Aggregator

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 AM CDT Sun Sep 15 2024 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN THE HIGH PLAINS... ...SUMMARY... Isolated severe thunderstorms will be possible across a large swath of the High Plains region, mainly from Tuesday late afternoon into the evening. Severe gusts should be the primary hazard. ...High Plains... A shortwave trough over the eastern Great Basin at 12Z Tuesday should take on a negative tilt as it advances towards the northern High Plains. This process will yield a separation of the strong upper-level jet surrounding the trough, from a meridional component shifting north into eastern WY and a zonal component holding over AZ/NM. Guidance has oscillated southward with the evolution of the meridional component relative to yesterday's guidance. Deep lee cyclogenesis is expected over northeast WY/southeast MT. This low will advance north towards the MT/SK border area by 12Z Wednesday. Large-scale ascent will be pronounced within this synoptic regime, with favorable upper-level difluence, mid-level height falls, and low-level convergence. But weak buoyancy and modest mid-level lapse rates will characterized much of the environment. The bulk of convective development will occur over the higher terrain, likely aided by the subtropical moisture plume over the Southwest. High-based storms should progress into a well-mixed boundary layer that may initially be devoid of appreciable CAPE. This lack of greater buoyancy during the late afternoon to early evening, outside of northeast MT into the Dakotas, yields substantial uncertainty in the degree of strong versus severe storms. But with scattered to widespread convection likely into the evening, sporadic severe gusts may occur. ...Eastern NC and southeast VA... The poor predictability of offshore cyclogenesis amplitude and inland progression on Monday renders minimal confidence in delineating a severe area on Tuesday. Slower and more aggressive ensemble members suggest an adequate SRH/buoyancy combination for low-topped tornado potential may linger over eastern NC early in the period and shift into parts of southeast VA. But overall trends indicate a generalized weakening low-level wind field may occur during the day. ..Grams.. 09/15/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 AM CDT Sun Sep 15 2024 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN THE HIGH PLAINS... ...SUMMARY... Isolated severe thunderstorms will be possible across a large swath of the High Plains region, mainly from Tuesday late afternoon into the evening. Severe gusts should be the primary hazard. ...High Plains... A shortwave trough over the eastern Great Basin at 12Z Tuesday should take on a negative tilt as it advances towards the northern High Plains. This process will yield a separation of the strong upper-level jet surrounding the trough, from a meridional component shifting north into eastern WY and a zonal component holding over AZ/NM. Guidance has oscillated southward with the evolution of the meridional component relative to yesterday's guidance. Deep lee cyclogenesis is expected over northeast WY/southeast MT. This low will advance north towards the MT/SK border area by 12Z Wednesday. Large-scale ascent will be pronounced within this synoptic regime, with favorable upper-level difluence, mid-level height falls, and low-level convergence. But weak buoyancy and modest mid-level lapse rates will characterized much of the environment. The bulk of convective development will occur over the higher terrain, likely aided by the subtropical moisture plume over the Southwest. High-based storms should progress into a well-mixed boundary layer that may initially be devoid of appreciable CAPE. This lack of greater buoyancy during the late afternoon to early evening, outside of northeast MT into the Dakotas, yields substantial uncertainty in the degree of strong versus severe storms. But with scattered to widespread convection likely into the evening, sporadic severe gusts may occur. ...Eastern NC and southeast VA... The poor predictability of offshore cyclogenesis amplitude and inland progression on Monday renders minimal confidence in delineating a severe area on Tuesday. Slower and more aggressive ensemble members suggest an adequate SRH/buoyancy combination for low-topped tornado potential may linger over eastern NC early in the period and shift into parts of southeast VA. But overall trends indicate a generalized weakening low-level wind field may occur during the day. ..Grams.. 09/15/2024 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0150 AM CDT Sun Sep 15 2024 Valid 161200Z - 171200Z ...Synopsis... A highly amplified midlevel trough, accompanied by strong deep-layer south-southwesterly flow, will overspread the Great Basin during the day. This will promote 20-30 mph sustained south-southwesterly surface winds (with higher gusts) across portions of the southern Great Basin. Despite cooling surface temperatures and increasing moisture/RH, diurnal heating should still contribute to a corridor of 15-20 percent RH amid the strong/gusty winds. Therefore, Elevated highlights are in place for the wind-driven fire-weather risk. ..Weinman.. 