Severe Storms

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0248 PM CDT Sun Sep 15 2024 Valid 152000Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN/CENTRAL PLAINS... ...SUMMARY... Thunderstorms capable of producing isolated severe gusts and hail may occur today and tonight across parts of the northern/central Plains. ...20z Update... Only minor adjustments were made to the D1 Convective Outlook to account for latest observational trends. See previous discussion below for more information. ..Thornton/Gleason.. 09/15/2024 .PREV DISCUSSION... /ISSUED 1128 AM CDT Sun Sep 15 2024/ ...Northern/Central Plains... An amplified upper trough along/near the West Coast this morning will further evolve into a closed upper low over northern CA and vicinity by late tonight. Ahead of this feature, modestly enhanced south-southwesterly mid-level flow will be in place over much of the western states and Rockies through the period. Although low-level moisture is expected to remain limited over much of this region, isolated strong to severe gusts may occur with any thunderstorms that can develop in a deeply mixed boundary layer favorable for gusty downdraft winds. Latest guidance continues to suggest that a relatively greater concentration of severe potential will be focused across parts of the northern/central Plains late this afternoon through tonight. Across this area, a weak surface lee trough and greater low-level moisture to its east should support weak to moderate instability with daytime heating. Steep mid-level lapse rates should also aid updraft accelerations/intensities, with around 20-30 kt of deep-layer shear supporting modest thunderstorm organization. Isolated severe hail may occur with initially more discrete convection, but a tendency for clustering should lead to a relatively greater wind threat with time as convection spreads generally east-northeastward through the evening. Regardless, the overall severe threat from northeast CO into western NE/SD and vicinity should remain fairly isolated/marginal given the modest deep-layer shear. Low-level warm advection is forecast to increase across much of the northern/central Plains tonight as a southerly low-level jet strengthens. A surface warm front is also expected to lift northward over ND late tonight into early Monday morning. With steepening mid-level lapse rates overspreading the northern Plains in tandem with increasing low-level moisture, ample MUCAPE should be available. Most guidance shows at least isolated convection developing across parts of ND tonight in this favorable thermodynamic environment. Although deep-layer shear may remain fairly modest, it may still be sufficient for updraft organization and an isolated threat for severe hail with any elevated convection that can form. Have therefore expanded the Marginal Risk northward to account for this potential. ...Coastal Carolinas... Latest NHC forecast continues to indicate some potential for sub-tropical or tropical development of a surface low currently off the SC Coast. Regardless of development, it still appears that the more moist/tropical low-level airmass over the Gulf Stream will struggle to advance inland over coastal portions of NC/SC through the end of the Day 1 forecast period early Monday morning (16/12Z). Accordingly, tornado potential with any low-topped supercells on the north to northeast periphery of the surface low should tend to remain offshore until Day 2/Monday (after 16/12Z). Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0248 PM CDT Sun Sep 15 2024 Valid 152000Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN/CENTRAL PLAINS... ...SUMMARY... Thunderstorms capable of producing isolated severe gusts and hail may occur today and tonight across parts of the northern/central Plains. ...20z Update... Only minor adjustments were made to the D1 Convective Outlook to account for latest observational trends. See previous discussion below for more information. ..Thornton/Gleason.. 09/15/2024 .PREV DISCUSSION... /ISSUED 1128 AM CDT Sun Sep 15 2024/ ...Northern/Central Plains... An amplified upper trough along/near the West Coast this morning will further evolve into a closed upper low over northern CA and vicinity by late tonight. Ahead of this feature, modestly enhanced south-southwesterly mid-level flow will be in place over much of the western states and Rockies through the period. Although low-level moisture is expected to remain limited over much of this region, isolated strong to severe gusts may occur with any thunderstorms that can develop in a deeply mixed boundary layer favorable for gusty downdraft winds. Latest guidance continues to suggest that a relatively greater concentration of severe potential will be focused across parts of the northern/central Plains late this afternoon through tonight. Across this area, a weak surface lee trough and greater low-level moisture to its east should support weak to moderate instability with daytime heating. Steep mid-level lapse rates should also aid updraft accelerations/intensities, with around 20-30 kt of deep-layer shear supporting modest thunderstorm organization. Isolated severe hail may occur with initially more discrete convection, but a tendency for clustering should lead to a relatively greater wind threat with time as convection spreads generally east-northeastward through the evening. Regardless, the overall severe threat from northeast CO into western NE/SD and vicinity should remain fairly isolated/marginal