Severe Storms

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1023 AM CDT Sun May 05 2024 Valid 051700Z - 061200Z ...CRITICAL FIRE WEATHER AREA FOR WESTERN TO NORTHERN NEW MEXICO... The previous forecast remains on track with only minor adjustments made based on recent surface observations and trends in high-res ensemble guidance. Conditions are currently rather benign across much of the risk area with sub-15 mph winds and RH above 30% due to lingering cloud cover. However, a dry air mass over central/southern AZ will spread northeast through the afternoon with increasing winds as surface pressure continues to fall across the central Rockies. The onset of elevated/critical fire weather conditions may be as early as 18 UTC along the AZ/NM border, with widespread elevated/critical conditions likely by 20 UTC. Regional VWPs are sampling 30-40 mph winds within the lowest 2 km, which should manifest at the surface as frequent wind gusts by late afternoon amid deep diurnal mixing. This appears most probable across southern NM where cloud cover should be minimal. ..Moore.. 05/05/2024 .PREV DISCUSSION... /ISSUED 0105 AM CDT Sun May 05 2024/ ...Synopsis... Critical fire-weather conditions are expected later today across portions of the Desert Southwest, particularly from central/western NM into extreme southeastern AZ. Sustained surface winds around 20-25 mph and relative humidities approaching the single digits are forecast across the region, collocated with fuels supporting fire spread. These conditions will be present throughout the afternoon and evening across the delineated Critical and Elevated areas. The meteorological setup will be strongly influenced by a potent upper-level trough moving eastward toward the Desert Southwest today. The associated surface cyclone -- expected to deepen in the northern Rockies -- will yield strong westerly surface flow across AZ/NM. Despite some possible upper-level cloud cover, deep boundary-layer mixing and drying are anticipated. Surface relative humidities around 10-15 percent, and perhaps in the single digits in some locations, are expected by mid-afternoon. These dry and windy conditions are anticipated across a region with fuels supporting large-fire spread (e.g., ERCs generally around 70 percent or greater, increasing with southward extent). These critical fire-weather conditions are anticipated from mid-afternoon until sunset, particularly from around Albuquerque south-southwest to the Chiricahua Mountains. ...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 1023 AM CDT Sun May 05 2024 Valid 051700Z - 061200Z ...CRITICAL FIRE WEATHER AREA FOR WESTERN TO NORTHERN NEW MEXICO... The previous forecast remains on track with only minor adjustments made based on recent surface observations and trends in high-res ensemble guidance. Conditions are currently rather benign across much of the risk area with sub-15 mph winds and RH above 30% due to lingering cloud cover. However, a dry air mass over central/southern AZ will spread northeast through the afternoon with increasing winds as surface pressure continues to fall across the central Rockies. The onset of elevated/critical fire weather conditions may be as early as 18 UTC along the AZ/NM border, with widespread elevated/critical conditions likely by 20 UTC. Regional VWPs are sampling 30-40 mph winds within the lowest 2 km, which should manifest at the surface as frequent wind gusts by late afternoon amid deep diurnal mixing. This appears most probable across southern NM where cloud cover should be minimal. ..Moore.. 05/05/2024 .PREV DISCUSSION... /ISSUED 0105 AM CDT Sun May 05 2024/ ...Synopsis... Critical fire-weather conditions are expected later today across portions of the Desert Southwest, particularly from central/western NM into extreme southeastern AZ. Sustained surface winds around 20-25 mph and relative humidities approaching the single digits are forecast across the region, collocated with fuels supporting fire spread. These conditions will be present throughout the afternoon and evening across the delineated Critical and Elevated areas. The meteorological setup will be strongly influenced by a potent upper-level trough moving eastward toward the Desert Southwest today. The associated surface cyclone -- expected to deepen in the northern Rockies -- will yield strong westerly surface flow across AZ/NM. Despite some possible upper-level cloud cover, deep boundary-layer mixing and drying are anticipated. Surface relative humidities around 10-15 percent, and perhaps in the single digits in some locations, are expected by mid-afternoon. These dry and windy conditions are anticipated across a region with fuels supporting large-fire spread (e.g., ERCs generally around 70 percent or greater, increasing with southward extent). These critical fire-weather conditions are anticipated from mid-afternoon until sunset, particularly from around Albuquerque south-southwest to the Chiricahua Mountains. ...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 1023 AM CDT Sun May 05 2024 Valid 051700Z - 061200Z ...CRITICAL FIRE WEATHER AREA FOR WESTERN TO NORTHERN NEW MEXICO... The previous forecast remains on track with only minor adjustments made based on recent surface observations and trends in high-res ensemble guidance. Conditions are currently rather benign across much of the risk area with sub-15 mph winds and RH above 30% due to lingering cloud cover. However, a dry air mass over central/southern AZ will spread northeast through the afternoon with increasing winds as surface pressure continues to fall across the central Rockies. The onset of elevated/critical fire weather conditions may be as early as 18 UTC along the AZ/NM border, with widespread elevated/critical conditions likely by 20 UTC. Regional VWPs are sampling 30-40 mph winds within the lowest 2 km, which should manifest at the surface as frequent wind gusts by late afternoon amid deep diurnal mixing. This appears most probable across southern NM where cloud cover should be minimal. ..Moore.. 05/05/2024 .PREV DISCUSSION... /ISSUED 0105 AM CDT Sun May 05 2024/ ...Synopsis... Critical fire-weather conditions are expected later today across portions of the Desert Southwest, particularly from central/western NM into extreme southeastern AZ. Sustained surface winds around 20-25 mph and relative humidities approaching the single digits are forecast across the region, collocated with fuels supporting fire spread. These conditions will be present throughout the afternoon and evening across the delineated Critical and Elevated areas. The meteorological setup will be strongly influenced by a potent upper-level trough moving eastward toward the Desert Southwest today. The associated surface cyclone -- expected to deepen in the northern Rockies -- will yield strong westerly surface flow across AZ/NM. Despite some possible upper-level cloud cover, deep boundary-layer mixing and drying are anticipated. Surface relative humidities around 10-15 percent, and perhaps in the single digits in some locations, are expected by mid-afternoon. These dry and windy conditions are anticipated across a region with fuels supporting large-fire spread (e.g., ERCs generally around 70 percent or greater, increasing with southward extent). These critical fire-weather conditions are anticipated from mid-afternoon until sunset, particularly from around Albuquerque south-southwest to the Chiricahua Mountains. ...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 1023 AM CDT Sun May 05 2024 Valid 051700Z - 061200Z ...CRITICAL FIRE WEATHER AREA FOR WESTERN TO NORTHERN NEW MEXICO... The previous forecast remains on track with only minor adjustments made based on recent surface observations and trends in high-res ensemble guidance. Conditions are currently rather benign across much of the risk area with sub-15 mph winds and RH above 30% due to lingering cloud cover. However, a dry air mass over central/southern AZ will spread northeast through the afternoon with increasing winds as surface pressure continues to fall across the central Rockies. The onset of elevated/critical fire weather conditions may be as early as 18 UTC along the AZ/NM border, with widespread elevated/critical conditions likely by 20 UTC. Regional VWPs are sampling 30-40 mph winds within the lowest 2 km, which should manifest at the surface as frequent wind gusts by late afternoon amid deep diurnal mixing. This appears most probable across southern NM where cloud cover should be minimal. ..Moore.. 