Severe Storms

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1128 AM CDT Tue Sep 17 2024 Valid 171700Z - 181200Z ...17z Update... No changes. Spotty elevated conditions are possible owing to strong southerly winds ahead of a cold front. Strong gusts may linger after the frontal passage and with shower/thunderstorms expected later today. Fire concerns will remain highest within patchy dry fuels across the southern most portions of the NE panhandle where less rainfall and lower humidity recoveries have occurred. See the prior discussion. ..Lyons.. 09/17/2024 .PREV DISCUSSION... /ISSUED 0156 AM CDT Tue Sep 17 2024/ ...Synopsis... A large-scale trough, accompanied by strong deep-layer south-southwesterly flow, will overspread the northern/central Rockies and adjacent High Plains. A related lee cyclone will deepen near western SD, promoting a tight pressure gradient and 20-25 mph sustained southerly surface winds (with higher gusts) over portions of western NE during the afternoon. Here, diurnal heating along the western edge of the richer boundary-layer moisture plume should yield 20-30 percent RH. Despite these marginal RH reductions, the strong/gusty winds will still favor a few hours of elevated fire-weather conditions, before a cold front and related precipitation overspread the area during the evening. ...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 1128 AM CDT Tue Sep 17 2024 Valid 171700Z - 181200Z ...17z Update... No changes. Spotty elevated conditions are possible owing to strong southerly winds ahead of a cold front. Strong gusts may linger after the frontal passage and with shower/thunderstorms expected later today. Fire concerns will remain highest within patchy dry fuels across the southern most portions of the NE panhandle where less rainfall and lower humidity recoveries have occurred. See the prior discussion. ..Lyons.. 09/17/2024 .PREV DISCUSSION... /ISSUED 0156 AM CDT Tue Sep 17 2024/ ...Synopsis... A large-scale trough, accompanied by strong deep-layer south-southwesterly flow, will overspread the northern/central Rockies and adjacent High Plains. A related lee cyclone will deepen near western SD, promoting a tight pressure gradient and 20-25 mph sustained southerly surface winds (with higher gusts) over portions of western NE during the afternoon. Here, diurnal heating along the western edge of the richer boundary-layer moisture plume should yield 20-30 percent RH. Despite these marginal RH reductions, the strong/gusty winds will still favor a few hours of elevated fire-weather conditions, before a cold front and related precipitation overspread the area during the evening. ...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 0706 AM CDT Tue Sep 17 2024 Valid 171300Z - 181200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL HIGH PLAINS... ...SUMMARY... Thunderstorms capable of severe wind gusts and isolated large hail will be possible this afternoon and evening across parts of the central and northern High Plains. ...High Plains/Central and Southern Rockies... Water-vapor imagery early this morning shows a potent mid-level low and associated trough centered over northeast NV. This feature will become negatively tilted and move into the High Plains late today while the low moves east-northeast reaching southeast MT Wednesday morning. Strong attendant forcing for ascent will overspread the High Plains this afternoon into the early evening with an accompanying 50-60 kt 500-mb speed max moving into CO and eventually western NE/SD. In the low levels, a lee trough will sharpen with southerly flow maintaining a fetch of seasonably adequate moisture (50s deg F surface dewpoints) into the High Plains. Ahead of the approaching trough, partial clearing will result in strong surface heating this afternoon over the central High Plains. MLCAPE is expected to peak near 1500 J/kg from eastern Colorado northward into western Nebraska. Initial storm activity late this morning through the early afternoon will develop over the high terrain of CO/northern NM and move/develop east into richer moisture by mid-late afternoon. The increasing large-scale ascent coupled with heating will eventually result in numerous storms mainly in the form of linear clusters evolving into linear bands of convection by early evening. The greatest combination of instability, lift and deep-layer shear is forecast across western Nebraska and northeast Colorado, suggesting an enhanced threat for severe wind gusts. Based on some of the latest CAM data, have expanded the Slight-Risk equivalent wind probabilities farther south into northeast NM/northwest TX Panhandle. Some consideration was given to expand the ENH Risk into southwestern SD, but the later timing of storms lends enough uncertainty to preclude this change this outlook update. ...Northern High Plains... Ahead of the approaching mid-level low, divergent