Severe Storms

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1138 AM CDT Fri Sep 20 2019 Valid 201700Z - 211200Z ...CRITICAL FIRE WEATHER AREA FOR THE FOUR CORNERS REGION INTO PARTS OF SOUTHEASTERN/EAST-CENTRAL UT AND WESTERN CO... ...CRITICAL FIRE WEATHER AREA FOR PARTS OF EASTERN CO... The critical area across the Four Corners region has been expanded northward to include more of southeastern/east-central UT and western CO. A 50-60+ kt mid-level jet will remain over this region today, and strong/gusty surface winds of 20-25 mph will likely overlap RH values of 10-15% for at least a few hours this afternoon. A separate critical area has been introduced across parts of eastern CO. Sustained southwesterly winds of 15-25 mph and RH values of 10-15% should develop this afternoon to the west of a surface trough/dryline. Generally minor adjustments have been made to the surrounding elevated delineation across parts of the central Rockies and adjacent High Plains based on latest observations and short-term model guidance. See the previous discussion below for more information. ..Gleason.. 09/20/2019 .PREV DISCUSSION... /ISSUED 1259 AM CDT Fri Sep 20 2019/ ...Synopsis... A highly amplified upper-level trough positioned over the Great Basin will shift east through the Northern Rockies into portions of the central/northern Plains. Enhanced mid-level flow of 60-70 kt will be present within the base of the trough during this progression. At the surface, a broad region of dry and breezy southwesterly winds will develop during the afternoon beneath the mid-level jet. ...Four Corners Region and portions of the central Rockies and central High Plains... Sustained winds of 15-25 mph will develop during the afternoon while RH values fall into the 15-20% range over much of the region. Fuels remain receptive to large-fire spread, and thus, elevated to critical fire-weather conditions are possible. Refinements were made to the existing elevated area over portions of the central High Plans and central Rockies, based on the position of moist boundaries as depicted in the latest high-resolution guidance. A critical area was added near the Four Corners region, where it appears most likely that critical wind/RH thresholds will be exceeded for a few hours during the afternoon. ...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 1138 AM CDT Fri Sep 20 2019 Valid 201700Z - 211200Z ...CRITICAL FIRE WEATHER AREA FOR THE FOUR CORNERS REGION INTO PARTS OF SOUTHEASTERN/EAST-CENTRAL UT AND WESTERN CO... ...CRITICAL FIRE WEATHER AREA FOR PARTS OF EASTERN CO... The critical area across the Four Corners region has been expanded northward to include more of southeastern/east-central UT and western CO. A 50-60+ kt mid-level jet will remain over this region today, and strong/gusty surface winds of 20-25 mph will likely overlap RH values of 10-15% for at least a few hours this afternoon. A separate critical area has been introduced across parts of eastern CO. Sustained southwesterly winds of 15-25 mph and RH values of 10-15% should develop this afternoon to the west of a surface trough/dryline. Generally minor adjustments have been made to the surrounding elevated delineation across parts of the central Rockies and adjacent High Plains based on latest observations and short-term model guidance. See the previous discussion below for more information. ..Gleason.. 09/20/2019 .PREV DISCUSSION... /ISSUED 1259 AM CDT Fri Sep 20 2019/ ...Synopsis... A highly amplified upper-level trough positioned over the Great Basin will shift east through the Northern Rockies into portions of the central/northern Plains. Enhanced mid-level flow of 60-70 kt will be present within the base of the trough during this progression. At the surface, a broad region of dry and breezy southwesterly winds will develop during the afternoon beneath the mid-level jet. ...Four Corners Region and portions of the central Rockies and central High Plains... Sustained winds of 15-25 mph will develop during the afternoon while RH values fall into the 15-20% range over much of the region. Fuels remain receptive to large-fire spread, and thus, elevated to critical fire-weather conditions are possible. Refinements were made to the existing elevated area over portions of the central High Plans and central Rockies, based on the position of moist boundaries as depicted in the latest high-resolution guidance. A critical area was added near the Four Corners region, where it appears most likely that critical wind/RH thresholds will be exceeded for a few hours during the afternoon. ...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 1138 AM CDT Fri Sep 20 2019 Valid 201700Z - 211200Z ...CRITICAL FIRE WEATHER AREA FOR THE FOUR CORNERS REGION INTO PARTS OF SOUTHEASTERN/EAST-CENTRAL UT AND WESTERN CO... ...CRITICAL FIRE WEATHER AREA FOR PARTS OF EASTERN CO... The critical area across the Four Corners region has been expanded northward to include more of southeastern/east-central UT and western CO. A 50-60+ kt mid-level jet will remain over this region today, and strong/gusty surface winds of 20-25 mph will likely overlap RH values of 10-15% for at least a few hours this afternoon. A separate critical area has been introduced across parts of eastern CO. Sustained southwesterly winds of 15-25 mph and RH values of 10-15% should develop this afternoon to the west of a surface trough/dryline. Generally minor adjustments have been made to the surrounding elevated delineation across parts of the central Rockies and adjacent High Plains based on latest observations and short-term model guidance. See the previous discussion below for more information. ..Gleason.. 