05/05/2024 .PREV DISCUSSION... /ISSUED 0105 AM CDT Sun May 05 2024/ ...Synopsis... Critical fire-weather conditions are expected later today across portions of the Desert Southwest, particularly from central/western NM into extreme southeastern AZ. Sustained surface winds around 20-25 mph and relative humidities approaching the single digits are forecast across the region, collocated with fuels supporting fire spread. These conditions will be present throughout the afternoon and evening across the delineated Critical and Elevated areas. The meteorological setup will be strongly influenced by a potent upper-level trough moving eastward toward the Desert Southwest today. The associated surface cyclone -- expected to deepen in the northern Rockies -- will yield strong westerly surface flow across AZ/NM. Despite some possible upper-level cloud cover, deep boundary-layer mixing and drying are anticipated. Surface relative humidities around 10-15 percent, and perhaps in the single digits in some locations, are expected by mid-afternoon. These dry and windy conditions are anticipated across a region with fuels supporting large-fire spread (e.g., ERCs generally around 70 percent or greater, increasing with southward extent). These critical fire-weather conditions are anticipated from mid-afternoon until sunset, particularly from around Albuquerque south-southwest to the Chiricahua Mountains. ...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 1023 AM CDT Sun May 05 2024 Valid 051700Z - 061200Z ...CRITICAL FIRE WEATHER AREA FOR WESTERN TO NORTHERN NEW MEXICO... The previous forecast remains on track with only minor adjustments made based on recent surface observations and trends in high-res ensemble guidance. Conditions are currently rather benign across much of the risk area with sub-15 mph winds and RH above 30% due to lingering cloud cover. However, a dry air mass over central/southern AZ will spread northeast through the afternoon with increasing winds as surface pressure continues to fall across the central Rockies. The onset of elevated/critical fire weather conditions may be as early as 18 UTC along the AZ/NM border, with widespread elevated/critical conditions likely by 20 UTC. Regional VWPs are sampling 30-40 mph winds within the lowest 2 km, which should manifest at the surface as frequent wind gusts by late afternoon amid deep diurnal mixing. This appears most probable across southern NM where cloud cover should be minimal. ..Moore.. 05/05/2024 .PREV DISCUSSION... /ISSUED 0105 AM CDT Sun May 05 2024/ ...Synopsis... Critical fire-weather conditions are expected later today across portions of the Desert Southwest, particularly from central/western NM into extreme southeastern AZ. Sustained surface winds around 20-25 mph and relative humidities approaching the single digits are forecast across the region, collocated with fuels supporting fire spread. These conditions will be present throughout the afternoon and evening across the delineated Critical and Elevated areas. The meteorological setup will be strongly influenced by a potent upper-level trough moving eastward toward the Desert Southwest today. The associated surface cyclone -- expected to deepen in the northern Rockies -- will yield strong westerly surface flow across AZ/NM. Despite some possible upper-level cloud cover, deep boundary-layer mixing and drying are anticipated. Surface relative humidities around 10-15 percent, and perhaps in the single digits in some locations, are expected by mid-afternoon. These dry and windy conditions are anticipated across a region with fuels supporting large-fire spread (e.g., ERCs generally around 70 percent or greater, increasing with southward extent). These critical fire-weather conditions are anticipated from mid-afternoon until sunset, particularly from around Albuquerque south-southwest to the Chiricahua Mountains. ...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 0750 AM CDT Sun May 05 2024 Valid 051300Z - 061200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF SOUTH TEXAS... ...SUMMARY... Scattered strong to severe thunderstorms are possible across parts of South Texas today. Isolated locally severe thunderstorms are also possible across the Mid-South and upper Ohio Valley. ...Synopsis... A substantial synoptic-scale trough has moved inland over the Pacific Coast States and NV, anchored by a cyclone now centered near the NV/OR border. The 500-mb low should move erratically eastward through the period, reaching southern WY by 12Z tomorrow, with a strong shortwave trough southward over western CO and NM. Associated height falls will shift eastward through the Intermountain West, Rockies, and eventually High Plains. As that occurs, a convectively reinforced, southern-stream perturbation -- apparent in moisture-channel imagery from western OK to central/ southeast TX -- will move eastward to the lower Mississippi Valley. An embedded MCV, initially evident over southern OK, should move northeastward toward the Ozarks through 00Z. Another MCV may be located over northeast TX, and should move over AR today. At the surface, 11Z analysis showed a weak low over northwestern OH, near a frontal triple point, with warm front arching across eastern OH, western WV and eastern KY. This front represents the western rim of a cold-damming airmass over the central Appalachians, and will be slow to erode from the west as the cold front catches up today. The cold front extended from the low across portions of northern/western KY to northern AR, to a frontal-wave low over northeastern OK, related to the northern MCV. The front then extended across eastern OK, and north-central/southwest TX. The trailing part of the cold front is expected to lose definition amidst: 1. A vast field of convective outflow air already in place across much of central/north/east TX, OK and AR, as well as 2. Intensifying low-level warm advection on both sides late in the period, contributing to frontolysis. ...South TX to Mid-South/lower Mississippi Valley... A dissipating convective complex is moving eastward across portions of LA, followed by a still-robust but mostly non-severe line of thunderstorms over southeast TX. The trailing line may produce isolated gusts near severe limits for a few more hours, but should move into an airmass modified by the leading activity. Meanwhile, the boundary layer farther north -- ahead of a belt of precip and embedded thunderstorms now over eastern OK and the Arklatex -- should destabilize diabatically through the afternoon. That, along with favorable low-level moisture (surface dewpoints generally in the mid/upper 60s F), should offset modest mid/upper-level lapse rates enough to support peak MLCAPE in the 1000-1500 J/kg range over much of the outlook area. Scattered thunderstorms are expected -- perhaps in the form of intensification along the northeastward- shifted leading edge of the current convection. With modest low-level and deep shear, severe potential should remain marginal and isolated, in the form of gusts and hail. Mesobeta-scale mass-response effects ahead of the MCVs might help organization over parts of the Mid-South region later today. Farther southwest, the aggregate outflow boundary from the morning complexes as analyzed from near HOU-COT and into northern Coahuila. This boundary should stall, then drift northward over south-central TX and the adjoining Rio Grande Valley today. The boundary should focus additional thunderstorm development from midday through the afternoon, some of which may become severe multicells or supercells with large hail, damaging gusts and at least marginal tornado potential. Though flow beneath the 700-mb level should be modest (generally 5-10 kt), two factors will favor severe potential: 1. Backed flow near the boundary, with maximized low-level vorticity, augmentation of weak ambient shear, and favorable storm-relative low-level winds on the mesoscale. 2. Favorable buoyancy, with MLCAPE commonly 2000-3000 J/kg along and south of the boundary, will be fostered by strong diurnal heating, rich low-level moisture (70s F surface dewpoints) and weak CINH. In the absence of notable mid/upper support behind the shortwave trough, convection may diminish rapidly through the evening, as the boundary layer stabilizes from both nocturnal cooling and spreading outflow air. ...Upper Ohio Valley vicinity... Episodes of widely scattered to scattered thunderstorms are expected to move roughly eastward across this outlook area today, with isolated damaging (but mainly subsevere) gusts possible. Activity will occur as weak MLCINH is breached by diabatic heating and frontal lift. In the pocket of favorable boundary-layer air between the warm and cold fronts, 60s F surface dewpoints should contribute to MLCAPE in the 1000-1500 J/kg range. Glancing influences of a northern-stream trough -- passing north of the area from the Upper Great Lakes across northeastern ON and adjoining QC -- will include somewhat tightened height gradients and enhanced mid/upper winds. However, low-level flow will remain weak and veered to southwesterly, with weak vertical shear in the lowest 500 mb. Mode therefore should be multicellular, with convection weakening considerably as low-level instability decreases near and after sunset. ..Edwards/Broyles.. 