Severe Storms

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1254 AM CDT Tue Sep 10 2019 Valid 111200Z - 121200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF NEBRASKA AND SOUTH DAKOTA... ...SUMMARY... Thunderstorms associated with large hail, damaging wind gusts and a tornado threat are expected to develop on Wednesday from parts of the central and northern Plains eastward into the Upper Mississippi Valley. ...Central and Northern Plains/Upper Mississippi Valley... An upper-level ridge will move eastward across eastern sections of the northern Plains on Wednesday as an upper-level trough moves through the Intermountain West. At the surface, a low is forecast to deepen across the central High Plains along a slow-moving warm front extending eastward from northern Nebraska into northern Iowa. Surface dewpoints south of the front should be in the mid to upper 60s F, contributing to moderate to strong instability by afternoon. Model consensus places the strongest instability across west-central Nebraska by late afternoon where convective initiation appears likely by early evening. NAM and GFS forecast sounding late Wednesday afternoon across west-central Nebraska show conditions favorable for supercells with MLCAPE values in the 2000 to 3000 J/kg range, 0-6 km shear of 40 to 50 kt and steep mid-level lapse rates. Supercells may be capable of producing hailstones greater than 2 inches in diameter. Wind damage will also be possible as an MCS grows upscale. A tornado threat is also expected as the low-level jet ramps up during the early to mid evening. The severe threat should develop northeastward across eastern South Dakota and southwestern Minnesota during the evening. Further to the east, some models suggest a secondary maximum of strong instability will develop across the Upper Mississippi Valley. This combined with enhanced low-level convergence along the warm front should result in scattered thunderstorm development Wednesday afternoon. Although an isolated severe threat will be possible, the upper-level ridge to the west will help to marginalize cell organization. ...Northeast... Westerly mid-level flow will be in place in the Northeast on Wednesday. At the surface, a cold front is forecast to move southward into New York. South of the front, surface dewpoints in the upper 60s to near 70 F should contribute to moderate instability by afternoon. Model forecasts suggest that scattered thunderstorms will initiate near peak heating along and south of the front where low-level lapse rates will be steep. This may be enough for marginally severe wind gusts. Some uncertainty exists concerning the magnitude of the severe threat mainly due to a large spread among model solutions regarding instability and deep-layer shear. ...MAXIMUM RISK BY HAZARD... Tornado: 5% - Slight Wind: 30% - Enhanced Hail: 30% SIG - Enhanced ..Broyles.. 09/10/2019 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1254 AM CDT Tue Sep 10 2019 Valid 111200Z - 121200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF NEBRASKA AND SOUTH DAKOTA... ...SUMMARY... Thunderstorms associated with large hail, damaging wind gusts and a tornado threat are expected to develop on Wednesday from parts of the central and northern Plains eastward into the Upper Mississippi Valley. ...Central and Northern Plains/Upper Mississippi Valley... An upper-level ridge will move eastward across eastern sections of the northern Plains on Wednesday as an upper-level trough moves through the Intermountain West. At the surface, a low is forecast to deepen across the central High Plains along a slow-moving warm front extending eastward from northern Nebraska into northern Iowa. Surface dewpoints south of the front should be in the mid to upper 60s F, contributing to moderate to strong instability by afternoon. Model consensus places the strongest instability across west-central Nebraska by late afternoon where convective initiation appears likely by early evening. NAM and GFS forecast sounding late Wednesday afternoon across west-central Nebraska show conditions favorable for supercells with MLCAPE values in the 2000 to 3000 J/kg range, 0-6 km shear of 40 to 50 kt and steep mid-level lapse rates. Supercells may be capable of producing hailstones greater than 2 inches in diameter. Wind damage will also be possible as an MCS grows upscale. A tornado threat is also expected as the low-level jet ramps up during the early to mid evening. The severe threat should develop northeastward across eastern South Dakota and southwestern Minnesota