Severe Storms

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

MD 1941 CONCERNING SEVERE POTENTIAL...TORNADO WATCH LIKELY FOR PORTIONS OF IA INTO SOUTHERN MN AND EXTREME SOUTHWEST WI
Mesoscale Discussion 1941 NWS Storm Prediction Center Norman OK 0249 PM CDT Mon Sep 09 2019 Areas affected...portions of IA into southern MN and extreme southwest WI Concerning...Severe potential...Tornado Watch likely Valid 091949Z - 092145Z Probability of Watch Issuance...80 percent SUMMARY...Storms will continue to develop and intensify this afternoon. Isolated supercells capable of all severe hazards are expected, and a watch will likely be need by 21z. DISCUSSION...A surface warm front was noted in 19z surface analysis near MBG to south of ABR in South Dakota and then extending east/southeast across northern/central IA. To the south of the front, southerly low level flow is maintaining upper 60s to low 70s dewpoints across southeast SD into eastern NE, and much of IA. Strong heating in broken cloudiness has resulted in temperatures in the mid 70s to mid 80s south of the front, supporting MLCAPE around 1000-2000 J/kg and weakening inhibition. Subtle forcing ejecting northeast across the central Plains is evident in water vapor imagery as well as via deepening CU both across the central Plains and into parts of southern/central IA. This is aiding in the development of isolated storms in low level confluence ahead of the surface low over western SD. Latest VWP data from KDMX indicates a shear profile supportive of supercells with backed low level winds increasing/veering with height. In fact, a 50 kt speed max was noted at around 1.5 kft. This is leading to enlarged, curved low level hodographs. Given deep boundary layer moisture, a tornado threat will accompany strongest cells, especially those nearer the warm front where low level SRH will be maximized. Midlevel lapse rates are modest, but given instability and strength of shear, hail is also possible, in addition to strong wind gusts. With time and increased forcing and the development of a southwesterly low level jet, convection may eventually grow upscale into a bowing line segment as activity spreads north and east into southeast MN and portions of southwest/south-central WI later this evening. ..Leitman/Hart.. 09/09/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...DVN...ARX...MPX...DMX...FSD...OAX... LAT...LON 41789576 42939520 43579496 44009443 44259356 44249278 44099197 43749118 42829060 42109097 41539155 41149235 41019317 40999440 41029543 41119575 41789576 Read more

No watches are valid as of Mon Sep 9 18:30:06 UTC 2019.

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0127 PM CDT Mon Sep 09 2019 Valid 101200Z - 111200Z Models remain somewhat inconsistent with depiction of minimum RH values during the afternoon on Tuesday. Nevertheless, with strong (20-25 mph) southwesterly surface winds and areas of 15-25% RH, localized areas of elevated fire weather appear likely. The greatest confidence of these conditions being observed is across south-central Utah and north-central Arizona, and a small elevated area has been introduced to address this. Locally elevated fire weather may be observed as far west as east-central Nevada and also into northwestern Colorado. Model trends will be monitored for potential reconfigurations of the new risk area in later outlook updates. In southern California, a persistent surface pattern favoring Sundowner winds will continue through late Tuesday. Gusty winds (perhaps exceeding 40 mph) and 20-30% RH values support elevated fire weather conditions and the ongoing risk area is maintained for this outlook. See the previous discussion below for more details. ..Cook.. 09/09/2019 .PREV DISCUSSION... /ISSUED 0134 AM CDT Mon Sep 09 2019/ ...Synopsis... Broad mid/upper-level cyclonic flow is forecast to remain over the western CONUS Day 2/Tuesday. As this occurs, an area of enhanced mid-level flow -- located near the base of the trough -- is forecast to strengthen while overspreading portions of Southern California, the Southwest, and the southern Great Basin. ...Southern California: Santa Barbara and Ventura Counties... Gusty Sundowner winds are forecast to continue through Day 2/Tuesday across eastern Santa Barbara and western Ventura Counties. While minimum RH values are forecast to be a bit higher than previous days (e.g., 20-25%), elevated fire weather conditions will likely persist given the gusty winds and receptive fuels. As with previous nights, locally elevated conditions may remain overnight at higher elevations (e.g., > 1 kft) due to relatively poor RH recoveries and lingering gusty winds. ...Nevada/Utah/Arizona... While strong/gusty winds are forecast across portions of southern Nevada/Utah and northern Arizona, increasing low-level moisture should temper fire weather conditions relative to recent days. Nevertheless, locally elevated conditions are possible. ...