman OK 1140 AM EDT Sun Sep 25 2022 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of District Of Columbia Maryland South central Pennsylvania Northern Virginia The eastern West Virginia Panhandle Coastal Waters * Effective this Sunday morning and evening from 1140 AM until 700 PM EDT. * Primary threats include... Scattered damaging wind gusts to 70 mph possible Isolated large hail events to 1.5 inches in diameter possible A tornado or two possible SUMMARY...Scattered thunderstorms will likely persist through the afternoon, with some additional storm development expected. The storm environment favors a mix of supercells and line segments with attendant threats of damaging winds and large hail. An isolated tornado or two may also occur. The severe thunderstorm watch area is approximately along and 60 statute miles east and west of a line from 15 miles north northwest of Harrisburg PA to 40 miles east of Staunton VA. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU3). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. Severe thunderstorms can and occasionally do produce tornadoes. && AVIATION...A few severe thunderstorms with hail surface and aloft to 1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 450. Mean storm motion vector 27045. ...Thompson Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1200 PM CDT Sun Sep 25 2022 Valid 251700Z - 261200Z Expanded the Elevated delineation farther west across South Dakota and south into Nebraska based on morning high resolution guidance. Elsewhere, the forecast appears on track and no additional changes were needed. See previous discussion below. ..Bentley.. 09/25/2022 .PREV DISCUSSION... /ISSUED 1144 PM CDT Sat Sep 24 2022/ ...Synopsis... An upper-level trough will intensify across the Great Lakes region into the Mid-Atlantic. In the West, ridging aloft will amplify while slowly shifting east. At the surface, A cold front will continue southward through the southern Plains while moving off the east coast during the evening. Elevated fire weather is expected within portions of the Plains as relatively dry and gusty northerly/northwesterly winds develop during the day/afternoon. Winds will be strongest in parts of the Dakotas into eastern Nebraska, with diminishing strength farther south into Oklahoma. RH of around 20-25% appears likely be afternoon along with wind speeds of 15-25 mph. While these conditions could extend from the northern Plains into the southern Plains, recent precipitation in many areas has reduced fuel dryness. The areas of greatest concern will be in central/eastern South Dakota, far northern Nebraska, and central/southern Oklahoma. Elsewhere, locally elevated conditions may still occur. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1200 PM CDT Sun Sep 25 2022 Valid 251700Z - 261200Z Expanded the Elevated delineation farther west across South Dakota and south into Nebraska based on morning high resolution guidance. Elsewhere, the forecast appears on track and no additional changes were needed. See previous discussion below. ..Bentley.. 09/25/2022 .PREV DISCUSSION... /ISSUED 1144 PM CDT Sat Sep 24 2022/ ...Synopsis... An upper-level trough will intensify across the Great Lakes region into the Mid-Atlantic. In the West, ridging aloft will amplify while slowly shifting east. At the surface, A cold front will continue southward through the southern Plains while moving off the east coast during the evening. Elevated fire weather is expected within portions of the Plains as relatively dry and gusty northerly/northwesterly winds develop during the day/afternoon. Winds will be strongest in parts of the Dakotas into eastern Nebraska, with diminishing strength farther south into Oklahoma. RH of around 20-25% appears likely be afternoon along with wind speeds of 15-25 mph. While these conditions could extend from the northern Plains into the southern Plains, recent precipitation in many areas has reduced fuel dryness. The areas of greatest concern will be in central/eastern South Dakota, far northern Nebraska, and central/southern Oklahoma. Elsewhere, locally elevated conditions may still occur. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1140 AM CDT Sun Sep 25 2022 Valid 261200Z - 271200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE MONDAY NIGHT ACROSS PARTS OF THE LOWER FLORIDA KEYS... ...SUMMARY... The risk for showers and isolated thunderstorms capable of producing strong wind gusts, and perhaps brief tornadoes, may begin to increase late Monday night (toward daybreak Tuesday) across parts of the lower Florida Keys. ...Discussion... Models suggest that there will be little change to the amplified mid/upper flow regime now developing across North America, through at least daybreak Tuesday. This will include prominent ridging across the Pacific coast through much of the Canadian Prairies and U.S. Great Plains, and large-scale downstream troughing across the Mississippi Valley through the Atlantic Seaboard. The cold front associated with a reinforcing intrusion of cool and/or dry air to the east of the Rockies is forecast to slowly