05/05/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0750 AM CDT Sun May 05 2024 Valid 051300Z - 061200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF SOUTH TEXAS... ...SUMMARY... Scattered strong to severe thunderstorms are possible across parts of South Texas today. Isolated locally severe thunderstorms are also possible across the Mid-South and upper Ohio Valley. ...Synopsis... A substantial synoptic-scale trough has moved inland over the Pacific Coast States and NV, anchored by a cyclone now centered near the NV/OR border. The 500-mb low should move erratically eastward through the period, reaching southern WY by 12Z tomorrow, with a strong shortwave trough southward over western CO and NM. Associated height falls will shift eastward through the Intermountain West, Rockies, and eventually High Plains. As that occurs, a convectively reinforced, southern-stream perturbation -- apparent in moisture-channel imagery from western OK to central/ southeast TX -- will move eastward to the lower Mississippi Valley. An embedded MCV, initially evident over southern OK, should move northeastward toward the Ozarks through 00Z. Another MCV may be located over northeast TX, and should move over AR today. At the surface, 11Z analysis showed a weak low over northwestern OH, near a frontal triple point, with warm front arching across eastern OH, western WV and eastern KY. This front represents the western rim of a cold-damming airmass over the central Appalachians, and will be slow to erode from the west as the cold front catches up today. The cold front extended from the low across portions of northern/western KY to northern AR, to a frontal-wave low over northeastern OK, related to the northern MCV. The front then extended across eastern OK, and north-central/southwest TX. The trailing part of the cold front is expected to lose definition amidst: 1. A vast field of convective outflow air already in place across much of central/north/east TX, OK and AR, as well as 2. Intensifying low-level warm advection on both sides late in the period, contributing to frontolysis. ...South TX to Mid-South/lower Mississippi Valley... A dissipating convective complex is moving eastward across portions of LA, followed by a still-robust but mostly non-severe line of thunderstorms over southeast TX. The trailing line may produce isolated gusts near severe limits for a few more hours, but should move into an airmass modified by the leading activity. Meanwhile, the boundary layer farther north -- ahead of a belt of precip and embedded thunderstorms now over eastern OK and the Arklatex -- should destabilize diabatically through the afternoon. That, along with favorable low-level moisture (surface dewpoints generally in the mid/upper 60s F), should offset modest mid/upper-level lapse rates enough to support peak MLCAPE in the 1000-1500 J/kg range over much of the outlook area. Scattered thunderstorms are expected -- perhaps in the form of intensification along the northeastward- shifted leading edge of the current convection. With modest low-level and deep shear, severe potential should remain marginal and isolated, in the form of gusts and hail. Mesobeta-scale mass-response effects ahead of the MCVs might help organization over parts of the Mid-South region later today. Farther southwest, the aggregate outflow boundary from the morning complexes as analyzed from near HOU-COT and into northern Coahuila. This boundary should stall, then drift northward over south-central TX and the adjoining Rio Grande Valley today. The boundary should focus additional thunderstorm development from midday through the afternoon, some of which may become severe multicells or supercells with large hail, damaging gusts and at least marginal tornado potential. Though flow beneath the 700-mb level should be modest (generally 5-10 kt), two factors will favor severe potential: 1. Backed flow near the boundary, with maximized low-level vorticity, augmentation of weak ambient shear, and favorable storm-relative low-level winds on the mesoscale. 2. Favorable buoyancy, with MLCAPE commonly 2000-3000 J/kg along and south of the boundary, will be fostered by strong diurnal heating, rich low-level moisture (70s F surface dewpoints) and weak CINH. In the absence of notable mid/upper support behind the shortwave trough, convection may diminish rapidly through the evening, as the boundary layer stabilizes from both nocturnal cooling and spreading outflow air. ...Upper Ohio Valley vicinity... Episodes of widely scattered to scattered thunderstorms are expected to move roughly eastward across this outlook area today, with isolated damaging (but mainly subsevere) gusts possible. Activity will occur as weak MLCINH is breached by diabatic heating and frontal lift. In the pocket of favorable boundary-layer air between the warm and cold fronts, 60s F surface dewpoints should contribute to MLCAPE in the 1000-1500 J/kg range. Glancing influences of a northern-stream trough -- passing north of the area from the Upper Great Lakes across northeastern ON and adjoining QC -- will include somewhat tightened height gradients and enhanced mid/upper winds. However, low-level flow will remain weak and veered to southwesterly, with weak vertical shear in the lowest 500 mb. Mode therefore should be multicellular, with convection weakening considerably as low-level instability decreases near and after sunset. ..Edwards/Broyles.. 05/05/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0750 AM CDT Sun May 05 2024 Valid 051300Z - 061200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF SOUTH TEXAS... ...SUMMARY... Scattered strong to severe thunderstorms are possible across parts of South Texas today. Isolated locally severe thunderstorms are also possible across the Mid-South and upper Ohio Valley. ...Synopsis... A substantial synoptic-scale trough has moved inland over the Pacific Coast States and NV, anchored by a cyclone now centered near the NV/OR border. The 500-mb low should move erratically eastward through the period, reaching southern WY by 12Z tomorrow, with a strong shortwave trough southward over western CO and NM. Associated height falls will shift eastward through the Intermountain West, Rockies, and eventually High Plains. As that occurs, a convectively reinforced, southern-stream perturbation -- apparent in moisture-channel imagery from western OK to central/ southeast TX -- will move eastward to the lower Mississippi Valley. An embedded MCV, initially evident over southern OK, should move northeastward toward the Ozarks through 00Z. Another MCV may be located over northeast TX, and should move over AR today. At the surface, 11Z analysis showed a weak low over northwestern OH, near a frontal triple point, with warm front arching across eastern OH, western WV and eastern KY. This front represents the western rim of a cold-damming airmass over the central Appalachians, and will be slow to erode from the west as the cold front catches up today. The cold front extended from the low across portions of northern/western KY to northern AR, to a frontal-wave low over northeastern OK, related to the northern MCV. The front then extended across eastern OK, and north-central/southwest TX. The trailing part of the cold front is expected to lose definition amidst: 1. A vast field of convective outflow air already in place across much of central/north/east TX, OK and AR, as well as 2. Intensifying low-level warm advection on both sides late in the period, contributing to frontolysis. ...South TX to Mid-South/lower Mississippi Valley... A dissipating convective complex is moving eastward across portions of LA, followed by a still-robust but mostly non-severe line of thunderstorms over southeast TX. The trailing line may produce isolated gusts near severe limits for a few more hours, but should move into an airmass modified by the leading activity. Meanwhile, the boundary layer farther north -- ahead of a belt of precip and embedded thunderstorms now over eastern OK and the Arklatex -- should destabilize diabatically through the afternoon. That, along with favorable low-level moisture (surface dewpoints generally in the mid/upper 60s F), should offset modest mid/upper-level lapse rates enough to support peak MLCAPE in the 1000-1500 J/kg range over much of the outlook area. Scattered thunderstorms are expected -- perhaps in the form of intensification along the northeastward- shifted leading edge of the current convection. With modest low-level and deep shear, severe potential should remain marginal and isolated, in the form of gusts and hail. Mesobeta-scale mass-response effects ahead of the MCVs might help organization over parts of the Mid-South region later today. Farther southwest, the aggregate outflow boundary from the morning complexes as analyzed from near HOU-COT and into northern Coahuila. This boundary should stall, then drift northward over south-central TX and the adjoining Rio Grande Valley today. The boundary should focus additional thunderstorm development from midday through the afternoon, some of which may become severe multicells or supercells with large hail, damaging gusts and at least marginal tornado potential. Though flow beneath the 700-mb level should be modest (generally 5-10 kt), two factors will favor severe potential: 1. Backed flow near the boundary, with maximized low-level vorticity, augmentation of weak ambient shear, and favorable storm-relative low-level winds on the mesoscale. 