given the modest deep-layer shear. Low-level warm advection is forecast to increase across much of the northern/central Plains tonight as a southerly low-level jet strengthens. A surface warm front is also expected to lift northward over ND late tonight into early Monday morning. With steepening mid-level lapse rates overspreading the northern Plains in tandem with increasing low-level moisture, ample MUCAPE should be available. Most guidance shows at least isolated convection developing across parts of ND tonight in this favorable thermodynamic environment. Although deep-layer shear may remain fairly modest, it may still be sufficient for updraft organization and an isolated threat for severe hail with any elevated convection that can form. Have therefore expanded the Marginal Risk northward to account for this potential. ...Coastal Carolinas... Latest NHC forecast continues to indicate some potential for sub-tropical or tropical development of a surface low currently off the SC Coast. Regardless of development, it still appears that the more moist/tropical low-level airmass over the Gulf Stream will struggle to advance inland over coastal portions of NC/SC through the end of the Day 1 forecast period early Monday morning (16/12Z). Accordingly, tornado potential with any low-topped supercells on the north to northeast periphery of the surface low should tend to remain offshore until Day 2/Monday (after 16/12Z). Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0248 PM CDT Sun Sep 15 2024 Valid 152000Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN/CENTRAL PLAINS... ...SUMMARY... Thunderstorms capable of producing isolated severe gusts and hail may occur today and tonight across parts of the northern/central Plains. ...20z Update... Only minor adjustments were made to the D1 Convective Outlook to account for latest observational trends. See previous discussion below for more information. ..Thornton/Gleason.. 09/15/2024 .PREV DISCUSSION... /ISSUED 1128 AM CDT Sun Sep 15 2024/ ...Northern/Central Plains... An amplified upper trough along/near the West Coast this morning will further evolve into a closed upper low over northern CA and vicinity by late tonight. Ahead of this feature, modestly enhanced south-southwesterly mid-level flow will be in place over much of the western states and Rockies through the period. Although low-level moisture is expected to remain limited over much of this region, isolated strong to severe gusts may occur with any thunderstorms that can develop in a deeply mixed boundary layer favorable for gusty downdraft winds. Latest guidance continues to suggest that a relatively greater concentration of severe potential will be focused across parts of the northern/central Plains late this afternoon through tonight. Across this area, a weak surface lee trough and greater low-level moisture to its east should support weak to moderate instability with daytime heating. Steep mid-level lapse rates should also aid updraft accelerations/intensities, with around 20-30 kt of deep-layer shear supporting modest thunderstorm organization. Isolated severe hail may occur with initially more discrete convection, but a tendency for clustering should lead to a relatively greater wind threat with time as convection spreads generally east-northeastward through the evening. Regardless, the overall severe threat from northeast CO into western NE/SD and vicinity should remain fairly isolated/marginal given the modest deep-layer shear. Low-level warm advection is forecast to increase across much of the northern/central Plains tonight as a southerly low-level jet strengthens. A surface warm front is also expected to lift northward over ND late tonight into early Monday morning. With steepening mid-level lapse rates overspreading the northern Plains in tandem with increasing low-level moisture, ample MUCAPE should be available. Most guidance shows at least isolated convection developing across parts of ND tonight in this favorable thermodynamic environment. Although deep-layer shear may remain fairly modest, it may still be sufficient for updraft organization and an isolated threat for severe hail with any elevated convection that can form. Have therefore expanded the Marginal Risk northward to account for this potential. ...Coastal Carolinas... Latest NHC forecast continues to indicate some potential for sub-tropical or tropical development of a surface low currently off the SC Coast. Regardless of development, it still appears that the more moist/tropical low-level airmass over the Gulf Stream will struggle to advance inland over coastal portions of NC/SC through the end of the Day 1 forecast period early Monday morning (16/12Z). Accordingly, tornado potential with any low-topped supercells on the north to northeast periphery of the surface low should tend to remain offshore until Day 2/Monday (after 16/12Z). Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0248 PM CDT Sun Sep 15 2024 Valid 152000Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN/CENTRAL PLAINS... ...SUMMARY... Thunderstorms capable of producing isolated severe gusts and hail may occur today and tonight across parts of the northern/central Plains. ...20z Update... Only minor adjustments were made to the D1 Convective Outlook to account for latest observational trends. See previous discussion below for more information. ..Thornton/Gleason.. 