south to south-southeasterly flow will be in place across the northern Rockies and northern Plains. During the afternoon, thunderstorms will develop in the north-central Rockies and move north to northeastward across the northern High Plains. An axis of moderate instability is forecast by afternoon from the Dakotas northwestward into northeast Montana. As large-scale ascent and moderate deep-layer shear overspread the northern High Plains late this afternoon and evening, organized storms will be possible. Severe wind gusts and isolated large hail will be the primary threats. ...Eastern Florida... A mid-level trough will move across the eastern Gulf of Mexico today, as an associated surface trough moves across the Florida Peninsula. Surface dewpoints in the lower to mid 70s F, along with surface heating will contribute to moderate instability by afternoon. As surface temperatures warm today, scattered thunderstorms are expected to develop along and ahead of the surface trough. RAP forecast soundings at 21Z in eastern Florida have MLCAPE in the 2000 to 3000 J/kg range, with 0-6 km shear around 20 knots. This, combined with steep low-level lapse rates could be enough for a marginal threat for locally severe wind gusts. ..Smith/Mosier.. 09/17/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0706 AM CDT Tue Sep 17 2024 Valid 171300Z - 181200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL HIGH PLAINS... ...SUMMARY... Thunderstorms capable of severe wind gusts and isolated large hail will be possible this afternoon and evening across parts of the central and northern High Plains. ...High Plains/Central and Southern Rockies... Water-vapor imagery early this morning shows a potent mid-level low and associated trough centered over northeast NV. This feature will become negatively tilted and move into the High Plains late today while the low moves east-northeast reaching southeast MT Wednesday morning. Strong attendant forcing for ascent will overspread the High Plains this afternoon into the early evening with an accompanying 50-60 kt 500-mb speed max moving into CO and eventually western NE/SD. In the low levels, a lee trough will sharpen with southerly flow maintaining a fetch of seasonably adequate moisture (50s deg F surface dewpoints) into the High Plains. Ahead of the approaching trough, partial clearing will result in strong surface heating this afternoon over the central High Plains. MLCAPE is expected to peak near 1500 J/kg from eastern Colorado northward into western Nebraska. Initial storm activity late this morning through the early afternoon will develop over the high terrain of CO/northern NM and move/develop east into richer moisture by mid-late afternoon. The increasing large-scale ascent coupled with heating will eventually result in numerous storms mainly in the form of linear clusters evolving into linear bands of convection by early evening. The greatest combination of instability, lift and deep-layer shear is forecast across western Nebraska and northeast Colorado, suggesting an enhanced threat for severe wind gusts. Based on some of the latest CAM data, have expanded the Slight-Risk equivalent wind probabilities farther south into northeast NM/northwest TX Panhandle. Some consideration was given to expand the ENH Risk into southwestern SD, but the later timing of storms lends enough uncertainty to preclude this change this outlook update. ...Northern High Plains... Ahead of the approaching mid-level low, divergent south to south-southeasterly flow will be in place across the northern Rockies and northern Plains. During the afternoon, thunderstorms will develop in the north-central Rockies and move north to northeastward across the northern High Plains. An axis of moderate instability is forecast by afternoon from the Dakotas northwestward into northeast Montana. As large-scale ascent and moderate deep-layer shear overspread the northern High Plains late this afternoon and evening, organized storms will be possible. Severe wind gusts and isolated large hail will be the primary threats. ...Eastern Florida... A mid-level trough will move across the eastern Gulf of Mexico today, as an associated surface trough moves across the Florida Peninsula. Surface dewpoints in the lower to mid 70s F, along with surface heating will contribute to moderate instability by afternoon. As surface temperatures warm today, scattered thunderstorms are expected to develop along and ahead of the surface trough. RAP forecast soundings at 21Z in eastern Florida have MLCAPE in the 2000 to 3000 J/kg range, with 0-6 km shear around 20 knots. This, combined with steep low-level lapse rates could be enough for a marginal threat for locally severe wind gusts. ..Smith/Mosier.. 