Severe Storms

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1206 PM CDT Tue Aug 13 2019 Valid 141200Z - 151200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL HIGH PLAINS... ...SUMMARY... Scattered strong to severe storms with damaging hail and wind will be possible over the central High Plains Wednesday afternoon and evening, with isolated severe wind gusts from parts of the Gulf Coast to the eastern Carolinas. ...Central High Plains... A west-northwesterly mid-level flow pattern will be in place across the High Plains on Wednesday. At the surface, a low will deepen during the day in eastern Colorado. As surface temperatures warm, a pocket of moderate instability may develop in far northeastern Colorado. Convection is expected to initiate along the front range by early afternoon. Thunderstorms should then develop and move southeastward into the central High Plains. In addition to the instability, NAM forecast soundings in far northeastern Colorado have moderate deep-layer shear mainly due to speed shear in 700 mb to 300 mb layer. This combined with steep lapse rates should be favorable for supercells and isolated large hail. Damaging wind gusts will also be possible especially as the storms move eastward away from the mountains into increasing low-level moisture and stronger instability. An isolated severe threat may continue through part of the overnight period as a shortwave trough moves southeastward and approaches the central High Plains. ...Southeast/Carolinas... A low-amplitude cyclonic mid-level flow pattern will be in place across the eastern third of the nation. At the surface, a cold front is forecast to advance into the western Carolinas and central Gulf Coast states on Wednesday. The airmass ahead of the front will be very moist with surface dewpoints in the lower to mid 70s F. In response, moderate instability is expected to develop by afternoon along and south of the front. Scattered convection should initiate along the front and move eastward along the northern edge of the stronger instability. In spite of the moisture and instability, deep-layer shear will be weak. This will make conditions favorable for isolated marginally severe wind gusts mainly as low-level lapse rates peak in the late afternoon. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 15% - Slight Hail: 15% - Slight ..Broyles.. 08/13/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1206 PM CDT Tue Aug 13 2019 Valid 141200Z - 151200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL HIGH PLAINS... ...SUMMARY... Scattered strong to severe storms with damaging hail and wind will be possible over the central High Plains Wednesday afternoon and evening, with isolated severe wind gusts from parts of the Gulf Coast to the eastern Carolinas. ...Central High Plains... A west-northwesterly mid-level flow pattern will be in place across the High Plains on Wednesday. At the surface, a low will deepen during the day in eastern Colorado. As surface temperatures warm, a pocket of moderate instability may develop in far northeastern Colorado. Convection is expected to initiate along the front range by early afternoon. Thunderstorms should then develop and move southeastward into the central High Plains. In addition to the instability, NAM forecast soundings in far northeastern Colorado have moderate deep-layer shear mainly due to speed shear in 700 mb to 300 mb layer. This combined with steep lapse rates should be favorable for supercells and isolated large hail. Damaging wind gusts will also be possible especially as the storms move eastward away from the mountains into increasing low-level moisture and stronger instability. An isolated severe threat may continue through part of the overnight period as a shortwave trough moves southeastward and approaches the central High Plains. ...Southeast/Carolinas... A low-amplitude cyclonic mid-level flow pattern will be in place across the eastern third of the nation. At the surface, a cold front is forecast to advance into the western Carolinas and central Gulf Coast states on Wednesday. The airmass ahead of the front will be very moist with surface dewpoints in the lower to mid 70s F. In response, moderate instability is expected to develop by afternoon along and south of the front. Scattered convection should initiate along the front and move eastward along the northern edge of the stronger instability. In spite of the moisture and instability, deep-layer shear will be weak. This will make conditions favorable for isolated marginally severe wind gusts mainly as low-level lapse rates peak in the late afternoon. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 15% - Slight Hail: 15% - Slight ..Broyles.. 08/13/2019 Read more

No watches are valid as of Tue Aug 13 17:08:02 UTC 2019.