2. Favorable buoyancy, with MLCAPE commonly 2000-3000 J/kg along and south of the boundary, will be fostered by strong diurnal heating, rich low-level moisture (70s F surface dewpoints) and weak CINH. In the absence of notable mid/upper support behind the shortwave trough, convection may diminish rapidly through the evening, as the boundary layer stabilizes from both nocturnal cooling and spreading outflow air. ...Upper Ohio Valley vicinity... Episodes of widely scattered to scattered thunderstorms are expected to move roughly eastward across this outlook area today, with isolated damaging (but mainly subsevere) gusts possible. Activity will occur as weak MLCINH is breached by diabatic heating and frontal lift. In the pocket of favorable boundary-layer air between the warm and cold fronts, 60s F surface dewpoints should contribute to MLCAPE in the 1000-1500 J/kg range. Glancing influences of a northern-stream trough -- passing north of the area from the Upper Great Lakes across northeastern ON and adjoining QC -- will include somewhat tightened height gradients and enhanced mid/upper winds. However, low-level flow will remain weak and veered to southwesterly, with weak vertical shear in the lowest 500 mb. Mode therefore should be multicellular, with convection weakening considerably as low-level instability decreases near and after sunset. ..Edwards/Broyles.. 05/05/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0750 AM CDT Sun May 05 2024 Valid 051300Z - 061200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF SOUTH TEXAS... ...SUMMARY... Scattered strong to severe thunderstorms are possible across parts of South Texas today. Isolated locally severe thunderstorms are also possible across the Mid-South and upper Ohio Valley. ...Synopsis... A substantial synoptic-scale trough has moved inland over the Pacific Coast States and NV, anchored by a cyclone now centered near the NV/OR border. The 500-mb low should move erratically eastward through the period, reaching southern WY by 12Z tomorrow, with a strong shortwave trough southward over western CO and NM. Associated height falls will shift eastward through the Intermountain West, Rockies, and eventually High Plains. As that occurs, a convectively reinforced, southern-stream perturbation -- apparent in moisture-channel imagery from western OK to central/ southeast TX -- will move eastward to the lower Mississippi Valley. An embedded MCV, initially evident over southern OK, should move northeastward toward the Ozarks through 00Z. Another MCV may be located over northeast TX, and should move over AR today. At the surface, 11Z analysis showed a weak low over northwestern OH, near a frontal triple point, with warm front arching across eastern OH, western WV and eastern KY. This front represents the western rim of a cold-damming airmass over the central Appalachians, and will be slow to erode from the west as the cold front catches up today. The cold front extended from the low across portions of northern/western KY to northern AR, to a frontal-wave low over northeastern OK, related to the northern MCV. The front then extended across eastern OK, and north-central/southwest TX. The trailing part of the cold front is expected to lose definition amidst: 1. A vast field of convective outflow air already in place across much of central/north/east TX, OK and AR, as well as 2. Intensifying low-level warm advection on both sides late in the period, contributing to frontolysis. ...South TX to Mid-South/lower Mississippi Valley... A dissipating convective complex is moving eastward across portions of LA, followed by a still-robust but mostly non-severe line of thunderstorms over southeast TX. The trailing line may produce isolated gusts near severe limits for a few more hours, but should move into an airmass modified by the leading activity. Meanwhile, the boundary layer farther north -- ahead of a belt of precip and embedded thunderstorms now over eastern OK and the Arklatex -- should destabilize diabatically through the afternoon. That, along with favorable low-level moisture (surface dewpoints generally in the mid/upper 60s F), should offset modest mid/upper-level lapse rates enough to support peak MLCAPE in the 1000-1500 J/kg range over much of the outlook area. Scattered thunderstorms are expected -- perhaps in the form of intensification along the northeastward- shifted leading edge of the current convection. With modest low-level and deep shear, severe potential should remain marginal and isolated, in the form of gusts and hail. Mesobeta-scale mass-response effects ahead of the MCVs might help organization over parts of the Mid-South region later today. Farther southwest, the aggregate outflow boundary from the morning complexes as analyzed from near HOU-COT and into northern Coahuila. This boundary should stall, then drift northward over south-central TX and the adjoining Rio Grande Valley today. The boundary should focus additional thunderstorm development from midday through the afternoon, some of which may become severe multicells or supercells with large hail, damaging gusts and at least marginal tornado potential. Though flow beneath the 700-mb level should be modest (generally 5-10 kt), two factors will favor severe potential: 1. Backed flow near the boundary, with maximized low-level vorticity, augmentation of weak ambient shear, and favorable storm-relative low-level winds on the mesoscale. 2. Favorable buoyancy, with MLCAPE commonly 2000-3000 J/kg along and south of the boundary, will be fostered by strong diurnal heating, rich low-level moisture (70s F surface dewpoints) and weak CINH. In the absence of notable mid/upper support behind the shortwave trough, convection may diminish rapidly through the evening, as the boundary layer stabilizes from both nocturnal cooling and spreading outflow air. ...Upper Ohio Valley vicinity... Episodes of widely scattered to scattered thunderstorms are expected to move roughly eastward across this outlook area today, with isolated damaging (but mainly subsevere) gusts possible. Activity will occur as weak MLCINH is breached by diabatic heating and frontal lift. In the pocket of favorable boundary-layer air between the warm and cold fronts, 60s F surface dewpoints should contribute to MLCAPE in the 1000-1500 J/kg range. Glancing influences of a northern-stream trough -- passing north of the area from the Upper Great Lakes across northeastern ON and adjoining QC -- will include somewhat tightened height gradients and enhanced mid/upper winds. However, low-level flow will remain weak and veered to southwesterly, with weak vertical shear in the lowest 500 mb. Mode therefore should be multicellular, with convection weakening considerably as low-level instability decreases near and after sunset. ..Edwards/Broyles.. 