09/15/2024 ...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 0150 AM CDT Sun Sep 15 2024 Valid 161200Z - 171200Z ...Synopsis... A highly amplified midlevel trough, accompanied by strong deep-layer south-southwesterly flow, will overspread the Great Basin during the day. This will promote 20-30 mph sustained south-southwesterly surface winds (with higher gusts) across portions of the southern Great Basin. Despite cooling surface temperatures and increasing moisture/RH, diurnal heating should still contribute to a corridor of 15-20 percent RH amid the strong/gusty winds. Therefore, Elevated highlights are in place for the wind-driven fire-weather risk. ..Weinman.. 09/15/2024 ...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 0150 AM CDT Sun Sep 15 2024 Valid 161200Z - 171200Z ...Synopsis... A highly amplified midlevel trough, accompanied by strong deep-layer south-southwesterly flow, will overspread the Great Basin during the day. This will promote 20-30 mph sustained south-southwesterly surface winds (with higher gusts) across portions of the southern Great Basin. Despite cooling surface temperatures and increasing moisture/RH, diurnal heating should still contribute to a corridor of 15-20 percent RH amid the strong/gusty winds. Therefore, Elevated highlights are in place for the wind-driven fire-weather risk. ..Weinman.. 09/15/2024 ...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 0150 AM CDT Sun Sep 15 2024 Valid 161200Z - 171200Z ...Synopsis... A highly amplified midlevel trough, accompanied by strong deep-layer south-southwesterly flow, will overspread the Great Basin during the day. This will promote 20-30 mph sustained south-southwesterly surface winds (with higher gusts) across portions of the southern Great Basin. Despite cooling surface temperatures and increasing moisture/RH, diurnal heating should still contribute to a corridor of 15-20 percent RH amid the strong/gusty winds. Therefore, Elevated highlights are in place for the wind-driven fire-weather risk. ..Weinman.. 09/15/2024 ...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 0150 AM CDT Sun Sep 15 2024 Valid 151200Z - 161200Z ...Synopsis... Preceding an amplifying large-scale trough over the West Coast, enhanced deep-layer meridional flow will overspread the Great Basin, while a related surface cyclone evolves over northern NV. Deep boundary-layer mixing into the enhanced flow aloft, along with a tightening pressure gradient peripheral to the surface cyclone, will yield 20-25 mph sustained southerly surface winds and 15-20 percent RH over southern/central NV. Given modestly receptive fuels here, elevated fire-weather conditions are expected during the afternoon. Additionally, large-scale ascent accompanying the amplifying midlevel trough will promote a mix of wet/dry thunderstorms across the northern Great Basin/Intermountain West. While quick storm motions and limited precipitation with some of this activity could yield a risk of lightning-induced ignitions, marginal fuels should generally limit the threat. Over the southern High Plains, breezy/gusty southerly surface winds will develop amid a warm/dry boundary layer near a lee trough during the afternoon. This will favor a few hours of elevated fire-weather conditions. ..Weinman.. 09/15/2024 ...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 0150 AM CDT Sun Sep 15 2024 Valid 151200Z - 161200Z ...Synopsis... Preceding an amplifying large-scale trough over the West Coast, enhanced deep-layer meridional flow will overspread the Great Basin, while a related surface cyclone evolves over northern NV. Deep boundary-layer mixing into the enhanced flow aloft, along with a tightening pressure gradient peripheral to the surface cyclone, will yield 20-25 mph sustained southerly surface winds and 15-20 percent RH over southern/central NV. Given modestly receptive fuels here, elevated fire-weather conditions are expected during the afternoon. Additionally, large-scale ascent accompanying the amplifying midlevel trough will promote a mix of wet/dry thunderstorms across the northern Great Basin/Intermountain West. While quick storm motions and limited precipitation with some of this activity could yield a risk of lightning-induced ignitions, marginal fuels should generally limit the threat. Over the southern High Plains, breezy/gusty southerly surface winds will develop amid a warm/dry boundary layer near a lee trough during the afternoon. This will favor a few hours of elevated fire-weather conditions. ..Weinman.. 09/15/2024 ...