MD 1722 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PORTIONS OF EASTERN TN...SOUTHWESTERN/SOUTHERN VA...AND WESTERN/CENTRAL NC
Mesoscale Discussion 1722 NWS Storm Prediction Center Norman OK 1052 AM CDT Tue Aug 13 2019 Areas affected...Portions of eastern TN...southwestern/southern VA...and western/central NC Concerning...Severe potential...Watch possible Valid 131552Z - 131745Z Probability of Watch Issuance...60 percent SUMMARY...A threat for strong/gusty winds capable of producing isolated damage should increase this afternoon. Watch issuance is possible. DISCUSSION...15Z surface analysis and visible satellite imagery shows an outflow boundary from earlier convection has moved southward into middle/eastern TN and southwestern VA. Storms have recently begun to increase in coverage along this boundary as daytime heating warms the boundary layer. A high precipitable water airmass is in place along/south of this boundary across much of eastern TN into southwestern/south-central VA and western/central NC. As surface air temperatures warm into the 80s and 90s this afternoon, low-level lapse rates will likewise steepen and instability will increase. A belt of modestly enhanced mid-level flow (around 30-40 kt at 500 mb) will overlie this region through peak diurnal heating, with area VWPs showing the strongest winds over southern VA gradually weakening into TN/NC. Strong/gusty winds may occur as this enhanced flow aloft reaches the surface through convective downdraft processes. Isolated damage from these winds will be possible given the potential for some multicell clustering as storms spread eastward through the early evening. Watch issuance may be needed within the next couple of hours (by 18Z/Noon EDT). ..Gleason/Grams.. 08/13/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...RAH...RNK...RLX...GSP...MRX... LAT...LON 37357942 37117863 36277891 35777954 35198053 35218237 35168316 35188427 35268495 35648503 37058245 37188164 37298031 37357942 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1129 AM CDT Tue Aug 13 2019 Valid 131630Z - 141200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS EASTERN CO AND WESTERN KS... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SOUTHERN VA TO NORTHERN SC WEST ACROSS THE TN VALLEY... ...SUMMARY... Significant severe hail and wind gusts are possible across the central High Plains during the late afternoon to mid evening. Scattered damaging winds are possible from the Tennessee Valley to the Carolinas and southern Virginia through early evening. ...Central High Plains... Weak warm-advection driven convection is ongoing across northwest/north-central NE. To its south, ample low-level moisture is prevalent. The difference between the NAM/RAP in the degree of boundary-layer mixing within the warm/moist sector is unusual in that the NAM is actually quite a bit more mixed at peak heating than the RAP (typically its the reverse). Surface dew points will probably mix to 60-65 F, contributing to a confined corridor of MLCAPE of 2000-3000 J/kg across the CO/KS/NE border area beneath rather steep mid-level lapse rates. Surface-based storm development is expected around 21Z near this tri-state region as convergence strengthens at the intersection of the lee trough and the southward-sagging cold front. Initial storms will likely be discrete supercells capable of producing isolated very large hail and perhaps a tornado or two. Convection should grow upscale into a southward propagating cluster into a weak nocturnal low-level jet across far eastern CO/western KS, with a continuing threat for severe wind gusts into early tonight. ...TN Valley to the Carolinas/southern VA... A separated belt of enhanced 700-mb westerlies should remain centered on the KY to VA area through early evening. Areas of decaying stratiform rain remnants of early morning MCSs are generally located within this belt of stronger flow, largely south of 12Z HREF members. Convection is ongoing an arc across eastern TN into far southwest VA along the remnant outflow. Ample heating is occurring downstream across the Carolinas and it is possible that this convection intensifies (see MCD 1722). With flow weakening with southern extent, the degree of organization becomes increasingly uncertain, but at least a few multicell clusters should develop with a risk for scattered damaging winds across southern Virginia and parts of the Carolinas. Additional clusters should also form west across the TN Valley along the remnant outflow towards late afternoon as large buoyancy develops amid upper 70s surface dew points. Somewhat weaker effective shear from 15-25 kt should foster multicell clusters with a risk for isolated to scattered damaging winds. ...Upper MS Valley... A shortwave trough along the Red River Valley should dampen as it tracks into WI tonight. Ascent preceding this trough will coincide with a pocket of stronger surface heating and low-level convergence along a weak northwest-southeast oriented front, which will support scattered thunderstorm development towards late afternoon. A confined corridor of MLCAPE from 1000-1500 J/kg may potentially coincide with effective bulk shear near 40 kt. However, modest mid-level lapse rates should temper overall storm intensity despite the expectation of a few transient supercells. Isolated damaging winds and severe hail will likely be the main threats. A brief tornado may also occur with storms moving southeast along the boundary, where low-level shear and vertical vorticity will be larger. ..Grams/Mosier.. 08/13/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1129 AM CDT Tue Aug 13 2019 Valid 131630Z - 141200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS EASTERN CO AND WESTERN KS... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SOUTHERN VA TO NORTHERN SC WEST ACROSS THE TN VALLEY... ...SUMMARY... Significant severe hail and wind gusts are possible across the central High Plains during the late afternoon to mid evening. Scattered damaging winds are possible from the Tennessee Valley to the Carolinas and southern Virginia through early evening. ...Central High Plains... Weak warm-advection driven convection is ongoing across northwest/north-central NE. To its south, ample low-level moisture is prevalent. The difference between the NAM/RAP in the degree of boundary-layer mixing within the warm/moist sector is unusual in that the NAM is actually quite a bit more mixed at peak heating than the RAP (typically its the reverse). Surface dew points will probably mix to 60-65 F, contributing to a confined corridor of MLCAPE of 2000-3000 J/kg across the CO/KS/NE border area beneath rather steep mid-level lapse rates. Surface-based storm development is expected around 21Z near this tri-state region as convergence strengthens at the intersection of the lee trough and the southward-sagging cold front. Initial storms will likely be discrete supercells capable of producing isolated very large hail and perhaps a tornado or two. Convection should grow upscale into a southward propagating cluster into a weak nocturnal low-level jet across far eastern CO/western KS, with a continuing threat for severe wind gusts into early tonight. ...TN Valley to the Carolinas/southern VA... A separated belt of enhanced 700-mb westerlies should remain centered on the KY to VA area through early evening. Areas of decaying stratiform rain remnants of early morning MCSs are generally located within this belt of stronger flow, largely south of 12Z HREF members. Convection is ongoing an arc across eastern TN into far southwest VA along the remnant outflow. Ample heating is occurring downstream across the Carolinas and it is possible that this convection intensifies (see MCD 1722). With flow weakening with southern extent, the degree of organization becomes increasingly uncertain, but at least a few multicell clusters should develop with a risk for scattered damaging winds across southern Virginia and parts of the Carolinas. Additional clusters should also form west across the TN Valley along the remnant outflow towards late afternoon as large buoyancy develops amid upper 70s surface dew points. Somewhat weaker effective shear from 15-25 kt should foster multicell clusters with a risk for isolated to scattered damaging winds. ...Upper MS Valley... A shortwave trough along the Red River Valley should dampen as it tracks into WI tonight. Ascent preceding this trough will coincide with a pocket of stronger surface heating and low-level convergence along a weak northwest-southeast oriented front, which will support scattered thunderstorm development towards late afternoon. A confined corridor of MLCAPE from 1000-1500 J/kg may potentially coincide with effective bulk shear near 40 kt. However, modest mid-level lapse rates should temper overall storm intensity despite the expectation of a few transient supercells. Isolated damaging winds and severe hail will likely be the main threats. A brief tornado may also occur with storms moving southeast along the boundary, where low-level shear and vertical vorticity will be larger. ..Grams/Mosier.. 08/13/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1129 AM CDT Tue Aug 13 2019 Valid 131630Z - 141200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS EASTERN CO AND WESTERN KS... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SOUTHERN VA TO NORTHERN SC WEST ACROSS THE TN VALLEY... ...SUMMARY... Significant severe hail and wind gusts are possible across the central High Plains during the late afternoon to mid evening. Scattered damaging winds are possible from the Tennessee Valley to the Carolinas and southern Virginia through early evening. ...Central High Plains... Weak warm-advection driven convection is ongoing across northwest/north-central NE. To its south, ample low-level moisture is prevalent. The difference between the NAM/RAP in the degree of boundary-layer mixing within the warm/moist sector is unusual in that the NAM is actually quite a bit more mixed at peak heating than the RAP (typically its the reverse). Surface dew points will probably mix to 60-65 F, contributing to a confined corridor of MLCAPE of 2000-3000 J/kg across the CO/KS/NE border area beneath rather steep mid-level lapse rates. Surface-based storm development is expected around 21Z near this tri-state region as convergence strengthens at the intersection of the lee trough and the southward-sagging cold front. Initial storms will likely be discrete supercells capable of producing isolated very large hail and perhaps a tornado or two. Convection should grow upscale into a southward propagating cluster into a weak nocturnal low-level jet across far eastern CO/western KS, with a continuing threat for severe wind gusts into early tonight. ...TN Valley to the Carolinas/southern VA... A separated belt of enhanced 700-mb westerlies should remain centered on the KY to VA area through early evening. Areas of decaying stratiform rain remnants of early morning MCSs are generally located within this belt of stronger flow, largely south of 12Z HREF members. Convection is ongoing an arc across eastern TN into far southwest VA along the remnant outflow. Ample heating is occurring downstream across the Carolinas and it is possible that this convection intensifies (see MCD 1722). With flow weakening with southern extent, the degree of organization becomes