during the evening. Further to the east, some models suggest a secondary maximum of strong instability will develop across the Upper Mississippi Valley. This combined with enhanced low-level convergence along the warm front should result in scattered thunderstorm development Wednesday afternoon. Although an isolated severe threat will be possible, the upper-level ridge to the west will help to marginalize cell organization. ...Northeast... Westerly mid-level flow will be in place in the Northeast on Wednesday. At the surface, a cold front is forecast to move southward into New York. South of the front, surface dewpoints in the upper 60s to near 70 F should contribute to moderate instability by afternoon. Model forecasts suggest that scattered thunderstorms will initiate near peak heating along and south of the front where low-level lapse rates will be steep. This may be enough for marginally severe wind gusts. Some uncertainty exists concerning the magnitude of the severe threat mainly due to a large spread among model solutions regarding instability and deep-layer shear. ...MAXIMUM RISK BY HAZARD... Tornado: 5% - Slight Wind: 30% - Enhanced Hail: 30% SIG - Enhanced ..Broyles.. 09/10/2019 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1259 AM CDT Tue Sep 10 2019 Valid 101200Z - 111200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER NORTHERN NEBRASKA AND SOUTHERN SOUTH DAKOTA... ...SUMMARY... Thunderstorms with severe wind gusts, large hail and a tornado or two are possible across parts of Nebraska, South Dakota and east-central Wyoming from late afternoon through evening. Some of the hail could be very large, with a few significant damaging wind gusts. ...Synopsis... An upper trough will amplify over the western states with significant cooling aloft and increasing shear developing over the Great Basin into the central Rockies. A cyclonically curved upper jet with midlevel speeds of 50-60 kt will nose into NV and UT late in the day, while shortwave ridging occurs over the Plains. At the surface, low pressure will deepen over northeast CO, where strong heating will occur. A warm front will develop northward toward the NE/SD border through evening, with eastward extension of this boundary becoming nearly stationary along the MN/IA border. South of this front, warm southerly winds will bring upper 60s F dewpoints northward, resulting in substantial instability from the northern High Plains eastward to southern WI. ...Northern Plains... Southerly low-level winds and heating within the large-scale warm advection regime will aid the northward transport of mid to upper 60s F dewpoints across NE and into southern SD. Weakening easterlies north of the warm front will also maintain 50s F dewpoints into southwest MT and eastern WY, where heating will lead to an uncapped air mass. Increasing convergence and upslope flow will lead to storm initiation over eastern WY by around 21Z, with long hodographs supporting large hail into western SD and NE. Additional storms are expected to develop late in the day and into the evening near the warm front, where substantial low-level shear and SRH will develop. A few supercells are possible over northern NE and southern SD, with very large hail and a couple tornadoes possible before storms grow upscale into an MCS with the primary risk damaging wind gusts. The damaging-wind threat may persist eastward into MN and IA where warm advection with the low-level jet will aid lift. ...Northeast NV...northern UT...southeast ID...western WY into southern MT... Strong heating near the surface trough will result in scattered thunderstorms during the late afternoon from northern NV into southern ID and western WY. Forecast soundings show steep lapse rates and lengthening hodographs which will support cells or small bows capable of marginally severe hail or wind. Storms are also expected to increase in coverage from eastern NV into UT during the evening as large-scale lift with the upper trough is maximized. Despite the time of day, marginal hail and a few severe wind gusts will remain possible as instability remains sufficient, given cold temperatures aloft. ..Jewell.. 