advance offshore of much of the middle and southern Atlantic coast, and into the northwestern Gulf of Mexico Monday through Monday night. This will leave generally stable conditions in its wake, aside from those areas beneath colder mid-level air across parts of the lower Great Lakes region into the St. Lawrence Valley vicinity, where a few thunderstorms are possible. In lower latitudes, the center of developing Hurricane Ian is forecast to migrate north-northwestward into the vicinity of far western Cuba by daybreak Tuesday. Strengthening easterly to southeasterly low-level wind fields may be accompanied by sufficient enlargement of increasingly clockwise curved low-level hodographs, and boundary-layer moistening, to begin contributing to increasing potential for brief tornadoes and/or severe wind gusts in convection as far northeast as the lower Florida Keys late Monday night. ..Kerr.. 09/25/2022 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1140 AM CDT Sun Sep 25 2022 Valid 261200Z - 271200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE MONDAY NIGHT ACROSS PARTS OF THE LOWER FLORIDA KEYS... ...SUMMARY... The risk for showers and isolated thunderstorms capable of producing strong wind gusts, and perhaps brief tornadoes, may begin to increase late Monday night (toward daybreak Tuesday) across parts of the lower Florida Keys. ...Discussion... Models suggest that there will be little change to the amplified mid/upper flow regime now developing across North America, through at least daybreak Tuesday. This will include prominent ridging across the Pacific coast through much of the Canadian Prairies and U.S. Great Plains, and large-scale downstream troughing across the Mississippi Valley through the Atlantic Seaboard. The cold front associated with a reinforcing intrusion of cool and/or dry air to the east of the Rockies is forecast to slowly advance offshore of much of the middle and southern Atlantic coast, and into the northwestern Gulf of Mexico Monday through Monday night. This will leave generally stable conditions in its wake, aside from those areas beneath colder mid-level air across parts of the lower Great Lakes region into the St. Lawrence Valley vicinity, where a few thunderstorms are possible. In lower latitudes, the center of developing Hurricane Ian is forecast to migrate north-northwestward into the vicinity of far western Cuba by daybreak Tuesday. Strengthening easterly to southeasterly low-level wind fields may be accompanied by sufficient enlargement of increasingly clockwise curved low-level hodographs, and boundary-layer moistening, to begin contributing to increasing potential for brief tornadoes and/or severe wind gusts in convection as far northeast as the lower Florida Keys late Monday night. ..Kerr.. 09/25/2022 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1120 AM CDT Sun Sep 25 2022 Valid 251630Z - 261200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THROUGH THIS EVENING ACROSS MUCH OF THE MID-ATLANTIC... ...SUMMARY... Scattered severe storms producing damaging winds and severe hail are expected across portions of the Appalachians and Mid-Atlantic States this afternoon through evening. ...Mid-Atlantic and vicinity through this evening... A midlevel shortwave trough over the upper OH Valley will eject eastward toward the Mid-Atlantic and southern New England, in response to an upstream shortwave trough digging south-southeastward from MB toward the upper MS Valley. Some deepening of a surface cyclone is expected in the vicinity of the lower Great Lakes in association with the ejecting midlevel trough, and a weak cold front will progress eastward across the Appalachians by this afternoon to the south of the deepening cyclone. The cyclone warm sector will not be particularly warm or moist, but a narrow zone of cloud breaks from southern PA into WV should allow surface temperatures to warm into the 70s with dewpoints in the mid 50s to near 60. The warming surface temperatures and notable midlevel cooling/steepening of low-midlevel lapse rates (observed at ILN from 00 to 12z) will boost MLCAPE into the 500-1000 J/kg range in a narrow zone immediately ahead of the weak cold front this afternoon. The specific location and evolution of the main severe threat is a bit uncertain given the presence of clouds and early convection, with the potential for the stronger storms to evolve from the leading edge of the ongoing convection in PA/WV, and farther west within the band of ascent. The weak buoyancy and steepening low-level lapse rates will combine with strengthening midlevel winds to provide an environment favorable for damaging winds with fast-moving, low-topped clusters/bands of convection spreading eastward toward the Mid-Atlantic coast through late afternoon/evening. Isolated large hail may also occur with any stronger storms/supercells given the long hodographs and cool midlevel temperatures, and low-level shear will be strong enough to support a low-end threat for a tornado or two. ...Southern Appalachians this afternoon... The southern fringe of the OH Valley midlevel trough