increasingly uncertain, but at least a few multicell clusters should develop with a risk for scattered damaging winds across southern Virginia and parts of the Carolinas. Additional clusters should also form west across the TN Valley along the remnant outflow towards late afternoon as large buoyancy develops amid upper 70s surface dew points. Somewhat weaker effective shear from 15-25 kt should foster multicell clusters with a risk for isolated to scattered damaging winds. ...Upper MS Valley... A shortwave trough along the Red River Valley should dampen as it tracks into WI tonight. Ascent preceding this trough will coincide with a pocket of stronger surface heating and low-level convergence along a weak northwest-southeast oriented front, which will support scattered thunderstorm development towards late afternoon. A confined corridor of MLCAPE from 1000-1500 J/kg may potentially coincide with effective bulk shear near 40 kt. However, modest mid-level lapse rates should temper overall storm intensity despite the expectation of a few transient supercells. Isolated damaging winds and severe hail will likely be the main threats. A brief tornado may also occur with storms moving southeast along the boundary, where low-level shear and vertical vorticity will be larger. ..Grams/Mosier.. 08/13/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1129 AM CDT Tue Aug 13 2019 Valid 131630Z - 141200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS EASTERN CO AND WESTERN KS... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SOUTHERN VA TO NORTHERN SC WEST ACROSS THE TN VALLEY... ...SUMMARY... Significant severe hail and wind gusts are possible across the central High Plains during the late afternoon to mid evening. Scattered damaging winds are possible from the Tennessee Valley to the Carolinas and southern Virginia through early evening. ...Central High Plains... Weak warm-advection driven convection is ongoing across northwest/north-central NE. To its south, ample low-level moisture is prevalent. The difference between the NAM/RAP in the degree of boundary-layer mixing within the warm/moist sector is unusual in that the NAM is actually quite a bit more mixed at peak heating than the RAP (typically its the reverse). Surface dew points will probably mix to 60-65 F, contributing to a confined corridor of MLCAPE of 2000-3000 J/kg across the CO/KS/NE border area beneath rather steep mid-level lapse rates. Surface-based storm development is expected around 21Z near this tri-state region as convergence strengthens at the intersection of the lee trough and the southward-sagging cold front. Initial storms will likely be discrete supercells capable of producing isolated very large hail and perhaps a tornado or two. Convection should grow upscale into a southward propagating cluster into a weak nocturnal low-level jet across far eastern CO/western KS, with a continuing threat for severe wind gusts into early tonight. ...TN Valley to the Carolinas/southern VA... A separated belt of enhanced 700-mb westerlies should remain centered on the KY to VA area through early evening. Areas of decaying stratiform rain remnants of early morning MCSs are generally located within this belt of stronger flow, largely south of 12Z HREF members. Convection is ongoing an arc across eastern TN into far southwest VA along the remnant outflow. Ample heating is occurring downstream across the Carolinas and it is possible that this convection intensifies (see MCD 1722). With flow weakening with southern extent, the degree of organization becomes increasingly uncertain, but at least a few multicell clusters should develop with a risk for scattered damaging winds across southern Virginia and parts of the Carolinas. Additional clusters should also form west across the TN Valley along the remnant outflow towards late afternoon as large buoyancy develops amid upper 70s surface dew points. Somewhat weaker effective shear from 15-25 kt should foster multicell clusters with a risk for isolated to scattered damaging winds. ...Upper MS Valley... A shortwave trough along the Red River Valley should dampen as it tracks into WI tonight. Ascent preceding this trough will coincide with a pocket of stronger surface heating and low-level convergence along a weak northwest-southeast oriented front, which will support scattered thunderstorm development towards late afternoon. A confined corridor of MLCAPE from 1000-1500 J/kg may potentially coincide with effective bulk shear near 40 kt. However, modest mid-level lapse rates should temper overall storm intensity despite the expectation of a few transient supercells. Isolated damaging winds and severe hail will likely be the main threats. A brief tornado may also occur with storms moving southeast along the boundary, where low-level shear and vertical vorticity will be larger. ..Grams/Mosier.. 08/13/2019 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1049 AM CDT Tue Aug 13 2019 Valid 131700Z - 141200Z ...NO CRITICAL AREAS... The previous forecast remains on track, with no changes or additions made. Please see below for details. ..Squitieri.. 08/13/2019 .PREV DISCUSSION... /ISSUED 1208 AM CDT Tue Aug 13 2019/ ...Synopsis... The synoptic pattern will continue to be generally unfavorable for fire weather concerns today. Weak, quasi-zonal flow aloft will extend across the northern tier of the CONUS today. Additionally, flow across dry areas of the West will remain relatively light outside of localized, terrain-favored areas. Given the minimal fire weather concerns, no highlights will be introduced for this outlook. ...