Severe Storms

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0157 PM CDT Thu Sep 07 2023 Valid 091200Z - 151200Z The potential for critical fire weather conditions remains low across the country through the extended period. Long-range ensemble guidance continues to show a building upper-level ridge over the Southwest/northern Mexico through the weekend, followed by a gradual ridge breakdown and an amplifying longwave trough east of the Rockies. This synoptic regime will favor a continuation of warm, dry conditions from west TX into the Four Corners through D4/Sunday, which should favor a slow curing of fuels and may support local fire weather concerns. Rain chances will increase across the Plains and Southwest beginning D5/Monday, limiting the fire weather potential through the remainder of the week. Ensemble precipitation forecasts show low probability for wetting rainfall across much of the West Coast and Pacific Northwest, suggesting some drying will occur across these regions. However, there are currently no appreciable signals for strong synoptic systems that would support widespread 20+ mph winds, which limits confidence in the fire weather potential. ..Moore.. 09/07/2023 ...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 1256 PM CDT Thu Sep 07 2023 Valid 081200Z - 091200Z An isolated dry-thunderstorm risk area is introduced for portions of west to northwest Texas. Latest CAM ensemble guidance has trended towards a higher probability and coverage of thunderstorms in the vicinity of the surface low over northwest TX tomorrow afternoon. Forecast soundings depict very dry boundary-layer conditions featuring LCL heights between 3.5 to 4 km and 50-60 F dewpoint depressions. These profiles will greatly limit rainfall amounts and promote dry lightning over a region with dry fuels. One conditionality is the potential for thunderstorms over the next 12-18 hours across this region; however, a similar thermodynamic environment today should yield very isolated patches of wetting rain, and is not expected to drastically alter the fuel landscape. ..Moore.. 09/07/2023 .PREV DISCUSSION... /ISSUED 1236 AM CDT Thu Sep 07 2023/ ...Synopsis... A slight westward shift in the upper-level ridge is expected on Friday. The surface pattern will remain relatively similar in the southern High Plains, though the surface low may shift farther south and east. ...Southern High Plains... Dry and breezy conditions will again be possible both north and south of the surface trough. Only marginally elevated conditions are probable to the north of the trough in the Texas Panhandle, as winds will be upslope and temperatures will be cooler than on Thursday. Winds to the south of the trough are expected to be weak. There is some additional potential for a thunderstorm or two to develop within the surface trough. While any storm that develops would likely be dry, coverage appears to be much less than 10% at this time. ...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 1245 PM CDT Thu Sep 07 2023 Valid 081200Z - 091200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS EASTERN PORTIONS OF THE SOUTHERN PLAINS AND ACROSS THE SABINE RIVER VALLEY...AND OVER PARTS OF THE NORTHEAST AND MID-ATLANTIC REGION... ...SUMMARY... Thunderstorms, associated with a marginal severe threat, will be possible on Friday across parts of the Northeast, Central Appalachians, Mid-Atlantic, Ark-La-Tex and Northern High Plains. ...Southeastern Oklahoma/eastern Texas/southwestern Arkansas/western Louisiana... Thunderstorms are forecast to be ongoing at the start of the period across parts of the eastern Oklahoma/western Arkansas region, possibly accompanied by some ongoing potential for strong winds/hail. A strong model signal remains apparent that storms will shift southward with time, strengthening gradually as daytime heating results in a corridor of moderate instability. Given a belt of 35 to 45 kt mid-level north-northwesterly flow around the eastern fringe of the southwestern U.S. upper ridge, potential for an organized MCS moving quickly southward roughly along the Sabine River Valley through the day may evolve. In this scenario, potential for damaging winds would be expected, along with some hail, with the risk shifting southward and likely reaching the Gulf Coast by late afternoon. While less certain, some hints exist within some models that late evening/overnight redevelopment of storms could occur on the western flank/remnant outflow from this initial band of storms, across the north-central Texas vicinity, with potential for a second/southeastward-moving MCS. These storms -- should they develop/organize, could also pose risk for hail and damaging winds through the overnight period. ...The Northeast and Mid-Atlantic region... Afternoon heating/destabilization is expected along and east of the Appalachians Friday, near a weak/stalled surface front. Terrain-induced ascent, and lift near the front, will result in scattered thunderstorm development during the afternoon, particularly from the mountains of Virginia and West Virginia northeastward into New England. With a belt of 25 to 35 kt south-southwesterly flow across this area, on the eastern fringe of the mid-level trough positioned over the Midwest/Tennessee Valley, shear will support a few organized storms/storm clusters. As these clusters shift northeastward, locally damaging wind gusts can be expected, lingering into the early evening hours before storms begin to nocturnally weaken. ...Northern Intermountain region... Daytime heating across the northern Intermountain region will result in modest destabilization, with mixed-layer CAPE averaging 500 J/kg during the afternoon atop a deep mixed layer. As a short-wave trough at mid levels sweeps eastward across the region, isolated to widely scattered thunderstorm development is expected, with peak convective coverage anticipated from late afternoon through mid evening. With a belt of 30 to 40 kt mid-level westerlies accompanying the short-wave trough, and potential for sub-cloud evaporative effects, a few stronger/longer-lived storms may produce gusty/locally damaging winds. ..Goss.. 09/07/2023 Read more

WW 0672 Status Updates
STATUS FOR WATCH 0672 HAS NOT BEEN ISSUED YET Read more

No Mesoscale Discussions are in effect as of Wed Sep 6 22:26:04 UTC 2023.