09/17/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0706 AM CDT Tue Sep 17 2024 Valid 171300Z - 181200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL HIGH PLAINS... ...SUMMARY... Thunderstorms capable of severe wind gusts and isolated large hail will be possible this afternoon and evening across parts of the central and northern High Plains. ...High Plains/Central and Southern Rockies... Water-vapor imagery early this morning shows a potent mid-level low and associated trough centered over northeast NV. This feature will become negatively tilted and move into the High Plains late today while the low moves east-northeast reaching southeast MT Wednesday morning. Strong attendant forcing for ascent will overspread the High Plains this afternoon into the early evening with an accompanying 50-60 kt 500-mb speed max moving into CO and eventually western NE/SD. In the low levels, a lee trough will sharpen with southerly flow maintaining a fetch of seasonably adequate moisture (50s deg F surface dewpoints) into the High Plains. Ahead of the approaching trough, partial clearing will result in strong surface heating this afternoon over the central High Plains. MLCAPE is expected to peak near 1500 J/kg from eastern Colorado northward into western Nebraska. Initial storm activity late this morning through the early afternoon will develop over the high terrain of CO/northern NM and move/develop east into richer moisture by mid-late afternoon. The increasing large-scale ascent coupled with heating will eventually result in numerous storms mainly in the form of linear clusters evolving into linear bands of convection by early evening. The greatest combination of instability, lift and deep-layer shear is forecast across western Nebraska and northeast Colorado, suggesting an enhanced threat for severe wind gusts. Based on some of the latest CAM data, have expanded the Slight-Risk equivalent wind probabilities farther south into northeast NM/northwest TX Panhandle. Some consideration was given to expand the ENH Risk into southwestern SD, but the later timing of storms lends enough uncertainty to preclude this change this outlook update. ...Northern High Plains... Ahead of the approaching mid-level low, divergent south to south-southeasterly flow will be in place across the northern Rockies and northern Plains. During the afternoon, thunderstorms will develop in the north-central Rockies and move north to northeastward across the northern High Plains. An axis of moderate instability is forecast by afternoon from the Dakotas northwestward into northeast Montana. As large-scale ascent and moderate deep-layer shear overspread the northern High Plains late this afternoon and evening, organized storms will be possible. Severe wind gusts and isolated large hail will be the primary threats. ...Eastern Florida... A mid-level trough will move across the eastern Gulf of Mexico today, as an associated surface trough moves across the Florida Peninsula. Surface dewpoints in the lower to mid 70s F, along with surface heating will contribute to moderate instability by afternoon. As surface temperatures warm today, scattered thunderstorms are expected to develop along and ahead of the surface trough. RAP forecast soundings at 21Z in eastern Florida have MLCAPE in the 2000 to 3000 J/kg range, with 0-6 km shear around 20 knots. This, combined with steep low-level lapse rates could be enough for a marginal threat for locally severe wind gusts. ..Smith/Mosier.. 09/17/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0706 AM CDT Tue Sep 17 2024 Valid 171300Z - 181200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL HIGH PLAINS... ...SUMMARY... Thunderstorms capable of severe wind gusts and isolated large hail will be possible this afternoon and evening across parts of the central and northern High Plains. ...High Plains/Central and Southern Rockies... Water-vapor imagery early this morning shows a potent mid-level low and associated trough centered over northeast NV. This feature will become negatively tilted and move into the High Plains late today while the low moves east-northeast reaching southeast MT Wednesday morning. Strong attendant forcing for ascent will overspread the High Plains this afternoon into the early evening with an accompanying 50-60 kt 500-mb speed max moving into CO and eventually western NE/SD. In the low levels, a lee trough will sharpen with southerly flow maintaining a fetch of seasonably adequate moisture (50s deg F surface dewpoints) into the High Plains. Ahead of the approaching trough, partial clearing will result in strong surface heating this afternoon over the central High Plains. MLCAPE is expected to peak near 1500 J/kg from eastern Colorado northward into western Nebraska. Initial storm activity late this morning through the early afternoon will develop over the high terrain of CO/northern NM and move/develop east into richer moisture by mid-late afternoon. The increasing large-scale ascent coupled with heating