will move over the southern Appalachians this afternoon, along with the remnant monsoonal moisture plume. Clouds/ongoing convection will tend to disrupt surface heating across northern AL/GA and southeast TN, and the southern fringe of the somewhat stronger forcing for ascent with the OH Valley trough is expected to pass over eastern KY/WV/VA. Thus, with modest buoyancy and the aforementioned concerns, storm coverage into the southern Appalachians is uncertain. Where storms form with afternoon heating in cloud breaks, there will be the potential for isolated damaging gusts and marginally severe hail. ...WI/southwest Lower MI this afternoon into early tonight... The shortwave trough now approaching northern MN will reach WI later this afternoon/evening, and then continue southeastward to Lower MI tonight. Cooling midlevel temperatures, residual low-level moisture, and surface heating in cloud breaks will support the potential for low-topped thunderstorm development by mid-late afternoon across WI. Lapse rates will be sufficiently steep and midlevel flow sufficiently strong for a low-end threat for wind damage. Despite arrival after the diurnal cycle, the threat for isolated wind damage could persist across Lake MI into southwest Lower MI, where the relatively warm lake will help maintain weak buoyancy and low-level lapse rates after sunset. ..Thompson/Weinman.. 09/25/2022 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1120 AM CDT Sun Sep 25 2022 Valid 251630Z - 261200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THROUGH THIS EVENING ACROSS MUCH OF THE MID-ATLANTIC... ...SUMMARY... Scattered severe storms producing damaging winds and severe hail are expected across portions of the Appalachians and Mid-Atlantic States this afternoon through evening. ...Mid-Atlantic and vicinity through this evening... A midlevel shortwave trough over the upper OH Valley will eject eastward toward the Mid-Atlantic and southern New England, in response to an upstream shortwave trough digging south-southeastward from MB toward the upper MS Valley. Some deepening of a surface cyclone is expected in the vicinity of the lower Great Lakes in association with the ejecting midlevel trough, and a weak cold front will progress eastward across the Appalachians by this afternoon to the south of the deepening cyclone. The cyclone warm sector will not be particularly warm or moist, but a narrow zone of cloud breaks from southern PA into WV should allow surface temperatures to warm into the 70s with dewpoints in the mid 50s to near 60. The warming surface temperatures and notable midlevel cooling/steepening of low-midlevel lapse rates (observed at ILN from 00 to 12z) will boost MLCAPE into the 500-1000 J/kg range in a narrow zone immediately ahead of the weak cold front this afternoon. The specific location and evolution of the main severe threat is a bit uncertain given the presence of clouds and early convection, with the potential for the stronger storms to evolve from the leading edge of the ongoing convection in PA/WV, and farther west within the band of ascent. The weak buoyancy and steepening low-level lapse rates will combine with strengthening midlevel winds to provide an environment favorable for damaging winds with fast-moving, low-topped clusters/bands of convection spreading eastward toward the Mid-Atlantic coast through late afternoon/evening. Isolated large hail may also occur with any stronger storms/supercells given the long hodographs and cool midlevel temperatures, and low-level shear will be strong enough to support a low-end threat for a tornado or two. ...Southern Appalachians this afternoon... The southern fringe of the OH Valley midlevel trough will move over the southern Appalachians this afternoon, along with the remnant monsoonal moisture plume. Clouds/ongoing convection will tend to disrupt surface heating across northern AL/GA and southeast TN, and the southern fringe of the somewhat stronger forcing for ascent with the OH Valley trough is expected to pass over eastern KY/WV/VA. Thus, with modest buoyancy and the aforementioned concerns, storm coverage into the southern Appalachians is uncertain. Where storms form with afternoon heating in cloud breaks, there will be the potential for isolated damaging gusts and marginally severe hail. ...WI/southwest Lower MI this afternoon into early tonight... The shortwave trough now approaching northern MN will reach WI later this afternoon/evening, and then continue southeastward to Lower MI tonight. Cooling midlevel temperatures, residual low-level moisture, and surface heating in cloud breaks will support the potential for low-topped thunderstorm development by mid-late afternoon across WI. Lapse rates will be sufficiently steep and midlevel flow sufficiently strong for a low-end threat for wind damage. Despite arrival after the diurnal cycle, the threat for isolated wind damage could persist across Lake MI into southwest Lower MI, where the relatively warm lake will help maintain weak buoyancy and low-level lapse rates after sunset. ..Thompson/Weinman.. 09/25/2022 Read more