SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1255 PM CST Tue Dec 17 2024 Valid 181200Z - 191200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF LOS ANGELES AND VENTURA COUNTIES IN SOUTHERN CALIFORNIA... No changes to the ongoing forecast. ..Wendt.. 12/17/2024 .PREV DISCUSSION... /ISSUED 0214 AM CST Tue Dec 17 2024/ ...Synopsis... Amplified mid-level ridging is expected to continue over the western US through D2/Wed. Surface high pressure over the Great Basin will continue to intensify, supporting offshore flow across parts of southern CA. Santa Ana winds, in combination with low RH values, should allow for several hours of elevated to critical fire-weather conditions across southern CA. Offshore winds should gradually dissipate early D3/Thur as high pressure shifts eastward, ending the fire-weather risk. ...Southern California... Moderately strong high pressure in the Great Basin will drive offshore winds across parts of southern California D2/Wed. Winds will increase overnight D1/Tues, with gusts reaching 35-45 mph through the terrain-favored corridors. Several hours of critical fire weather conditions are expected across portions of Los Angeles and Ventura Counties, as RH decreases with daytime heating. Winds are expected to diminish during the afternoon/evening, with elevated fire-weather conditions ending into early D3/Thur. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1255 PM CST Tue Dec 17 2024 Valid 181200Z - 191200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF LOS ANGELES AND VENTURA COUNTIES IN SOUTHERN CALIFORNIA... No changes to the ongoing forecast. ..Wendt.. 12/17/2024 .PREV DISCUSSION... /ISSUED 0214 AM CST Tue Dec 17 2024/ ...Synopsis... Amplified mid-level ridging is expected to continue over the western US through D2/Wed. Surface high pressure over the Great Basin will continue to intensify, supporting offshore flow across parts of southern CA. Santa Ana winds, in combination with low RH values, should allow for several hours of elevated to critical fire-weather conditions across southern CA. Offshore winds should gradually dissipate early D3/Thur as high pressure shifts eastward, ending the fire-weather risk. ...Southern California... Moderately strong high pressure in the Great Basin will drive offshore winds across parts of southern California D2/Wed. Winds will increase overnight D1/Tues, with gusts reaching 35-45 mph through the terrain-favored corridors. Several hours of critical fire weather conditions are expected across portions of Los Angeles and Ventura Counties, as RH decreases with daytime heating. Winds are expected to diminish during the afternoon/evening, with elevated fire-weather conditions ending into early D3/Thur. ...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 1130 AM CST Tue Dec 17 2024 Valid 181200Z - 191200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE TENNESSEE VALLEY... ...SUMMARY... Isolated damaging wind gusts and a brief tornado are possible through mid-day Wednesday across portions of the Tennessee Valley. ...Synopsis... A positively tilted upper trough will develop east across the eastern U.S. on Wednesday. Moderate mid/upper level southwesterly flow ahead of the trough will overspread the OH/TN Valleys into the Carolinas and Mid-Atlantic regions. At the surface, a cold front will extend from southern OH to southeast AR to central TX at the beginning of the period. This front will develop southeast across the Southeast and Mid-Atlantic, mostly moving offshore from the Gulf and Atlantic coasts by Thursday morning. ...Northeast Texas to the Tennessee Valley... Thunderstorms will be ongoing along a frontal zone from northeast Texas to western Tennessee at the beginning of the forecast period. These storms will likely be mostly anafrontal due to the southeastward advancing cold front and storm motion parallel to the front. In addition, these storms should already be in their weakening phase by 12Z as they outrun the better low-level instability. The only exception will be across western/middle Tennessee between 12 and 18Z where some instability will remain and stronger flow could promote more organization/propagation ahead of the cold front. A damaging wind gust or a brief tornado cannot be ruled out early in the forecast period. Despite the weakening instability through the morning, some damaging wind threat could persist into parts of eastern Tennessee and far southern Kentucky through mid-day as the low-level jet strengthens to over 50 knots during the morning hours. ...FL/GA/Carolinas... Southerly flow ahead of the approaching mid-level trough will establish low to mid 60s dewpoints across much of Florida into eastern Georgia and the eastern Carolinas by Wednesday afternoon. Weak to moderate instability is expected within a broad region of weak isentropic ascent across the region. Upper-level forcing will lag well behind the front which should keep any thunderstorm development isolated. However, if any storms develop, they could have some marginal hail/wind threat given moderate instability and shear present across the region Wednesday afternoon. Storm coverage concerns related to weak forcing are the primary limiting factor to severe weather probabilities at this time. ..Bentley.. 