09/20/2019 .PREV DISCUSSION... /ISSUED 1259 AM CDT Fri Sep 20 2019/ ...Synopsis... A highly amplified upper-level trough positioned over the Great Basin will shift east through the Northern Rockies into portions of the central/northern Plains. Enhanced mid-level flow of 60-70 kt will be present within the base of the trough during this progression. At the surface, a broad region of dry and breezy southwesterly winds will develop during the afternoon beneath the mid-level jet. ...Four Corners Region and portions of the central Rockies and central High Plains... Sustained winds of 15-25 mph will develop during the afternoon while RH values fall into the 15-20% range over much of the region. Fuels remain receptive to large-fire spread, and thus, elevated to critical fire-weather conditions are possible. Refinements were made to the existing elevated area over portions of the central High Plans and central Rockies, based on the position of moist boundaries as depicted in the latest high-resolution guidance. A critical area was added near the Four Corners region, where it appears most likely that critical wind/RH thresholds will be exceeded for a few hours during the afternoon. ...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 1138 AM CDT Fri Sep 20 2019 Valid 201700Z - 211200Z ...CRITICAL FIRE WEATHER AREA FOR THE FOUR CORNERS REGION INTO PARTS OF SOUTHEASTERN/EAST-CENTRAL UT AND WESTERN CO... ...CRITICAL FIRE WEATHER AREA FOR PARTS OF EASTERN CO... The critical area across the Four Corners region has been expanded northward to include more of southeastern/east-central UT and western CO. A 50-60+ kt mid-level jet will remain over this region today, and strong/gusty surface winds of 20-25 mph will likely overlap RH values of 10-15% for at least a few hours this afternoon. A separate critical area has been introduced across parts of eastern CO. Sustained southwesterly winds of 15-25 mph and RH values of 10-15% should develop this afternoon to the west of a surface trough/dryline. Generally minor adjustments have been made to the surrounding elevated delineation across parts of the central Rockies and adjacent High Plains based on latest observations and short-term model guidance. See the previous discussion below for more information. ..Gleason.. 09/20/2019 .PREV DISCUSSION... /ISSUED 1259 AM CDT Fri Sep 20 2019/ ...Synopsis... A highly amplified upper-level trough positioned over the Great Basin will shift east through the Northern Rockies into portions of the central/northern Plains. Enhanced mid-level flow of 60-70 kt will be present within the base of the trough during this progression. At the surface, a broad region of dry and breezy southwesterly winds will develop during the afternoon beneath the mid-level jet. ...Four Corners Region and portions of the central Rockies and central High Plains... Sustained winds of 15-25 mph will develop during the afternoon while RH values fall into the 15-20% range over much of the region. Fuels remain receptive to large-fire spread, and thus, elevated to critical fire-weather conditions are possible. Refinements were made to the existing elevated area over portions of the central High Plans and central Rockies, based on the position of moist boundaries as depicted in the latest high-resolution guidance. A critical area was added near the Four Corners region, where it appears most likely that critical wind/RH thresholds will be exceeded for a few hours during the afternoon. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1115 AM CDT Fri Sep 20 2019 Valid 201630Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND EVENING OVER PORTIONS OF THE NORTHERN PLAINS... ...SUMMARY... Scattered severe storms capable of producing wind damage, isolated large hail and a couple tornadoes are possible today across the northern Plains, with more isolated severe storms possible in parts of the southern High Plains. ...Northern and Central Plains... Morning water vapor loop shows a large upper trough over the western US, with southwesterly midlevel flow strengthening across the Rockies and High Plains. Several weak impulses are noted from CO northeastward into the Dakotas, with clusters of showers and thunderstorms occurring at this time. The timing and effects of this ongoing convection will result in a rather complex forecast for this afternoon and evening. Activity currently over the western Dakotas is expected to intensify later today as air mass destabilizes and winds aloft strengthen. Occasionally severe storms are expected to affect parts of central and northeast ND into central SD through the mid-late afternoon, with damaging winds, hail, and a couple of tornadoes possible. Later this afternoon, forcing associated with the a stronger shortwave trough will help to initiate thunderstorms from southern MT into eastern WY. These storms will be in a favorable environment for supercells early in the convective life cycle, capable of large hail and a couple of tornadoes. These storms will likely congeal and grow upscale during the evening as they track across parts of NE/SD with a continued threat of damaging winds and hail. ...Southern Plains... A weak remnant outflow boundary extends from near LBB into southern OK. Thunderstorms are expected to develop in vicinity of this boundary this afternoon in a moist and very unstable