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 1049 AM CDT Tue Aug 13 2019 Valid 131700Z - 141200Z ...NO CRITICAL AREAS... The previous forecast remains on track, with no changes or additions made. Please see below for details. ..Squitieri.. 08/13/2019 .PREV DISCUSSION... /ISSUED 1208 AM CDT Tue Aug 13 2019/ ...Synopsis... The synoptic pattern will continue to be generally unfavorable for fire weather concerns today. Weak, quasi-zonal flow aloft will extend across the northern tier of the CONUS today. Additionally, flow across dry areas of the West will remain relatively light outside of localized, terrain-favored areas. Given the minimal fire weather concerns, no highlights will be introduced for this outlook. ...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 1049 AM CDT Tue Aug 13 2019 Valid 131700Z - 141200Z ...NO CRITICAL AREAS... The previous forecast remains on track, with no changes or additions made. Please see below for details. ..Squitieri.. 08/13/2019 .PREV DISCUSSION... /ISSUED 1208 AM CDT Tue Aug 13 2019/ ...Synopsis... The synoptic pattern will continue to be generally unfavorable for fire weather concerns today. Weak, quasi-zonal flow aloft will extend across the northern tier of the CONUS today. Additionally, flow across dry areas of the West will remain relatively light outside of localized, terrain-favored areas. Given the minimal fire weather concerns, no highlights will be introduced for this outlook. ...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 1049 AM CDT Tue Aug 13 2019 Valid 131700Z - 141200Z ...NO CRITICAL AREAS... The previous forecast remains on track, with no changes or additions made. Please see below for details. ..Squitieri.. 08/13/2019 .PREV DISCUSSION... /ISSUED 1208 AM CDT Tue Aug 13 2019/ ...Synopsis... The synoptic pattern will continue to be generally unfavorable for fire weather concerns today. Weak, quasi-zonal flow aloft will extend across the northern tier of the CONUS today. Additionally, flow across dry areas of the West will remain relatively light outside of localized, terrain-favored areas. Given the minimal fire weather concerns, no highlights will be introduced for this outlook. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No Mesoscale Discussions are in effect as of Tue Aug 13 15:31:03 UTC 2019.

MD 1721 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF WESTERN/CENTRAL NE
Mesoscale Discussion 1721 NWS Storm Prediction Center Norman OK 0856 AM CDT Tue Aug 13 2019 Areas affected...Portions of western/central NE Concerning...Severe potential...Watch unlikely Valid 131356Z - 131530Z Probability of Watch Issuance...20 percent SUMMARY...An isolated large hail risk may continue this morning with ongoing thunderstorms. Watch issuance is unlikely in the short term. DISCUSSION...A pair of elevated supercells has evolved this morning in southern Cherry County NE within a warm air advection regime maximized around 700 mb. Short-term guidance, including the latest run of the RAP, suggests that 25-35 kt of southwesterly flow centered around 700 mb may persist through the rest of the morning. These winds, along with 35-40 kt of effective bulk shear, could maintain storm intensities as they develop southeastward along an instability gradient present across western/central NE. Isolated large hail will remain the primary threat for the next couple of hours given a stable near-surface layer noted on the 12Z sounding from LBF. Regardless, this hail threat will likely remain too isolated to justify watch issuance in the short term (through the rest of the morning). But, the severe threat will likely increase later today across parts of southern/western NE as the atmosphere destabilizes and surface-based storms develop. ..Gleason/Grams.. 08/13/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LBF...CYS... LAT...LON 42580301 42870292 42910242 42280099 41710028 41140025 40740043 40740117 41310187 41990253 42580301 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0759 AM CDT Tue Aug 13 2019 Valid 131300Z - 141200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON ACROSS VA...AND THIS AFTERNOON/EVENING ACROSS THE CENTRAL HIGH PLAINS... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS EXTENDING WESTWARD FROM THE MID-ATLANTIC ACROSS TN... ...SUMMARY... Scattered severe thunderstorms with damaging winds are expected across the southern Middle Atlantic into the Tennessee Valley. Severe thunderstorms with very large hail and damaging winds should also develop across the central High Plains. ...Synopsis... The primary larger-scale features today are northern stream troughs moving east-southeastward over Quebec and ND/MN, though a separate/weaker belt of westerlies is located farther south from the central Plains across the OH Valley to the Mid-Atlantic. Within this southern flow belt, diffuse MCVs are progressing east-southeastward over MO/IL and OH/WV, with ongoing convection in multiple clusters through this corridor. The stronger storms along the lower OH River are producing a cold pool and will likely persist until at least late morning, with the southward extent of the outflow likely demarcating the zone of afternoon redevelopment of storms this afternoon across TN. A few damaging gusts will be the main threats with multicell clusters/line segments in an environment of rich low-level moisture and moderate buoyancy along the southern edge of the 25-35 kt midlevel flow. The ongoing convection from southern OH to WV has shown signs of weakening slowly this morning. Still, residual clouds and some rain will slow surface heating from roughly 15-19z across central/northern VA, with the more probable zone of stronger destabilization along the southern fringe of the morning clouds/rain in the vicinity of southern VA. Upstream