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SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0213 AM CDT Wed Sep 11 2019 Valid 131200Z - 141200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE LOWER GREAT LAKES SOUTHWESTWARD INTO THE MID MISSISSIPPI VALLEY... ...SUMMARY... Thunderstorms associated with an isolated wind-damage threat will be possible on Friday from the Lower Great Lakes southwestward into the mid Mississippi Valley. ...Lower Great Lakes/Lower Ohio Valley/Mid Mississippi Valley... An upper-level low is forecast to move across the Upper Mississippi Valley on Friday as warm advection takes place across the Great Lakes region. At the surface, a cold front is forecast to advance eastward across the Great Lakes and mid Mississippi Valley. Some thunderstorm activity should be ongoing along the front in the morning. As surface heating takes place across the warm sector, moderate instability appears likely to develop by afternoon. In response, convection along the front should increase in coverage by late afternoon with formation of a linear MCS possible. At this point, model consensus between the NAM, GFS and ECMWF suggests the best combination of shear and instability will exist late Friday afternoon from near Detroit southwestward to Indianapolis. This would be the area with the greatest potential for damaging gusts. Severe threat coverage is expected to remain isolated mainly due to the position of the upper-level trough, which is forecast to remain well to the northwest of the front. ..Broyles.. 09/11/2019 Read more

MD 1954 CONCERNING SEVERE THUNDERSTORM WATCH 643...644... FOR SOUTHERN MINNESOTA THROUGH NORTHERN IOWA
Mesoscale Discussion 1954 NWS Storm Prediction Center Norman OK 0209 AM CDT Wed Sep 11 2019 Areas affected...southern Minnesota through northern Iowa Concerning...Severe Thunderstorm Watch 643...644... Valid 110709Z - 110845Z The severe weather threat for Severe Thunderstorm Watch 643, 644 continues. SUMMARY...Line of storms will continue to pose a risk for damaging wind as it continues through southern Minnesota and northern IA into the early morning hours. As needed, WW 644 can be expanded another row or two of counties farther south to account for intensification along the southern half of the line. DISCUSSION...Line of storms extending from southwest MN through northwest IA is moving east at 30-35 kt. A quasi-stationary front extends across southern MN, and the atmosphere along and south of this boundary remains moderately unstable with up to 2500 J/kg MUCAPE. A 40 kt southerly low-level jet will maintain influx of higher theta-e air as well as augment convergence along gust front, supporting forward propagation next few hours. Some strengthening has recently been observed along portion of the line moving into northwest IA. The squall line remains organized with a comma-head circulation on northern end along with a rear inflow jet supporting a continued threat for damaging wind next couple hours. ..Dial.. 09/11/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...ARX...MPX...DMX...FSD... LAT...LON 42889530 43279498 43689471 44039448 44139334 44089267 43559247 43249252 42929294 42719425 42289539 42429588 42889530 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0156 AM CDT Wed Sep 11 2019 Valid 121200Z - 131200Z ...Synopsis... As the first in a series of mid-level shortwaves ejects into the Plains, a second, smaller mid-level impulse will traverse the Pacific Northwest during the Day 2/Thursday period. Otherwise, weak zonal flow aloft will prevail across the remainder of the western CONUS. A modest surface pressure gradient however, may become established across parts of southern California, encouraging dry offshore flow across the higher terrain near the southwest California coastline. ...Southern Coastal California... With the modest aforementioned pressure gradient in place across the area, elevated surface wind/RH conditions (15-20 mph east-northeasterly flow with 15-20% RH) are expected to transpire by late afternoon and continue into the overnight hours, towards the end of the period. These conditions will especially prevail along the higher terrain, from the San Gabriel to San Jacinto Mountains, where lack of rainfall and dry fuels will support at least marginal wildfire-spread potential, warranting an elevated delineation. ..Squitieri.. 