12/17/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1030 AM CST Tue Dec 17 2024 Valid 171630Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF NORTHEAST TEXAS/SOUTHEAST OKLAHOMA TO WESTERN TENNESSEE... ...SUMMARY... Isolated strong to severe thunderstorms are possible tonight through early Wednesday morning across parts of northeast Texas and vicinity into western Tennessee. ...Synopsis... Gradual trough amplification will occur through the period across the Plains into the Midwest, as a shortwave trough digs from the central Rockies to the southern Plains tonight. At the surface, a weak cyclone should develop from the central High Plains to the Mid-South and lower OH Valley by early Wednesday morning. Greater low-level moisture, characterized by upper 50s to mid 60s surface dewpoints, is in place across parts of the ArkLaTex to northern MS along/south of a convective outflow boundary/front. This moisture is forecast to spread gradually northward through tonight ahead of the approaching shortwave trough. A separate cold front will spread east-southeastward over parts of the southern Plains and mid MS Valley/Mid-South this evening and overnight. ...Northeast Texas to Western Tennessee... Robust convective development will likely be delayed until near/after 05Z tonight, as low-level warm advection and large-scale ascent preceding the upper trough gradually overspread the warm sector. Even though steeper mid-level lapse rates should lag/remain generally north of the cold front, weak instability (around 500-1000 J/kg MLCAPE) should be present in a narrow corridor along and just ahead of the front. This instability will become weaker and more limited with northeastward extent into middle TN, with an ill-defined cutoff to isolated severe potential somewhere in the western to middle TN vicinity. Strengthening mid-level southwesterly flow with the amplifying upper trough will eventually move into the ArkLaTex and Mid-South, mainly after 06Z, in tandem with modestly enhanced low-level southwesterlies. Sufficient speed shear should exist to support some updraft organization, although the orientation of the deep-layer shear vector will be nearly parallel to the surface front. Thunderstorm mergers and interactions appear likely, with eventual upscale growth into a line anticipated as the cold front intercepts the greater low-level moisture, especially after 09Z. Isolated hail may occur with initial convective development, before strong to occasionally damaging winds become the main threat in the last few hours of the period with the line. A brief tornado cannot be ruled out. The overall severe threat should remain isolated due to the somewhat marginal thermodynamic environment. ..Gleason/Dean.. 12/17/2024 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0954 AM CST Tue Dec 17 2024 Valid 171700Z - 181200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF LOS ANGELES AND VENTURA COUNTIES IN SOUTHERN CALIFORNIA... No changes to the ongoing forecast. ..Wendt.. 12/17/2024 .PREV DISCUSSION... /ISSUED 0213 AM CST Tue Dec 17 2024/ ...Synopsis... Quasi-zonal mid-level flow is expected to quickly amplify as ridging develops over the western US today and tonight. Surface high pressure will quickly build over the Great Basin as a cold front moves eastward across the central US. The high pressure will allow for moderate offshore winds and a much drier air mass to move into portions of southern CA. The strong winds and low humidity will support elevated to critical fire-weather concerns over portions of southern CA. ...Southern California... Offshore winds are expected to develop this afternoon and intensify this evening, as high pressure builds over the Great Basin. Northeast surface winds of 25-35 mph are likely through the Santa Clara River Valley and Oxnard Plain by late this evening and into early D2/Wed. The intensifying downslope winds and the arrival of drier air overnight should allow for several hours of 10-15% RH across southern California. The overlap of low RH and strong winds should support several hours of elevated to critical fire-weather conditions across parts of Los Angeles and Ventura Counties. ...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 0954 AM CST Tue Dec 17 2024 Valid 171700Z - 181200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF LOS ANGELES AND VENTURA COUNTIES IN SOUTHERN CALIFORNIA... No changes to the ongoing forecast. ..Wendt.. 