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 0150 AM CDT Sun Sep 15 2024 Valid 151200Z - 161200Z ...Synopsis... Preceding an amplifying large-scale trough over the West Coast, enhanced deep-layer meridional flow will overspread the Great Basin, while a related surface cyclone evolves over northern NV. Deep boundary-layer mixing into the enhanced flow aloft, along with a tightening pressure gradient peripheral to the surface cyclone, will yield 20-25 mph sustained southerly surface winds and 15-20 percent RH over southern/central NV. Given modestly receptive fuels here, elevated fire-weather conditions are expected during the afternoon. Additionally, large-scale ascent accompanying the amplifying midlevel trough will promote a mix of wet/dry thunderstorms across the northern Great Basin/Intermountain West. While quick storm motions and limited precipitation with some of this activity could yield a risk of lightning-induced ignitions, marginal fuels should generally limit the threat. Over the southern High Plains, breezy/gusty southerly surface winds will develop amid a warm/dry boundary layer near a lee trough during the afternoon. This will favor a few hours of elevated fire-weather conditions. ..Weinman.. 09/15/2024 ...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 0150 AM CDT Sun Sep 15 2024 Valid 151200Z - 161200Z ...Synopsis... Preceding an amplifying large-scale trough over the West Coast, enhanced deep-layer meridional flow will overspread the Great Basin, while a related surface cyclone evolves over northern NV. Deep boundary-layer mixing into the enhanced flow aloft, along with a tightening pressure gradient peripheral to the surface cyclone, will yield 20-25 mph sustained southerly surface winds and 15-20 percent RH over southern/central NV. Given modestly receptive fuels here, elevated fire-weather conditions are expected during the afternoon. Additionally, large-scale ascent accompanying the amplifying midlevel trough will promote a mix of wet/dry thunderstorms across the northern Great Basin/Intermountain West. While quick storm motions and limited precipitation with some of this activity could yield a risk of lightning-induced ignitions, marginal fuels should generally limit the threat. Over the southern High Plains, breezy/gusty southerly surface winds will develop amid a warm/dry boundary layer near a lee trough during the afternoon. This will favor a few hours of elevated fire-weather conditions. ..Weinman.. 09/15/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1256 AM CDT Sun Sep 15 2024 Valid 161200Z - 171200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN THE EASTERN GREAT BASIN TO FOUR CORNERS...THE RED RIVER VALLEY OF THE NORTH...AND EASTERN NC... ...SUMMARY... On Monday, sporadic severe gusts and marginally severe hail will be possible during the afternoon to early evening across parts of the eastern Great Basin to Four Corners. Isolated, marginally severe storms are possible over eastern North Dakota into northwest Minnesota during the late afternoon and evening. A low-probability tornado threat may develop over eastern North Carolina. ...Eastern Great Basin to the Four Corners... An amplified mid-level low near the Bay Area at 12Z Monday should initially move east before curling northeast Monday night towards the NV/UT/ID border area. This will occur in response to a strong mid-level jet translating through the basal portion of the large-scale trough across the Desert Southwest into the eastern Great Basin. Convection should be ongoing Monday morning immediately ahead of the mid-level low and separately in the low-level warm/moist conveyor over the Four Corners region. Greater boundary-layer heating should occur between these two regimes across eastern NV into UT, west of the Wasatch Range. Despite meager MLCAPE, the deepening boundary layer amid a strengthening meridional wind profile should yield efficient downward mixing. This will be further augmented by evaporatively cooled downdraft accelerations and promote a threat for sporadic severe gusts. Farther southeast, a more southwesterly mid to upper-flow regime should yield hodograph elongation, supporting a few splitting supercells. Warmer mid-level temperatures and correspondingly weaker lapse rates will temper parcel acceleration to an extent, but this may be offset by somewhat higher PW values. Marginal severe hail/gusts will be possible. ...Eastern ND to northwest MN... With the primary upper-level trough displaced well to the west, deep-layer shear will remain weak across much of the Great Plains. However, most guidance suggests an MCV will emanate out of D1 central High Plains convection and gradually progress northeast towards the Red River Valley. In conjunction with the northern nose of a strengthening central to northern Great Plains low-level jet, a focused corridor for regenerative thunderstorm development may occur during the late afternoon and evening. Some low-level hodograph enlargement should support a predominantly clustered convective mode, with transient supercell structures possible. An isolated, lower-end severe hail/wind threat may develop, and a brief tornado is also possible. ...Coastal NC... While guidance consensus increasingly favors offshore cyclogenesis, the amplitude of this development along with timing of inland progression remain quite varied for a D2 forecast. The 00Z NAM and some of the 18Z ECMWF ENS members suggest particularly robust deepening will occur. The more aggressive scenarios would yield substantial enlargement of low-level hodographs, likely becoming coupled with a narrow swath of high theta-e air spreading west-northwestward from the Gulf Stream. Given the potential range of scenarios from nil threat to multiple tornadic supercells, a low-probability tornado highlight appears warranted. ..Grams.. 