09/10/2019 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1259 AM CDT Tue Sep 10 2019 Valid 101200Z - 111200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER NORTHERN NEBRASKA AND SOUTHERN SOUTH DAKOTA... ...SUMMARY... Thunderstorms with severe wind gusts, large hail and a tornado or two are possible across parts of Nebraska, South Dakota and east-central Wyoming from late afternoon through evening. Some of the hail could be very large, with a few significant damaging wind gusts. ...Synopsis... An upper trough will amplify over the western states with significant cooling aloft and increasing shear developing over the Great Basin into the central Rockies. A cyclonically curved upper jet with midlevel speeds of 50-60 kt will nose into NV and UT late in the day, while shortwave ridging occurs over the Plains. At the surface, low pressure will deepen over northeast CO, where strong heating will occur. A warm front will develop northward toward the NE/SD border through evening, with eastward extension of this boundary becoming nearly stationary along the MN/IA border. South of this front, warm southerly winds will bring upper 60s F dewpoints northward, resulting in substantial instability from the northern High Plains eastward to southern WI. ...Northern Plains... Southerly low-level winds and heating within the large-scale warm advection regime will aid the northward transport of mid to upper 60s F dewpoints across NE and into southern SD. Weakening easterlies north of the warm front will also maintain 50s F dewpoints into southwest MT and eastern WY, where heating will lead to an uncapped air mass. Increasing convergence and upslope flow will lead to storm initiation over eastern WY by around 21Z, with long hodographs supporting large hail into western SD and NE. Additional storms are expected to develop late in the day and into the evening near the warm front, where substantial low-level shear and SRH will develop. A few supercells are possible over northern NE and southern SD, with very large hail and a couple tornadoes possible before storms grow upscale into an MCS with the primary risk damaging wind gusts. The damaging-wind threat may persist eastward into MN and IA where warm advection with the low-level jet will aid lift. ...Northeast NV...northern UT...southeast ID...western WY into southern MT... Strong heating near the surface trough will result in scattered thunderstorms during the late afternoon from northern NV into southern ID and western WY. Forecast soundings show steep lapse rates and lengthening hodographs which will support cells or small bows capable of marginally severe hail or wind. Storms are also expected to increase in coverage from eastern NV into UT during the evening as large-scale lift with the upper trough is maximized. Despite the time of day, marginal hail and a few severe wind gusts will remain possible as instability remains sufficient, given cold temperatures aloft. ..Jewell.. 09/10/2019 Read more

WW 0639 Status Updates
STATUS REPORT ON WW 639 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 30 WSW DBQ TO 40 SSW ALO TO 30 NW ALO TO 15 S LSE. ..KERR..09/10/19 ATTN...WFO...DMX...ARX...DVN...MPX... STATUS REPORT FOR WT 639 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS IAC005-011-013-017-019-023-037-043-055-065-075-171-191-100240- IA . IOWA COUNTIES INCLUDED ARE ALLAMAKEE BENTON BLACK HAWK BREMER BUCHANAN BUTLER CHICKASAW CLAYTON DELAWARE FAYETTE GRUNDY TAMA WINNESHIEK MNC055-100240- MN . MINNESOTA COUNTIES INCLUDED ARE HOUSTON THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY. PLEASE REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL INFORMATION ON COUNTIES...INDEPENDENT CITIES AND MARINE ZONES CLEARED FROM SEVERE THUNDERSTORM AND TORNADO WATCHES. Read more

WW 639 TORNADO IA MN 092030Z - 100300Z
URGENT - IMMEDIATE BROADCAST REQUESTED Tornado Watch Number 639 NWS Storm Prediction Center Norman OK 330 PM CDT Mon Sep 9 2019 The NWS Storm Prediction Center has issued a * Tornado Watch for portions of Central and Northern Iowa Southeast Minnesota * Effective this Monday afternoon and evening from 330 PM until 1000 PM CDT. * Primary threats include... A few tornadoes possible Scattered damaging wind gusts to 70 mph possible Scattered large hail events to 1.5 inches in diameter possible SUMMARY...Thunderstorms are expected to intensify this afternoon over central Iowa and track northeastward across the watch area. Initial storms may pose a risk of a few tornadoes and large hail, with an increasing risk of damaging wind gusts this evening. The tornado watch area is approximately along and 75 statute miles north and south of a line from 55 miles west southwest of Fort Dodge IA to 60 miles east northeast of Waterloo IA. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU9). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Tornado Watch means conditions are favorable for tornadoes and severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. && AVIATION...Tornadoes and a few severe thunderstorms with hail surface and aloft to 1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 25030. ...Hart Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0746 PM CDT Mon Sep 09 2019 Valid 100100Z - 101200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS NORTHEAST IOWA INTO SOUTHWEST WISCONSIN AND SOUTHEAST MINNESOTA... ...SUMMARY... A few severe thunderstorms remain possible from Iowa into southwest Wisconsin, and over northeast South Dakota this evening. ...IA into southwest WI... Storms persist this evening over northeast IA near a warm front which will continue advancing northeastward tonight. Strong low-level shear near this boundary may support a localized tornado threat with any of the strong cells. Otherwise, damaging winds appear possible. For more information see mesoscale discussion 1943. ...Northeast SD into western MN... Cells are beginning to develop over northeast SD near the surface low. The 00Z ABR sounding shows sufficient instability to support severe storms, but cooler surface temperatures exist just north and east of the area. Therefore, it appears the severe threat will remain confined to a small area, perhaps extending into west-central MN later this evening. A supercell or two is possible, with hail, or even a brief tornado should cells become severe before becoming elevated. For more information see mesoscale discussion 1944. ..Jewell.. 09/10/2019 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0746 PM CDT Mon Sep 09 2019 Valid 100100Z - 101200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS NORTHEAST IOWA INTO SOUTHWEST WISCONSIN AND SOUTHEAST MINNESOTA... ...SUMMARY... A few severe thunderstorms remain possible from Iowa into southwest Wisconsin, and over northeast South Dakota this evening. ...IA into southwest WI... Storms persist this evening over northeast IA near a warm front which will continue advancing northeastward tonight. Strong low-level shear near this boundary may support a localized tornado threat with any of the strong cells. Otherwise, damaging winds appear possible. For more information see mesoscale discussion 1943. ...Northeast SD into western MN... Cells are beginning to develop over northeast SD near the surface low. The 00Z ABR sounding shows sufficient instability to support severe storms, but cooler surface temperatures exist just north and east of the area. Therefore, it appears the severe threat will remain confined to a small area, perhaps extending into west-central MN later this evening. A supercell or two is possible, with hail, or even a brief tornado should cells become severe before becoming elevated. For more information see mesoscale discussion 1944. ..Jewell.. 09/10/2019 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0746 PM CDT Mon Sep 09 2019 Valid 100100Z - 101200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS NORTHEAST IOWA INTO SOUTHWEST WISCONSIN AND SOUTHEAST MINNESOTA... ...SUMMARY... A few severe thunderstorms remain possible from Iowa into southwest Wisconsin, and over northeast South Dakota this evening. ...IA into southwest WI... Storms persist this evening over northeast IA near a warm front which will continue advancing northeastward tonight. Strong low-level shear near this boundary may support a localized tornado threat with any of the strong cells. Otherwise, damaging winds appear possible. For more information see mesoscale discussion 1943. ...Northeast SD into western MN... Cells are beginning to develop over northeast SD near the surface low. The 00Z ABR sounding shows sufficient instability to support severe storms, but cooler surface temperatures exist just north and east of the area. Therefore, it appears the severe threat will remain confined to a small area, perhaps extending into west-central MN later this evening. A supercell or two is possible, with hail, or even a brief tornado should cells become severe before becoming elevated. For more information see mesoscale discussion 1944. ..Jewell.. 09/10/2019 Read more

MD 1945 CONCERNING TORNADO WATCH 639... FOR PARTS OF NORTHEAST IOWA AND ADJACENT SOUTHEAST MINNESOTA...SOUTHWEST WISCONSIN...NORTHWEST ILLINOIS
