Severe Storms

SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0215 AM CST Sun Feb 18 2024 Valid 201200Z - 211200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not forecast across the contiguous United States on Tuesday. ...Synopsis... A large-scale mid-level trough will remain situated along the West Coast while a downstream ridge resides over the High Plains. Farther east, mean troughing due to two mid-level troughs will encompass much of the East. Isolated to scattered showers will continue over parts of the West Coast in association with the mid-level trough. Pockets of weak instability will likely develop and may result in isolated thunderstorms over mainly CA, but perhaps on a much more localized/widely spaced basis in NV and ID. Tranquil weather conditions are forecast over the central and eastern states. ..Smith.. 02/18/2024 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0151 AM CST Sun Feb 18 2024 Valid 191200Z - 201200Z ...NO CRITICAL AREAS... ...Synopsis... Fire weather potential will likely remain limited through Monday across the country. A lee trough along the central to southern High Plains at the start of the period is forecast to drift east into the central Plains through the day. As this occurs, the downslope pressure gradient along the central/southern Rockies should abate, resulting in weaker downslope winds by peak heating compared to Sunday afternoon (though 20-30 mph gusts are probable in the immediate lee of terrain features). Despite the potential for weaker winds, diurnal RH reductions into the low 20s are expected and may coincide with 15-20 mph gusts. Consequently, pockets of transient elevated fire weather conditions are possible along the central/southern High Plains. As with Sunday, confidence in the extent and duration of such conditions - along with the potential for overlap with sufficiently dry fuels - is limited. Highlights are withheld for this forecast, but trends will be monitored. Elsewhere across the country, dry conditions are expected across the eastern third of the CONUS; however, weak winds along the axis of a surface ridge, combined with generally unreceptive fuels, should preclude fire concerns. ..Moore.. 02/18/2024 ...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 0151 AM CST Sun Feb 18 2024 Valid 191200Z - 201200Z ...NO CRITICAL AREAS... ...Synopsis... Fire weather potential will likely remain limited through Monday across the country. A lee trough along the central to southern High Plains at the start of the period is forecast to drift east into the central Plains through the day. As this occurs, the downslope pressure gradient along the central/southern Rockies should abate, resulting in weaker downslope winds by peak heating compared to Sunday afternoon (though 20-30 mph gusts are probable in the immediate lee of terrain features). Despite the potential for weaker winds, diurnal RH reductions into the low 20s are expected and may coincide with 15-20 mph gusts. Consequently, pockets of transient elevated fire weather conditions are possible along the central/southern High Plains. As with Sunday, confidence in the extent and duration of such conditions - along with the potential for overlap with sufficiently dry fuels - is limited. Highlights are withheld for this forecast, but trends will be monitored. Elsewhere across the country, dry conditions are expected across the eastern third of the CONUS; however, weak winds along the axis of a surface ridge, combined with generally unreceptive fuels, should preclude fire concerns. ..Moore.. 02/18/2024 ...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 0151 AM CST Sun Feb 18 2024 Valid 191200Z - 201200Z ...NO CRITICAL AREAS... ...Synopsis... Fire weather potential will likely remain limited through Monday across the country. A lee trough along the central to southern High Plains at the start of the period is forecast to drift east into the central Plains through the day. As this occurs, the downslope pressure gradient along the central/southern Rockies should abate, resulting in weaker downslope winds by peak heating compared to Sunday afternoon (though 20-30 mph gusts are probable in the immediate lee of terrain features). Despite the potential for weaker winds, diurnal RH reductions into the low 20s are expected and may coincide with 15-20 mph gusts. Consequently, pockets of transient elevated fire weather conditions are possible along the central/southern High Plains. As with Sunday, confidence in the extent and duration of such conditions - along with the potential for overlap with sufficiently dry fuels - is limited. Highlights are withheld for this forecast, but trends will be monitored. Elsewhere across the country, dry conditions are expected across the eastern third of the CONUS; however, weak winds along the axis of a surface ridge, combined with generally unreceptive fuels, should preclude fire concerns. ..Moore.. 