VWPs reveal 40 kt midlevel flow as low as 4 km above ground level over southern OH/eastern KY/WV, and this somewhat stronger flow will translate over VA this afternoon with the remnant MCV. Will maintain the 30% wind/Enhanced risk area in this update, though the influence of clouds on destabilization through early afternoon will likely modulate additional storm development this afternoon, and potentially reduce the severe threat. ...Central High Plains this afternoon through early tonight... A low-level upslope flow regime will establish today across eastern CO, prior to a weak reinforcing frontal surge overnight. South of an ongoing band of elevated storms driven by midlevel warm advection/frontogenesis, the low levels will warm and MLCAPE is expected to increase to 2000-3000 J/kg by mid-late afternoon. Deep-layer vertical shear will be favorable for supercells from northeast CO/northwest KS northward. Surface-based storm development is expected 21-00z across northeast CO along a surface trough on the northeast edge of the steeper low-level lapse rates and deeper mixing. The initial storms will likely be discrete supercells capable of producing isolated very large hail and perhaps a tornado or two. Convection may grow into a larger cluster this evening and propagate southward into a weak nocturnal low-level jet across far eastern CO/western KS, with a continuing threat for damaging winds into early tonight. ...Upper MS Valley area this afternoon... A midlevel shortwave trough over eastern ND this morning will move southeastward over MN/western WI by this evening. Ascent preceding the midlevel trough will coincide with daytime heating and low-level convergence along a weak northwest-southeast oriented front, which will support thunderstorm development this afternoon. Boundary-layer dewpoints in the 60s and afternoon surface temperatures approaching 80 F will drive MLCAPE of 1000-1500 J/kg, in an environment with effective bulk shear near 40 kt. The net result will be the potential for a few organized/supercell storms capable of producing isolated damaging winds/large hail. An isolated tornado may also occur with storms moving southeastward along the boundary, where low-level shear and vertical vorticity will be larger. ..Thompson/Kerr.. 08/13/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0759 AM CDT Tue Aug 13 2019 Valid 131300Z - 141200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON ACROSS VA...AND THIS AFTERNOON/EVENING ACROSS THE CENTRAL HIGH PLAINS... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS EXTENDING WESTWARD FROM THE MID-ATLANTIC ACROSS TN... ...SUMMARY... Scattered severe thunderstorms with damaging winds are expected across the southern Middle Atlantic into the Tennessee Valley. Severe thunderstorms with very large hail and damaging winds should also develop across the central High Plains. ...Synopsis... The primary larger-scale features today are northern stream troughs moving east-southeastward over Quebec and ND/MN, though a separate/weaker belt of westerlies is located farther south from the central Plains across the OH Valley to the Mid-Atlantic. Within this southern flow belt, diffuse MCVs are progressing east-southeastward over MO/IL and OH/WV, with ongoing convection in multiple clusters through this corridor. The stronger storms along the lower OH River are producing a cold pool and will likely persist until at least late morning, with the southward extent of the outflow likely demarcating the zone of afternoon redevelopment of storms this afternoon across TN. A few damaging gusts will be the main threats with multicell clusters/line segments in an environment of rich low-level moisture and moderate buoyancy along the southern edge of the 25-35 kt midlevel flow. The ongoing convection from southern OH to WV has shown signs of weakening slowly this morning. Still, residual clouds and some rain will slow surface heating from roughly 15-19z across central/northern VA, with the more probable zone of stronger destabilization along the southern fringe of the morning clouds/rain in the vicinity of southern VA. Upstream VWPs reveal 40 kt midlevel flow as low as 4 km above ground level over southern OH/eastern KY/WV, and this somewhat stronger flow will translate over VA this afternoon with the remnant MCV. Will maintain the 30% wind/Enhanced risk area in this update, though the influence of clouds on destabilization through early afternoon will likely modulate additional storm development this afternoon, and potentially reduce the severe threat. ...Central High Plains this afternoon through early tonight... A low-level upslope flow regime will establish today across eastern CO, prior to a weak reinforcing frontal surge overnight. South of an ongoing band of elevated storms driven by midlevel warm advection/frontogenesis, the low levels will warm and MLCAPE is expected to increase to 2000-3000 J/kg by mid-late afternoon. Deep-layer vertical shear will be favorable for supercells from northeast CO/northwest KS northward. Surface-based storm development is expected 21-00z across northeast CO along a surface trough on the northeast edge of the steeper low-level lapse rates and deeper mixing. The initial storms will likely be discrete supercells capable of producing isolated very large hail and perhaps a tornado or two. Convection may grow into a larger cluster this evening and propagate southward into a weak nocturnal low-level jet across far eastern CO/western KS, with a continuing threat for damaging winds into early tonight. ...Upper MS Valley area this afternoon... A midlevel shortwave trough over eastern ND this morning will move southeastward over MN/western