Mesoscale Discussion 1945 NWS Storm Prediction Center Norman OK 0749 PM CDT Mon Sep 09 2019 Areas affected...Parts of northeast Iowa and adjacent southeast Minnesota...southwest Wisconsin...northwest Illinois Concerning...Tornado Watch 639... Valid 100049Z - 100215Z The severe weather threat for Tornado Watch 639 continues. SUMMARY...Strong to severe thunderstorm development may continue across parts of northeastern Iowa another couple of hours, but storms spreading to the northeast of the watch are expected to weaken and result in diminishing severe weather potential. A new severe weather watch probably will not be needed. DISCUSSION...Lift, aided by low-level warm advection along the frontal zone, and continuing inflow of seasonably moist air characterized by CAPE of 2000-3000 J/kg, may maintain vigorous thunderstorm development northwest through northeast of Cedar Rapids into the 02-03Z time frame. Otherwise, as the forward/northeastward propagating portion of the convective system continues to spread above/to the cool side of the front, instability within the inflow to this activity likely will decrease and result in diminishing intensity to storms, as well as lessening potential for strong surface gusts. ..Kerr.. 09/10/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...MKX...DVN...ARX...DMX... LAT...LON 43739212 43629084 42719011 42129082 42059204 42249281 42989298 43739212 Read more

MD 1944 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PARTS OF NORTHEASTERN SOUTH DAKOTA AND ADJACENT PORTIONS OF SOUTHEASTERN NORTH DAKOTA AND WESTERN MINNESOTA
Mesoscale Discussion 1944 NWS Storm Prediction Center Norman OK 0641 PM CDT Mon Sep 09 2019 Areas affected...Parts of northeastern South Dakota and adjacent portions of southeastern North Dakota and western Minnesota Concerning...Severe potential...Watch possible Valid 092341Z - 100115Z Probability of Watch Issuance...40 percent SUMMARY...A period of rapid thunderstorm intensification appears possible this evening, which may include the development of isolated supercells into and through the 8-10 PM CDT time frame. Due to the somewhat isolated and possibly short-lived nature of the threat, a severe weather watch issuance is not certain, but trends are being monitored. DISCUSSION...Sustained thunderstorm activity appears in the process of initiating near/southwest through east of Aberdeen. This is focused to the northeast of a modest surface low, within a zone of strong low-level warm advection along a frontal zone, as the axis of a low amplitude mid-level short wave trough overspreads the region. With increasing inflow of moist boundary layer air characterized by CAPE of 1000-2000+ J/kg, a period of rapid intensification appears likely, in the presence of strong deep-layer shear beneath a 40 kt westerly 500 mb jet. This may include the evolution of at least an isolated supercell or two into and through the 01-03Z time frame, which probably will pose at least a risk for severe hail and locally strong surface gusts. Although the primary low-level jet appears well to the east and southeast of the region, low-level hodographs may still be favorably large and clockwise curved to support some tornado potential. As the stronger mid-level support rapidly shifts to the northeast of the warm front, it remains unclear how long activity will maintain intensity this evening. ..Kerr/Thompson.. 09/09/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...MPX...FGF...ABR...BIS... LAT...LON 45709920 46289790 45649522 44809577 44589701 45169928 45709920 Read more

MD 1943 CONCERNING TORNADO WATCH 639... FOR PARTS OF CENTRAL/EASTERN IOWA
Mesoscale Discussion 1943 NWS Storm Prediction Center Norman OK 0607 PM CDT Mon Sep 09 2019 Areas affected...Parts of central/eastern Iowa Concerning...Tornado Watch 639... Valid 092307Z - 100030Z The severe weather threat for Tornado Watch 639 continues. SUMMARY...An organized cluster of storms overspreading the region may continue to pose a risk for potentially damaging wind gusts, with perhaps a period with increasing tornado potential near/west through south of Waterloo by around 7 PM CDT. DISCUSSION...A small but organized convective system which has evolved and recently spread northeast of the Des Moines area, appears supported by mid-level forcing for ascent associated with a small-scale perturbation within larger-scale troughing progressing northeastward through the northern Plains vicinity. Activity appears embedded within moderate to strongly sheared 30-40 kt southwesterly mean ambient flow, and may still be intensifying, aided by increasing inflow of moist boundary layer air with CAPE up to 2000-2500 J/kg. Occasional strong surface gusts approaching or briefly exceeding severe limits have been noted with the convective system, and this could still increase during the next few hours. It appears that the evolving convective system will increasingly interact with a warm frontal zone southwest through south of the Waterloo area by around 7 PM CDT. As it does, larger clockwise curved low-level hodographs may provide support for a period of increasing tornado potential. ..Kerr.. 09/09/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...DVN...ARX...DMX... LAT...LON 42609126 42019169 41889213 41809279 41869342 42409316 42689355 43129281 43139162 42609126 Read more