02/18/2024 ...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 0151 AM CST Sun Feb 18 2024 Valid 191200Z - 201200Z ...NO CRITICAL AREAS... ...Synopsis... Fire weather potential will likely remain limited through Monday across the country. A lee trough along the central to southern High Plains at the start of the period is forecast to drift east into the central Plains through the day. As this occurs, the downslope pressure gradient along the central/southern Rockies should abate, resulting in weaker downslope winds by peak heating compared to Sunday afternoon (though 20-30 mph gusts are probable in the immediate lee of terrain features). Despite the potential for weaker winds, diurnal RH reductions into the low 20s are expected and may coincide with 15-20 mph gusts. Consequently, pockets of transient elevated fire weather conditions are possible along the central/southern High Plains. As with Sunday, confidence in the extent and duration of such conditions - along with the potential for overlap with sufficiently dry fuels - is limited. Highlights are withheld for this forecast, but trends will be monitored. Elsewhere across the country, dry conditions are expected across the eastern third of the CONUS; however, weak winds along the axis of a surface ridge, combined with generally unreceptive fuels, should preclude fire concerns. ..Moore.. 02/18/2024 ...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 0151 AM CST Sun Feb 18 2024 Valid 191200Z - 201200Z ...NO CRITICAL AREAS... ...Synopsis... Fire weather potential will likely remain limited through Monday across the country. A lee trough along the central to southern High Plains at the start of the period is forecast to drift east into the central Plains through the day. As this occurs, the downslope pressure gradient along the central/southern Rockies should abate, resulting in weaker downslope winds by peak heating compared to Sunday afternoon (though 20-30 mph gusts are probable in the immediate lee of terrain features). Despite the potential for weaker winds, diurnal RH reductions into the low 20s are expected and may coincide with 15-20 mph gusts. Consequently, pockets of transient elevated fire weather conditions are possible along the central/southern High Plains. As with Sunday, confidence in the extent and duration of such conditions - along with the potential for overlap with sufficiently dry fuels - is limited. Highlights are withheld for this forecast, but trends will be monitored. Elsewhere across the country, dry conditions are expected across the eastern third of the CONUS; however, weak winds along the axis of a surface ridge, combined with generally unreceptive fuels, should preclude fire concerns. ..Moore.. 02/18/2024 ...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 0151 AM CST Sun Feb 18 2024 Valid 191200Z - 201200Z ...NO CRITICAL AREAS... ...Synopsis... Fire weather potential will likely remain limited through Monday across the country. A lee trough along the central to southern High Plains at the start of the period is forecast to drift east into the central Plains through the day. As this occurs, the downslope pressure gradient along the central/southern Rockies should abate, resulting in weaker downslope winds by peak heating compared to Sunday afternoon (though 20-30 mph gusts are probable in the immediate lee of terrain features). Despite the potential for weaker winds, diurnal RH reductions into the low 20s are expected and may coincide with 15-20 mph gusts. Consequently, pockets of transient elevated fire weather conditions are possible along the central/southern High Plains. As with Sunday, confidence in the extent and duration of such conditions - along with the potential for overlap with sufficiently dry fuels - is limited. Highlights are withheld for this forecast, but trends will be monitored. Elsewhere across the country, dry conditions are expected across the eastern third of the CONUS; however, weak winds along the axis of a surface ridge, combined with generally unreceptive fuels, should preclude fire concerns. ..Moore.. 02/18/2024 ...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 0121 AM CST Sun Feb 18 2024 Valid 181200Z - 191200Z ...NO CRITICAL AREAS... ...Synopsis... Fire weather concerns are expected to remain limited for today across much of the country. Localized concerns may develop in the immediate lee of the central to southern Rockies as a lee trough deepens through the afternoon. Strong westerly downslope winds may gust as high as 30-40 mph across eastern WY where surface pressure falls are expected to be strongest. Relative-humidity reductions into the twenties, to perhaps upper teens, are possible and may support localized elevated fire weather conditions. Elevated fire weather conditions are also possible southward into CO and NM in the lee of more prominent terrain features, but with more subdued wind speeds. The spatial extent and duration of such conditions remains fairly uncertain away from the terrain into the High Plains based on recent ensemble guidance, and latest fuel guidance continues to suggests fuels are not currently receptive. These concerns preclude the introduction of highlights. ..Moore.. 