air mass. Deep-layer shear will be marginal for convective organization. However, convergence along the boundary coupled with slightly enhanced low-level shear may be sufficient for a few supercell storms capable of hail, damaging winds, and perhaps a tornado. ..Hart/Dial.. 09/20/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1115 AM CDT Fri Sep 20 2019 Valid 201630Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND EVENING OVER PORTIONS OF THE NORTHERN PLAINS... ...SUMMARY... Scattered severe storms capable of producing wind damage, isolated large hail and a couple tornadoes are possible today across the northern Plains, with more isolated severe storms possible in parts of the southern High Plains. ...Northern and Central Plains... Morning water vapor loop shows a large upper trough over the western US, with southwesterly midlevel flow strengthening across the Rockies and High Plains. Several weak impulses are noted from CO northeastward into the Dakotas, with clusters of showers and thunderstorms occurring at this time. The timing and effects of this ongoing convection will result in a rather complex forecast for this afternoon and evening. Activity currently over the western Dakotas is expected to intensify later today as air mass destabilizes and winds aloft strengthen. Occasionally severe storms are expected to affect parts of central and northeast ND into central SD through the mid-late afternoon, with damaging winds, hail, and a couple of tornadoes possible. Later this afternoon, forcing associated with the a stronger shortwave trough will help to initiate thunderstorms from southern MT into eastern WY. These storms will be in a favorable environment for supercells early in the convective life cycle, capable of large hail and a couple of tornadoes. These storms will likely congeal and grow upscale during the evening as they track across parts of NE/SD with a continued threat of damaging winds and hail. ...Southern Plains... A weak remnant outflow boundary extends from near LBB into southern OK. Thunderstorms are expected to develop in vicinity of this boundary this afternoon in a moist and very unstable air mass. Deep-layer shear will be marginal for convective organization. However, convergence along the boundary coupled with slightly enhanced low-level shear may be sufficient for a few supercell storms capable of hail, damaging winds, and perhaps a tornado. ..Hart/Dial.. 09/20/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1115 AM CDT Fri Sep 20 2019 Valid 201630Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND EVENING OVER PORTIONS OF THE NORTHERN PLAINS... ...SUMMARY... Scattered severe storms capable of producing wind damage, isolated large hail and a couple tornadoes are possible today across the northern Plains, with more isolated severe storms possible in parts of the southern High Plains. ...Northern and Central Plains... Morning water vapor loop shows a large upper trough over the western US, with southwesterly midlevel flow strengthening across the Rockies and High Plains. Several weak impulses are noted from CO northeastward into the Dakotas, with clusters of showers and thunderstorms occurring at this time. The timing and effects of this ongoing convection will result in a rather complex forecast for this afternoon and evening. Activity currently over the western Dakotas is expected to intensify later today as air mass destabilizes and winds aloft strengthen. Occasionally severe storms are expected to affect parts of central and northeast ND into central SD through the mid-late afternoon, with damaging winds, hail, and a couple of tornadoes possible. Later this afternoon, forcing associated with the a stronger shortwave trough will help to initiate thunderstorms from southern MT into eastern WY. These storms will be in a favorable environment for supercells early in the convective life cycle, capable of large hail and a couple of tornadoes. These storms will likely congeal and grow upscale during the evening as they track across parts of NE/SD with a continued threat of damaging winds and hail. ...Southern Plains... A weak remnant outflow boundary extends from near LBB into southern OK. Thunderstorms are expected to develop in vicinity of this boundary this afternoon in a moist and very unstable air mass. Deep-layer shear will be marginal for convective organization. However, convergence along the boundary coupled with slightly enhanced low-level shear may be sufficient for a few supercell storms capable of hail, damaging winds, and perhaps a tornado. ..Hart/Dial.. 09/20/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1115 AM CDT Fri Sep 20 2019 Valid 201630Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND EVENING OVER PORTIONS OF THE NORTHERN PLAINS... ...SUMMARY... Scattered severe storms capable of producing wind damage, isolated large hail and a couple tornadoes are possible today across the northern Plains, with more isolated severe storms possible in parts of the southern High Plains. ...Northern and Central Plains... Morning water vapor loop shows a large upper trough over the western US, with southwesterly midlevel flow strengthening across the Rockies and High Plains. Several weak impulses are noted from CO northeastward into the Dakotas, with clusters of showers and thunderstorms occurring at this time. The timing and effects of this ongoing convection will result in a rather complex forecast for this afternoon and evening. Activity currently over the western