will eventually result in numerous storms mainly in the form of linear clusters evolving into linear bands of convection by early evening. The greatest combination of instability, lift and deep-layer shear is forecast across western Nebraska and northeast Colorado, suggesting an enhanced threat for severe wind gusts. Based on some of the latest CAM data, have expanded the Slight-Risk equivalent wind probabilities farther south into northeast NM/northwest TX Panhandle. Some consideration was given to expand the ENH Risk into southwestern SD, but the later timing of storms lends enough uncertainty to preclude this change this outlook update. ...Northern High Plains... Ahead of the approaching mid-level low, divergent south to south-southeasterly flow will be in place across the northern Rockies and northern Plains. During the afternoon, thunderstorms will develop in the north-central Rockies and move north to northeastward across the northern High Plains. An axis of moderate instability is forecast by afternoon from the Dakotas northwestward into northeast Montana. As large-scale ascent and moderate deep-layer shear overspread the northern High Plains late this afternoon and evening, organized storms will be possible. Severe wind gusts and isolated large hail will be the primary threats. ...Eastern Florida... A mid-level trough will move across the eastern Gulf of Mexico today, as an associated surface trough moves across the Florida Peninsula. Surface dewpoints in the lower to mid 70s F, along with surface heating will contribute to moderate instability by afternoon. As surface temperatures warm today, scattered thunderstorms are expected to develop along and ahead of the surface trough. RAP forecast soundings at 21Z in eastern Florida have MLCAPE in the 2000 to 3000 J/kg range, with 0-6 km shear around 20 knots. This, combined with steep low-level lapse rates could be enough for a marginal threat for locally severe wind gusts. ..Smith/Mosier.. 09/17/2024 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0355 AM CDT Tue Sep 17 2024 Valid 201200Z - 251200Z ...DISCUSSION... A shortwave trough that amplifies into the Southwest should remain positive tilt and slow moving into this weekend. Guidance has trended towards greater consistency with the evolution of its attendant belt of enhanced mid-level flow ahead of the trough. Based on current timing, a focused corridor of severe potential may develop on D5/Saturday afternoon in the southern High Plains. With a stout mid-level anticyclone anchored over south TX and 500-mb temperatures warmer than -2 C across roughly the southeast two-thirds of TX, a potential corridor of 15 percent probabilities would likely be confined to the mesoscale. Predictability is too low to confidently highlight such a corridor at this temporal scale. After D5, predictability on the synoptic scale wanes considerably. Guidance spread becomes large with the evolution of northern-stream shortwave troughs and their influence on this southern-stream wave. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0355 AM CDT Tue Sep 17 2024 Valid 201200Z - 251200Z ...DISCUSSION... A shortwave trough that amplifies into the Southwest should remain positive tilt and slow moving into this weekend. Guidance has trended towards greater consistency with the evolution of its attendant belt of enhanced mid-level flow ahead of the trough. Based on current timing, a focused corridor of severe potential may develop on D5/Saturday afternoon in the southern High Plains. With a stout mid-level anticyclone anchored over south TX and 500-mb temperatures warmer than -2 C across roughly the southeast two-thirds of TX, a potential corridor of 15 percent probabilities would likely be confined to the mesoscale. Predictability is too low to confidently highlight such a corridor at this temporal scale. After D5, predictability on the synoptic scale wanes considerably. Guidance spread becomes large with the evolution of northern-stream shortwave troughs and their influence on this southern-stream wave. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0355 AM CDT Tue Sep 17 2024 Valid 201200Z - 251200Z ...DISCUSSION... A shortwave trough that amplifies into the Southwest should remain positive tilt and slow moving into this weekend. Guidance has trended towards greater consistency with the evolution of its attendant belt of enhanced mid-level flow ahead of the trough. Based on current timing, a focused corridor of severe potential may develop on D5/Saturday afternoon in the southern High Plains. With a stout mid-level anticyclone anchored over south TX and 500-mb temperatures warmer than -2 C across roughly the southeast two-thirds of TX, a potential corridor of 15 percent probabilities would likely be confined to the mesoscale. Predictability is too low to confidently highlight such a corridor at this temporal scale. After D5, predictability on the synoptic scale wanes considerably. Guidance spread becomes large with the evolution of northern-stream shortwave troughs and their influence on this southern-stream wave. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0355 AM CDT Tue Sep 17 2024 Valid 201200Z - 251200Z ...DISCUSSION... A shortwave trough that amplifies into the Southwest should remain positive tilt and slow moving into this weekend. Guidance has trended towards greater consistency with the evolution of its attendant belt of enhanced mid-level flow ahead of the trough. Based on current timing, a focused corridor of severe potential may develop on D5/Saturday afternoon in the southern High Plains. With a stout mid-level anticyclone anchored over south TX and 500-mb temperatures warmer than -2 C across roughly the southeast two-thirds of TX, a potential corridor of 15 percent probabilities would likely be confined to the mesoscale. Predictability is too low to confidently highlight such a corridor at this temporal scale. After D5, predictability on the synoptic scale wanes considerably. Guidance spread becomes large with the evolution of northern-stream shortwave troughs and their influence on this southern-stream wave. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0355 AM CDT Tue Sep 17 2024 Valid 201200Z - 251200Z ...DISCUSSION... A shortwave trough that amplifies into the Southwest should remain positive tilt and slow moving into this weekend. Guidance has trended towards greater consistency with the evolution of its attendant belt of enhanced mid-level flow ahead of the trough. Based on current timing, a focused corridor of severe potential may develop on D5/Saturday afternoon in the southern High Plains. With a stout mid-level anticyclone anchored over south TX and 500-mb temperatures warmer than -2 C across roughly the southeast two-thirds of TX, a potential corridor of 15 percent probabilities would likely be confined to the mesoscale. Predictability is too low to confidently highlight such a corridor at this temporal scale. After D5, predictability on the synoptic scale wanes considerably. Guidance spread becomes large with the evolution of northern-stream shortwave troughs and their influence on this southern-stream wave. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 AM CDT Tue Sep 17 2024 Valid 191200Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN A PART OF THE UPPER MIDWEST... ...SUMMARY... Scattered severe thunderstorms are possible from mid-afternoon to early evening on Thursday across central to eastern Minnesota and north-central Iowa. ...Upper Midwest... A vertically stacked cyclone near the ND/SK/MB border should move northeast over MB through the period. Predictability has increased with the placement of the trailing cold front arcing south on Thursday afternoon. In the mid-levels, modestly steepened lapse rates should overspread this boundary within a belt of moderately enhanced west-southwesterly flow. Given a confined plume of rich boundary-layer moisture, a corridor of MLCAPE from 1500-2500 J/kg should develop by mid-afternoon. Guidance consensus suggests scattered thunderstorms should form along the MN portion of the cold front towards mid to late afternoon amid an upper-level difluent flow regime. More isolated activity may occur southward into the Mid to Lower MO Valley. A vertically veering wind profile with height should support supercells with a primary initial risk of large hail. With relatively modest upper-level winds and the expected coverage of storms along the front, upscale growth into linear clusters will be possible with a corresponding increase in damaging winds. A couple tornadoes may occur given adequate low-level hodograph curvature and the moist boundary layer. The overall severe threat may diminish relatively rapidly after sunset. With neutral mid-level height change as the MB cyclone pulls away, in conjunction with progged weakening of 700-mb wind fields after 00Z, convective intensity should wane. This will likely be further aided by the confined buoyancy plume and drier airmass east. ..Grams.. 09/17/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 AM CDT Tue Sep 17 2024 Valid 191200Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN A PART OF THE UPPER MIDWEST... ...SUMMARY... Scattered severe thunderstorms are possible from mid-afternoon to early evening on Thursday across central to eastern Minnesota and north-central Iowa. ...Upper Midwest... A vertically stacked cyclone near the ND/SK/MB border should move northeast over MB through the period. Predictability has increased with the placement of the trailing cold front arcing south on Thursday afternoon. In the mid-levels, modestly steepened lapse rates should overspread this boundary within a belt of moderately enhanced west-southwesterly flow. Given a confined plume of