09/15/2024 .PREV DISCUSSION... /ISSUED 1128 AM CDT Sun Sep 15 2024/ ...Northern/Central Plains... An amplified upper trough along/near the West Coast this morning will further evolve into a closed upper low over northern CA and vicinity by late tonight. Ahead of this feature, modestly enhanced south-southwesterly mid-level flow will be in place over much of the western states and Rockies through the period. Although low-level moisture is expected to remain limited over much of this region, isolated strong to severe gusts may occur with any thunderstorms that can develop in a deeply mixed boundary layer favorable for gusty downdraft winds. Latest guidance continues to suggest that a relatively greater concentration of severe potential will be focused across parts of the northern/central Plains late this afternoon through tonight. Across this area, a weak surface lee trough and greater low-level moisture to its east should support weak to moderate instability with daytime heating. Steep mid-level lapse rates should also aid updraft accelerations/intensities, with around 20-30 kt of deep-layer shear supporting modest thunderstorm organization. Isolated severe hail may occur with initially more discrete convection, but a tendency for clustering should lead to a relatively greater wind threat with time as convection spreads generally east-northeastward through the evening. Regardless, the overall severe threat from northeast CO into western NE/SD and vicinity should remain fairly isolated/marginal given the modest deep-layer shear. Low-level warm advection is forecast to increase across much of the northern/central Plains tonight as a southerly low-level jet strengthens. A surface warm front is also expected to lift northward over ND late tonight into early Monday morning. With steepening mid-level lapse rates overspreading the northern Plains in tandem with increasing low-level moisture, ample MUCAPE should be available. Most guidance shows at least isolated convection developing across parts of ND tonight in this favorable thermodynamic environment. Although deep-layer shear may remain fairly modest, it may still be sufficient for updraft organization and an isolated threat for severe hail with any elevated convection that can form. Have therefore expanded the Marginal Risk northward to account for this potential. ...Coastal Carolinas... Latest NHC forecast continues to indicate some potential for sub-tropical or tropical development of a surface low currently off the SC Coast. Regardless of development, it still appears that the more moist/tropical low-level airmass over the Gulf Stream will struggle to advance inland over coastal portions of NC/SC through the end of the Day 1 forecast period early Monday morning (16/12Z). Accordingly, tornado potential with any low-topped supercells on the north to northeast periphery of the surface low should tend to remain offshore until Day 2/Monday (after 16/12Z). Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0229 PM CDT Sun Sep 15 2024 Valid 171200Z - 231200Z A broad mid-level trough will progress across the Interior West toward the Rockies this week, with multiple mid-level impulses likely to eject into the Northern Plains as the broader mid-level trough gradually de-amplifies. Spotty rainfall should dampen fuels for several areas west of the Rockies through the week. Potentially Elevated-equivalent fire weather conditions may develop over portions of the High Plains on Day 3/Tuesday and especially Day 4/Wednesday. However, scattered to potentially widespread showers and thunderstorms (with the first in a series of mid-level impulses) may dampen fuels in several locales Tuesday into Tuesday night. As such, no Critical probabilities were introduced this outlook. ..Squitieri.. 09/15/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0229 PM CDT Sun Sep 15 2024 Valid 171200Z - 231200Z A broad mid-level trough will progress across the Interior West toward the Rockies this week, with multiple mid-level impulses likely to eject into the Northern Plains as the broader mid-level trough gradually de-amplifies. Spotty rainfall should dampen fuels for several areas west of the Rockies through the week. Potentially Elevated-equivalent fire weather conditions may develop over portions of the High Plains on Day 3/Tuesday and especially Day 4/Wednesday. However, scattered to potentially widespread showers and thunderstorms (with the first in a series of mid-level impulses) may dampen fuels in several locales Tuesday into Tuesday night. As such, no Critical probabilities were introduced this outlook. ..Squitieri.. 09/15/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0229 PM CDT Sun Sep 15 2024 Valid 171200Z - 231200Z A broad mid-level trough will progress across the Interior West toward the Rockies this week, with multiple mid-level impulses likely to eject into the Northern Plains as the broader mid-level trough gradually de-amplifies. Spotty rainfall should dampen fuels for several areas west of the Rockies through the week. Potentially Elevated-equivalent fire weather conditions may develop over portions of the High Plains on Day 3/Tuesday and especially Day 4/Wednesday. However, scattered to potentially widespread showers and thunderstorms (with the first in a series of mid-level impulses) may dampen fuels in several locales Tuesday into Tuesday night. As such, no Critical probabilities were introduced this outlook. ..Squitieri.. 