09/11/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0156 AM CDT Wed Sep 11 2019 Valid 121200Z - 131200Z ...Synopsis... As the first in a series of mid-level shortwaves ejects into the Plains, a second, smaller mid-level impulse will traverse the Pacific Northwest during the Day 2/Thursday period. Otherwise, weak zonal flow aloft will prevail across the remainder of the western CONUS. A modest surface pressure gradient however, may become established across parts of southern California, encouraging dry offshore flow across the higher terrain near the southwest California coastline. ...Southern Coastal California... With the modest aforementioned pressure gradient in place across the area, elevated surface wind/RH conditions (15-20 mph east-northeasterly flow with 15-20% RH) are expected to transpire by late afternoon and continue into the overnight hours, towards the end of the period. These conditions will especially prevail along the higher terrain, from the San Gabriel to San Jacinto Mountains, where lack of rainfall and dry fuels will support at least marginal wildfire-spread potential, warranting an elevated delineation. ..Squitieri.. 09/11/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0156 AM CDT Wed Sep 11 2019 Valid 121200Z - 131200Z ...Synopsis... As the first in a series of mid-level shortwaves ejects into the Plains, a second, smaller mid-level impulse will traverse the Pacific Northwest during the Day 2/Thursday period. Otherwise, weak zonal flow aloft will prevail across the remainder of the western CONUS. A modest surface pressure gradient however, may become established across parts of southern California, encouraging dry offshore flow across the higher terrain near the southwest California coastline. ...Southern Coastal California... With the modest aforementioned pressure gradient in place across the area, elevated surface wind/RH conditions (15-20 mph east-northeasterly flow with 15-20% RH) are expected to transpire by late afternoon and continue into the overnight hours, towards the end of the period. These conditions will especially prevail along the higher terrain, from the San Gabriel to San Jacinto Mountains, where lack of rainfall and dry fuels will support at least marginal wildfire-spread potential, warranting an elevated delineation. ..Squitieri.. 09/11/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

WW 0643 Status Updates
STATUS REPORT ON WW 643 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 25 WNW SUX TO 5 ESE OTG TO 30 NNE OTG. ..DIAL..09/11/19 ATTN...WFO...FSD...LBF...OAX... STATUS REPORT FOR WS 643 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS IAC021-035-041-059-093-141-143-149-167-193-110740- IA . IOWA COUNTIES INCLUDED ARE BUENA VISTA CHEROKEE CLAY DICKINSON IDA O'BRIEN OSCEOLA PLYMOUTH SIOUX WOODBURY MNC033-063-110740- MN . MINNESOTA COUNTIES INCLUDED ARE COTTONWOOD JACKSON NEC043-051-110740- NE . NEBRASKA COUNTIES INCLUDED ARE DAKOTA DIXON Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1257 AM CDT Wed Sep 11 2019 Valid 121200Z - 131200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE SOUTHERN PLAINS...OZARKS AND UPPER MISSISSIPPI VALLEY... ...SUMMARY... Thunderstorms associated with wind damage and isolated large hail will be possible on Thursday from southern Plains north-northeastward into the Upper Mississippi Valley. ...Southern Plains/Lower Missouri Valley/Upper Mississippi Valley... An upper-level low will move into the northern Plains on Thursday as a 50 to 70 kt mid-level jet moves across the central Plains and mid Missouri Valley. At the surface, a low will track eastward across Iowa as a cold front advances southeastward across eastern Kansas and northwest Oklahoma. Thunderstorms appear likely to be ongoing along the front in the morning but convective coverage should expand during the afternoon. As convection fills in along the front, a line of thunderstorms seems probable with that line moving eastward into the mid Mississippi Valley and Ozarks during the late afternoon and early evening. Ahead of the cold front, model forecasts suggest that surface dewpoints will be in the upper 60s to near 70 F which will contribute to moderate destabilization by afternoon. NAM and GFS forecast soundings at 00Z/Thursday from Des Moines south-southwestward to near Kansas City show MLCAPE from 1200 to 2500 J/kg. Wind profiles are forecast to be veered to the southwest at the low-levels. 0-6 km shear values are forecast to range from near 30 kt in eastern Kansas to about 45 kt in Iowa. This would favor a wind damage threat with bowing segments along the stronger parts of the line. An isolated hail threat could also occur with rotating cells embedded in the line. Further south into parts of central and northern Oklahoma, deep-layer shear is forecast to be weak suggesting the severe threat will stay marginal there. In the northern part of the threat area, a few severe storms may also develop across parts of eastern Minnesota and western Wisconsin but weak instability should temper the threat there. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 15% - Slight Hail: 15% - Slight ..Broyles.. 