Dakotas is expected to intensify later today as air mass destabilizes and winds aloft strengthen. Occasionally severe storms are expected to affect parts of central and northeast ND into central SD through the mid-late afternoon, with damaging winds, hail, and a couple of tornadoes possible. Later this afternoon, forcing associated with the a stronger shortwave trough will help to initiate thunderstorms from southern MT into eastern WY. These storms will be in a favorable environment for supercells early in the convective life cycle, capable of large hail and a couple of tornadoes. These storms will likely congeal and grow upscale during the evening as they track across parts of NE/SD with a continued threat of damaging winds and hail. ...Southern Plains... A weak remnant outflow boundary extends from near LBB into southern OK. Thunderstorms are expected to develop in vicinity of this boundary this afternoon in a moist and very unstable air mass. Deep-layer shear will be marginal for convective organization. However, convergence along the boundary coupled with slightly enhanced low-level shear may be sufficient for a few supercell storms capable of hail, damaging winds, and perhaps a tornado. ..Hart/Dial.. 09/20/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1115 AM CDT Fri Sep 20 2019 Valid 201630Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND EVENING OVER PORTIONS OF THE NORTHERN PLAINS... ...SUMMARY... Scattered severe storms capable of producing wind damage, isolated large hail and a couple tornadoes are possible today across the northern Plains, with more isolated severe storms possible in parts of the southern High Plains. ...Northern and Central Plains... Morning water vapor loop shows a large upper trough over the western US, with southwesterly midlevel flow strengthening across the Rockies and High Plains. Several weak impulses are noted from CO northeastward into the Dakotas, with clusters of showers and thunderstorms occurring at this time. The timing and effects of this ongoing convection will result in a rather complex forecast for this afternoon and evening. Activity currently over the western Dakotas is expected to intensify later today as air mass destabilizes and winds aloft strengthen. Occasionally severe storms are expected to affect parts of central and northeast ND into central SD through the mid-late afternoon, with damaging winds, hail, and a couple of tornadoes possible. Later this afternoon, forcing associated with the a stronger shortwave trough will help to initiate thunderstorms from southern MT into eastern WY. These storms will be in a favorable environment for supercells early in the convective life cycle, capable of large hail and a couple of tornadoes. These storms will likely congeal and grow upscale during the evening as they track across parts of NE/SD with a continued threat of damaging winds and hail. ...Southern Plains... A weak remnant outflow boundary extends from near LBB into southern OK. Thunderstorms are expected to develop in vicinity of this boundary this afternoon in a moist and very unstable air mass. Deep-layer shear will be marginal for convective organization. However, convergence along the boundary coupled with slightly enhanced low-level shear may be sufficient for a few supercell storms capable of hail, damaging winds, and perhaps a tornado. ..Hart/Dial.. 09/20/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0744 AM CDT Fri Sep 20 2019 Valid 201300Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THROUGH EARLY TONIGHT FOR MUCH OF THE NORTHERN PLAINS... ...SUMMARY... Scattered severe storms capable of producing wind damage, isolated large hail and a couple tornadoes are possible today across the northern Plains, with more isolated severe storms possible in parts of the southern High Plains. ...Northern High Plains into the Dakotas through tonight... A closed midlevel low over southern ID/northeastern NV will evolve into an open wave while ejecting northeastward to the western Dakotas by Saturday morning. At the surface, lee cyclogenesis will occur today near the CO/NE/WY border intersection, with a dryline extending southward across eastern CO. Farther north, a front will stall today from northeastern WY into western ND in advance of the midlevel trough over the Great Basin. The front will move eastward into the Dakotas tonight as a surface cyclone develops northeastward along the boundary, in the zone of ascent preceding the ejecting midlevel trough. A few elevated storms will likely continue through the morning and into the afternoon in association with a lead shortwave trough and midlevel moisture plume now moving north-northeastward over the northern High Plains. Surface heating in cloud breaks will contribute to destabilization and weakening of convective inhibition for surface parcels, and some of the morning convection could evolve into surface-based clusters along the front this afternoon. Embedded supercells may occur where vertical shear is maximized along the front, but the primary storm mode should be multicells growing into line segments. The more discrete/supercell storms could pose a threat for a tornado or two along the boundary, but large hail and damaging winds will be the main concerns as convection spreads east across ND tonight. Farther south into eastern WY and the western NE Panhandle, more discrete storm development is expected this afternoon near the lee cyclone and dryline, in advance of the ejecting midlevel