09/15/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0229 PM CDT Sun Sep 15 2024 Valid 171200Z - 231200Z A broad mid-level trough will progress across the Interior West toward the Rockies this week, with multiple mid-level impulses likely to eject into the Northern Plains as the broader mid-level trough gradually de-amplifies. Spotty rainfall should dampen fuels for several areas west of the Rockies through the week. Potentially Elevated-equivalent fire weather conditions may develop over portions of the High Plains on Day 3/Tuesday and especially Day 4/Wednesday. However, scattered to potentially widespread showers and thunderstorms (with the first in a series of mid-level impulses) may dampen fuels in several locales Tuesday into Tuesday night. As such, no Critical probabilities were introduced this outlook. ..Squitieri.. 09/15/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0229 PM CDT Sun Sep 15 2024 Valid 171200Z - 231200Z A broad mid-level trough will progress across the Interior West toward the Rockies this week, with multiple mid-level impulses likely to eject into the Northern Plains as the broader mid-level trough gradually de-amplifies. Spotty rainfall should dampen fuels for several areas west of the Rockies through the week. Potentially Elevated-equivalent fire weather conditions may develop over portions of the High Plains on Day 3/Tuesday and especially Day 4/Wednesday. However, scattered to potentially widespread showers and thunderstorms (with the first in a series of mid-level impulses) may dampen fuels in several locales Tuesday into Tuesday night. As such, no Critical probabilities were introduced this outlook. ..Squitieri.. 09/15/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0229 PM CDT Sun Sep 15 2024 Valid 171200Z - 231200Z A broad mid-level trough will progress across the Interior West toward the Rockies this week, with multiple mid-level impulses likely to eject into the Northern Plains as the broader mid-level trough gradually de-amplifies. Spotty rainfall should dampen fuels for several areas west of the Rockies through the week. Potentially Elevated-equivalent fire weather conditions may develop over portions of the High Plains on Day 3/Tuesday and especially Day 4/Wednesday. However, scattered to potentially widespread showers and thunderstorms (with the first in a series of mid-level impulses) may dampen fuels in several locales Tuesday into Tuesday night. As such, no Critical probabilities were introduced this outlook. ..Squitieri.. 09/15/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0229 PM CDT Sun Sep 15 2024 Valid 171200Z - 231200Z A broad mid-level trough will progress across the Interior West toward the Rockies this week, with multiple mid-level impulses likely to eject into the Northern Plains as the broader mid-level trough gradually de-amplifies. Spotty rainfall should dampen fuels for several areas west of the Rockies through the week. Potentially Elevated-equivalent fire weather conditions may develop over portions of the High Plains on Day 3/Tuesday and especially Day 4/Wednesday. However, scattered to potentially widespread showers and thunderstorms (with the first in a series of mid-level impulses) may dampen fuels in several locales Tuesday into Tuesday night. As such, no Critical probabilities were introduced this outlook. ..Squitieri.. 09/15/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0229 PM CDT Sun Sep 15 2024 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR THE HIGH PLAINS... ...SUMMARY... Strong to locally severe thunderstorms will be possible Tuesday across a large swath of the High Plains region, mainly from late afternoon into the evening. Severe gusts should be the primary hazard, though some hail may also be possible. ...High Plains... A mid/upper-level shortwave trough initially over the eastern Great Basin should take on a negative tilt as it advances towards the northern High Plains. Deep lee cyclogenesis is expected over northeast WY/southeast MT, with a warm front extending east-northeast of the low somewhere from eastern MT into the Dakotas during the afternoon and evening. 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. However, weak buoyancy and modest mid-level lapse rates will characterize much of the environment to the south of the surface low and warm front. Aided by the subtropical moisture plume over the Southwest, morning convection near the Four Corners region may move across the higher terrain toward the High Plains, with additional terrain-driven development possible during the afternoon. High-based storms will 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 areas north of the warm front) yields substantial uncertainty regarding the degree of storm organization into the lower elevations. But with scattered to widespread convection and increasingly extensive outflow expected with time, sporadic severe gusts may occur during the afternoon and evening. Somewhat more favorable low-level moisture and buoyancy may reside near/north of the warm front, from eastern MT into the western Dakotas. While stronger ascent and deep-layer flow may not impinge upon areas north of the front later in the forecast period, there will be some potential for organized convection to develop during the evening as the shortwave trough ejects northeastward. A couple of supercells and/or stronger clusters will be possible within this regime, with a threat of hail and isolated severe gusts. ...Four Corners region... Despite the unfavorable time of day, a few strong storms cannot be ruled out Tuesday morning across the Four Corners region into