09/15/2024 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1256 AM CDT Sun Sep 15 2024 Valid 161200Z - 171200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN THE EASTERN GREAT BASIN TO FOUR CORNERS...THE RED RIVER VALLEY OF THE NORTH...AND EASTERN NC... ...SUMMARY... On Monday, sporadic severe gusts and marginally severe hail will be possible during the afternoon to early evening across parts of the eastern Great Basin to Four Corners. Isolated, marginally severe storms are possible over eastern North Dakota into northwest Minnesota during the late afternoon and evening. A low-probability tornado threat may develop over eastern North Carolina. ...Eastern Great Basin to the Four Corners... An amplified mid-level low near the Bay Area at 12Z Monday should initially move east before curling northeast Monday night towards the NV/UT/ID border area. This will occur in response to a strong mid-level jet translating through the basal portion of the large-scale trough across the Desert Southwest into the eastern Great Basin. Convection should be ongoing Monday morning immediately ahead of the mid-level low and separately in the low-level warm/moist conveyor over the Four Corners region. Greater boundary-layer heating should occur between these two regimes across eastern NV into UT, west of the Wasatch Range. Despite meager MLCAPE, the deepening boundary layer amid a strengthening meridional wind profile should yield efficient downward mixing. This will be further augmented by evaporatively cooled downdraft accelerations and promote a threat for sporadic severe gusts. Farther southeast, a more southwesterly mid to upper-flow regime should yield hodograph elongation, supporting a few splitting supercells. Warmer mid-level temperatures and correspondingly weaker lapse rates will temper parcel acceleration to an extent, but this may be offset by somewhat higher PW values. Marginal severe hail/gusts will be possible. ...Eastern ND to northwest MN... With the primary upper-level trough displaced well to the west, deep-layer shear will remain weak across much of the Great Plains. However, most guidance suggests an MCV will emanate out of D1 central High Plains convection and gradually progress northeast towards the Red River Valley. In conjunction with the northern nose of a strengthening central to northern Great Plains low-level jet, a focused corridor for regenerative thunderstorm development may occur during the late afternoon and evening. Some low-level hodograph enlargement should support a predominantly clustered convective mode, with transient supercell structures possible. An isolated, lower-end severe hail/wind threat may develop, and a brief tornado is also possible. ...Coastal NC... While guidance consensus increasingly favors offshore cyclogenesis, the amplitude of this development along with timing of inland progression remain quite varied for a D2 forecast. The 00Z NAM and some of the 18Z ECMWF ENS members suggest particularly robust deepening will occur. The more aggressive scenarios would yield substantial enlargement of low-level hodographs, likely becoming coupled with a narrow swath of high theta-e air spreading west-northwestward from the Gulf Stream. Given the potential range of scenarios from nil threat to multiple tornadic supercells, a low-probability tornado highlight appears warranted. ..Grams.. 09/15/2024 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1256 AM CDT Sun Sep 15 2024 Valid 161200Z - 171200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN THE EASTERN GREAT BASIN TO FOUR CORNERS...THE RED RIVER VALLEY OF THE NORTH...AND EASTERN NC... ...SUMMARY... On Monday, sporadic severe gusts and marginally severe hail will be possible during the afternoon to early evening across parts of the eastern Great Basin to Four Corners. Isolated, marginally severe storms are possible over eastern North Dakota into northwest Minnesota during the late afternoon and evening. A low-probability tornado threat may develop over eastern North Carolina. ...Eastern Great Basin to the Four Corners... An amplified mid-level low near the Bay Area at 12Z Monday should initially move east before curling northeast Monday night towards the NV/UT/ID border area. This will occur in response to a strong mid-level jet translating through the basal portion of the large-scale trough across the Desert Southwest into the eastern Great Basin. Convection should be ongoing Monday morning immediately ahead of the mid-level low and separately in the low-level warm/moist conveyor over the Four Corners region. Greater boundary-layer heating should occur between these two regimes across eastern NV into UT, west of the Wasatch Range. Despite meager MLCAPE, the deepening boundary layer amid a strengthening meridional wind profile should yield efficient downward mixing. This will be further augmented by evaporatively cooled downdraft accelerations and promote a threat for sporadic severe gusts. Farther southeast, a more southwesterly mid to upper-flow regime should yield hodograph elongation, supporting a few splitting supercells. Warmer