05/05/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0750 AM CDT Sun May 05 2024 Valid 051300Z - 061200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF SOUTH TEXAS... ...SUMMARY... Scattered strong to severe thunderstorms are possible across parts of South Texas today. Isolated locally severe thunderstorms are also possible across the Mid-South and upper Ohio Valley. ...Synopsis... A substantial synoptic-scale trough has moved inland over the Pacific Coast States and NV, anchored by a cyclone now centered near the NV/OR border. The 500-mb low should move erratically eastward through the period, reaching southern WY by 12Z tomorrow, with a strong shortwave trough southward over western CO and NM. Associated height falls will shift eastward through the Intermountain West, Rockies, and eventually High Plains. As that occurs, a convectively reinforced, southern-stream perturbation -- apparent in moisture-channel imagery from western OK to central/ southeast TX -- will move eastward to the lower Mississippi Valley. An embedded MCV, initially evident over southern OK, should move northeastward toward the Ozarks through 00Z. Another MCV may be located over northeast TX, and should move over AR today. At the surface, 11Z analysis showed a weak low over northwestern OH, near a frontal triple point, with warm front arching across eastern OH, western WV and eastern KY. This front represents the western rim of a cold-damming airmass over the central Appalachians, and will be slow to erode from the west as the cold front catches up today. The cold front extended from the low across portions of northern/western KY to northern AR, to a frontal-wave low over northeastern OK, related to the northern MCV. The front then extended across eastern OK, and north-central/southwest TX. The trailing part of the cold front is expected to lose definition amidst: 1. A vast field of convective outflow air already in place across much of central/north/east TX, OK and AR, as well as 2. Intensifying low-level warm advection on both sides late in the period, contributing to frontolysis. ...South TX to Mid-South/lower Mississippi Valley... A dissipating convective complex is moving eastward across portions of LA, followed by a still-robust but mostly non-severe line of thunderstorms over southeast TX. The trailing line may produce isolated gusts near severe limits for a few more hours, but should move into an airmass modified by the leading activity. Meanwhile, the boundary layer farther north -- ahead of a belt of precip and embedded thunderstorms now over eastern OK and the Arklatex -- should destabilize diabatically through the afternoon. That, along with favorable low-level moisture (surface dewpoints generally in the mid/upper 60s F), should offset modest mid/upper-level lapse rates enough to support peak MLCAPE in the 1000-1500 J/kg range over much of the outlook area. Scattered thunderstorms are expected -- perhaps in the form of intensification along the northeastward- shifted leading edge of the current convection. With modest low-level and deep shear, severe potential should remain marginal and isolated, in the form of gusts and hail. Mesobeta-scale mass-response effects ahead of the MCVs might help organization over parts of the Mid-South region later today. Farther southwest, the aggregate outflow boundary from the morning complexes as analyzed from near HOU-COT and into northern Coahuila. This boundary should stall, then drift northward over south-central TX and the adjoining Rio Grande Valley today. The boundary should focus additional thunderstorm development from midday through the afternoon, some of which may become severe multicells or supercells with large hail, damaging gusts and at least marginal tornado potential. Though flow beneath the 700-mb level should be modest (generally 5-10 kt), two factors will favor severe potential: 1. Backed flow near the boundary, with maximized low-level vorticity, augmentation of weak ambient shear, and favorable storm-relative low-level winds on the mesoscale. 2. Favorable buoyancy, with MLCAPE commonly 2000-3000 J/kg along and south of the boundary, will be fostered by strong diurnal heating, rich low-level moisture (70s F surface dewpoints) and weak CINH. In the absence of notable mid/upper support behind the shortwave trough, convection may diminish rapidly through the evening, as the boundary layer stabilizes from both nocturnal cooling and spreading outflow air. ...Upper Ohio Valley vicinity... Episodes of widely scattered to scattered thunderstorms are expected to move roughly eastward across this outlook area today, with isolated damaging (but mainly subsevere) gusts possible. Activity will occur as weak MLCINH is breached by diabatic heating and frontal lift. In the pocket of favorable boundary-layer air between the warm and cold fronts, 60s F surface dewpoints should contribute to MLCAPE in the 1000-1500 J/kg range. Glancing influences of a northern-stream trough -- passing north of the area from the Upper Great Lakes across northeastern ON and adjoining QC -- will include somewhat tightened height gradients and enhanced mid/upper winds. However, low-level flow will remain weak and veered to southwesterly, with weak vertical shear in the lowest 500 mb. Mode therefore should be multicellular, with convection weakening considerably as low-level instability decreases near and after sunset. ..Edwards/Broyles.. 05/05/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0750 AM CDT Sun May 05 2024 Valid 051300Z - 061200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF SOUTH TEXAS... ...SUMMARY... Scattered strong to severe thunderstorms are possible across parts of South Texas today. Isolated locally severe thunderstorms are also possible across the Mid-South and upper Ohio Valley. ...Synopsis... A substantial synoptic-scale trough has moved inland over the Pacific Coast States and NV, anchored by a cyclone now centered near the NV/OR border. The 500-mb low should move erratically eastward through the period, reaching southern WY by 12Z tomorrow, with a strong shortwave trough southward over western CO and NM. Associated height falls will shift eastward through the Intermountain West, Rockies, and eventually High Plains. As that occurs, a convectively reinforced, southern-stream perturbation -- apparent in moisture-channel imagery from western OK to central/ southeast TX -- will move eastward to the lower Mississippi Valley. An embedded MCV, initially evident over southern OK, should move northeastward toward the Ozarks through 00Z. Another MCV may be located over northeast TX, and should move over AR today. At the surface, 11Z analysis showed a weak low over northwestern OH, near a frontal triple point, with warm front arching across eastern OH, western WV and eastern KY. This front represents the western rim of a cold-damming airmass over the central Appalachians, and will be slow to erode from the west as the cold front catches up today. The cold front extended from the low across portions of northern/western KY to northern AR, to a frontal-wave low over northeastern OK, related to the northern MCV. The front then extended across eastern OK, and north-central/southwest TX. The trailing part of the cold front is expected to lose definition amidst: 1. A vast field of convective outflow air already in place across much of central/north/east TX, OK and AR, as well as 2. Intensifying low-level warm advection on both sides late in the period, contributing to frontolysis. ...South TX to Mid-South/lower Mississippi Valley... A dissipating convective complex is moving eastward across portions of LA, followed by a still-robust but mostly non-severe line of thunderstorms over southeast TX. The trailing line may produce isolated gusts near severe limits for a few more hours, but should move into an airmass modified by the leading activity. Meanwhile, the boundary layer farther north -- ahead of a belt of precip and embedded thunderstorms now over eastern OK and the Arklatex -- should destabilize diabatically through the afternoon. That, along with favorable low-level moisture (surface dewpoints generally in the mid/upper 60s F), should offset modest mid/upper-level lapse rates enough to support peak MLCAPE in the 1000-1500 J/kg range over much of the outlook area. Scattered thunderstorms are expected -- perhaps in the form of intensification along the northeastward- shifted leading edge of the current convection. With modest low-level and deep shear, severe potential should remain marginal and isolated, in the form of gusts and hail. Mesobeta-scale mass-response effects ahead of the MCVs might help organization over parts of the Mid-South region later today. Farther southwest, the aggregate outflow boundary from the morning complexes as analyzed from near HOU-COT and into northern Coahuila. This boundary should stall, then drift northward over south-central TX and the adjoining Rio Grande Valley today. The boundary should focus additional thunderstorm development from midday through the afternoon, some of which may become severe multicells or supercells with large hail, damaging gusts and at least marginal tornado potential. Though flow beneath the 700-mb level should be modest (generally 5-10 kt), two factors will favor severe potential: 1. Backed flow near the boundary, with maximized low-level vorticity, augmentation of weak ambient shear, and favorable storm-relative low-level winds on the mesoscale. 