western CO/NM, in close proximity to the ejecting shortwave trough. Wind profiles will be quite favorable for organized convection, though it remains uncertain if sufficient buoyancy will be present to support any severe threat during the early part of the day. ...Eastern NC/VA... With uncertainty already relatively high regarding evolution of the currently developing offshore low into D2/Monday, confidence remains too low to delineate severe probabilities for D3/Tuesday. Slower and more aggressive ensemble members continue to suggest an adequate SRH/buoyancy combination for low-topped supercells may linger over eastern NC early in the period and shift into parts of eastern VA. However, the bulk of guidance still indicates a general weakening of the low-level wind field during the day. ..Dean.. 09/15/2024 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0229 PM CDT Sun Sep 15 2024 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR THE HIGH PLAINS... ...SUMMARY... Strong to locally severe thunderstorms will be possible Tuesday across a large swath of the High Plains region, mainly from late afternoon into the evening. Severe gusts should be the primary hazard, though some hail may also be possible. ...High Plains... A mid/upper-level shortwave trough initially over the eastern Great Basin should take on a negative tilt as it advances towards the northern High Plains. Deep lee cyclogenesis is expected over northeast WY/southeast MT, with a warm front extending east-northeast of the low somewhere from eastern MT into the Dakotas during the afternoon and evening. 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. However, weak buoyancy and modest mid-level lapse rates will characterize much of the environment to the south of the surface low and warm front. Aided by the subtropical moisture plume over the Southwest, morning convection near the Four Corners region may move across the higher terrain toward the High Plains, with additional terrain-driven development possible during the afternoon. High-based storms will 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 areas north of the warm front) yields substantial uncertainty regarding the degree of storm organization into the lower elevations. But with scattered to widespread convection and increasingly extensive outflow expected with time, sporadic severe gusts may occur during the afternoon and evening. Somewhat more favorable low-level moisture and buoyancy may reside near/north of the warm front, from eastern MT into the western Dakotas. While stronger ascent and deep-layer flow may not impinge upon areas north of the front later in the forecast period, there will be some potential for organized convection to develop during the evening as the shortwave trough ejects northeastward. A couple of supercells and/or stronger clusters will be possible within this regime, with a threat of hail and isolated severe gusts. ...Four Corners region... Despite the unfavorable time of day, a few strong storms cannot be ruled out Tuesday morning across the Four Corners region into western CO/NM, in close proximity to the ejecting shortwave trough. Wind profiles will be quite favorable for organized convection, though it remains uncertain if sufficient buoyancy will be present to support any severe threat during the early part of the day. ...Eastern NC/VA... With uncertainty already relatively high regarding evolution of the currently developing offshore low into D2/Monday, confidence remains too low to delineate severe probabilities for D3/Tuesday. Slower and more aggressive ensemble members continue to suggest an adequate SRH/buoyancy combination for low-topped supercells may linger over eastern NC early in the period and shift into parts of eastern VA. However, the bulk of guidance still indicates a general weakening of the low-level wind field during the day. ..Dean.. 09/15/2024 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0229 PM CDT Sun Sep 15 2024 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR THE HIGH PLAINS... ...SUMMARY... Strong to locally severe thunderstorms will be possible Tuesday across a large swath of the High Plains region, mainly from late afternoon into the evening. Severe gusts should be the primary hazard, though some hail may also be possible. ...High Plains... A mid/upper-level shortwave trough initially over the eastern Great Basin should take on a negative tilt as it advances towards the northern High Plains. Deep lee cyclogenesis is expected over northeast WY/southeast MT, with a warm front extending east-northeast of the low somewhere from eastern MT into the Dakotas during the afternoon and evening. 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. However, weak buoyancy and modest mid-level lapse rates will characterize much of the environment to the south of the surface low and warm front. Aided by the subtropical moisture plume over the Southwest, morning convection near the Four Corners region may move across the higher terrain toward the High Plains, with additional terrain-driven development possible during the afternoon. High-based storms will 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 areas north of the warm front) yields substantial uncertainty regarding the degree of storm organization into the lower elevations. But with scattered to widespread convection and increasingly extensive outflow expected with time, sporadic severe gusts may occur during the afternoon and evening. Somewhat more