rich boundary-layer moisture, a corridor of MLCAPE from 1500-2500 J/kg should develop by mid-afternoon. Guidance consensus suggests scattered thunderstorms should form along the MN portion of the cold front towards mid to late afternoon amid an upper-level difluent flow regime. More isolated activity may occur southward into the Mid to Lower MO Valley. A vertically veering wind profile with height should support supercells with a primary initial risk of large hail. With relatively modest upper-level winds and the expected coverage of storms along the front, upscale growth into linear clusters will be possible with a corresponding increase in damaging winds. A couple tornadoes may occur given adequate low-level hodograph curvature and the moist boundary layer. The overall severe threat may diminish relatively rapidly after sunset. With neutral mid-level height change as the MB cyclone pulls away, in conjunction with progged weakening of 700-mb wind fields after 00Z, convective intensity should wane. This will likely be further aided by the confined buoyancy plume and drier airmass east. ..Grams.. 09/17/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 AM CDT Tue Sep 17 2024 Valid 191200Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN A PART OF THE UPPER MIDWEST... ...SUMMARY... Scattered severe thunderstorms are possible from mid-afternoon to early evening on Thursday across central to eastern Minnesota and north-central Iowa. ...Upper Midwest... A vertically stacked cyclone near the ND/SK/MB border should move northeast over MB through the period. Predictability has increased with the placement of the trailing cold front arcing south on Thursday afternoon. In the mid-levels, modestly steepened lapse rates should overspread this boundary within a belt of moderately enhanced west-southwesterly flow. Given a confined plume of rich boundary-layer moisture, a corridor of MLCAPE from 1500-2500 J/kg should develop by mid-afternoon. Guidance consensus suggests scattered thunderstorms should form along the MN portion of the cold front towards mid to late afternoon amid an upper-level difluent flow regime. More isolated activity may occur southward into the Mid to Lower MO Valley. A vertically veering wind profile with height should support supercells with a primary initial risk of large hail. With relatively modest upper-level winds and the expected coverage of storms along the front, upscale growth into linear clusters will be possible with a corresponding increase in damaging winds. A couple tornadoes may occur given adequate low-level hodograph curvature and the moist boundary layer. The overall severe threat may diminish relatively rapidly after sunset. With neutral mid-level height change as the MB cyclone pulls away, in conjunction with progged weakening of 700-mb wind fields after 00Z, convective intensity should wane. This will likely be further aided by the confined buoyancy plume and drier airmass east. ..Grams.. 09/17/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 AM CDT Tue Sep 17 2024 Valid 191200Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN A PART OF THE UPPER MIDWEST... ...SUMMARY... Scattered severe thunderstorms are possible from mid-afternoon to early evening on Thursday across central to eastern Minnesota and north-central Iowa. ...Upper Midwest... A vertically stacked cyclone near the ND/SK/MB border should move northeast over MB through the period. Predictability has increased with the placement of the trailing cold front arcing south on Thursday afternoon. In the mid-levels, modestly steepened lapse rates should overspread this boundary within a belt of moderately enhanced west-southwesterly flow. Given a confined plume of rich boundary-layer moisture, a corridor of MLCAPE from 1500-2500 J/kg should develop by mid-afternoon. Guidance consensus suggests scattered thunderstorms should form along the MN portion of the cold front towards mid to late afternoon amid an upper-level difluent flow regime. More isolated activity may occur southward into the Mid to Lower MO Valley. A vertically veering wind profile with height should support supercells with a primary initial risk of large hail. With relatively modest upper-level winds and the expected coverage of storms along the front, upscale growth into linear clusters will be possible with a corresponding increase in damaging winds. A couple tornadoes may occur given adequate low-level hodograph curvature and the moist boundary layer. The overall severe threat may diminish relatively rapidly after sunset. With neutral mid-level height change as the MB cyclone pulls away, in conjunction with progged weakening of 700-mb wind fields after 00Z, convective intensity should wane. This will likely be further aided by the confined buoyancy plume and drier airmass east. ..Grams.. 