02/18/2024 ...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 0121 AM CST Sun Feb 18 2024 Valid 181200Z - 191200Z ...NO CRITICAL AREAS... ...Synopsis... Fire weather concerns are expected to remain limited for today across much of the country. Localized concerns may develop in the immediate lee of the central to southern Rockies as a lee trough deepens through the afternoon. Strong westerly downslope winds may gust as high as 30-40 mph across eastern WY where surface pressure falls are expected to be strongest. Relative-humidity reductions into the twenties, to perhaps upper teens, are possible and may support localized elevated fire weather conditions. Elevated fire weather conditions are also possible southward into CO and NM in the lee of more prominent terrain features, but with more subdued wind speeds. The spatial extent and duration of such conditions remains fairly uncertain away from the terrain into the High Plains based on recent ensemble guidance, and latest fuel guidance continues to suggests fuels are not currently receptive. These concerns preclude the introduction of highlights. ..Moore.. 02/18/2024 ...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 0121 AM CST Sun Feb 18 2024 Valid 181200Z - 191200Z ...NO CRITICAL AREAS... ...Synopsis... Fire weather concerns are expected to remain limited for today across much of the country. Localized concerns may develop in the immediate lee of the central to southern Rockies as a lee trough deepens through the afternoon. Strong westerly downslope winds may gust as high as 30-40 mph across eastern WY where surface pressure falls are expected to be strongest. Relative-humidity reductions into the twenties, to perhaps upper teens, are possible and may support localized elevated fire weather conditions. Elevated fire weather conditions are also possible southward into CO and NM in the lee of more prominent terrain features, but with more subdued wind speeds. The spatial extent and duration of such conditions remains fairly uncertain away from the terrain into the High Plains based on recent ensemble guidance, and latest fuel guidance continues to suggests fuels are not currently receptive. These concerns preclude the introduction of highlights. ..Moore.. 02/18/2024 ...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 0121 AM CST Sun Feb 18 2024 Valid 181200Z - 191200Z ...NO CRITICAL AREAS... ...Synopsis... Fire weather concerns are expected to remain limited for today across much of the country. Localized concerns may develop in the immediate lee of the central to southern Rockies as a lee trough deepens through the afternoon. Strong westerly downslope winds may gust as high as 30-40 mph across eastern WY where surface pressure falls are expected to be strongest. Relative-humidity reductions into the twenties, to perhaps upper teens, are possible and may support localized elevated fire weather conditions. Elevated fire weather conditions are also possible southward into CO and NM in the lee of more prominent terrain features, but with more subdued wind speeds. The spatial extent and duration of such conditions remains fairly uncertain away from the terrain into the High Plains based on recent ensemble guidance, and latest fuel guidance continues to suggests fuels are not currently receptive. These concerns preclude the introduction of highlights. ..Moore.. 02/18/2024 ...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 0121 AM CST Sun Feb 18 2024 Valid 181200Z - 191200Z ...NO CRITICAL AREAS... ...Synopsis... Fire weather concerns are expected to remain limited for today across much of the country. Localized concerns may develop in the immediate lee of the central to southern Rockies as a lee trough deepens through the afternoon. Strong westerly downslope winds may gust as high as 30-40 mph across eastern WY where surface pressure falls are expected to be strongest. Relative-humidity reductions into the twenties, to perhaps upper teens, are possible and may support localized elevated fire weather conditions. Elevated fire weather conditions are also possible southward into CO and NM in the lee of more prominent terrain features, but with more subdued wind speeds. The spatial extent and duration of such conditions remains fairly uncertain away from the terrain into the High Plains based on recent ensemble guidance, and latest fuel guidance continues to suggests fuels are not currently receptive. These concerns preclude the introduction of highlights. ..Moore.. 02/18/2024 ...