12/17/2024 .PREV DISCUSSION... /ISSUED 0213 AM CST Tue Dec 17 2024/ ...Synopsis... Quasi-zonal mid-level flow is expected to quickly amplify as ridging develops over the western US today and tonight. Surface high pressure will quickly build over the Great Basin as a cold front moves eastward across the central US. The high pressure will allow for moderate offshore winds and a much drier air mass to move into portions of southern CA. The strong winds and low humidity will support elevated to critical fire-weather concerns over portions of southern CA. ...Southern California... Offshore winds are expected to develop this afternoon and intensify this evening, as high pressure builds over the Great Basin. Northeast surface winds of 25-35 mph are likely through the Santa Clara River Valley and Oxnard Plain by late this evening and into early D2/Wed. The intensifying downslope winds and the arrival of drier air overnight should allow for several hours of 10-15% RH across southern California. The overlap of low RH and strong winds should support several hours of elevated to critical fire-weather conditions across parts of Los Angeles and Ventura Counties. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0655 AM CST Tue Dec 17 2024 Valid 171300Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE RED RIVER REGION INTO WESTERN TENNESSEE... ...SUMMARY... Isolated severe thunderstorms are possible tonight through early morning Wednesday across parts of the Red River region into western Tennessee. ...Synopsis... In mid/upper levels, nearly zonal flow was evident over the CONUS from coast to coast, perturbed by several minor shortwaves. One of these, however, will amplify through the period and influence convective potential: a trough now apparent in moisture-channel imagery over the interior Pacific Northwest. This feature will dig southeastward today and begin to phase with a lesser trough now over southeastern MT and eastern WY. The combined trough should reach western MN, eastern SD, central NE, and central/western CO by 00Z. By 12Z, the trough should strengthen further, and extend near a line from DBQ-IRK-TUL-CDS. At 11Z, an outflow boundary was drawn from northwestern GA across central parts of AL/MS to northeastern LA and near TXK, where it intersected a slow-moving, weakening, cold to quasistationary front drawn near a CRW-CSV-HSV-ELD-CRS line. Farther north, frontogenesis and cyclogenesis will occur today over the central Plains, as the amplifying mid/upper trough approaches. By 00Z, a frontal-wave low should be located near TOP, with cold front southwestward across south-central KS, northwestern OK, the TX Panhandle, and northeastern NM. The low should move past PAH into western KY by 12Z, with cold front over eastern to southwestern AR, central to southwest TX, and the TX Big Bend region. The outflow boundary and residual front are expected to move slowly northward over the Arklatex and Mid-South regions through late evening, before being overtaken by the cold front. ...Red River region to Mid-South... Isolated to widely scattered thunderstorms may develop on either side of the northward-moving, slowly modifying outflow boundary from this afternoon into this evening. As the cold front intercepts that boundary, scattered thunderstorms should form tonight along the cold front. A marginal threat for all severe hazards exists, mainly overnight. As the pre-cold-frontal boundaries shift northward, a relatively undisturbed warm-sector airmass will spread over most of the outlook area before the cold front arrives late tonight. The strongest DCVA/cooling aloft and steep midlevel lapse rates related to the approaching trough will remain behind the cold front. However, a tightening height gradient, related strengthening deep shear, and large-scale lift within an intensifying LLJ/WAA plume will spread across the warm sector this evening and overnight. These processes will destabilize, moisten and increase shear in low levels. Surface dewpoints generally in the 60s F (greater southwestward) will contribute to MLCAPE near 1000 J/kg from the Arklatex into at least southwestern TN, diminishing northeastward from there. A shallow, neutral to stable near-surface thermal profile will be present nocturnally, but may not preclude strong gusts or a tornado. Substantially front-parallel flow aloft will lead to a dominant quasi-linear mode with the frontal activity, but the marginal hail/tornado threat should exist with any antecedent, persistent, relatively discrete cells. Embedded LEWP/bowing configurations in the frontal band will pose the greatest local gust potential. ..Edwards/Goss.. 12/17/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0655 