WW 0639 Status Updates
STATUS REPORT ON WW 639 THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA. ..KERR..09/09/19 ATTN...WFO...DMX...ARX...DVN...MPX... STATUS REPORT FOR WT 639 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS IAC001-005-009-011-013-015-017-019-023-025-027-029-033-037-043- 047-049-055-061-063-065-067-069-073-075-077-079-081-083-089-091- 095-099-103-105-109-113-121-127-131-147-151-153-157-161-169-171- 181-187-189-191-195-197-092340- IA . IOWA COUNTIES INCLUDED ARE ADAIR ALLAMAKEE AUDUBON BENTON BLACK HAWK BOONE BREMER BUCHANAN BUTLER CALHOUN CARROLL CASS CERRO GORDO CHICKASAW CLAYTON CRAWFORD DALLAS DELAWARE DUBUQUE EMMET FAYETTE FLOYD FRANKLIN GREENE GRUNDY GUTHRIE HAMILTON HANCOCK HARDIN HOWARD HUMBOLDT IOWA JASPER JOHNSON JONES KOSSUTH LINN MADISON MARSHALL MITCHELL PALO ALTO POCAHONTAS POLK POWESHIEK SAC STORY TAMA WARREN WEBSTER WINNEBAGO WINNESHIEK WORTH WRIGHT Read more

WW 639 TORNADO IA MN 092030Z - 100300Z
URGENT - IMMEDIATE BROADCAST REQUESTED Tornado Watch Number 639 NWS Storm Prediction Center Norman OK 330 PM CDT Mon Sep 9 2019 The NWS Storm Prediction Center has issued a * Tornado Watch for portions of Central and Northern Iowa Southeast Minnesota * Effective this Monday afternoon and evening from 330 PM until 1000 PM CDT. * Primary threats include... A few tornadoes possible Scattered damaging wind gusts to 70 mph possible Scattered large hail events to 1.5 inches in diameter possible SUMMARY...Thunderstorms are expected to intensify this afternoon over central Iowa and track northeastward across the watch area. Initial storms may pose a risk of a few tornadoes and large hail, with an increasing risk of damaging wind gusts this evening. The tornado watch area is approximately along and 75 statute miles north and south of a line from 55 miles west southwest of Fort Dodge IA to 60 miles east northeast of Waterloo IA. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU9). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Tornado Watch means conditions are favorable for tornadoes and severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. && AVIATION...Tornadoes and a few severe thunderstorms with hail surface and aloft to 1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 25030. ...Hart Read more

MD 1942 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PARTS OF WESTERN KANSAS INTO SOUTH CENTRAL NEBRASKA
Mesoscale Discussion 1942 NWS Storm Prediction Center Norman OK 0539 PM CDT Mon Sep 09 2019 Areas affected...Parts of western Kansas into south central Nebraska Concerning...Severe potential...Watch unlikely Valid 092239Z - 100045Z Probability of Watch Issuance...20 percent SUMMARY...Widely scattered strong storms may pose at least some risk for severe hail and localized strong surface gusts into the 7-9 PM CDT time frame. DISCUSSION...Scattered discrete thunderstorms have recently developed and intensified across western Kansas. This may be largely driven by locally enhanced convergence near the lee surface trough, as convective temperatures were approached or reached, and may continue to develop northeastward into south central Nebraska through early evening. Convection is occurring in the wake of stronger mid-level height falls associated with one significant short wave trough progressing northeastward through the Dakotas, and stronger lower/mid tropospheric wind fields are shifting off to the north and east of the region. However, storms still appear embedded within modestly sheared, 20-30 kt southwesterly deep-layer mean ambient flow, which may contribute to occasional isolated supercell structures. Mixed-layer CAPE appears on the order of 2000-3000 J/kg, which will remain potentially supportive of vigorous updrafts at least until the onset of boundary layer cooling results in increasing inhibition by 01-02Z. ..Kerr/Thompson.. 09/09/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...GID...DDC...GLD...PUB... LAT...LON 38860127 41249871 41079822 40569851 39399956 37980096 37440208 37710248 38860127 Read more

No Mesoscale Discussions are in effect as of Mon Sep 9 21:45:08 UTC 2019.