trough. Backing/strengthening low-level flow this evening will result in sufficient hodograph length and curvature for supercells capable of producing a couple of tornadoes and large hail. Some upscale growth into clusters/line segments is probable tonight across SD as the cold front begins to surge eastward. ...Southern High Plains this afternoon/evening... Convection is ongoing across the TX Panhandle. These storms should weaken later this morning, but remnant outflow could linger into the afternoon across the southern Panhandle and South Plains. Additional storm development is expected this afternoon from eastern NM into the TX Panhandle and South Plains, and storms will spread east-northeastward through late evening. Though midlevel lapse rates will not be particularly steep in proximity to the midlevel moisture plume, boundary-layer dewpoints in the 60s and surface heating in cloud breaks will contribute to MLCAPE of 1000-1500 J/kg. Deep-layer vertical shear will be sufficient for supercells, especially if storms can interact with a remnant outflow boundary from morning convection. Isolated damaging winds, large hail, and a tornado or two will all be possible. ..Thompson/Leitman.. 09/20/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0744 AM CDT Fri Sep 20 2019 Valid 201300Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THROUGH EARLY TONIGHT FOR MUCH OF THE NORTHERN PLAINS... ...SUMMARY... Scattered severe storms capable of producing wind damage, isolated large hail and a couple tornadoes are possible today across the northern Plains, with more isolated severe storms possible in parts of the southern High Plains. ...Northern High Plains into the Dakotas through tonight... A closed midlevel low over southern ID/northeastern NV will evolve into an open wave while ejecting northeastward to the western Dakotas by Saturday morning. At the surface, lee cyclogenesis will occur today near the CO/NE/WY border intersection, with a dryline extending southward across eastern CO. Farther north, a front will stall today from northeastern WY into western ND in advance of the midlevel trough over the Great Basin. The front will move eastward into the Dakotas tonight as a surface cyclone develops northeastward along the boundary, in the zone of ascent preceding the ejecting midlevel trough. A few elevated storms will likely continue through the morning and into the afternoon in association with a lead shortwave trough and midlevel moisture plume now moving north-northeastward over the northern High Plains. Surface heating in cloud breaks will contribute to destabilization and weakening of convective inhibition for surface parcels, and some of the morning convection could evolve into surface-based clusters along the front this afternoon. Embedded supercells may occur where vertical shear is maximized along the front, but the primary storm mode should be multicells growing into line segments. The more discrete/supercell storms could pose a threat for a tornado or two along the boundary, but large hail and damaging winds will be the main concerns as convection spreads east across ND tonight. Farther south into eastern WY and the western NE Panhandle, more discrete storm development is expected this afternoon near the lee cyclone and dryline, in advance of the ejecting midlevel trough. Backing/strengthening low-level flow this evening will result in sufficient hodograph length and curvature for supercells capable of producing a couple of tornadoes and large hail. Some upscale growth into clusters/line segments is probable tonight across SD as the cold front begins to surge eastward. ...Southern High Plains this afternoon/evening... Convection is ongoing across the TX Panhandle. These storms should weaken later this morning, but remnant outflow could linger into the afternoon across the southern Panhandle and South Plains. Additional storm development is expected this afternoon from eastern NM into the TX Panhandle and South Plains, and storms will spread east-northeastward through late evening. Though midlevel lapse rates will not be particularly steep in proximity to the midlevel moisture plume, boundary-layer dewpoints in the 60s and surface heating in cloud breaks will contribute to MLCAPE of 1000-1500 J/kg. Deep-layer vertical shear will be sufficient for supercells, especially if storms can interact with a remnant outflow boundary from morning convection. Isolated damaging winds, large hail, and a tornado or two will all be possible. ..Thompson/Leitman.. 09/20/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0744 AM CDT Fri Sep 20 2019 Valid 201300Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THROUGH EARLY TONIGHT FOR MUCH OF THE NORTHERN PLAINS... ...SUMMARY... Scattered severe storms capable of producing wind damage, isolated large hail and a couple tornadoes are possible today across the northern Plains, with more isolated severe storms possible in parts of the southern High Plains. ...Northern High Plains into the Dakotas through tonight... A closed midlevel low over southern ID/northeastern NV will evolve into an open wave while ejecting northeastward to the western Dakotas by Saturday morning. At the surface, lee cyclogenesis will occur today near the CO/NE/WY border intersection, with a dryline extending southward across eastern CO. Farther north, a front will stall today from northeastern WY into western ND in advance of the midlevel trough over the Great Basin. The front will move eastward into the Dakotas