09/11/2019 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1257 AM CDT Wed Sep 11 2019 Valid 121200Z - 131200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE SOUTHERN PLAINS...OZARKS AND UPPER MISSISSIPPI VALLEY... ...SUMMARY... Thunderstorms associated with wind damage and isolated large hail will be possible on Thursday from southern Plains north-northeastward into the Upper Mississippi Valley. ...Southern Plains/Lower Missouri Valley/Upper Mississippi Valley... An upper-level low will move into the northern Plains on Thursday as a 50 to 70 kt mid-level jet moves across the central Plains and mid Missouri Valley. At the surface, a low will track eastward across Iowa as a cold front advances southeastward across eastern Kansas and northwest Oklahoma. Thunderstorms appear likely to be ongoing along the front in the morning but convective coverage should expand during the afternoon. As convection fills in along the front, a line of thunderstorms seems probable with that line moving eastward into the mid Mississippi Valley and Ozarks during the late afternoon and early evening. Ahead of the cold front, model forecasts suggest that surface dewpoints will be in the upper 60s to near 70 F which will contribute to moderate destabilization by afternoon. NAM and GFS forecast soundings at 00Z/Thursday from Des Moines south-southwestward to near Kansas City show MLCAPE from 1200 to 2500 J/kg. Wind profiles are forecast to be veered to the southwest at the low-levels. 0-6 km shear values are forecast to range from near 30 kt in eastern Kansas to about 45 kt in Iowa. This would favor a wind damage threat with bowing segments along the stronger parts of the line. An isolated hail threat could also occur with rotating cells embedded in the line. Further south into parts of central and northern Oklahoma, deep-layer shear is forecast to be weak suggesting the severe threat will stay marginal there. In the northern part of the threat area, a few severe storms may also develop across parts of eastern Minnesota and western Wisconsin but weak instability should temper the threat there. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 15% - Slight Hail: 15% - Slight ..Broyles.. 09/11/2019 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1257 AM CDT Wed Sep 11 2019 Valid 121200Z - 131200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE SOUTHERN PLAINS...OZARKS AND UPPER MISSISSIPPI VALLEY... ...SUMMARY... Thunderstorms associated with wind damage and isolated large hail will be possible on Thursday from southern Plains north-northeastward into the Upper Mississippi Valley. ...Southern Plains/Lower Missouri Valley/Upper Mississippi Valley... An upper-level low will move into the northern Plains on Thursday as a 50 to 70 kt mid-level jet moves across the central Plains and mid Missouri Valley. At the surface, a low will track eastward across Iowa as a cold front advances southeastward across eastern Kansas and northwest Oklahoma. Thunderstorms appear likely to be ongoing along the front in the morning but convective coverage should expand during the afternoon. As convection fills in along the front, a line of thunderstorms seems probable with that line moving eastward into the mid Mississippi Valley and Ozarks during the late afternoon and early evening. Ahead of the cold front, model forecasts suggest that surface dewpoints will be in the upper 60s to near 70 F which will contribute to moderate destabilization by afternoon. NAM and GFS forecast soundings at 00Z/Thursday from Des Moines south-southwestward to near Kansas City show MLCAPE from 1200 to 2500 J/kg. Wind profiles are forecast to be veered to the southwest at the low-levels. 0-6 km shear values are forecast to range from near 30 kt in eastern Kansas to about 45 kt in Iowa. This would favor a wind damage threat with bowing segments along the stronger parts of the line. An isolated hail threat could also occur with rotating cells embedded in the line. Further south into parts of central and northern Oklahoma, deep-layer shear is forecast to be weak suggesting the severe threat will stay marginal there. In the northern part of the threat area, a few severe storms may also develop across parts of eastern Minnesota and western Wisconsin but weak instability should temper the threat there. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 15% - Slight Hail: 15% - Slight ..Broyles.. 