mid-level temperatures and correspondingly weaker lapse rates will temper parcel acceleration to an extent, but this may be offset by somewhat higher PW values. Marginal severe hail/gusts will be possible. ...Eastern ND to northwest MN... With the primary upper-level trough displaced well to the west, deep-layer shear will remain weak across much of the Great Plains. However, most guidance suggests an MCV will emanate out of D1 central High Plains convection and gradually progress northeast towards the Red River Valley. In conjunction with the northern nose of a strengthening central to northern Great Plains low-level jet, a focused corridor for regenerative thunderstorm development may occur during the late afternoon and evening. Some low-level hodograph enlargement should support a predominantly clustered convective mode, with transient supercell structures possible. An isolated, lower-end severe hail/wind threat may develop, and a brief tornado is also possible. ...Coastal NC... While guidance consensus increasingly favors offshore cyclogenesis, the amplitude of this development along with timing of inland progression remain quite varied for a D2 forecast. The 00Z NAM and some of the 18Z ECMWF ENS members suggest particularly robust deepening will occur. The more aggressive scenarios would yield substantial enlargement of low-level hodographs, likely becoming coupled with a narrow swath of high theta-e air spreading west-northwestward from the Gulf Stream. Given the potential range of scenarios from nil threat to multiple tornadic supercells, a low-probability tornado highlight appears warranted. ..Grams.. 09/15/2024 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1256 AM CDT Sun Sep 15 2024 Valid 161200Z - 171200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN THE EASTERN GREAT BASIN TO FOUR CORNERS...THE RED RIVER VALLEY OF THE NORTH...AND EASTERN NC... ...SUMMARY... On Monday, sporadic severe gusts and marginally severe hail will be possible during the afternoon to early evening across parts of the eastern Great Basin to Four Corners. Isolated, marginally severe storms are possible over eastern North Dakota into northwest Minnesota during the late afternoon and evening. A low-probability tornado threat may develop over eastern North Carolina. ...Eastern Great Basin to the Four Corners... An amplified mid-level low near the Bay Area at 12Z Monday should initially move east before curling northeast Monday night towards the NV/UT/ID border area. This will occur in response to a strong mid-level jet translating through the basal portion of the large-scale trough across the Desert Southwest into the eastern Great Basin. Convection should be ongoing Monday morning immediately ahead of the mid-level low and separately in the low-level warm/moist conveyor over the Four Corners region. Greater boundary-layer heating should occur between these two regimes across eastern NV into UT, west of the Wasatch Range. Despite meager MLCAPE, the deepening boundary layer amid a strengthening meridional wind profile should yield efficient downward mixing. This will be further augmented by evaporatively cooled downdraft accelerations and promote a threat for sporadic severe gusts. Farther southeast, a more southwesterly mid to upper-flow regime should yield hodograph elongation, supporting a few splitting supercells. Warmer mid-level temperatures and correspondingly weaker lapse rates will temper parcel acceleration to an extent, but this may be offset by somewhat higher PW values. Marginal severe hail/gusts will be possible. ...Eastern ND to northwest MN... With the primary upper-level trough displaced well to the west, deep-layer shear will remain weak across much of the Great Plains. However, most guidance suggests an MCV will emanate out of D1 central High Plains convection and gradually progress northeast towards the Red River Valley. In conjunction with the northern nose of a strengthening central to northern Great Plains low-level jet, a focused corridor for regenerative thunderstorm development may occur during the late afternoon and evening. Some low-level hodograph enlargement should support a predominantly clustered convective mode, with transient supercell structures possible. An isolated, lower-end severe hail/wind threat may develop, and a brief tornado is also possible. ...Coastal NC... While guidance consensus increasingly favors offshore cyclogenesis, the amplitude of this development along with timing of inland progression remain quite varied for a D2 forecast. The 00Z NAM and some of the 18Z ECMWF ENS members suggest particularly robust deepening will occur. The more aggressive scenarios would yield substantial enlargement of low-level hodographs, likely becoming coupled with a narrow swath of high theta-e air spreading west-northwestward from the Gulf Stream. Given the potential range of scenarios from nil threat to multiple tornadic supercells, a low-probability tornado highlight appears warranted. ..Grams.. 