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 0127 PM CDT Mon Sep 09 2019 Valid 101200Z - 111200Z Models remain somewhat inconsistent with depiction of minimum RH values during the afternoon on Tuesday. Nevertheless, with strong (20-25 mph) southwesterly surface winds and areas of 15-25% RH, localized areas of elevated fire weather appear likely. The greatest confidence of these conditions being observed is across south-central Utah and north-central Arizona, and a small elevated area has been introduced to address this. Locally elevated fire weather may be observed as far west as east-central Nevada and also into northwestern Colorado. Model trends will be monitored for potential reconfigurations of the new risk area in later outlook updates. In southern California, a persistent surface pattern favoring Sundowner winds will continue through late Tuesday. Gusty winds (perhaps exceeding 40 mph) and 20-30% RH values support elevated fire weather conditions and the ongoing risk area is maintained for this outlook. See the previous discussion below for more details. ..Cook.. 09/09/2019 .PREV DISCUSSION... /ISSUED 0134 AM CDT Mon Sep 09 2019/ ...Synopsis... Broad mid/upper-level cyclonic flow is forecast to remain over the western CONUS Day 2/Tuesday. As this occurs, an area of enhanced mid-level flow -- located near the base of the trough -- is forecast to strengthen while overspreading portions of Southern California, the Southwest, and the southern Great Basin. ...Southern California: Santa Barbara and Ventura Counties... Gusty Sundowner winds are forecast to continue through Day 2/Tuesday across eastern Santa Barbara and western Ventura Counties. While minimum RH values are forecast to be a bit higher than previous days (e.g., 20-25%), elevated fire weather conditions will likely persist given the gusty winds and receptive fuels. As with previous nights, locally elevated conditions may remain overnight at higher elevations (e.g., > 1 kft) due to relatively poor RH recoveries and lingering gusty winds. ...Nevada/Utah/Arizona... While strong/gusty winds are forecast across portions of southern Nevada/Utah and northern Arizona, increasing low-level moisture should temper fire weather conditions relative to recent days. Nevertheless, locally elevated conditions are possible. ...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 0127 PM CDT Mon Sep 09 2019 Valid 101200Z - 111200Z Models remain somewhat inconsistent with depiction of minimum RH values during the afternoon on Tuesday. Nevertheless, with strong (20-25 mph) southwesterly surface winds and areas of 15-25% RH, localized areas of elevated fire weather appear likely. The greatest confidence of these conditions being observed is across south-central Utah and north-central Arizona, and a small elevated area has been introduced to address this. Locally elevated fire weather may be observed as far west as east-central Nevada and also into northwestern Colorado. Model trends will be monitored for potential reconfigurations of the new risk area in later outlook updates. In southern California, a persistent surface pattern favoring Sundowner winds will continue through late Tuesday. Gusty winds (perhaps exceeding 40 mph) and 20-30% RH values support elevated fire weather conditions and the ongoing risk area is maintained for this outlook. See the previous discussion below for more details. ..Cook.. 09/09/2019 .PREV DISCUSSION... /ISSUED 0134 AM CDT Mon Sep 09 2019/ ...Synopsis... Broad mid/upper-level cyclonic flow is forecast to remain over the western CONUS Day 2/Tuesday. As this occurs, an area of enhanced mid-level flow -- located near the base of the trough -- is forecast to strengthen while overspreading portions of Southern California, the Southwest, and the southern Great Basin. ...Southern California: Santa Barbara and Ventura Counties... Gusty Sundowner winds are forecast to continue through Day 2/Tuesday across eastern Santa Barbara and western Ventura Counties. While minimum RH values are forecast to be a bit higher than previous days (e.g., 20-25%), elevated fire weather conditions will likely persist given the gusty winds and receptive fuels. As with previous nights, locally elevated conditions may remain overnight at higher elevations (e.g., > 1 kft) due to relatively poor RH recoveries and lingering gusty winds. ...Nevada/Utah/Arizona... While strong/gusty winds are forecast across portions of southern Nevada/Utah and northern Arizona, increasing low-level moisture should temper fire weather conditions relative to recent days. Nevertheless, locally elevated conditions are possible. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Mon Sep 09 2019 Valid 101200Z - 111200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN AND CENTRAL PLAINS... ...SUMMARY... Thunderstorms with severe wind gusts, large hail and isolated tornadoes will be possible across parts of the northern and central Plains on Tuesday. Some of the hail could be very large, and significant damaging winds may occur. ...Northern/Central Plains into the Upper Midwest... An upper trough over the western CONUS is forecast to amplify through the period, while downstream upper ridging builds over parts of the northern Plains and Upper Midwest. At the surface, a broad area of low pressure should gradually deepen across eastern WY/CO by Tuesday afternoon, with a pronounced baroclinic zone becoming established along the NE/SD border. Persistent easterly low-level upslope flow along with modest ascent preceding the upper trough will likely encourage convective initiation across parts of eastern WY by early Tuesday afternoon, with storms then spreading eastward across northern NE and southern SD through the evening and overnight. Steep mid-level lapse rates emanating from the central Rockies will likely overspread this region, and strong surface heating is