2. Favorable buoyancy, with MLCAPE commonly 2000-3000 J/kg along and south of the boundary, will be fostered by strong diurnal heating, rich low-level moisture (70s F surface dewpoints) and weak CINH. In the absence of notable mid/upper support behind the shortwave trough, convection may diminish rapidly through the evening, as the boundary layer stabilizes from both nocturnal cooling and spreading outflow air. ...Upper Ohio Valley vicinity... Episodes of widely scattered to scattered thunderstorms are expected to move roughly eastward across this outlook area today, with isolated damaging (but mainly subsevere) gusts possible. Activity will occur as weak MLCINH is breached by diabatic heating and frontal lift. In the pocket of favorable boundary-layer air between the warm and cold fronts, 60s F surface dewpoints should contribute to MLCAPE in the 1000-1500 J/kg range. Glancing influences of a northern-stream trough -- passing north of the area from the Upper Great Lakes across northeastern ON and adjoining QC -- will include somewhat tightened height gradients and enhanced mid/upper winds. However, low-level flow will remain weak and veered to southwesterly, with weak vertical shear in the lowest 500 mb. Mode therefore should be multicellular, with convection weakening considerably as low-level instability decreases near and after sunset. ..Edwards/Broyles.. 05/05/2024 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Sun May 05 2024 Valid 081200Z - 131200Z ...DISCUSSION... ...Day 4/Wednesday... The upper cyclone over the northern Plains should evolve into an open wave as it moves slowly eastward across the Upper Midwest on Wednesday. A belt of enhanced west-southwesterly mid-level flow will likely persist from parts of the southern/central Plains into the mid MS Valley and OH Valley/Midwest. An embedded shortwave trough should encourage the development of a weak surface low over the mid MS Valley by late Wednesday afternoon. A warm front should extend eastward from this low across the OH Valley, while a cold front is forecast to extend southward from the low across the southern Plains. Moderate to strong instability should develop from north-central/northeast TX into the Mid-South/mid MS Valley and parts of the OH/TN Valleys, as daytime heating acts on a rich/moist low-level airmass. Strong deep-layer shear will act to organize convection that can develop along both the warm and cold fronts through Wednesday afternoon/evening. Supercells posing a threat for all severe hazards appear possible, as well as clusters capable of producing damaging winds. Given that convection may be ongoing Wednesday morning across parts of these regions, confidence in a corridor of greater severe potential remains too low to include a 30% severe area at this time. ...Day 5/Thursday... Differences in model guidance regarding the position and amplitude of an upper trough across the Midwest/OH Valley become more pronounced by Thursday. Still, some chance for organized severe thunderstorms remains apparent from parts of the Mid-Atlantic southwestward into portions of the Southeast, and perhaps TX too. Confidence in the location of relevant surface boundaries and areas of greater instability to their south remains low, owing to multiple days of prior convection and various associated outflows. Trends in model guidance will continue to be monitored for possible inclusion of one or more 15% severe areas, pending better model agreement. ...Day 6/Friday... Severe potential should become confined to parts of the Southeast on Friday, as a cold front generally moves east-southeastward across the eastern CONUS in tandem with an upper trough. Similar concerns as Thursday exist regarding where better severe potential will focus, with generally low predictability at this time. ...Day 7/Saturday and Day 8/Sunday... Any lingering severe threat should be confined to parts of FL on Saturday, along/south of a cold front. With limited low-level convergence forecast, overall severe potential seems fairly low. Minimal severe threat across the CONUS is currently evident for next Sunday, as the cold front clears the East Coast. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Sun May 05 2024 Valid 081200Z - 131200Z ...DISCUSSION... ...Day 4/Wednesday... The upper cyclone over the northern Plains should evolve into an open wave as it moves slowly eastward across the Upper Midwest on Wednesday. A belt of enhanced west-southwesterly mid-level flow will likely persist from parts of the southern/central Plains into the mid MS Valley and OH Valley/Midwest. An embedded shortwave trough should encourage the development of a weak surface low over the mid MS Valley by late Wednesday afternoon. A warm front should extend eastward from this low across the OH Valley, while a cold front is forecast to extend southward from the low across the southern Plains. Moderate to strong instability should develop from north-central/northeast TX into the Mid-South/mid MS Valley and parts of the OH/TN Valleys, as daytime heating acts on a rich/moist low-level airmass. Strong deep-layer shear will act to organize convection that can develop along both the warm and cold fronts through Wednesday afternoon/evening. Supercells posing a threat for all severe hazards appear possible, as well as clusters capable of producing damaging winds. Given that convection may be ongoing Wednesday morning across parts of these regions, confidence in a corridor of greater severe potential remains too low to include a 30% severe area at this time. ...Day 5/Thursday... Differences in model guidance regarding the position and amplitude of an upper trough across the Midwest/OH Valley become more pronounced by Thursday. Still, some chance for organized severe thunderstorms remains apparent from parts of the Mid-Atlantic southwestward into portions of the Southeast, and perhaps TX too. Confidence in the location of relevant surface boundaries and areas of greater instability to their south remains low, owing to multiple days of prior convection and various associated outflows. Trends in model guidance will continue to be monitored for possible inclusion of one or more 15% severe areas, pending better model agreement. ...Day 6/Friday... Severe potential should become confined to parts of the Southeast on Friday, as a cold front generally moves east-southeastward across the eastern CONUS in tandem with an upper trough. Similar concerns as Thursday exist regarding where better severe potential will focus, with generally low predictability at this time. ...Day 7/Saturday and Day 8/Sunday... Any lingering severe threat should be confined to parts of FL on Saturday, along/south of a cold front. With limited low-level convergence forecast, overall severe potential seems fairly low. Minimal severe threat across the CONUS is currently evident for next Sunday, as the cold front clears the East Coast. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Sun May 05 2024 Valid 081200Z - 131200Z ...DISCUSSION... ...Day 4/Wednesday... The upper cyclone over the northern Plains should evolve into an open wave as it moves slowly eastward across the Upper Midwest on Wednesday. A belt of enhanced west-southwesterly mid-level flow will likely persist from parts of the southern/central Plains into the mid MS Valley and OH Valley/Midwest. An embedded shortwave trough should encourage the development of a weak surface low over the mid MS Valley by late Wednesday afternoon. A warm front should extend eastward from this low across the OH Valley, while a cold front is forecast to extend southward from the low across the southern Plains. Moderate to strong instability should develop from north-central/northeast TX into the Mid-South/mid MS Valley and parts of the OH/TN Valleys, as daytime heating acts on a rich/moist low-level airmass. Strong deep-layer shear will act to organize convection that can develop along both the warm and cold fronts through Wednesday afternoon/evening. Supercells posing a threat for all severe hazards appear possible, as well as clusters capable of producing damaging winds. Given that convection may be ongoing Wednesday morning across parts of these regions, confidence in a corridor of greater severe potential remains too low to include a 30% severe area at this time. ...Day 5/Thursday... Differences in model guidance regarding the position and amplitude of an upper trough across the Midwest/OH Valley become more pronounced by Thursday. Still, some chance for organized severe thunderstorms remains apparent from parts of the Mid-Atlantic southwestward into portions of the Southeast, and perhaps TX too. Confidence in the location of relevant surface boundaries and areas of greater instability to their south remains low, owing to multiple days of prior convection and various associated outflows. Trends in model guidance will continue to be monitored for possible inclusion of one or more 15% severe areas, pending better model agreement. ...Day 6/Friday... Severe potential should become confined to parts of the Southeast on Friday, as a cold front generally moves east-southeastward across the eastern CONUS in tandem with an upper trough. Similar concerns as Thursday exist regarding where better severe potential will focus, with generally low predictability at this time. ...Day 7/Saturday and Day 8/Sunday... Any lingering severe threat should be confined to parts of FL on Saturday, along/south of a cold front. With limited low-level convergence forecast, overall severe potential seems fairly low. Minimal severe threat across the CONUS is currently evident for next Sunday, as the cold front clears the East Coast. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Sun May 05 2024 Valid 081200Z - 131200Z ...DISCUSSION... ...Day 4/Wednesday... The upper cyclone over the northern Plains should evolve into an open wave as it moves slowly eastward across the Upper Midwest on Wednesday. A belt of enhanced west-southwesterly mid-level flow will likely persist from parts of the southern/central Plains into the mid MS Valley and OH Valley/Midwest. An embedded shortwave trough should encourage the development of a weak surface low over the mid MS Valley by late Wednesday afternoon. A warm front should extend eastward from this low across the OH Valley, while a cold front is forecast to extend southward from the low across the southern Plains. Moderate to strong instability should develop from north-central/northeast TX into the Mid-South/mid MS Valley and parts of the OH/TN Valleys, as daytime heating acts on a rich/moist low-level airmass. Strong deep-layer shear will act to organize convection that can develop along both the warm and cold fronts through Wednesday afternoon/evening. Supercells posing a threat for all severe hazards appear possible, as well as clusters capable of producing damaging winds. Given that convection may be ongoing Wednesday morning across parts of these regions, confidence in a corridor of greater severe potential remains too low to include a 30% severe area at this time. ...Day 5/Thursday... Differences in model guidance regarding the position and amplitude of an upper trough across the Midwest/OH Valley become more pronounced by Thursday. Still, some chance for organized severe thunderstorms remains apparent from parts of the Mid-Atlantic southwestward into portions of the Southeast, and perhaps TX too. Confidence in the location of relevant surface boundaries and areas of greater instability to their south remains low, owing to multiple days of prior convection and various associated outflows. Trends in model guidance will continue to be monitored for possible inclusion of one or more 15% severe areas, pending better model agreement. ...Day 6/Friday... Severe potential should become confined to parts of the Southeast on Friday, as a cold front generally moves east-southeastward across the eastern CONUS in tandem with an upper trough. Similar concerns as Thursday exist regarding where better severe potential will focus, with generally low predictability at this time. ...Day 7/Saturday and Day 8/Sunday... Any lingering severe threat should be confined to parts of FL on Saturday, along/south of a cold front. With limited low-level convergence forecast, overall severe potential seems fairly low. Minimal severe threat across the CONUS is currently evident for next Sunday, as the cold front clears the East Coast. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Sun May 05 2024 Valid 081200Z - 131200Z ...DISCUSSION... ...Day 4/Wednesday... The upper cyclone over the northern Plains should evolve into an open wave as it moves slowly eastward across the Upper Midwest on Wednesday. A belt of enhanced west-southwesterly mid-level flow will likely persist from parts of the southern/central Plains into the mid MS Valley and OH Valley/Midwest. An embedded shortwave trough should encourage the development of a weak surface low over the mid MS Valley by late Wednesday afternoon. A warm front should extend eastward from this low across the OH Valley, while a cold front is forecast to extend southward from the low across the southern Plains. Moderate to strong instability should develop from north-central/northeast TX into the Mid-South/mid MS Valley and parts of the OH/TN Valleys, as daytime heating acts on a rich/moist low-level airmass. Strong deep-layer shear will act to organize convection that can develop along both the warm and cold fronts through Wednesday afternoon/evening. Supercells posing a threat for all severe hazards appear possible, as well as clusters capable of producing damaging winds. Given that convection may be ongoing Wednesday morning across parts of these regions, confidence in a corridor of greater severe potential remains too low to include a 30% severe area at this time. ...Day 5/Thursday... Differences in model guidance regarding the position and amplitude of an upper trough across the Midwest/OH Valley become more pronounced by Thursday. Still, some chance for organized severe thunderstorms remains apparent from parts of the Mid-Atlantic southwestward into portions of the Southeast, and perhaps TX too. Confidence in the location of relevant surface boundaries and areas of greater instability to their south remains low, owing to multiple days of prior convection and various associated outflows. Trends in model guidance will continue to be monitored for possible inclusion of one or more 15% severe areas, pending better model agreement. ...Day 6/Friday... Severe potential should become confined to parts of the Southeast on Friday, as a cold front generally moves east-southeastward across the eastern CONUS in tandem with an upper trough. Similar concerns as Thursday exist regarding where better severe potential will focus, with generally low predictability at this time. ...Day 7/Saturday and Day 8/Sunday... Any lingering severe threat should be confined to parts of FL on Saturday, along/south of a cold front. With limited low-level convergence forecast, overall severe potential seems fairly low. Minimal severe threat across the CONUS is currently evident for next Sunday, as the cold front clears the East Coast. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Sun May 05 2024 Valid 081200Z - 131200Z ...DISCUSSION... ...Day 4/Wednesday... The upper cyclone over the northern Plains should evolve into an open wave as it moves slowly eastward across the Upper Midwest on Wednesday. A belt of enhanced west-southwesterly mid-level flow will likely persist from parts of the southern/central Plains into the mid MS Valley and OH Valley/Midwest. An embedded shortwave trough should encourage the development of a weak surface low over the mid MS Valley by late Wednesday afternoon. A warm front should extend eastward from this low across the OH Valley, while a cold front is forecast to extend southward from the low across the southern Plains. Moderate to strong instability should develop from north-central/northeast TX into the Mid-South/mid MS Valley and parts of the OH/TN Valleys, as daytime heating acts on a rich/moist low-level airmass. Strong deep-layer shear will act to organize convection that can develop along both the warm and cold fronts through Wednesday afternoon/evening. Supercells posing a threat for all severe hazards appear possible, as well as clusters capable of producing damaging winds. Given that convection may be ongoing Wednesday morning across parts of these regions, confidence in a corridor of greater severe potential remains too low to include a 30% severe area at this time. ...Day 5/Thursday... Differences in model guidance regarding the position and amplitude of an upper trough across the Midwest/OH Valley become more pronounced by Thursday. Still, some chance for organized severe thunderstorms remains apparent from parts of the Mid-Atlantic southwestward into portions of the Southeast, and perhaps TX too. Confidence in the location of relevant surface boundaries and areas of greater instability to their south remains low, owing to multiple days of prior convection and various associated outflows. Trends in model guidance will continue to be monitored for possible inclusion of one or more 15% severe areas, pending better model agreement. ...Day 6/Friday... Severe potential should become confined to parts of the Southeast on Friday, as a cold front generally moves east-southeastward across the eastern CONUS in tandem with an upper trough. Similar concerns as Thursday exist regarding where better severe potential will focus, with generally low predictability at this time. ...Day 7/Saturday and Day 8/Sunday... Any lingering severe threat should be confined to parts of FL on Saturday, along/south of a cold front. With limited low-level convergence forecast, overall severe potential seems fairly low. Minimal severe threat across the CONUS is currently evident for next Sunday, as the cold front clears the East Coast. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 AM CDT Sun May 05 2024 Valid 071200Z - 081200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE MID-SOUTH INTO THE OHIO VALLEY... ...SUMMARY... Scattered severe thunderstorms appear possible Tuesday from the Mid-South northeastward into parts of the Ohio Valley. ...Synopsis... A large, closed upper cyclone over the northern Plains should move little on Tuesday. A lead mid-level shortwave trough with attendant enhanced mid-level jet is forecast to move quickly northeastward across the Upper Midwest and Great Lakes through the day. The southern fringe of this shortwave trough and modest large-scale ascent should overspread parts of the Mid-South into the OH Valley Tuesday afternoon. At the surface, a deep low over ND should slowly occlude, while a weak secondary low develops northeastward in tandem with the shortwave trough across parts of the Upper Midwest and Great Lakes. A moist and unstable airmass should exist along and southeast of a convectively reinforced surface front, generally extending northeastward from the ArkLaTex vicinity into parts of the mid MS and OH Valleys. ...Mid-South into the Ohio Valley... A line of thunderstorms will probably be ongoing Tuesday morning over parts of AR/MO/IL, associated with convection that developed on Monday across the Plains. This activity may tend to weaken though the morning. But, it could still pose an isolated strong/gusty wind threat. Weak to moderate instability should develop ahead of and to the southwest of these early-day thunderstorms, with greater instability forecast across the Mid-South and lower OH Valley. Deep-layer shear is forecast to be strong enough to support organized convection, including some supercells. However, with mid-level flow generally aligned with the forecast position of the surface boundary, tendency may be for clusters/bowing line segments to prevail. Regardless, scattered strong to severe thunderstorms should spread east-northeastward across the OH Valley Tuesday afternoon and evening, posing a threat for mainly damaging winds and severe hail. Across the Mid-South/TN Valley into AR, the severe threat appears more conditional, owing to this region generally being displaced to the south of the better forcing aloft. An isolated threat for severe hail may develop late in the period (early Wednesday morning) across the Ozarks as low-level flow/ascent increases with a strengthening low-level jet. Given latest model trends and the likelihood for morning convection across the mid MS Valley, it appears that the potential for appreciable destabilization and severe thunderstorms is lower across much of IA, MO, and IL. Have therefore reduced severe probabilities across these areas. ..Gleason.. 05/05/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 AM CDT Sun May 05 2024 Valid 071200Z - 081200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE MID-SOUTH INTO THE OHIO VALLEY... ...SUMMARY... Scattered severe thunderstorms appear possible Tuesday from the Mid-South northeastward into parts of the Ohio Valley. ...Synopsis... A large, closed upper cyclone over the northern Plains should move little on Tuesday. A lead mid-level shortwave trough with attendant enhanced mid-level jet is forecast to move quickly northeastward across the Upper Midwest and Great Lakes through the day. The southern fringe of this shortwave trough and modest large-scale ascent should overspread parts of the Mid-South into the OH Valley Tuesday afternoon. At the surface, a deep low over ND should slowly occlude, while a weak secondary low develops northeastward in tandem with the shortwave trough across parts of the Upper Midwest and Great Lakes. A moist and unstable airmass should exist along and southeast of a convectively reinforced surface front, generally extending northeastward from the ArkLaTex vicinity into parts of the mid MS and OH Valleys. ...Mid-South into the Ohio Valley... A line of thunderstorms will probably be ongoing Tuesday morning over parts of AR/MO/IL, associated with convection that developed on Monday across the Plains. This activity may tend to weaken though the morning. But, it could still pose an isolated strong/gusty wind threat. Weak to moderate instability should develop ahead of and to the southwest of these early-day thunderstorms, with greater instability forecast across the Mid-South and lower OH Valley. Deep-layer shear is forecast to be strong enough to support organized convection, including some supercells. However, with mid-level flow generally aligned with the forecast position of the surface boundary, tendency may be for clusters/bowing line segments to prevail. Regardless, scattered strong to severe thunderstorms should spread east-northeastward across the OH Valley Tuesday afternoon and evening, posing a threat for mainly damaging winds and severe hail. Across the Mid-South/TN Valley into AR, the severe threat appears more conditional, owing to this region generally being displaced to the south of the better forcing aloft. An isolated threat for severe hail may develop late in the period (early Wednesday morning) across the Ozarks as low-level flow/ascent increases with a strengthening low-level jet. Given latest model trends and the likelihood for morning convection across the mid MS Valley, it appears that the potential for appreciable destabilization and severe thunderstorms is lower across much of IA, MO, and IL. Have therefore reduced severe probabilities across these areas. ..Gleason.. 05/05/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 AM CDT Sun May 05 2024 Valid 071200Z - 081200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE MID-SOUTH INTO THE OHIO VALLEY... ...SUMMARY... Scattered severe thunderstorms appear possible Tuesday from the Mid-South northeastward into parts of the Ohio Valley. ...Synopsis... A large, closed upper cyclone over the northern Plains should move little on Tuesday. A lead mid-level shortwave trough with attendant enhanced mid-level jet is forecast to move quickly northeastward across the Upper Midwest and Great Lakes through the day. The southern fringe of this shortwave trough and modest large-scale ascent should overspread parts of the Mid-South into the OH Valley Tuesday afternoon. At the surface, a deep low over ND should slowly occlude, while a weak secondary low develops northeastward in tandem with the shortwave trough across parts of the Upper Midwest and Great Lakes. A moist and unstable airmass should exist along and southeast of a convectively reinforced surface front, generally extending northeastward from the ArkLaTex vicinity into parts of the mid MS and OH Valleys. ...Mid-South into the Ohio Valley... A line of thunderstorms will probably be ongoing Tuesday morning over parts of AR/MO/IL, associated with convection that developed on Monday across the Plains. This activity may tend to weaken though the morning. But, it could still pose an isolated strong/gusty wind threat. Weak to moderate instability should develop ahead of and to the southwest of these early-day thunderstorms, with greater instability forecast across the Mid-South and lower OH Valley. Deep-layer shear is forecast to be strong enough to support organized convection, including some supercells. However, with mid-level flow generally aligned with the forecast position of the surface boundary, tendency may be for clusters/bowing line segments to prevail. Regardless, scattered strong to severe thunderstorms should spread east-northeastward across the OH Valley Tuesday afternoon and evening, posing a threat for mainly damaging winds and severe hail. Across the Mid-South/TN Valley into AR, the severe threat appears more conditional, owing to this region generally being displaced to the south of the better forcing aloft. An isolated threat for severe hail may develop late in the period (early Wednesday morning) across the Ozarks as low-level flow/ascent increases with a strengthening low-level jet. Given latest model trends and the likelihood for morning convection across the mid MS Valley, it appears that the potential for appreciable destabilization and severe thunderstorms is lower across much of IA, MO, and IL. Have therefore reduced severe probabilities across these areas. ..Gleason.. 05/05/2024 Read more