09/11/2019 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1257 AM CDT Wed Sep 11 2019 Valid 121200Z - 131200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE SOUTHERN PLAINS...OZARKS AND UPPER MISSISSIPPI VALLEY... ...SUMMARY... Thunderstorms associated with wind damage and isolated large hail will be possible on Thursday from southern Plains north-northeastward into the Upper Mississippi Valley. ...Southern Plains/Lower Missouri Valley/Upper Mississippi Valley... An upper-level low will move into the northern Plains on Thursday as a 50 to 70 kt mid-level jet moves across the central Plains and mid Missouri Valley. At the surface, a low will track eastward across Iowa as a cold front advances southeastward across eastern Kansas and northwest Oklahoma. Thunderstorms appear likely to be ongoing along the front in the morning but convective coverage should expand during the afternoon. As convection fills in along the front, a line of thunderstorms seems probable with that line moving eastward into the mid Mississippi Valley and Ozarks during the late afternoon and early evening. Ahead of the cold front, model forecasts suggest that surface dewpoints will be in the upper 60s to near 70 F which will contribute to moderate destabilization by afternoon. NAM and GFS forecast soundings at 00Z/Thursday from Des Moines south-southwestward to near Kansas City show MLCAPE from 1200 to 2500 J/kg. Wind profiles are forecast to be veered to the southwest at the low-levels. 0-6 km shear values are forecast to range from near 30 kt in eastern Kansas to about 45 kt in Iowa. This would favor a wind damage threat with bowing segments along the stronger parts of the line. An isolated hail threat could also occur with rotating cells embedded in the line. Further south into parts of central and northern Oklahoma, deep-layer shear is forecast to be weak suggesting the severe threat will stay marginal there. In the northern part of the threat area, a few severe storms may also develop across parts of eastern Minnesota and western Wisconsin but weak instability should temper the threat there. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 15% - Slight Hail: 15% - Slight ..Broyles.. 09/11/2019 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0107 AM CDT Wed Sep 11 2019 Valid 111200Z - 121200Z ...Synopsis... A well-defined mid-level shortwave trough will move across the western CONUS, ejecting into the Plains states by the end of the period. Over 50 knots of 500 mb flow will accompany the trough, that when mixed down to the surface via a deepening boundary layer, will support dry and breezy conditions across the Four Corners areas. ...Four Corners Region... By mid to late afternoon, 15-25 mph sustained southwesterly surface winds, coincident with 15-25% RH, will become prevalent across northern portions of the Colorado Plateau, where an elevated area has been maintained. Very locally critical conditions will also be possible in terrain favoring locations, especially by peak afternoon heating. Given the sparse nature of the critical conditions, some modest precipitation accumulations within the last week, and fuels that are modestly receptive to fire spread, a critical delineation does not currently appear warranted. ..Squitieri.. 09/11/2019 ...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 0107 AM CDT Wed Sep 11 2019 Valid 111200Z - 121200Z ...Synopsis... A well-defined mid-level shortwave trough will move across the western CONUS, ejecting into the Plains states by the end of the period. Over 50 knots of 500 mb flow will accompany the trough, that when mixed down to the surface via a deepening boundary layer, will support dry and breezy conditions across the Four Corners areas. ...Four Corners Region... By mid to late afternoon, 15-25 mph sustained southwesterly surface winds, coincident with 15-25% RH, will become prevalent across northern portions of the Colorado Plateau, where an elevated area has been maintained. Very locally critical conditions will also be possible in terrain favoring locations, especially by peak afternoon heating. Given the sparse nature of the critical conditions, some modest precipitation accumulations within the last week, and fuels that are modestly receptive to fire spread, a critical delineation does not currently appear warranted. ..Squitieri.. 09/11/2019 ...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 0107 AM CDT Wed Sep 11 2019 Valid 111200Z - 121200Z ...Synopsis... A well-defined mid-level shortwave trough will move across the western CONUS, ejecting into the Plains states by the end of the period. Over 50 knots of 500 mb flow will accompany the trough, that when mixed down to the surface via a deepening boundary layer, will support dry and breezy conditions across the Four Corners areas. ...Four Corners Region... By mid to late afternoon, 15-25 mph sustained southwesterly surface winds, coincident with 15-25% RH, will become prevalent across northern portions of the Colorado Plateau, where an elevated area has been maintained. Very locally critical conditions will also be possible in terrain favoring locations, especially by peak afternoon heating. Given the sparse nature of the critical conditions, some modest precipitation accumulations within the last week, and fuels that are modestly receptive to fire spread, a critical delineation does not currently appear warranted. ..Squitieri.. 