AM CST Tue Dec 17 2024 Valid 171300Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE RED RIVER REGION INTO WESTERN TENNESSEE... ...SUMMARY... Isolated severe thunderstorms are possible tonight through early morning Wednesday across parts of the Red River region into western Tennessee. ...Synopsis... In mid/upper levels, nearly zonal flow was evident over the CONUS from coast to coast, perturbed by several minor shortwaves. One of these, however, will amplify through the period and influence convective potential: a trough now apparent in moisture-channel imagery over the interior Pacific Northwest. This feature will dig southeastward today and begin to phase with a lesser trough now over southeastern MT and eastern WY. The combined trough should reach western MN, eastern SD, central NE, and central/western CO by 00Z. By 12Z, the trough should strengthen further, and extend near a line from DBQ-IRK-TUL-CDS. At 11Z, an outflow boundary was drawn from northwestern GA across central parts of AL/MS to northeastern LA and near TXK, where it intersected a slow-moving, weakening, cold to quasistationary front drawn near a CRW-CSV-HSV-ELD-CRS line. Farther north, frontogenesis and cyclogenesis will occur today over the central Plains, as the amplifying mid/upper trough approaches. By 00Z, a frontal-wave low should be located near TOP, with cold front southwestward across south-central KS, northwestern OK, the TX Panhandle, and northeastern NM. The low should move past PAH into western KY by 12Z, with cold front over eastern to southwestern AR, central to southwest TX, and the TX Big Bend region. The outflow boundary and residual front are expected to move slowly northward over the Arklatex and Mid-South regions through late evening, before being overtaken by the cold front. ...Red River region to Mid-South... Isolated to widely scattered thunderstorms may develop on either side of the northward-moving, slowly modifying outflow boundary from this afternoon into this evening. As the cold front intercepts that boundary, scattered thunderstorms should form tonight along the cold front. A marginal threat for all severe hazards exists, mainly overnight. As the pre-cold-frontal boundaries shift northward, a relatively undisturbed warm-sector airmass will spread over most of the outlook area before the cold front arrives late tonight. The strongest DCVA/cooling aloft and steep midlevel lapse rates related to the approaching trough will remain behind the cold front. However, a tightening height gradient, related strengthening deep shear, and large-scale lift within an intensifying LLJ/WAA plume will spread across the warm sector this evening and overnight. These processes will destabilize, moisten and increase shear in low levels. Surface dewpoints generally in the 60s F (greater southwestward) will contribute to MLCAPE near 1000 J/kg from the Arklatex into at least southwestern TN, diminishing northeastward from there. A shallow, neutral to stable near-surface thermal profile will be present nocturnally, but may not preclude strong gusts or a tornado. Substantially front-parallel flow aloft will lead to a dominant quasi-linear mode with the frontal activity, but the marginal hail/tornado threat should exist with any antecedent, persistent, relatively discrete cells. Embedded LEWP/bowing configurations in the frontal band will pose the greatest local gust potential. ..Edwards/Goss.. 12/17/2024 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0333 AM CST Tue Dec 17 2024 Valid 201200Z - 251200Z ...DISCUSSION... Strong surface high pressure over the central U.S. and a prior cold front intruding into the southern Gulf of Mexico will result in a dearth of boundary layer moisture across much of the CONUS through at least Day 6/Sun. As a result, thunderstorm chances will be low. Toward the end of the period, some forecast guidance suggests lee troughing will allow southeasterly low-level flow to bring modest Gulf moisture northward across TX. This may result in some increased thunderstorm chances across south/central TX on Day 7-8/Mon-Tue. However, severe-thunderstorm potential will remain low during the Day 4-8 time frame. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0333 AM CST Tue Dec 17 2024 Valid 201200Z - 251200Z ...DISCUSSION... Strong surface high pressure over the central U.S. and a prior cold front intruding into the southern Gulf of Mexico will result in a dearth of boundary layer moisture across much of the CONUS through at least Day 6/Sun. As a result, thunderstorm chances will be low. Toward the end of the period, some forecast guidance suggests lee troughing will allow southeasterly low-level flow to bring modest Gulf moisture northward across TX. This may result in some increased thunderstorm chances across south/central TX on Day 7-8/Mon-Tue. However, severe-thunderstorm potential will remain low during the Day 4-8 time frame. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0214 AM CST Tue Dec 17 2024 Valid 181200Z - 191200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN CALIFORNIA... ...Synopsis... Amplified mid-level ridging is expected to continue over the western US through D2/Wed. Surface high pressure over the Great Basin will continue to intensify, supporting offshore flow across parts of southern CA. Santa Ana winds, in combination with low RH values, should allow for several hours of elevated to critical fire-weather conditions across southern CA. Offshore winds should gradually dissipate early D3/Thur as high pressure shifts eastward, ending the fire-weather risk. ...Southern California... Moderately strong high pressure in the Great Basin will drive offshore winds across parts of southern California D2/Wed. Winds will increase overnight D1/Tues, with gusts reaching 35-45 mph through the terrain-favored corridors. Several hours of critical fire weather conditions are expected across portions of Los Angeles and Ventura Counties, as RH decreases with daytime heating. Winds are expected to diminish during the afternoon/evening, with elevated fire-weather conditions ending into early D3/Thur. ..Lyons.. 12/17/2024 ...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 0213 AM CST Tue Dec 17 2024 Valid 171200Z - 181200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF LOS ANGELES AND VENTURA COUNTIES IN SOUTHERN CALIFORNIA... ...Synopsis... Quasi-zonal mid-level flow is expected to quickly amplify as ridging develops over the western US today and tonight. Surface high pressure will quickly build over the Great Basin as a cold front moves eastward across the central US. The high pressure will allow for moderate offshore winds and a much drier air mass to move into portions of southern CA. The strong winds and low humidity will support elevated to critical fire-weather concerns over portions of southern CA. ...Southern California... Offshore winds are expected to develop this afternoon and intensify this evening, as high pressure builds over the Great Basin. Northeast surface winds of 25-35 mph are likely through the Santa Clara River Valley and Oxnard Plain by late this evening and into early D2/Wed. The intensifying downslope winds and the arrival of drier air overnight should allow for several hours of 10-15% RH across southern California. The overlap of low RH and strong winds should support several hours of elevated to critical fire-weather conditions across parts of Los Angeles and Ventura Counties. ..Lyons.. 12/17/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0152 AM CST Tue Dec 17 2024 Valid 191200Z - 201200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected on Thursday. ...Synopsis... An upper trough extending along the Atlantic coast into the eastern Gulf of Mexico will shift east across FL and moving offshore early in the forecast period. Meanwhile, a shortwave trough over the northern/central Plains will deepen and pivot east, maintaining a mean upper trough over the eastern U.S. through the period. A surface cold front will be located over north-central FL Thursday morning, and quickly develop south through the day. Weak instability is forecast ahead of the front across portions of the southeast FL Peninsula, supporting isolated thunderstorms. Poor midlevel lapse rates and very weak low and midlevel flow will preclude severe thunderstorm potential. ..Leitman.. 12/17/2024 Read more

SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1231 AM CST Tue Dec 17 2024 Valid 181200Z - 191200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are possible from the lower Ohio Valley southwest into northeast/central Texas early on Wednesday and across the Southeast, Carolinas, and Florida Wednesday afternoon and evening. ...Synopsis... A positively tilted upper trough will develop east across the eastern U.S. on Wednesday. Moderate mid/upper level southwesterly flow ahead of the trough will overspread the OH/TN Valleys into the Carolinas and Mid-Atlantic regions. At the surface, a cold front will extend from southern OH to southeast AR to central TX at the beginning of the period. This front will develop southeast across the Southeast and Mid-Atlantic, mostly moving offshore from the Gulf and Atlantic coasts by Thursday morning. ...Northeast TX to the TN Valley... Showers and elevated thunderstorms will likely be ongoing near the surface cold front Wednesday morning. Forecast soundings show poor low-level lapse rates and little surface-based instability. However, up to 500 J/kg MUCAPE will be present, courtesy of cool midlevel temperatures and modest midlevel lapse rates. Deep-layer flow is forecast to