WW 0639 Status Updates
STATUS FOR WATCH 0639 HAS NOT BEEN ISSUED YET Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Mon Sep 09 2019 Valid 092000Z - 101200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF NORTHERN/CENTRAL IOWA...SOUTHERN MINNESOTA...AND WESTERN WISCONSIN... ...SUMMARY... Severe thunderstorms will remain possible this afternoon and evening over parts of the Upper Midwest and upper Mississippi Valley regions. Isolated tornadoes, large hail, and damaging winds could occur. ...20Z Update... A subtle shortwave trough near the NE/IA border will likely encourage additional storm development later this afternoon across northern/central IA. A surface warm front will continue lifting slowly northward over this region and into southern MN through this evening. Isolated tornadoes along with some risk for large hail and damaging winds will be possible with any storms that form in the warm sector and then cross the front. Generally small changes have been made to the southern extent of the Marginal and Slight Risk areas in central IA to account for observational and short-term model trends. See Mesoscale Discussion 1941 for more information on the near-term severe threat across this region. The Marginal Risk has been expanded a little westward to include more of northeastern/eastern SD. Isolated storms may form along a surface trough and to the east of a weak low centered over central SD, posing some threat for hail, gusty winds, and perhaps a tornado or two. No changes have been made to the Marginal Risk across parts of VA/NC. Isolated hail and strong/gusty winds will remain possible through the early evening with any storms that can develop and move southeastward. ..Gleason.. 09/09/2019 .PREV DISCUSSION... /ISSUED 1113 AM CDT Mon Sep 09 2019/ ...IA/MN/WI... A series of shortwave troughs are rotating across the central/northern Plains today. Forcing for ascent is evident in water vapor imagery ahead of these features, moving into eastern SD/NE and much of MN/IA. Meanwhile at the surface, a warm front extends from southeast SD across central IA. This boundary will lift slowly northward through the afternoon. Forecast soundings suggest that continued slow heating along/south of the warm front will sufficiently weaken the capping inversion, leading to scattered thunderstorms by late afternoon over western IA. These storms will track into the frontal zone, where backed low-level winds and enhanced vorticity may aid in the development of low-level mesocyclones and isolated tornadoes. Forecast hodographs show effective helicity values of 300-400 m2/s2 and sufficient deep layer shear to maintain supercell characteristics. Otherwise, hail and gusty winds will be possible in the strongest cells. This activity should persist into the early evening - moving across parts of southern MN and into western WI. ...Eastern SD... Widespread cloud cover is present this morning over eastern SD. This should limit the risk of strong convection through much of the day. However, the combination of a midlevel dry slot and the approach of the surface low may result in a few thunderstorms developing late this afternoon over northeast SD. The strongest of these cells could produce gusty winds. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Mon Sep 09 2019 Valid 092000Z - 101200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF NORTHERN/CENTRAL IOWA...SOUTHERN MINNESOTA...AND WESTERN WISCONSIN... ...SUMMARY... Severe thunderstorms will remain possible this afternoon and evening over parts of the Upper Midwest and upper Mississippi Valley regions. Isolated tornadoes, large hail, and damaging winds could occur. ...20Z Update... A subtle shortwave trough near the NE/IA border will likely encourage additional storm development later this afternoon across northern/central IA. A surface warm front will continue lifting slowly northward over this region and into southern MN through this evening. Isolated tornadoes along with some risk for large hail and damaging winds will be possible with any storms that form in the warm sector and then cross the front. Generally small changes have been made to the southern extent of the Marginal and Slight Risk areas in central IA to account for observational and short-term model trends. See Mesoscale Discussion 1941 for more information on the near-term severe threat across this region. The Marginal Risk has been expanded a little westward to include more of northeastern/eastern SD. Isolated storms may form along a surface trough and to the east of a weak low centered over central SD, posing some threat for hail, gusty winds, and perhaps a tornado or two. No changes have been made to the Marginal Risk across parts of VA/NC. Isolated hail and strong/gusty winds will remain possible through the early evening with any storms that can develop and move southeastward. ..Gleason.. 