WI by this evening. Ascent preceding the midlevel trough will coincide with daytime heating and low-level convergence along a weak northwest-southeast oriented front, which will support thunderstorm development this afternoon. Boundary-layer dewpoints in the 60s and afternoon surface temperatures approaching 80 F will drive MLCAPE of 1000-1500 J/kg, in an environment with effective bulk shear near 40 kt. The net result will be the potential for a few organized/supercell storms capable of producing isolated damaging winds/large hail. An isolated tornado may also occur with storms moving southeastward along the boundary, where low-level shear and vertical vorticity will be larger. ..Thompson/Kerr.. 08/13/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0759 AM CDT Tue Aug 13 2019 Valid 131300Z - 141200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON ACROSS VA...AND THIS AFTERNOON/EVENING ACROSS THE CENTRAL HIGH PLAINS... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS EXTENDING WESTWARD FROM THE MID-ATLANTIC ACROSS TN... ...SUMMARY... Scattered severe thunderstorms with damaging winds are expected across the southern Middle Atlantic into the Tennessee Valley. Severe thunderstorms with very large hail and damaging winds should also develop across the central High Plains. ...Synopsis... The primary larger-scale features today are northern stream troughs moving east-southeastward over Quebec and ND/MN, though a separate/weaker belt of westerlies is located farther south from the central Plains across the OH Valley to the Mid-Atlantic. Within this southern flow belt, diffuse MCVs are progressing east-southeastward over MO/IL and OH/WV, with ongoing convection in multiple clusters through this corridor. The stronger storms along the lower OH River are producing a cold pool and will likely persist until at least late morning, with the southward extent of the outflow likely demarcating the zone of afternoon redevelopment of storms this afternoon across TN. A few damaging gusts will be the main threats with multicell clusters/line segments in an environment of rich low-level moisture and moderate buoyancy along the southern edge of the 25-35 kt midlevel flow. The ongoing convection from southern OH to WV has shown signs of weakening slowly this morning. Still, residual clouds and some rain will slow surface heating from roughly 15-19z across central/northern VA, with the more probable zone of stronger destabilization along the southern fringe of the morning clouds/rain in the vicinity of southern VA. Upstream VWPs reveal 40 kt midlevel flow as low as 4 km above ground level over southern OH/eastern KY/WV, and this somewhat stronger flow will translate over VA this afternoon with the remnant MCV. Will maintain the 30% wind/Enhanced risk area in this update, though the influence of clouds on destabilization through early afternoon will likely modulate additional storm development this afternoon, and potentially reduce the severe threat. ...Central High Plains this afternoon through early tonight... A low-level upslope flow regime will establish today across eastern CO, prior to a weak reinforcing frontal surge overnight. South of an ongoing band of elevated storms driven by midlevel warm advection/frontogenesis, the low levels will warm and MLCAPE is expected to increase to 2000-3000 J/kg by mid-late afternoon. Deep-layer vertical shear will be favorable for supercells from northeast CO/northwest KS northward. Surface-based storm development is expected 21-00z across northeast CO along a surface trough on the northeast edge of the steeper low-level lapse rates and deeper mixing. The initial storms will likely be discrete supercells capable of producing isolated very large hail and perhaps a tornado or two. Convection may grow into a larger cluster this evening and propagate southward into a weak nocturnal low-level jet across far eastern CO/western KS, with a continuing threat for damaging winds into early tonight. ...Upper MS Valley area this afternoon... A midlevel shortwave trough over eastern ND this morning will move southeastward over MN/western WI by this evening. Ascent preceding the midlevel trough will coincide with daytime heating and low-level convergence along a weak northwest-southeast oriented front, which will support thunderstorm development this afternoon. Boundary-layer dewpoints in the 60s and afternoon surface temperatures approaching 80 F will drive MLCAPE of 1000-1500 J/kg, in an environment with effective bulk shear near 40 kt. The net result will be the potential for a few organized/supercell storms capable of producing isolated damaging winds/large hail. An isolated tornado may also occur with storms moving southeastward along the boundary, where low-level shear and vertical vorticity will be larger. ..Thompson/Kerr.. 08/13/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0759 AM CDT Tue Aug 13 2019 Valid 131300Z - 141200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON ACROSS VA...AND THIS AFTERNOON/EVENING ACROSS THE CENTRAL HIGH PLAINS... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS EXTENDING WESTWARD FROM THE MID-ATLANTIC ACROSS TN... ...SUMMARY... Scattered severe thunderstorms with damaging winds are expected across the southern Middle Atlantic into the Tennessee Valley. Severe thunderstorms with very large hail and damaging winds should also develop across the central High Plains. ...Synopsis... The primary larger-scale features today are northern stream troughs moving east-southeastward over Quebec and ND/MN, though a separate/weaker belt of westerlies is located farther south from the central Plains across the OH Valley to the Mid-Atlantic. Within this southern flow belt, diffuse MCVs are progressing east-southeastward over MO/IL and OH/WV, with ongoing convection in multiple clusters through this corridor. The stronger storms along the lower OH River are producing a cold pool and will likely persist until at least late morning, with the southward extent of the outflow likely demarcating the zone of afternoon redevelopment of storms this afternoon across TN. A few damaging gusts will be the main threats with multicell clusters/line segments in an environment of rich low-level moisture and moderate buoyancy along the southern edge of the 25-35 kt midlevel flow. The ongoing convection from southern OH to WV has shown signs of weakening slowly this morning. Still, residual clouds and some rain will slow surface heating from roughly 15-19z across central/northern VA, with the more probable zone of stronger destabilization along the southern fringe of the morning clouds/rain in the vicinity of southern VA. Upstream VWPs reveal 40 kt midlevel flow as low as 4 km above ground level over southern OH/eastern KY/WV, and this somewhat stronger flow will translate over VA this afternoon with the remnant MCV. Will maintain the 30% wind/Enhanced risk area in this update, though the influence of clouds on destabilization through early afternoon will likely modulate additional storm development this afternoon, and potentially reduce the severe threat. ...Central High Plains this afternoon through early tonight... A low-level upslope flow regime will establish today across eastern CO, prior to a weak reinforcing frontal surge overnight. South of an ongoing band of elevated storms driven by midlevel warm advection/frontogenesis, the low levels will warm and MLCAPE is expected to increase to 2000-3000 J/kg by mid-late afternoon. Deep-layer vertical shear will be favorable for supercells from northeast CO/northwest KS northward. Surface-based storm development is expected 21-00z across northeast CO along a surface trough on the northeast edge of the steeper low-level lapse rates and deeper mixing. The initial storms will likely be discrete supercells capable of producing isolated very large hail and perhaps a tornado or two. Convection may grow into a larger cluster this evening and propagate southward into a weak nocturnal low-level jet across far eastern CO/western KS, with a continuing threat for damaging winds into early tonight. ...Upper MS Valley area this afternoon... A midlevel shortwave trough over eastern ND this morning will move southeastward over MN/western WI by this evening. Ascent preceding the midlevel trough will coincide with daytime heating and low-level convergence along a weak northwest-southeast oriented front, which will support thunderstorm development this afternoon. Boundary-layer dewpoints in the 60s and afternoon surface temperatures approaching 80 F will drive MLCAPE of 1000-1500 J/kg, in an environment with effective bulk shear near 40 kt. The net result will be the potential for a few organized/supercell storms capable of producing isolated damaging winds/large hail. An isolated tornado may also occur with storms moving southeastward along the boundary, where low-level shear and vertical vorticity will be larger. ..Thompson/Kerr.. 08/13/2019 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0245 AM CDT Tue Aug 13 2019 Valid 161200Z - 211200Z ...DISCUSSION... An area of moderate westerlies aloft will remain over the northern CONUS on Fri/D4 and Sat/D5, but will lift north into Canada during the Sun/D6-Sat/D7 period. During that time, an upper ridge will build over the West with the high centered over AZ. On Fri/D4, the GFS indicates a low-amplitude shortwave trough moving from WY across SD, NE, and into IA, with an associated cold front, but the ECMWF is less amplified with this feature. In addition, there are major discrepancies with latitudinal placement of the larger instability (KS vs NE). As such, predictability is too low for Friday, though severe weather is possible (mainly wind gusts) in this general region. For the period from Sat/D5 into Sun/D6, ample moisture and instability will remain from the central Plains into the mid and upper MS Valley as a larger trough amplification occurs over south-central Canada, extending south into the northern Plains. Aside from timing issues amongst the various models with this trough, daily cycles of thunderstorms further decrease predictability regarding the best threat corridors. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0245 AM CDT Tue Aug 13 2019 Valid 161200Z - 211200Z ...DISCUSSION... An area of moderate westerlies aloft will remain over the northern CONUS on Fri/D4 and Sat/D5, but will lift north into Canada during the Sun/D6-Sat/D7 period. During that time, an upper ridge will build over the West with the high centered over AZ. On Fri/D4, the GFS indicates a low-amplitude shortwave trough moving from WY across SD, NE, and into IA, with an associated cold front, but the ECMWF is less amplified with this feature. In addition, there are major discrepancies with latitudinal placement of the larger instability (KS vs NE). As such, predictability is too low for Friday, though severe weather is possible (mainly wind gusts) in this general region. For the period from Sat/D5 into Sun/D6, ample moisture and instability will remain from the central Plains into the mid and upper MS Valley as a larger trough amplification occurs over south-central Canada, extending south into the northern Plains. Aside from timing issues amongst the various models with this trough, daily cycles of thunderstorms further decrease predictability regarding the best threat corridors. Read more