remain mostly unidirectional and parallel to the front, suggesting convective undercutting by the boundary/outflows. While some briefly organized structure may persist the first hour or two of the forecast period, convection is expected to rapidly decrease in intensity with southeast extent across the TN Valley/Gulf Coast states. This is largely due to more modest boundary-layer moisture and weakening vertical shear across MS/AL. ...FL/GA/Carolinas... Isentropic ascent ahead of the approaching upper trough/surface front will increase across the region through day. However, large-scale ascent will remain weak until late, with the vorticity maxima trailing well behind the surface front. Nevertheless, showers and isolated thunderstorms will be possible within the low-level warm-advection regime, especially during the afternoon/early evening. Forecast guidance varies in the depiction of the low-level thermodynamics and degree of destabilization. Though some support for an organized storm or two is plausible, given around 750-1000 J/kg MLCAPE and effective shear magnitudes around 20-30 kt. While a strong storm could produce gusty winds or even small hail (given somewhat elongated/straight hodographs and cool midlevel temps), forecast confidence regarding severe potential remains fairly low. Will refrain from introducing low-end/Marginal (level 1 of 5) risk probabilities at this time, though an outlook area may be required in subsequent outlooks. ..Leitman.. 12/17/2024 Read more

SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1231 AM CST Tue Dec 17 2024 Valid 181200Z - 191200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are possible from the lower Ohio Valley southwest into northeast/central Texas early on Wednesday and across the Southeast, Carolinas, and Florida Wednesday afternoon and evening. ...Synopsis... A positively tilted upper trough will develop east across the eastern U.S. on Wednesday. Moderate mid/upper level southwesterly flow ahead of the trough will overspread the OH/TN Valleys into the Carolinas and Mid-Atlantic regions. At the surface, a cold front will extend from southern OH to southeast AR to central TX at the beginning of the period. This front will develop southeast across the Southeast and Mid-Atlantic, mostly moving offshore from the Gulf and Atlantic coasts by Thursday morning. ...Northeast TX to the TN Valley... Showers and elevated thunderstorms will likely be ongoing near the surface cold front Wednesday morning. Forecast soundings show poor low-level lapse rates and little surface-based instability. However, up to 500 J/kg MUCAPE will be present, courtesy of cool midlevel temperatures and modest midlevel lapse rates. Deep-layer flow is forecast to remain mostly unidirectional and parallel to the front, suggesting convective undercutting by the boundary/outflows. While some briefly organized structure may persist the first hour or two of the forecast period, convection is expected to rapidly decrease in intensity with southeast extent across the TN Valley/Gulf Coast states. This is largely due to more modest boundary-layer moisture and weakening vertical shear across MS/AL. ...FL/GA/Carolinas... Isentropic ascent ahead of the approaching upper trough/surface front will increase across the region through day. However, large-scale ascent will remain weak until late, with the vorticity maxima trailing well behind the surface front. Nevertheless, showers and isolated thunderstorms will be possible within the low-level warm-advection regime, especially during the afternoon/early evening. Forecast guidance varies in the depiction of the low-level thermodynamics and degree of destabilization. Though some support for an organized storm or two is plausible, given around 750-1000 J/kg MLCAPE and effective shear magnitudes around 20-30 kt. While a strong storm could produce gusty winds or even small hail (given somewhat elongated/straight hodographs and cool midlevel temps), forecast confidence regarding severe potential remains fairly low. Will refrain from introducing low-end/Marginal (level 1 of 5) risk probabilities at this time, though an outlook area may be required in subsequent outlooks. ..Leitman.. 