tonight as a surface cyclone develops northeastward along the boundary, in the zone of ascent preceding the ejecting midlevel trough. A few elevated storms will likely continue through the morning and into the afternoon in association with a lead shortwave trough and midlevel moisture plume now moving north-northeastward over the northern High Plains. Surface heating in cloud breaks will contribute to destabilization and weakening of convective inhibition for surface parcels, and some of the morning convection could evolve into surface-based clusters along the front this afternoon. Embedded supercells may occur where vertical shear is maximized along the front, but the primary storm mode should be multicells growing into line segments. The more discrete/supercell storms could pose a threat for a tornado or two along the boundary, but large hail and damaging winds will be the main concerns as convection spreads east across ND tonight. Farther south into eastern WY and the western NE Panhandle, more discrete storm development is expected this afternoon near the lee cyclone and dryline, in advance of the ejecting midlevel trough. Backing/strengthening low-level flow this evening will result in sufficient hodograph length and curvature for supercells capable of producing a couple of tornadoes and large hail. Some upscale growth into clusters/line segments is probable tonight across SD as the cold front begins to surge eastward. ...Southern High Plains this afternoon/evening... Convection is ongoing across the TX Panhandle. These storms should weaken later this morning, but remnant outflow could linger into the afternoon across the southern Panhandle and South Plains. Additional storm development is expected this afternoon from eastern NM into the TX Panhandle and South Plains, and storms will spread east-northeastward through late evening. Though midlevel lapse rates will not be particularly steep in proximity to the midlevel moisture plume, boundary-layer dewpoints in the 60s and surface heating in cloud breaks will contribute to MLCAPE of 1000-1500 J/kg. Deep-layer vertical shear will be sufficient for supercells, especially if storms can interact with a remnant outflow boundary from morning convection. Isolated damaging winds, large hail, and a tornado or two will all be possible. ..Thompson/Leitman.. 09/20/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0744 AM CDT Fri Sep 20 2019 Valid 201300Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THROUGH EARLY TONIGHT FOR MUCH OF THE NORTHERN PLAINS... ...SUMMARY... Scattered severe storms capable of producing wind damage, isolated large hail and a couple tornadoes are possible today across the northern Plains, with more isolated severe storms possible in parts of the southern High Plains. ...Northern High Plains into the Dakotas through tonight... A closed midlevel low over southern ID/northeastern NV will evolve into an open wave while ejecting northeastward to the western Dakotas by Saturday morning. At the surface, lee cyclogenesis will occur today near the CO/NE/WY border intersection, with a dryline extending southward across eastern CO. Farther north, a front will stall today from northeastern WY into western ND in advance of the midlevel trough over the Great Basin. The front will move eastward into the Dakotas tonight as a surface cyclone develops northeastward along the boundary, in the zone of ascent preceding the ejecting midlevel trough. A few elevated storms will likely continue through the morning and into the afternoon in association with a lead shortwave trough and midlevel moisture plume now moving north-northeastward over the northern High Plains. Surface heating in cloud breaks will contribute to destabilization and weakening of convective inhibition for surface parcels, and some of the morning convection could evolve into surface-based clusters along the front this afternoon. Embedded supercells may occur where vertical shear is maximized along the front, but the primary storm mode should be multicells growing into line segments. The more discrete/supercell storms could pose a threat for a tornado or two along the boundary, but large hail and damaging winds will be the main concerns as convection spreads east across ND tonight. Farther south into eastern WY and the western NE Panhandle, more discrete storm development is expected this afternoon near the lee cyclone and dryline, in advance of the ejecting midlevel trough. Backing/strengthening low-level flow this evening will result in sufficient hodograph length and curvature for supercells capable of producing a couple of tornadoes and large hail. Some upscale growth into clusters/line segments is probable tonight across SD as the cold front begins to surge eastward. ...Southern High Plains this afternoon/evening... Convection is ongoing across the TX Panhandle. These storms should weaken later this morning, but remnant outflow could linger into the afternoon across the southern Panhandle and South Plains. Additional storm development is expected this afternoon from eastern NM into the TX Panhandle and South Plains, and storms will spread east-northeastward through late evening. Though midlevel lapse rates will not be particularly steep in proximity to the midlevel moisture plume, boundary-layer dewpoints in the 60s and surface heating in cloud breaks will contribute to MLCAPE of 1000-1500 J/kg. Deep-layer vertical shear will be sufficient for supercells, especially if storms can interact with a remnant outflow boundary from morning convection. Isolated damaging winds, large hail, and a tornado or two will all be possible. ..Thompson/Leitman.. 