favorable low-level moisture and buoyancy may reside near/north of the warm front, from eastern MT into the western Dakotas. While stronger ascent and deep-layer flow may not impinge upon areas north of the front later in the forecast period, there will be some potential for organized convection to develop during the evening as the shortwave trough ejects northeastward. A couple of supercells and/or stronger clusters will be possible within this regime, with a threat of hail and isolated severe gusts. ...Four Corners region... Despite the unfavorable time of day, a few strong storms cannot be ruled out Tuesday morning across the Four Corners region into western CO/NM, in close proximity to the ejecting shortwave trough. Wind profiles will be quite favorable for organized convection, though it remains uncertain if sufficient buoyancy will be present to support any severe threat during the early part of the day. ...Eastern NC/VA... With uncertainty already relatively high regarding evolution of the currently developing offshore low into D2/Monday, confidence remains too low to delineate severe probabilities for D3/Tuesday. Slower and more aggressive ensemble members continue to suggest an adequate SRH/buoyancy combination for low-topped supercells may linger over eastern NC early in the period and shift into parts of eastern VA. However, the bulk of guidance still indicates a general weakening of the low-level wind field during the day. ..Dean.. 09/15/2024 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0229 PM CDT Sun Sep 15 2024 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR THE HIGH PLAINS... ...SUMMARY... Strong to locally severe thunderstorms will be possible Tuesday across a large swath of the High Plains region, mainly from late afternoon into the evening. Severe gusts should be the primary hazard, though some hail may also be possible. ...High Plains... A mid/upper-level shortwave trough initially over the eastern Great Basin should take on a negative tilt as it advances towards the northern High Plains. Deep lee cyclogenesis is expected over northeast WY/southeast MT, with a warm front extending east-northeast of the low somewhere from eastern MT into the Dakotas during the afternoon and evening. 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. However, weak buoyancy and modest mid-level lapse rates will characterize much of the environment to the south of the surface low and warm front. Aided by the subtropical moisture plume over the Southwest, morning convection near the Four Corners region may move across the higher terrain toward the High Plains, with additional terrain-driven development possible during the afternoon. High-based storms will 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 areas north of the warm front) yields substantial uncertainty regarding the degree of storm organization into the lower elevations. But with scattered to widespread convection and increasingly extensive outflow expected with time, sporadic severe gusts may occur during the afternoon and evening. Somewhat more favorable low-level moisture and buoyancy may reside near/north of the warm front, from eastern MT into the western Dakotas. While stronger ascent and deep-layer flow may not impinge upon areas north of the front later in the forecast period, there will be some potential for organized convection to develop during the evening as the shortwave trough ejects northeastward. A couple of supercells and/or stronger clusters will be possible within this regime, with a threat of hail and isolated severe gusts. ...Four Corners region... Despite the unfavorable time of day, a few strong storms cannot be ruled out Tuesday morning across the Four Corners region into western CO/NM, in close proximity to the ejecting shortwave trough. Wind profiles will be quite favorable for organized convection, though it remains uncertain if sufficient buoyancy will be present to support any severe threat during the early part of the day. ...Eastern NC/VA... With uncertainty already relatively high regarding evolution of the currently developing offshore low into D2/Monday, confidence remains too low to delineate severe probabilities for D3/Tuesday. Slower and more aggressive ensemble members continue to suggest an adequate SRH/buoyancy combination for low-topped supercells may linger over eastern NC early in the period and shift into parts of eastern VA. However, the bulk of guidance still indicates a general weakening of the low-level wind field during the day. ..Dean.. 09/15/2024 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0229 PM CDT Sun Sep 15 2024 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR THE HIGH PLAINS... ...SUMMARY... Strong to locally severe thunderstorms will be possible Tuesday across a large swath of the High Plains region, mainly from late afternoon into the evening. Severe gusts should be the primary hazard, though some hail may also be possible. ...High Plains... A mid/upper-level shortwave trough initially over the eastern Great Basin should take on a negative tilt as it advances towards the northern High Plains. Deep lee cyclogenesis is expected over northeast WY/southeast MT, with a warm front extending east-northeast of the low somewhere from eastern MT into the Dakotas during the afternoon and evening. 