09/17/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 AM CDT Tue Sep 17 2024 Valid 191200Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN A PART OF THE UPPER MIDWEST... ...SUMMARY... Scattered severe thunderstorms are possible from mid-afternoon to early evening on Thursday across central to eastern Minnesota and north-central Iowa. ...Upper Midwest... A vertically stacked cyclone near the ND/SK/MB border should move northeast over MB through the period. Predictability has increased with the placement of the trailing cold front arcing south on Thursday afternoon. In the mid-levels, modestly steepened lapse rates should overspread this boundary within a belt of moderately enhanced west-southwesterly flow. Given a confined plume of rich boundary-layer moisture, a corridor of MLCAPE from 1500-2500 J/kg should develop by mid-afternoon. Guidance consensus suggests scattered thunderstorms should form along the MN portion of the cold front towards mid to late afternoon amid an upper-level difluent flow regime. More isolated activity may occur southward into the Mid to Lower MO Valley. A vertically veering wind profile with height should support supercells with a primary initial risk of large hail. With relatively modest upper-level winds and the expected coverage of storms along the front, upscale growth into linear clusters will be possible with a corresponding increase in damaging winds. A couple tornadoes may occur given adequate low-level hodograph curvature and the moist boundary layer. The overall severe threat may diminish relatively rapidly after sunset. With neutral mid-level height change as the MB cyclone pulls away, in conjunction with progged weakening of 700-mb wind fields after 00Z, convective intensity should wane. This will likely be further aided by the confined buoyancy plume and drier airmass east. ..Grams.. 09/17/2024 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0156 AM CDT Tue Sep 17 2024 Valid 181200Z - 191200Z ...NO CRITICAL AREAS... ...Synopsis... Strong deep-layer southwesterly flow will overspread the Dakotas, within the base of a negatively tilted midlevel trough/low moving northeastward across the northern High Plains. A tight pressure gradient peripheral to a related surface cyclone over eastern MT will promote strong post-frontal surface winds across western SD. While these winds and around 20 percent RH would typically warrant fire-weather highlights, substantial precipitation over the past week, and additional expected rainfall on Day 1/Tuesday, limit confidence in fuel receptiveness. ..Weinman.. 09/17/2024 ...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 0156 AM CDT Tue Sep 17 2024 Valid 181200Z - 191200Z ...NO CRITICAL AREAS... ...Synopsis... Strong deep-layer southwesterly flow will overspread the Dakotas, within the base of a negatively tilted midlevel trough/low moving northeastward across the northern High Plains. A tight pressure gradient peripheral to a related surface cyclone over eastern MT will promote strong post-frontal surface winds across western SD. While these winds and around 20 percent RH would typically warrant fire-weather highlights, substantial precipitation over the past week, and additional expected rainfall on Day 1/Tuesday, limit confidence in fuel receptiveness. ..Weinman.. 09/17/2024 ...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 0156 AM CDT Tue Sep 17 2024 Valid 181200Z - 191200Z ...NO CRITICAL AREAS... ...Synopsis... Strong deep-layer southwesterly flow will overspread the Dakotas, within the base of a negatively tilted midlevel trough/low moving northeastward across the northern High Plains. A tight pressure gradient peripheral to a related surface cyclone over eastern MT will promote strong post-frontal surface winds across western SD. While these winds and around 20 percent RH would typically warrant fire-weather highlights, substantial precipitation over the past week, and additional expected rainfall on Day 1/Tuesday, limit confidence in fuel receptiveness. ..Weinman.. 09/17/2024 ...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 0156 AM CDT Tue Sep 17 2024 Valid 171200Z - 181200Z ...Synopsis... A large-scale trough, accompanied by strong deep-layer south-southwesterly flow, will overspread the northern/central Rockies and adjacent High Plains. A related lee cyclone will deepen near western SD, promoting a tight pressure gradient and 20-25 mph sustained southerly surface winds (with higher gusts) over portions of western NE during the afternoon. Here, diurnal heating along the western edge of the richer boundary-layer moisture plume should yield 20-30 percent RH. Despite these marginal RH reductions, the strong/gusty winds will still favor a few hours of elevated fire-weather conditions, before a cold front and related precipitation overspread the area during the evening. ..Weinman.. 09/17/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more