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 0121 AM CST Sun Feb 18 2024 Valid 181200Z - 191200Z ...NO CRITICAL AREAS... ...Synopsis... Fire weather concerns are expected to remain limited for today across much of the country. Localized concerns may develop in the immediate lee of the central to southern Rockies as a lee trough deepens through the afternoon. Strong westerly downslope winds may gust as high as 30-40 mph across eastern WY where surface pressure falls are expected to be strongest. Relative-humidity reductions into the twenties, to perhaps upper teens, are possible and may support localized elevated fire weather conditions. Elevated fire weather conditions are also possible southward into CO and NM in the lee of more prominent terrain features, but with more subdued wind speeds. The spatial extent and duration of such conditions remains fairly uncertain away from the terrain into the High Plains based on recent ensemble guidance, and latest fuel guidance continues to suggests fuels are not currently receptive. These concerns preclude the introduction of highlights. ..Moore.. 02/18/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CST Sun Feb 18 2024 Valid 191200Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR A PORTION OF THE CENTRAL VALLEY OF CALIFORNIA... ...SUMMARY... An isolated risk for a tornado is forecast across the Central Valley of California on Monday afternoon and early evening. ...Synopsis... A mid-level low located over the eastern Pacific to the west of the CA/OR border will move little during the period. A belt of strong southwesterly 500-mb flow will extend from the base of the larger-scale eastern Pacific trough and into CA/NV. In the low levels, a surface low will meander to the west of the northern CA/OR coast. ...Central Valley of CA... Several members of the latest HREF convection-allowing model ensemble show cellular storms developing during peak heating in the Central Valley. The NAM model appears to be consistently exhibiting a surface-temperature cool bias of several degrees F compared to expected high temperatures (e.g., 55-60 deg F vs. 60-65 deg F). Model data also shows some erosion of low clouds during the day over the valley and would align with slightly warmer temperatures than the NAM model forecast. When modifying forecast soundings for slightly warmer surface temperatures, it seems probable 250-500 J/kg MLCAPE will develop during the afternoon. The 18/03z RAP model shows some veering of surface winds (south-southwesterly) that appears incongruent with the terrain-channeled flow (surface winds south-southeasterly) that typically occurs with these types of setups. Large 0-3 km MLCAPE (150 J/kg) co-located with very favorably curved and elongated hodographs amidst a moist boundary layer (dewpoints in the upper 40s to low-mid 50s), indicate an environment favorable for shallow rotating cells (i.e., transient supercells). The more robust storms will potentially yield an isolated threat for a tornado in addition to localized gusts. This activity will likely dissipate by the early evening as instability wanes. ..Smith.. 02/18/2024 Read more

SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CST Sun Feb 18 2024 Valid 191200Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR A PORTION OF THE CENTRAL VALLEY OF CALIFORNIA... ...SUMMARY... An isolated risk for a tornado is forecast across the Central Valley of California on Monday afternoon and early evening. ...Synopsis... A mid-level low located over the eastern Pacific to the west of the CA/OR border will move little during the period. A belt of strong southwesterly 500-mb flow will extend from the base of the larger-scale eastern Pacific trough and into CA/NV. In the low levels, a surface low will meander to the west of the northern CA/OR coast. ...Central Valley of CA... Several members of the latest HREF convection-allowing model ensemble show cellular storms developing during peak heating in the Central Valley. The NAM model appears to be consistently exhibiting a surface-temperature cool bias of several degrees F compared to expected high temperatures (e.g., 55-60 deg F vs. 60-65 deg F). Model data also shows some erosion of low clouds during the day over the valley and would align with slightly warmer temperatures than the NAM model forecast. When modifying forecast soundings for slightly warmer surface temperatures, it seems probable 250-500 J/kg MLCAPE will develop during the afternoon. The 18/03z RAP model shows some veering of surface winds (south-southwesterly) that appears incongruent with the terrain-channeled flow (surface winds south-southeasterly) that typically occurs with these types of setups. Large 0-3 km MLCAPE (150 J/kg) co-located with very favorably curved and elongated hodographs amidst a moist boundary layer (dewpoints in the upper 40s to low-mid 50s), indicate an environment favorable for shallow rotating cells (i.e., transient supercells). The more robust storms will potentially yield an isolated threat for a tornado in addition to localized gusts. This activity will likely dissipate by the early evening as instability wanes. ..Smith.. 02/18/2024 Read more

SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CST Sun Feb 18 2024 Valid 191200Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR A PORTION OF THE CENTRAL VALLEY OF CALIFORNIA... ...SUMMARY... An isolated risk for a tornado is forecast across the Central Valley of California on Monday afternoon and early evening. ...Synopsis... A mid-level low located over the eastern Pacific to the west of the CA/OR border will move little during the period. A belt of strong southwesterly 500-mb flow will extend from the base of the larger-scale eastern Pacific trough and into CA/NV. In the low levels, a surface low will meander to the west of the northern CA/OR coast. ...Central Valley of CA... Several members of the latest HREF convection-allowing model ensemble show cellular storms developing during peak heating in the Central Valley. The NAM model appears to be consistently exhibiting a surface-temperature cool bias of several degrees F compared to expected high temperatures (e.g., 55-60 deg F vs. 60-65 deg F). Model data also shows some erosion of low clouds during the day over the valley and would align with slightly warmer temperatures than the NAM model forecast. When modifying forecast soundings for slightly warmer surface temperatures, it seems probable 250-500 J/kg MLCAPE will develop during the afternoon. The 18/03z RAP model shows some veering of surface winds (south-southwesterly) that appears incongruent with the terrain-channeled flow (surface winds south-southeasterly) that typically occurs with these types of setups. Large 0-3 km MLCAPE (150 J/kg) co-located with very favorably curved and elongated hodographs amidst a moist boundary layer (dewpoints in the upper 40s to low-mid 50s), indicate an environment favorable for shallow rotating cells (i.e., transient supercells). The more robust storms will potentially yield an isolated threat for a tornado in addition to localized gusts. This activity will likely dissipate by the early evening as instability wanes. ..Smith.. 02/18/2024 Read more

SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CST Sun Feb 18 2024 Valid 191200Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR A PORTION OF THE CENTRAL VALLEY OF CALIFORNIA... ...SUMMARY... An isolated risk for a tornado is forecast across the Central Valley of California on Monday afternoon and early evening. ...Synopsis... A mid-level low located over the eastern Pacific to the west of the CA/OR border will move little during the period. A belt of strong southwesterly 500-mb flow will extend from the base of the larger-scale eastern Pacific trough and into CA/NV. In the low levels, a surface low will meander to the west of the northern CA/OR coast. ...Central Valley of CA... Several members of the latest HREF convection-allowing model ensemble show cellular storms developing during peak heating in the Central Valley. The NAM model appears to be consistently exhibiting a surface-temperature cool bias of several degrees F compared to expected high temperatures (e.g., 55-60 deg F vs. 60-65 deg F). Model data also shows some erosion of low clouds during the day over the valley and would align with slightly warmer temperatures than the NAM model forecast. When modifying forecast soundings for slightly warmer surface temperatures, it seems probable 250-500 J/kg MLCAPE will develop during the afternoon. The 18/03z RAP model shows some veering of surface winds (south-southwesterly) that appears incongruent with the terrain-channeled flow (surface winds south-southeasterly) that typically occurs with these types of setups. Large 0-3 km MLCAPE (150 J/kg) co-located with very favorably curved and elongated hodographs amidst a moist boundary layer (dewpoints in the upper 40s to low-mid 50s), indicate an environment favorable for shallow rotating cells (i.e., transient supercells). The more robust storms will potentially yield an isolated threat for a tornado in addition to localized gusts. This activity will likely dissipate by the early evening as instability wanes. ..Smith.. 02/18/2024 Read more

SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CST Sun Feb 18 2024 Valid 191200Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR A PORTION OF THE CENTRAL VALLEY OF CALIFORNIA... ...SUMMARY... An isolated risk for a tornado is forecast across the Central Valley of California on Monday afternoon and early evening. ...Synopsis... A mid-level low located over the eastern Pacific to the west of the CA/OR border will move little during the period. A belt of strong southwesterly 500-mb flow will extend from the base of the larger-scale eastern Pacific trough and into CA/NV. In the low levels, a surface low will meander to the west of the northern CA/OR coast. ...Central Valley of CA... Several members of the latest HREF convection-allowing model ensemble show cellular storms developing during peak heating in the Central Valley. The NAM model appears to be consistently exhibiting a surface-temperature cool bias of several degrees F compared to expected high temperatures (e.g., 55-60 deg F vs. 60-65 deg F). Model data also shows some erosion of low clouds during the day over the valley and would align with slightly warmer temperatures than the NAM model forecast. When modifying forecast soundings for slightly warmer surface temperatures, it seems probable 250-500 J/kg MLCAPE will develop during the afternoon. The 18/03z RAP model shows some veering of surface winds (south-southwesterly) that appears incongruent with the terrain-channeled flow (surface winds south-southeasterly) that typically occurs with these types of setups. Large 0-3 km MLCAPE (150 J/kg) co-located with very favorably curved and elongated hodographs amidst a moist boundary layer (dewpoints in the upper 40s to low-mid 50s), indicate an environment favorable for shallow rotating cells (i.e., transient supercells). The more robust storms will potentially yield an isolated threat for a tornado in addition to localized gusts. This activity will likely dissipate by the early evening as instability wanes. ..Smith.. 02/18/2024 Read more

SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CST Sun Feb 18 2024 Valid 191200Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR A PORTION OF THE CENTRAL VALLEY OF CALIFORNIA... ...SUMMARY... An isolated risk for a tornado is forecast across the Central Valley of California on Monday afternoon and early evening. ...Synopsis... A mid-level low located over the eastern Pacific to the west of the CA/OR border will move little during the period. A belt of strong southwesterly 500-mb flow will extend from the base of the larger-scale eastern Pacific trough and into CA/NV. In the low levels, a surface low will meander to the west of the northern CA/OR coast. ...Central Valley of CA... Several members of the latest HREF convection-allowing model ensemble show cellular storms developing during peak heating in the Central Valley. The NAM model appears to be consistently exhibiting a surface-temperature cool bias of several degrees F compared to expected high temperatures (e.g., 55-60 deg F vs. 60-65 deg F). Model data also shows some erosion of low clouds during the day over the valley and would align with slightly warmer temperatures than the NAM model forecast. When modifying forecast soundings for slightly warmer surface temperatures, it seems probable 250-500 J/kg MLCAPE will develop during the afternoon. The 18/03z RAP model shows some veering of surface winds (south-southwesterly) that appears incongruent with the terrain-channeled flow (surface winds south-southeasterly) that typically occurs with these types of setups. Large 0-3 km MLCAPE (150 J/kg) co-located with very favorably curved and elongated hodographs amidst a moist boundary layer (dewpoints in the upper 40s to low-mid 50s), indicate an environment favorable for shallow rotating cells (i.e., transient supercells). The more robust storms will potentially yield an isolated threat for a tornado in addition to localized gusts. This activity will likely dissipate by the early evening as instability wanes. ..Smith.. 02/18/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1159 PM CST Sat Feb 17 2024 Valid 181200Z - 191200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF SOUTH FLORIDA... ...SUMMARY... Isolated to scattered thunderstorms, associated with a marginal wind/tornado threat, will be possible across parts of south Florida today. ...South Florida... A shortwave trough will move into the lower Mississippi Valley today, with west-southwesterly mid-level flow located across the eastern Gulf of Mexico and Florida. At the surface, a cold front will likely remain quasi-stationary across south Florida. To the south of the front, surface dewpoints will be in the lower 70s F. As surface temperatures warm across the moist airmass, MLCAPE is forecast to approach 500 J/kg across parts of south Florida. As instability increases during the day, thunderstorm development is expected near and to the south of the front over parts of south Florida. In addition to the instability, RAP forecast soundings within the moist airmass in the vicinity of Miami between 18Z and 21Z have 0-6 km shear around 60 knots, with 0-3 storm-relative helicity near 250 m2/s2. The amount of shear will support storm rotation with cells that are near the strong instability in the early to mid afternoon. If a few rotating storms can develop, then a marginal wind damage/tornado threat will be possible. ..Broyles/Moore.. 02/18/2024 Read more