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. However, weak buoyancy and modest mid-level lapse rates will characterize much of the environment to the south of the surface low and warm front. Aided by the subtropical moisture plume over the Southwest, morning convection near the Four Corners region may move across the higher terrain toward the High Plains, with additional terrain-driven development possible during the afternoon. High-based storms will 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 areas north of the warm front) yields substantial uncertainty regarding the degree of storm organization into the lower elevations. But with scattered to widespread convection and increasingly extensive outflow expected with time, sporadic severe gusts may occur during the afternoon and evening. Somewhat more favorable low-level moisture and buoyancy may reside near/north of the warm front, from eastern MT into the western Dakotas. While stronger ascent and deep-layer flow may not impinge upon areas north of the front later in the forecast period, there will be some potential for organized convection to develop during the evening as the shortwave trough ejects northeastward. A couple of supercells and/or stronger clusters will be possible within this regime, with a threat of hail and isolated severe gusts. ...Four Corners region... Despite the unfavorable time of day, a few strong storms cannot be ruled out Tuesday morning across the Four Corners region into western CO/NM, in close proximity to the ejecting shortwave trough. Wind profiles will be quite favorable for organized convection, though it remains uncertain if sufficient buoyancy will be present to support any severe threat during the early part of the day. ...Eastern NC/VA... With uncertainty already relatively high regarding evolution of the currently developing offshore low into D2/Monday, confidence remains too low to delineate severe probabilities for D3/Tuesday. Slower and more aggressive ensemble members continue to suggest an adequate SRH/buoyancy combination for low-topped supercells may linger over eastern NC early in the period and shift into parts of eastern VA. However, the bulk of guidance still indicates a general weakening of the low-level wind field during the day. ..Dean.. 09/15/2024 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0229 PM CDT Sun Sep 15 2024 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR THE HIGH PLAINS... ...SUMMARY... Strong to locally severe thunderstorms will be possible Tuesday across a large swath of the High Plains region, mainly from late afternoon into the evening. Severe gusts should be the primary hazard, though some hail may also be possible. ...High Plains... A mid/upper-level shortwave trough initially over the eastern Great Basin should take on a negative tilt as it advances towards the northern High Plains. Deep lee cyclogenesis is expected over northeast WY/southeast MT, with a warm front extending east-northeast of the low somewhere from eastern MT into the Dakotas during the afternoon and evening. 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. However, weak buoyancy and modest mid-level lapse rates will characterize much of the environment to the south of the surface low and warm front. Aided by the subtropical moisture plume over the Southwest, morning convection near the Four Corners region may move across the higher terrain toward the High Plains, with additional terrain-driven development possible during the afternoon. High-based storms will 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 areas north of the warm front) yields substantial uncertainty regarding the degree of storm organization into the lower elevations. But with scattered to widespread convection and increasingly extensive outflow expected with time, sporadic severe gusts may occur during the afternoon and evening. Somewhat more favorable low-level moisture and buoyancy may reside near/north of the warm front, from eastern MT into the western Dakotas. While stronger ascent and deep-layer flow may not impinge upon areas north of the front later in the forecast period, there will be some potential for organized convection to develop during the evening as the shortwave trough ejects northeastward. A couple of supercells and/or stronger clusters will be possible within this regime, with a threat of hail and isolated severe gusts. ...Four Corners region... Despite the unfavorable time of day, a few strong storms cannot be ruled out Tuesday morning across the Four Corners region into western CO/NM, in close proximity to the ejecting shortwave trough. Wind profiles will be quite favorable for organized convection, though it remains uncertain if sufficient buoyancy will be present to support any severe threat during the early part of the day. ...Eastern NC/VA... With uncertainty already relatively high regarding evolution of the currently developing offshore low into D2/Monday, confidence remains too low to delineate severe probabilities for D3/Tuesday. Slower and more aggressive ensemble members continue to suggest an adequate SRH/buoyancy combination for low-topped supercells may linger over eastern NC early in the period and shift into parts of eastern VA. However, the bulk of guidance still indicates a general weakening of the low-level wind field during the day. ..Dean.. 09/15/2024 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0229 PM CDT Sun Sep 15 2024 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR THE HIGH PLAINS... ...SUMMARY... Strong to locally severe thunderstorms will be possible Tuesday across a large swath of the High Plains region, mainly from late afternoon into the evening. Severe gusts should be the primary hazard, though some hail may also be possible. ...High Plains... A mid/upper-level shortwave trough initially over the eastern Great Basin should take on a negative tilt as it advances towards the northern High Plains. Deep lee cyclogenesis is expected over northeast WY/southeast MT, with a warm front extending east-northeast of the low somewhere from eastern MT into the Dakotas during the afternoon and evening. 