expected to the south of the front along the NE/SD border. Moderate to strong instability, with MLCAPE around 2000-4000+ J/kg, will likely develop in response and as surface dewpoints increase into the mid 60s to lower 70s. Mid-level winds should gradually increase through the day as the upper trough amplifies over the western CONUS, and some guidance hints at a shortwave trough embedded within the southwesterly mid-level flow over the northern/central High Plains overspreading western NE/SD by midday. Related effective bulk shear values will likely increase into the 40-50 kt range along/near the surface front, which will easily support supercells with initial development. Large hail will be a threat with these storms across eastern WY into southwestern SD and the NE Panhandle, and some of the hail could be very large (2+ inches in diameter) given the forecast values of both instability and shear. Isolated tornadoes may also occur, especially with any storms that form along the surface front where low-level flow will be locally backed to east-southeasterly. A 35-45 kt southerly low-level jet will strengthen across the central Plains Tuesday evening, and upscale growth into a MCS appears likely as storms move into south-central SD and north-central NE. Severe, damaging winds should become an increasing concern with eastward extent across NE/SD Tuesday evening, and some of these winds could be significant. At least an isolated damaging wind threat may persist into parts of eastern NE/SD and the Upper Midwest through the early overnight hours, although instability will decrease farther east. There is still some uncertainty in the placement of the surface front along/near the NE/SD border, and the potential track of the MCS. Greater severe probabilities may be needed in a future outlook update if confidence increases in a more focused corridor of scattered damaging winds. ...Great Basin/Northern Rockies... Mid-level southwesterly winds are forecast to strengthen across parts of the northern Great Basin into the northern Rockies on Tuesday. Although instability will remain limited, enough MLCAPE may develop in combination with sufficient shear by late afternoon to support some organized storms across northern UT into southeastern ID and western WY. Isolated strong to damaging winds would be the main threat with this activity. ...MAXIMUM RISK BY HAZARD... Tornado: 5% - Slight Wind: 15% SIG - Slight Hail: 15% SIG - Slight ..Gleason.. 09/09/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Mon Sep 09 2019 Valid 101200Z - 111200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN AND CENTRAL PLAINS... ...SUMMARY... Thunderstorms with severe wind gusts, large hail and isolated tornadoes will be possible across parts of the northern and central Plains on Tuesday. Some of the hail could be very large, and significant damaging winds may occur. ...Northern/Central Plains into the Upper Midwest... An upper trough over the western CONUS is forecast to amplify through the period, while downstream upper ridging builds over parts of the northern Plains and Upper Midwest. At the surface, a broad area of low pressure should gradually deepen across eastern WY/CO by Tuesday afternoon, with a pronounced baroclinic zone becoming established along the NE/SD border. Persistent easterly low-level upslope flow along with modest ascent preceding the upper trough will likely encourage convective initiation across parts of eastern WY by early Tuesday afternoon, with storms then spreading eastward across northern NE and southern SD through the evening and overnight. Steep mid-level lapse rates emanating from the central Rockies will likely overspread this region, and strong surface heating is expected to the south of the front along the NE/SD border. Moderate to strong instability, with MLCAPE around 2000-4000+ J/kg, will likely develop in response and as surface dewpoints increase into the mid 60s to lower 70s. Mid-level winds should gradually increase through the day as the upper trough amplifies over the western CONUS, and some guidance hints at a shortwave trough embedded within the southwesterly mid-level flow over the northern/central High Plains overspreading western NE/SD by midday. Related effective bulk shear values will likely increase into the 40-50 kt range along/near the surface front, which will easily support supercells with initial development. Large hail will be a threat with these storms across eastern WY into southwestern SD and the NE Panhandle, and some of the hail could be very large (2+ inches in diameter) given the forecast values of both instability and shear. Isolated tornadoes may also occur, especially with any storms that form along the surface front where low-level flow will be locally backed to east-southeasterly. A 35-45 kt southerly low-level jet will strengthen across the central Plains Tuesday evening, and upscale growth into a MCS appears likely as storms move into south-central SD and north-central NE. Severe, damaging winds should become an increasing concern with eastward extent across NE/SD Tuesday evening, and some of these winds could be significant. At least an isolated damaging wind threat may persist into parts of eastern NE/SD and the Upper Midwest through the early overnight hours, although instability will decrease farther east. There is still some uncertainty in the placement of the surface front along/near the NE/SD border, and the potential track of the MCS. Greater severe probabilities may be needed in a future outlook update if confidence increases in a more focused corridor of scattered damaging winds. ...Great Basin/Northern Rockies... Mid-level southwesterly winds are forecast to strengthen across parts of the northern Great Basin into the northern Rockies on Tuesday. Although instability will remain limited, enough MLCAPE may develop in combination with sufficient shear by late afternoon to support some organized storms across northern UT into southeastern ID and western WY. Isolated strong to damaging winds would be the main threat with this activity. ...MAXIMUM RISK BY HAZARD... Tornado: 5% - Slight Wind: 15% SIG - Slight Hail: 15% SIG - Slight ..Gleason.. 