09/15/2024 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1256 AM CDT Sun Sep 15 2024 Valid 161200Z - 171200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN THE EASTERN GREAT BASIN TO FOUR CORNERS...THE RED RIVER VALLEY OF THE NORTH...AND EASTERN NC... ...SUMMARY... On Monday, sporadic severe gusts and marginally severe hail will be possible during the afternoon to early evening across parts of the eastern Great Basin to Four Corners. Isolated, marginally severe storms are possible over eastern North Dakota into northwest Minnesota during the late afternoon and evening. A low-probability tornado threat may develop over eastern North Carolina. ...Eastern Great Basin to the Four Corners... An amplified mid-level low near the Bay Area at 12Z Monday should initially move east before curling northeast Monday night towards the NV/UT/ID border area. This will occur in response to a strong mid-level jet translating through the basal portion of the large-scale trough across the Desert Southwest into the eastern Great Basin. Convection should be ongoing Monday morning immediately ahead of the mid-level low and separately in the low-level warm/moist conveyor over the Four Corners region. Greater boundary-layer heating should occur between these two regimes across eastern NV into UT, west of the Wasatch Range. Despite meager MLCAPE, the deepening boundary layer amid a strengthening meridional wind profile should yield efficient downward mixing. This will be further augmented by evaporatively cooled downdraft accelerations and promote a threat for sporadic severe gusts. Farther southeast, a more southwesterly mid to upper-flow regime should yield hodograph elongation, supporting a few splitting supercells. Warmer mid-level temperatures and correspondingly weaker lapse rates will temper parcel acceleration to an extent, but this may be offset by somewhat higher PW values. Marginal severe hail/gusts will be possible. ...Eastern ND to northwest MN... With the primary upper-level trough displaced well to the west, deep-layer shear will remain weak across much of the Great Plains. However, most guidance suggests an MCV will emanate out of D1 central High Plains convection and gradually progress northeast towards the Red River Valley. In conjunction with the northern nose of a strengthening central to northern Great Plains low-level jet, a focused corridor for regenerative thunderstorm development may occur during the late afternoon and evening. Some low-level hodograph enlargement should support a predominantly clustered convective mode, with transient supercell structures possible. An isolated, lower-end severe hail/wind threat may develop, and a brief tornado is also possible. ...Coastal NC... While guidance consensus increasingly favors offshore cyclogenesis, the amplitude of this development along with timing of inland progression remain quite varied for a D2 forecast. The 00Z NAM and some of the 18Z ECMWF ENS members suggest particularly robust deepening will occur. The more aggressive scenarios would yield substantial enlargement of low-level hodographs, likely becoming coupled with a narrow swath of high theta-e air spreading west-northwestward from the Gulf Stream. Given the potential range of scenarios from nil threat to multiple tornadic supercells, a low-probability tornado highlight appears warranted. ..Grams.. 09/15/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1258 AM CDT Sun Sep 15 2024 Valid 151200Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL AND NORTHERN HIGH PLAINS... ...SUMMARY... Thunderstorms capable of isolated severe gusts and hail will be possible today across parts of the central and northern High Plains. ...Central and Northern High Plains... An upper-level low will move southward along the West Coast today, as southwest mid-level flow remains over much of the western third of the U.S. A subtle shortwave trough is forecast to move northeastward through the central Rockies. Ahead of the trough, a moist airmass will be in place in the central and northern Plains, where surface dewpoints will mostly be from the upper 50s to the mid 60s F. As surface temperatures warm, moderate instability is expected to develop over much of this airmass. MLCAPE is forecast to peak in the 2000 to 3000 J/kg range in areas that heat up the most. The instability axis is forecast to be located from northwest Kansas northward into western Nebraska and southwest South Dakota by mid to late afternoon. At this time, RAP forecast soundings near the instability axis have low to mid-level lapse rates exceeding 8 C/km, and enough deep-layer shear for a marginal severe threat. Isolated severe gusts and hail will be possible with the stronger cells, mainly during the late afternoon and early evening. ..Broyles/Weinman.. 