12/17/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1145 PM CST Mon Dec 16 2024 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN PARTS OF THE MID-SOUTH... ...SUMMARY... Isolated severe thunderstorms are possible tonight through early morning Wednesday across parts of the Red River into Western Tennessee. ...Synopsis... A shortwave trough over the Northwest will amplify across the central states, with an embedded impulse moving into the Lower MO Valley to TX Panhandle by early morning Wednesday. Mid-level height falls and the southern periphery of west-southwesterlies above 40 kts at 500 mb will overspread the Red River to KY/TN. At the surface, a front in the Ark-La-Tex to TN Valley will gradually advance north. A minor surface cyclone should develop over the Lower MO Valley, with a trailing cold front accelerating late as a surface ridge builds down the High Plains. ...Mid-South... Convective potential will be focused tonight, when large-scale ascent increases ahead of the sharpening shortwave trough. Scattered to eventually widespread thunderstorms are expected overnight into early morning Wednesday. Deep-layer shear will initially be modest within a unidirectional west-southwesterly profile, but will increase late, especially along and east of the MS River. A pocket of modest buoyancy characterized by MLCAPE near 1000 J/kg should be centered near the Ark-La-Tex. Progressively weaker surface-based instability is expected with northeast extent, with uncertainty on how far that may extend beyond western TN. The western portion of sustained convection will offer potential for small to marginally severe hail and locally strong gusts. But these storms should tend to get undercut during the early morning, given the orientation of the deep-layer shear vector and the accelerating cold front. A broadening southwest/northeast-oriented convective line will probably evolve across parts of AR/TN. Hodograph curvature should be adequate for a threat of a brief tornado and isolated damaging gusts with the strongest embedded cells through the pre-dawn hours. ..Grams/Lyons.. 12/17/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1145 PM CST Mon Dec 16 2024 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN PARTS OF THE MID-SOUTH... ...SUMMARY... Isolated severe thunderstorms are possible tonight through early morning Wednesday across parts of the Red River into Western Tennessee. ...Synopsis... A shortwave trough over the Northwest will amplify across the central states, with an embedded impulse moving into the Lower MO Valley to TX Panhandle by early morning Wednesday. Mid-level height falls and the southern periphery of west-southwesterlies above 40 kts at 500 mb will overspread the Red River to KY/TN. At the surface, a front in the Ark-La-Tex to TN Valley will gradually advance north. A minor surface cyclone should develop over the Lower MO Valley, with a trailing cold front accelerating late as a surface ridge builds down the High Plains. ...Mid-South... Convective potential will be focused tonight, when large-scale ascent increases ahead of the sharpening shortwave trough. Scattered to eventually widespread thunderstorms are expected overnight into early morning Wednesday. Deep-layer shear will initially be modest within a unidirectional west-southwesterly profile, but will increase late, especially along and east of the MS River. A pocket of modest buoyancy characterized by MLCAPE near 1000 J/kg should be centered near the Ark-La-Tex. Progressively weaker surface-based instability is expected with northeast extent, with uncertainty on how far that may extend beyond western TN. The western portion of sustained convection will offer potential for small to marginally severe hail and locally strong gusts. But these storms should tend to get undercut during the early morning, given the orientation of the deep-layer shear vector and the accelerating cold front. A broadening southwest/northeast-oriented convective line will probably evolve across parts of AR/TN. Hodograph curvature should be adequate for a threat of a brief tornado and isolated damaging gusts with the strongest embedded cells through the pre-dawn hours. ..Grams/Lyons.. 12/17/2024 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0649 PM CST Mon Dec 16 2024 Valid 170100Z - 171200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN NORTHEAST TX TO SOUTHERN AR... ...SUMMARY... Small to marginally severe hail will remain possible into late evening across a portion of northeast Texas into southern Arkansas. ...Northeast TX to southern AR... A swath of scattered convection is ongoing from the Mid-South to the southeast side of the Metroplex, along a slow-moving cold front. 00Z SHV sounding sampled MLCAPE near 800 J/kg with moderately steep mid-level lapse rates around 7 C/km and modest effective bulk shear of 25-30 kts. MRMS MESH signatures of 0.5-1.0 hail have been noted over the past few hours within weakly rotating updrafts. This trend may persist for another couple hours before the effects of gradual boundary-layer cooling mitigate stronger storms. With negligible large-scale ascent, beyond convergence along the front, convective activity appears unlikely to greatly strengthen tonight. ..Grams.. 12/17/2024 Read more

No Mesoscale Discussions are in effect as of Mon Dec 16 22:20:01 UTC 2024.

No watches are valid as of Mon Dec 16 22:20:01 UTC 2024.