09/09/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Mon Sep 09 2019 Valid 101200Z - 111200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN AND CENTRAL PLAINS... ...SUMMARY... Thunderstorms with severe wind gusts, large hail and isolated tornadoes will be possible across parts of the northern and central Plains on Tuesday. Some of the hail could be very large, and significant damaging winds may occur. ...Northern/Central Plains into the Upper Midwest... An upper trough over the western CONUS is forecast to amplify through the period, while downstream upper ridging builds over parts of the northern Plains and Upper Midwest. At the surface, a broad area of low pressure should gradually deepen across eastern WY/CO by Tuesday afternoon, with a pronounced baroclinic zone becoming established along the NE/SD border. Persistent easterly low-level upslope flow along with modest ascent preceding the upper trough will likely encourage convective initiation across parts of eastern WY by early Tuesday afternoon, with storms then spreading eastward across northern NE and southern SD through the evening and overnight. Steep mid-level lapse rates emanating from the central Rockies will likely overspread this region, and strong surface heating is expected to the south of the front along the NE/SD border. Moderate to strong instability, with MLCAPE around 2000-4000+ J/kg, will likely develop in response and as surface dewpoints increase into the mid 60s to lower 70s. Mid-level winds should gradually increase through the day as the upper trough amplifies over the western CONUS, and some guidance hints at a shortwave trough embedded within the southwesterly mid-level flow over the northern/central High Plains overspreading western NE/SD by midday. Related effective bulk shear values will likely increase into the 40-50 kt range along/near the surface front, which will easily support supercells with initial development. Large hail will be a threat with these storms across eastern WY into southwestern SD and the NE Panhandle, and some of the hail could be very large (2+ inches in diameter) given the forecast values of both instability and shear. Isolated tornadoes may also occur, especially with any storms that form along the surface front where low-level flow will be locally backed to east-southeasterly. A 35-45 kt southerly low-level jet will strengthen across the central Plains Tuesday evening, and upscale growth into a MCS appears likely as storms move into south-central SD and north-central NE. Severe, damaging winds should become an increasing concern with eastward extent across NE/SD Tuesday evening, and some of these winds could be significant. At least an isolated damaging wind threat may persist into parts of eastern NE/SD and the Upper Midwest through the early overnight hours, although instability will decrease farther east. There is still some uncertainty in the placement of the surface front along/near the NE/SD border, and the potential track of the MCS. Greater severe probabilities may be needed in a future outlook update if confidence increases in a more focused corridor of scattered damaging winds. ...Great Basin/Northern Rockies... Mid-level southwesterly winds are forecast to strengthen across parts of the northern Great Basin into the northern Rockies on Tuesday. Although instability will remain limited, enough MLCAPE may develop in combination with sufficient shear by late afternoon to support some organized storms across northern UT into southeastern ID and western WY. Isolated strong to damaging winds would be the main threat with this activity. ...MAXIMUM RISK BY HAZARD... Tornado: 5% - Slight Wind: 15% SIG - Slight Hail: 15% SIG - Slight ..Gleason.. 09/09/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1113 AM CDT Mon Sep 09 2019 Valid 091630Z - 101200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF NORTHERN IOWA...SOUTHERN MINNESOTA...AND WESTERN WISCONSIN... ...SUMMARY... Severe thunderstorms are possible this afternoon and evening over parts of the Upper Midwest and upper Mississippi Valley regions. ...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. ..Hart/Wendt.. 09/09/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1113 AM CDT Mon Sep 09 2019 Valid 091630Z - 101200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF NORTHERN IOWA...SOUTHERN MINNESOTA...AND WESTERN WISCONSIN... ...SUMMARY... Severe thunderstorms are possible this afternoon and evening over parts of the Upper Midwest and upper Mississippi Valley regions. ...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. ..Hart/Wendt.. 09/09/2019 Read more