09/11/2019 ...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 0107 AM CDT Wed Sep 11 2019 Valid 111200Z - 121200Z ...Synopsis... A well-defined mid-level shortwave trough will move across the western CONUS, ejecting into the Plains states by the end of the period. Over 50 knots of 500 mb flow will accompany the trough, that when mixed down to the surface via a deepening boundary layer, will support dry and breezy conditions across the Four Corners areas. ...Four Corners Region... By mid to late afternoon, 15-25 mph sustained southwesterly surface winds, coincident with 15-25% RH, will become prevalent across northern portions of the Colorado Plateau, where an elevated area has been maintained. Very locally critical conditions will also be possible in terrain favoring locations, especially by peak afternoon heating. Given the sparse nature of the critical conditions, some modest precipitation accumulations within the last week, and fuels that are modestly receptive to fire spread, a critical delineation does not currently appear warranted. ..Squitieri.. 09/11/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1253 AM CDT Wed Sep 11 2019 Valid 111200Z - 121200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER MUCH OF WESTERN NEBRASKA...AND SMALL ADJACENT PARTS OF WYOMING AND COLORADO... ...SUMMARY... Severe thunderstorms capable of producing large hail, damaging wind gusts, and a tornado or two are possible mainly over parts of the central and northern Plains. More isolated and/or marginal severe storms are possible extending eastward across the southern Great Lakes and to the East Coast from Virginia to New Jersey. ...Synopsis... A shortwave trough will progress east across the Rockies, with a 50-60 kt midlevel speed max moving from the central High Plains during the day to the central Plains by Thursday morning. Modest westerly winds aloft will extend across the Great Lakes, north of a gradually weakening upper high over the Southeast. At the surface, low pressure will move from northeast CO across NE, with a stationary front roughly from northern NE, IA and into southern WI. Early day storms and outflow may change the position of this front. During the evening and overnight, a cold front will move east across the central Plains behind the low. Dewpoints in the 65-70 F range will be common south of the stationary front and ahead of the cold front, aiding the development of ample instability supporting strong to severe storms from eastern WY into southern WI. ...Eastern WY...far northeast CO...NE... An outflow boundary now over west-central NE and northeast CO is expected to mix during the day, and may retreat north as southerly winds increase ahead of the upper trough. Heating south of the outflow (and ahead of the developing cold front over eastern WY) along with ample moisture will lead to strong instability. Low-level winds will veer with height, but will remain relatively weak below 700 mb resulting in long, mostly straight hodographs as the upper jet overspreads the High Plains. Storms are expected to form over eastern WY by early afternoon, and over northeast CO and western NE near a triple point. Supercells capable of very large hail will be possible, with perhaps brief tornadoes although effective SRH will average 100-150 m2/s2 prior to 00Z. Thereafter, storms are expected to merge into an MCS with damaging wind the main concern. ...Upper MS Valley and Great Lakes... Storms may be ongoing early in the day as an MCS (now over SD/MN/IA) continues east along the instability gradient. Southwest winds at 850 mb will also maintain warm/moist advection into the region, supporting continued development or rejuvenation of the pre-existing system. Damaging winds appears to be the main concern. ...PA and NJ southwestward into northern GA... Although beneath an upper ridge, the air mass will remain moist and the region will experience strong heating. MLCAPE of 2000-3000 J/kg will develop, and will conditionally favor pulse storms capable of marginally severe wind or hail over the Appalachians. Storm mode over northern areas such as PA and NJ may trend toward multicells with 20-30 kt mid to high-level flow. The severe threat will be tied to the diurnal cycle, and will dwindle by early evening. ..Jewell/Squitieri.. 