09/20/2019 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0339 AM CDT Fri Sep 20 2019 Valid 231200Z - 281200Z ...DISCUSSION... On Monday/D4, an upper trough/low will drop south across the Great Basin and into AZ, with low pressure over the lower CO River Valley. Due to strong lift and a lack of a cap, storms are expected to become widespread after about 18Z from southwest into central AZ. Low-level winds are forecast to be relatively weak, but increasing mid and high level flow may support some risk of cells capable of hail or small bows producing wind. Despite winds in the low-levels being weak, they will veer with height and a brief supercell cannot be ruled out. Severe probabilities may be needed in future outlooks as predictability increases. To the east, an upper trough will continue moving from the Great Lakes into the northeastern states, with a narrow plume of low 60s F dewpoints ahead of the front. Instability will be weak, and therefore severe weather is not currently anticipated with this system. Areas of rain and thunderstorms will develop out of AZ and NM into the southern Plains during the D5-D7 period ahead of the cut-off low, but severe chances appear low. Toward the end of the D8 period, a larger-scale trough amplification is forecast across the West. Low-level moisture will likely be in place over the southern Plains and lower/mid MS Valley, and may provide a setup for severe storms beyond the current forecast period. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0339 AM CDT Fri Sep 20 2019 Valid 231200Z - 281200Z ...DISCUSSION... On Monday/D4, an upper trough/low will drop south across the Great Basin and into AZ, with low pressure over the lower CO River Valley. Due to strong lift and a lack of a cap, storms are expected to become widespread after about 18Z from southwest into central AZ. Low-level winds are forecast to be relatively weak, but increasing mid and high level flow may support some risk of cells capable of hail or small bows producing wind. Despite winds in the low-levels being weak, they will veer with height and a brief supercell cannot be ruled out. Severe probabilities may be needed in future outlooks as predictability increases. To the east, an upper trough will continue moving from the Great Lakes into the northeastern states, with a narrow plume of low 60s F dewpoints ahead of the front. Instability will be weak, and therefore severe weather is not currently anticipated with this system. Areas of rain and thunderstorms will develop out of AZ and NM into the southern Plains during the D5-D7 period ahead of the cut-off low, but severe chances appear low. Toward the end of the D8 period, a larger-scale trough amplification is forecast across the West. Low-level moisture will likely be in place over the southern Plains and lower/mid MS Valley, and may provide a setup for severe storms beyond the current forecast period. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0339 AM CDT Fri Sep 20 2019 Valid 231200Z - 281200Z ...DISCUSSION... On Monday/D4, an upper trough/low will drop south across the Great Basin and into AZ, with low pressure over the lower CO River Valley. Due to strong lift and a lack of a cap, storms are expected to become widespread after about 18Z from southwest into central AZ. Low-level winds are forecast to be relatively weak, but increasing mid and high level flow may support some risk of cells capable of hail or small bows producing wind. Despite winds in the low-levels being weak, they will veer with height and a brief supercell cannot be ruled out. Severe probabilities may be needed in future outlooks as predictability increases. To the east, an upper trough will continue moving from the Great Lakes into the northeastern states, with a narrow plume of low 60s F dewpoints ahead of the front. Instability will be weak, and therefore severe weather is not currently anticipated with this system. Areas of rain and thunderstorms will develop out of AZ and NM into the southern Plains during the D5-D7 period ahead of the cut-off low, but severe chances appear low. Toward the end of the D8 period, a larger-scale trough amplification is forecast across the West. Low-level moisture will likely be in place over the southern Plains and lower/mid MS Valley, and may provide a setup for severe storms beyond the current forecast period. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0339 AM CDT Fri Sep 20 2019 Valid 231200Z - 281200Z ...DISCUSSION... On Monday/D4, an upper trough/low will drop south across the Great Basin and into AZ, with low pressure over the lower CO River Valley. Due to strong lift and a lack of a cap, storms are expected to become widespread after about 18Z from southwest into central AZ. Low-level winds are forecast to be relatively weak, but increasing mid and high level flow may support some risk of cells capable of hail or small bows producing wind. Despite winds in the low-levels being weak, they will veer with height and a brief supercell cannot be ruled out. Severe probabilities may be needed in future outlooks as predictability increases. To the east, an upper trough will continue moving from the Great Lakes into the northeastern states, with a narrow plume of low 60s F dewpoints ahead of the front. Instability will be weak, and therefore severe weather is not currently anticipated with this system. Areas of rain and thunderstorms will develop out of AZ and NM into the southern Plains during the D5-D7 period ahead of the cut-off low, but severe chances appear low. Toward the end of the D8 period, a larger-scale trough amplification is forecast across the West. Low-level moisture will likely be in place over the southern Plains and lower/mid MS Valley, and may provide a setup for severe storms beyond the current forecast period. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0222 AM CDT Fri Sep 20 2019 Valid 221200Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM OKLAHOMA INTO THE OHIO VALLEY... ...SUMMARY... A few severe storms are expected from Oklahoma northeastward toward the Ohio Valley on Sunday. ...Synopsis... A powerful upper trough will move from the upper MS Valley across the Great Lakes during the day on Sunday, and into the Northeast overnight. Large-scale ascent will be most pronounced from the mid MS Valley across the OH Valley, where 30-40 kt southwest 850 mb winds will maintain warm advection. At the surface, a cold front will move east across WI and MI during the day, extending southwestward into OK, with a moist and unstable air mass developing particularly across TX, OK and MO. ...OK and northwest TX to the OH Valley... Storms are likely to be ongoing from eastern KS across MO and into IL near the cold front, and possibly in the form of an MCS. Moderate deep-layer wind fields will support a continued eastward motion, and some of this activity could be severe with damaging winds. Instability looks to be modest toward the OH Valley ahead of this potential system, but large-scale lift will likely support at least an isolated severe threat. Parts of the area may require a Slight Risk in later outlooks when predictability regarding an MCS increases. To the southwest, better heating will occur ahead of the front from TX into central OK which will also lead to stronger instability. While low-level winds will be weakening with time in this area, westerly flow parallel to the front may support marginally severe hail or wind during the day. ..Jewell.. 09/20/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0222 AM CDT Fri Sep 20 2019 Valid 221200Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM OKLAHOMA INTO THE OHIO VALLEY... ...SUMMARY... A few severe storms are expected from Oklahoma northeastward toward the Ohio Valley on Sunday. ...Synopsis... A powerful upper trough will move from the upper MS Valley across the Great Lakes during the day on Sunday, and into the Northeast overnight. Large-scale ascent will be most pronounced from the mid MS Valley across the OH Valley, where 30-40 kt southwest 850 mb winds will maintain warm advection. At the surface, a cold front will move east across WI and MI during the day, extending southwestward into OK, with a moist and unstable air mass developing particularly across TX, OK and MO. ...OK and northwest TX to the OH Valley... Storms are likely to be ongoing from eastern KS across MO and into IL near the cold front, and possibly in the form of an MCS. Moderate deep-layer wind fields will support a continued eastward motion, and some of this activity could be severe with damaging winds. Instability looks to be modest toward the OH Valley ahead of this potential system, but large-scale lift will likely support at least an isolated severe threat. Parts of the area may require a Slight Risk in later outlooks when predictability regarding an MCS increases. To the southwest, better heating will occur ahead of the front from TX into central OK which will also lead to stronger instability. While low-level winds will be weakening with time in this area, westerly flow parallel to the front may support marginally severe hail or wind during the day. ..Jewell.. 09/20/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0222 AM CDT Fri Sep 20 2019 Valid 221200Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM OKLAHOMA INTO THE OHIO VALLEY... ...SUMMARY... A few severe storms are expected from Oklahoma northeastward toward the Ohio Valley on Sunday. ...Synopsis... A powerful upper trough will move from the upper MS Valley across the Great Lakes during the day on Sunday, and into the Northeast overnight. Large-scale ascent will be most pronounced from the mid MS Valley across the OH Valley, where 30-40 kt southwest 850 mb winds will maintain warm advection. At the surface, a cold front will move east across WI and MI during the day, extending southwestward into OK, with a moist and unstable air mass developing particularly across TX, OK and MO. ...OK and northwest TX to the OH Valley... Storms are likely to be ongoing from eastern KS across MO and into IL near the cold front, and possibly in the form of an MCS. Moderate deep-layer wind fields will support a continued eastward motion, and some of this activity could be severe with damaging winds. Instability looks to be modest toward the OH Valley ahead of this potential system, but large-scale lift will likely support at least an isolated severe threat. Parts of the area may require a Slight Risk in later outlooks when predictability regarding an MCS increases. To the southwest, better heating will occur ahead of the front from TX into central OK which will also lead to stronger instability. While low-level winds will be weakening with time in this area, westerly flow parallel to the front may support marginally severe hail or wind during the day. ..Jewell.. 09/20/2019 Read more