09/15/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1258 AM CDT Sun Sep 15 2024 Valid 151200Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL AND NORTHERN HIGH PLAINS... ...SUMMARY... Thunderstorms capable of isolated severe gusts and hail will be possible today across parts of the central and northern High Plains. ...Central and Northern High Plains... An upper-level low will move southward along the West Coast today, as southwest mid-level flow remains over much of the western third of the U.S. A subtle shortwave trough is forecast to move northeastward through the central Rockies. Ahead of the trough, a moist airmass will be in place in the central and northern Plains, where surface dewpoints will mostly be from the upper 50s to the mid 60s F. As surface temperatures warm, moderate instability is expected to develop over much of this airmass. MLCAPE is forecast to peak in the 2000 to 3000 J/kg range in areas that heat up the most. The instability axis is forecast to be located from northwest Kansas northward into western Nebraska and southwest South Dakota by mid to late afternoon. At this time, RAP forecast soundings near the instability axis have low to mid-level lapse rates exceeding 8 C/km, and enough deep-layer shear for a marginal severe threat. Isolated severe gusts and hail will be possible with the stronger cells, mainly during the late afternoon and early evening. ..Broyles/Weinman.. 09/15/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1258 AM CDT Sun Sep 15 2024 Valid 151200Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL AND NORTHERN HIGH PLAINS... ...SUMMARY... Thunderstorms capable of isolated severe gusts and hail will be possible today across parts of the central and northern High Plains. ...Central and Northern High Plains... An upper-level low will move southward along the West Coast today, as southwest mid-level flow remains over much of the western third of the U.S. A subtle shortwave trough is forecast to move northeastward through the central Rockies. Ahead of the trough, a moist airmass will be in place in the central and northern Plains, where surface dewpoints will mostly be from the upper 50s to the mid 60s F. As surface temperatures warm, moderate instability is expected to develop over much of this airmass. MLCAPE is forecast to peak in the 2000 to 3000 J/kg range in areas that heat up the most. The instability axis is forecast to be located from northwest Kansas northward into western Nebraska and southwest South Dakota by mid to late afternoon. At this time, RAP forecast soundings near the instability axis have low to mid-level lapse rates exceeding 8 C/km, and enough deep-layer shear for a marginal severe threat. Isolated severe gusts and hail will be possible with the stronger cells, mainly during the late afternoon and early evening. ..Broyles/Weinman.. 09/15/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1258 AM CDT Sun Sep 15 2024 Valid 151200Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL AND NORTHERN HIGH PLAINS... ...SUMMARY... Thunderstorms capable of isolated severe gusts and hail will be possible today across parts of the central and northern High Plains. ...Central and Northern High Plains... An upper-level low will move southward along the West Coast today, as southwest mid-level flow remains over much of the western third of the U.S. A subtle shortwave trough is forecast to move northeastward through the central Rockies. Ahead of the trough, a moist airmass will be in place in the central and northern Plains, where surface dewpoints will mostly be from the upper 50s to the mid 60s F. As surface temperatures warm, moderate instability is expected to develop over much of this airmass. MLCAPE is forecast to peak in the 2000 to 3000 J/kg range in areas that heat up the most. The instability axis is forecast to be located from northwest Kansas northward into western Nebraska and southwest South Dakota by mid to late afternoon. At this time, RAP forecast soundings near the instability axis have low to mid-level lapse rates exceeding 8 C/km, and enough deep-layer shear for a marginal severe threat. Isolated severe gusts and hail will be possible with the stronger cells, mainly during the late afternoon and early evening. ..Broyles/Weinman.. 09/15/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1258 AM CDT Sun Sep 15 2024 Valid 151200Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL AND NORTHERN HIGH PLAINS... ...SUMMARY... Thunderstorms capable of isolated severe gusts and hail will be possible today across parts of the central and northern High Plains. ...Central and Northern High Plains... An upper-level low will move southward along the West Coast today, as southwest mid-level flow remains over much of the western third of the U.S. A subtle shortwave trough is forecast to move northeastward through the central Rockies. Ahead of the trough, a moist airmass will be in place in the central and northern Plains, where surface dewpoints will mostly be from the upper 50s to the mid 60s F. As surface temperatures warm, moderate instability is expected to develop over much of this airmass. MLCAPE is forecast to peak in the 2000 to 3000 J/kg range in areas that heat up the most. The instability axis is forecast to be located from northwest Kansas northward into western Nebraska and southwest South Dakota by mid to late afternoon. At this time, RAP forecast soundings near the instability axis have low to mid-level lapse rates exceeding 8 C/km, and enough deep-layer shear for a marginal severe threat. Isolated severe gusts and hail will be possible with the stronger cells, mainly during the late afternoon and early evening. ..Broyles/Weinman.. 09/15/2024 Read more