09/11/2019 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1253 AM CDT Wed Sep 11 2019 Valid 111200Z - 121200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER MUCH OF WESTERN NEBRASKA...AND SMALL ADJACENT PARTS OF WYOMING AND COLORADO... ...SUMMARY... Severe thunderstorms capable of producing large hail, damaging wind gusts, and a tornado or two are possible mainly over parts of the central and northern Plains. More isolated and/or marginal severe storms are possible extending eastward across the southern Great Lakes and to the East Coast from Virginia to New Jersey. ...Synopsis... A shortwave trough will progress east across the Rockies, with a 50-60 kt midlevel speed max moving from the central High Plains during the day to the central Plains by Thursday morning. Modest westerly winds aloft will extend across the Great Lakes, north of a gradually weakening upper high over the Southeast. At the surface, low pressure will move from northeast CO across NE, with a stationary front roughly from northern NE, IA and into southern WI. Early day storms and outflow may change the position of this front. During the evening and overnight, a cold front will move east across the central Plains behind the low. Dewpoints in the 65-70 F range will be common south of the stationary front and ahead of the cold front, aiding the development of ample instability supporting strong to severe storms from eastern WY into southern WI. ...Eastern WY...far northeast CO...NE... An outflow boundary now over west-central NE and northeast CO is expected to mix during the day, and may retreat north as southerly winds increase ahead of the upper trough. Heating south of the outflow (and ahead of the developing cold front over eastern WY) along with ample moisture will lead to strong instability. Low-level winds will veer with height, but will remain relatively weak below 700 mb resulting in long, mostly straight hodographs as the upper jet overspreads the High Plains. Storms are expected to form over eastern WY by early afternoon, and over northeast CO and western NE near a triple point. Supercells capable of very large hail will be possible, with perhaps brief tornadoes although effective SRH will average 100-150 m2/s2 prior to 00Z. Thereafter, storms are expected to merge into an MCS with damaging wind the main concern. ...Upper MS Valley and Great Lakes... Storms may be ongoing early in the day as an MCS (now over SD/MN/IA) continues east along the instability gradient. Southwest winds at 850 mb will also maintain warm/moist advection into the region, supporting continued development or rejuvenation of the pre-existing system. Damaging winds appears to be the main concern. ...PA and NJ southwestward into northern GA... Although beneath an upper ridge, the air mass will remain moist and the region will experience strong heating. MLCAPE of 2000-3000 J/kg will develop, and will conditionally favor pulse storms capable of marginally severe wind or hail over the Appalachians. Storm mode over northern areas such as PA and NJ may trend toward multicells with 20-30 kt mid to high-level flow. The severe threat will be tied to the diurnal cycle, and will dwindle by early evening. ..Jewell/Squitieri.. 09/11/2019 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1253 AM CDT Wed Sep 11 2019 Valid 111200Z - 121200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER MUCH OF WESTERN NEBRASKA...AND SMALL ADJACENT PARTS OF WYOMING AND COLORADO... ...SUMMARY... Severe thunderstorms capable of producing large hail, damaging wind gusts, and a tornado or two are possible mainly over parts of the central and northern Plains. More isolated and/or marginal severe storms are possible extending eastward across the southern Great Lakes and to the East Coast from Virginia to New Jersey. ...Synopsis... A shortwave trough will progress east across the Rockies, with a 50-60 kt midlevel speed max moving from the central High Plains during the day to the central Plains by Thursday morning. Modest westerly winds aloft will extend across the Great Lakes, north of a gradually weakening upper high over the Southeast. At the surface, low pressure will move from northeast CO across NE, with a stationary front roughly from northern NE, IA and into southern WI. Early day storms and outflow may change the position of this front. During the evening and overnight, a cold front will move east across the central Plains behind the low. Dewpoints in the 65-70 F range will be common south of the stationary front and ahead of the cold front, aiding the development of ample instability supporting strong to severe storms from eastern WY into southern WI. ...Eastern WY...far northeast CO...NE... An outflow boundary now over west-central NE and northeast CO is expected to mix during the day, and may retreat north as southerly winds increase ahead of the upper trough. Heating south of the outflow (and ahead of the developing cold front over eastern WY) along with ample moisture will lead to strong instability. Low-level winds will veer with height, but