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. However, weak buoyancy and modest mid-level lapse rates will characterize much of the environment to the south of the surface low and warm front. Aided by the subtropical moisture plume over the Southwest, morning convection near the Four Corners region may move across the higher terrain toward the High Plains, with additional terrain-driven development possible during the afternoon. High-based storms will 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 areas north of the warm front) yields substantial uncertainty regarding the degree of storm organization into the lower elevations. But with scattered to widespread convection and increasingly extensive outflow expected with time, sporadic severe gusts may occur during the afternoon and evening. Somewhat more favorable low-level moisture and buoyancy may reside near/north of the warm front, from eastern MT into the western Dakotas. While stronger ascent and deep-layer flow may not impinge upon areas north of the front later in the forecast period, there will be some potential for organized convection to develop during the evening as the shortwave trough ejects northeastward. A couple of supercells and/or stronger clusters will be possible within this regime, with a threat of hail and isolated severe gusts. ...Four Corners region... Despite the unfavorable time of day, a few strong storms cannot be ruled out Tuesday morning across the Four Corners region into western CO/NM, in close proximity to the ejecting shortwave trough. Wind profiles will be quite favorable for organized convection, though it remains uncertain if sufficient buoyancy will be present to support any severe threat during the early part of the day. ...Eastern NC/VA... With uncertainty already relatively high regarding evolution of the currently developing offshore low into D2/Monday, confidence remains too low to delineate severe probabilities for D3/Tuesday. Slower and more aggressive ensemble members continue to suggest an adequate SRH/buoyancy combination for low-topped supercells may linger over eastern NC early in the period and shift into parts of eastern VA. However, the bulk of guidance still indicates a general weakening of the low-level wind field during the day. ..Dean.. 09/15/2024 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0204 PM CDT Sun Sep 15 2024 Valid 161200Z - 171200Z The primary changes to the Day 2 Fire Weather Outlook were to add Elevated highlights to portions of the central High Plains. Surface lee troughing ahead of an approaching broad mid-level trough will encourage 15-20 mph sustained southerly surface winds over the central High Plains (particularly along the KS/CO border), in tandem with 20-25 percent RH. These surface meteorological conditions will overspread modestly dry fuels, warranting Elevated highlights in this region. Surface high pressure over the Northeast will encourage dry easterly surface flow across portions of Ohio and immediate surrounding areas tomorrow, where fuels are anomalously dry and highly supportive of wildfire spread. RH may drop into the 20-25 percent range over these fuels by afternoon peak heating. However, surface sustained wind speeds should be generally under 15 mph, precluding the addition of Elevated highlights this outlook. Nonetheless, given such dry fuels (with a severe to locally extreme drought in place), gusty conditions may support localized brush-fire growth in this regime. ..Squitieri.. 09/15/2024 .PREV DISCUSSION... /ISSUED 0150 AM CDT Sun Sep 15 2024/ ...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. ...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 0204 PM CDT Sun Sep 15 2024 Valid 161200Z - 171200Z The primary changes to the Day 2 Fire Weather Outlook were to add Elevated highlights to portions of the central High Plains. Surface lee troughing ahead of an approaching broad mid-level trough will encourage 15-20 mph sustained southerly surface winds over the central High Plains (particularly along the KS/CO border), in tandem with 20-25 percent RH. These surface meteorological conditions will overspread modestly dry fuels, warranting Elevated highlights in this region. Surface high pressure over the Northeast will encourage dry easterly surface flow across portions of Ohio and immediate surrounding areas tomorrow, where fuels are anomalously dry and highly supportive of wildfire spread. RH may drop into the 20-25 percent range over these fuels by afternoon peak heating. However, surface sustained wind speeds should be generally under 15 mph, precluding the addition of Elevated highlights this outlook. Nonetheless, given such dry fuels (with a severe to locally extreme drought in place), gusty conditions may support localized brush-fire growth in this regime. ..Squitieri.. 09/15/2024 .PREV DISCUSSION... /ISSUED 0150 AM CDT Sun Sep 15 2024/ ...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. ...Please see www.spc.noaa.gov/fire for graphic product... Read more