09/09/2019 .PREV DISCUSSION... /ISSUED 1113 AM CDT Mon Sep 09 2019/ ...IA/MN/WI... A series of shortwave troughs are rotating across the central/northern Plains today. Forcing for ascent is evident in water vapor imagery ahead of these features, moving into eastern SD/NE and much of MN/IA. Meanwhile at the surface, a warm front extends from southeast SD across central IA. This boundary will lift slowly northward through the afternoon. Forecast soundings suggest that continued slow heating along/south of the warm front will sufficiently weaken the capping inversion, leading to scattered thunderstorms by late afternoon over western IA. These storms will track into the frontal zone, where backed low-level winds and enhanced vorticity may aid in the development of low-level mesocyclones and isolated tornadoes. Forecast hodographs show effective helicity values of 300-400 m2/s2 and sufficient deep layer shear to maintain supercell characteristics. Otherwise, hail and gusty winds will be possible in the strongest cells. This activity should persist into the early evening - moving across parts of southern MN and into western WI. ...Eastern SD... Widespread cloud cover is present this morning over eastern SD. This should limit the risk of strong convection through much of the day. However, the combination of a midlevel dry slot and the approach of the surface low may result in a few thunderstorms developing late this afternoon over northeast SD. The strongest of these cells could produce gusty winds. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Mon Sep 09 2019 Valid 092000Z - 101200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF NORTHERN/CENTRAL IOWA...SOUTHERN MINNESOTA...AND WESTERN WISCONSIN... ...SUMMARY... Severe thunderstorms will remain possible this afternoon and evening over parts of the Upper Midwest and upper Mississippi Valley regions. Isolated tornadoes, large hail, and damaging winds could occur. ...20Z Update... A subtle shortwave trough near the NE/IA border will likely encourage additional storm development later this afternoon across northern/central IA. A surface warm front will continue lifting slowly northward over this region and into southern MN through this evening. Isolated tornadoes along with some risk for large hail and damaging winds will be possible with any storms that form in the warm sector and then cross the front. Generally small changes have been made to the southern extent of the Marginal and Slight Risk areas in central IA to account for observational and short-term model trends. See Mesoscale Discussion 1941 for more information on the near-term severe threat across this region. The Marginal Risk has been expanded a little westward to include more of northeastern/eastern SD. Isolated storms may form along a surface trough and to the east of a weak low centered over central SD, posing some threat for hail, gusty winds, and perhaps a tornado or two. No changes have been made to the Marginal Risk across parts of VA/NC. Isolated hail and strong/gusty winds will remain possible through the early evening with any storms that can develop and move southeastward. ..Gleason.. 09/09/2019 .PREV DISCUSSION... /ISSUED 1113 AM CDT Mon Sep 09 2019/ ...IA/MN/WI... A series of shortwave troughs are rotating across the central/northern Plains today. Forcing for ascent is evident in water vapor imagery ahead of these features, moving into eastern SD/NE and much of MN/IA. Meanwhile at the surface, a warm front extends from southeast SD across central IA. This boundary will lift slowly northward through the afternoon. Forecast soundings suggest that continued slow heating along/south of the warm front will sufficiently weaken the capping inversion, leading to scattered thunderstorms by late afternoon over western IA. These storms will track into the frontal zone, where backed low-level winds and enhanced vorticity may aid in the development of low-level mesocyclones and isolated tornadoes. Forecast hodographs show effective helicity values of 300-400 m2/s2 and sufficient deep layer shear to maintain supercell characteristics. Otherwise, hail and gusty winds will be possible in the strongest cells. This activity should persist into the early evening - moving across parts of southern MN and into western WI. ...Eastern SD... Widespread cloud cover is present this morning over eastern SD. This should limit the risk of strong convection through much of the day. However, the combination of a midlevel dry slot and the approach of the surface low may result in a few thunderstorms developing late this afternoon over northeast SD. The strongest of these cells could produce gusty winds. Read more