will remain relatively weak below 700 mb resulting in long, mostly straight hodographs as the upper jet overspreads the High Plains. Storms are expected to form over eastern WY by early afternoon, and over northeast CO and western NE near a triple point. Supercells capable of very large hail will be possible, with perhaps brief tornadoes although effective SRH will average 100-150 m2/s2 prior to 00Z. Thereafter, storms are expected to merge into an MCS with damaging wind the main concern. ...Upper MS Valley and Great Lakes... Storms may be ongoing early in the day as an MCS (now over SD/MN/IA) continues east along the instability gradient. Southwest winds at 850 mb will also maintain warm/moist advection into the region, supporting continued development or rejuvenation of the pre-existing system. Damaging winds appears to be the main concern. ...PA and NJ southwestward into northern GA... Although beneath an upper ridge, the air mass will remain moist and the region will experience strong heating. MLCAPE of 2000-3000 J/kg will develop, and will conditionally favor pulse storms capable of marginally severe wind or hail over the Appalachians. Storm mode over northern areas such as PA and NJ may trend toward multicells with 20-30 kt mid to high-level flow. The severe threat will be tied to the diurnal cycle, and will dwindle by early evening. ..Jewell/Squitieri.. 09/11/2019 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1253 AM CDT Wed Sep 11 2019 Valid 111200Z - 121200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER MUCH OF WESTERN NEBRASKA...AND SMALL ADJACENT PARTS OF WYOMING AND COLORADO... ...SUMMARY... Severe thunderstorms capable of producing large hail, damaging wind gusts, and a tornado or two are possible mainly over parts of the central and northern Plains. More isolated and/or marginal severe storms are possible extending eastward across the southern Great Lakes and to the East Coast from Virginia to New Jersey. ...Synopsis... A shortwave trough will progress east across the Rockies, with a 50-60 kt midlevel speed max moving from the central High Plains during the day to the central Plains by Thursday morning. Modest westerly winds aloft will extend across the Great Lakes, north of a gradually weakening upper high over the Southeast. At the surface, low pressure will move from northeast CO across NE, with a stationary front roughly from northern NE, IA and into southern WI. Early day storms and outflow may change the position of this front. During the evening and overnight, a cold front will move east across the central Plains behind the low. Dewpoints in the 65-70 F range will be common south of the stationary front and ahead of the cold front, aiding the development of ample instability supporting strong to severe storms from eastern WY into southern WI. ...Eastern WY...far northeast CO...NE... An outflow boundary now over west-central NE and northeast CO is expected to mix during the day, and may retreat north as southerly winds increase ahead of the upper trough. Heating south of the outflow (and ahead of the developing cold front over eastern WY) along with ample moisture will lead to strong instability. Low-level winds will veer with height, but will remain relatively weak below 700 mb resulting in long, mostly straight hodographs as the upper jet overspreads the High Plains. Storms are expected to form over eastern WY by early afternoon, and over northeast CO and western NE near a triple point. Supercells capable of very large hail will be possible, with perhaps brief tornadoes although effective SRH will average 100-150 m2/s2 prior to 00Z. Thereafter, storms are expected to merge into an MCS with damaging wind the main concern. ...Upper MS Valley and Great Lakes... Storms may be ongoing early in the day as an MCS (now over SD/MN/IA) continues east along the instability gradient. Southwest winds at 850 mb will also maintain warm/moist advection into the region, supporting continued development or rejuvenation of the pre-existing system. Damaging winds appears to be the main concern. ...PA and NJ southwestward into northern GA... Although beneath an upper ridge, the air mass will remain moist and the region will experience strong heating. MLCAPE of 2000-3000 J/kg will develop, and will conditionally favor pulse storms capable of marginally severe wind or hail over the Appalachians. Storm mode over northern areas such as PA and NJ may trend toward multicells with 20-30 kt mid to high-level flow. The severe threat will be tied to the diurnal cycle, and will dwindle by early evening. ..Jewell/Squitieri.. 09/11/2019 Read more

WW 0644 Status Updates
STATUS FOR WATCH 0644 HAS NOT BEEN ISSUED YET Read more

WW 0644 Status Updates
STATUS FOR WATCH 0644 HAS NOT BEEN ISSUED YET Read more