WW 672 SEVERE TSTM AR LA MS 062225Z - 070400Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 672 NWS Storm Prediction Center Norman OK 525 PM CDT Wed Sep 6 2023 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Extreme southeast Arkansas Extreme northeast Louisiana Northern into west central Mississippi * Effective this Wednesday afternoon and evening from 525 PM until 1100 PM CDT. * Primary threats include... Scattered damaging wind gusts to 70 mph possible Isolated large hail events to 1 inch in diameter possible SUMMARY...Clusters of storms will continue to form and spread south-southeastward through early tonight, with the potential to produce occasional damaging winds of 60-70 mph and isolated large hail near 1 inch in diameter. The severe thunderstorm watch area is approximately along and 65 statute miles east and west of a line from 65 miles south of Greenville MS to 45 miles north northeast of Oxford MS. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU2). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for 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. Severe thunderstorms can and occasionally do produce tornadoes. && AVIATION...A few severe thunderstorms with hail surface and aloft to 1 inch. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 550. Mean storm motion vector 34020. ...Thompson Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0241 PM CDT Wed Sep 06 2023 Valid 081200Z - 141200Z The potential for critical fire weather conditions remains low through the extended period. Long-range ensemble means and cluster analyses show high confidence in a building upper-level ridge over northern Mexico into the Southwest and southern Great Basin through the weekend followed by a gradual ridge breakdown as a longwave trough becomes established over the central and eastern CONUS next week. This synoptic pattern will favor warm and dry conditions across the southern High Plains and Southwest over the weekend, which should aid in curing currently unreceptive fuels. Fire weather concerns may emerge from west TX into the Four Corners/southern Great Basin during the D3/Friday to D5/Sunday period amid the hot, dry conditions, but uncertainties regarding fuel status and low confidence in the strength of low-level winds under the building ridge casts considerable uncertainty on the fire weather potential. Rain chances will increase across the southern Plains and Southwest/Four Corners region heading into next week, which should limit fire concerns. ..Moore.. 09/06/2023 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0238 PM CDT Wed Sep 06 2023 Valid 062000Z - 071200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF THE TENNESSEE VALLEY AREA WEST-SOUTHWESTWARD TO PARTS OF ARKANSAS AND NORTHERN LOUISIANA... ...SUMMARY... Strong/locally severe storms remain possible ahead of a weak/advancing cold front -- potentially most numerous over parts of the Tennessee and Lower Mississippi Valleys and vicinity. ...Discussion... Aside from minor line adjustments to reflect ongoing and anticipated convective evolution, changes appear unnecessary at this time as prior reasoning continues to reflect current expectations for evolution of severe-weather potential this afternoon and evening. ..Goss.. 09/06/2023 .PREV DISCUSSION... /ISSUED 1115 AM CDT Wed Sep 06 2023/ ...Synopsis... Amplified, but weak, mid-level troughing lingers offshore of the Atlantic Seaboard, with a modest cyclone, slowly migrating northeastward to the south of Nova Scotia, the most prominent embedded perturbation. Upstream, models indicate that mid-level troughing may also begin to amplify across and east of the Mississippi Valley, downstream of building short wave ridging to the north of a prominent subtropical high centered over southeastern New Mexico. The amplifying trough will include one generally weakening short wave impulse progressing across the Great Lakes region today through tonight, while an additional couple of perturbations dig within northwesterly flow southeast of the Black Hills vicinity through the Ozark Plateau/lower Mississippi Valley. Stronger wind fields are becoming largely confined to the northwesterly regime upstream of the evolving larger-scale mid-level trough axis, though a remnant belt of modest southwesterly flow (including 30+ kt in the 850-700 mb layer) downstream of the trough axis is forecast to nose northeast of lower Michigan through Ontario by mid/late afternoon. The latter speed maximum will accompany a weakening migratory low within weak surface troughing, along a cold front forecast to slowly advance eastward across the upper Great Lakes region, Ontario and central Quebec. An initial cold frontal surge already has reached the lower Ohio Valley, Ozark Plateau and Texas South Plains vicinity. Across parts of western Kentucky and Tennessee into northeastern Arkansas, the front is preceded by a remnant MCV and convective outflow associated with a dissipating cluster of thunderstorms. ...Great Lakes through southern Great Plains... While deep-layer mean wind fields and vertical shear have generally weakened ahead/south of the cold front, modestly steep lapse rates in lower through mid-levels, coupled with residual boundary-layer moisture, may contribute to areas of sizable mixed-layer CAPE in excess of 2000 J/kg by late afternoon. From the Tennessee Valley into the Great Lakes region, this may be more sparse in nature due to early day cloud cover and weak low-level focus for convective development. However, it seems probable that a more prominent zone of differential surface heating, across parts of central Arkansas into western Tennessee, will become a focus for at least scattered strong thunderstorm development by late this afternoon. Given thermodynamic profiles characterized by large CAPE and a very warm well-mixed boundary layer, various guidance has been suggestive that an upscale growing cluster could eventually evolve along consolidating, south/southwestward propagating cold pools into this evening. If this occurs, a hail/downburst threat in stronger initial storms may transition to a more widespread marginal severe wind threat. Other more widely scattered strong thunderstorm development is possible west-southwestward into a hotter, drier and more deeply mixed boundary layer across parts of west central Texas. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0147 PM CDT Wed Sep 06 2023 Valid 071200Z - 081200Z A dry thunderstorm risk area has been introduced for parts of the TX Panhandle/northwest TX into southwest OK. Recent CAM ensemble guidance has trended towards higher probability of very isolated thunderstorms along the surface trough from west TX into northwest OK. PWAT values along this axis should range from 0.75 to 1.25 inches, but forecast soundings depict very deep, well-mixed boundary layers with LCLs between 3-3.5 km. This should modulate rainfall amounts to some degree, and given antecedent dry fuels (much of this region received little to no rainfall over the past 24 hours), dry lightning is possible and will pose a fire weather concern. Elevated fire weather conditions are likely across northern NM and southeast WY as westerly winds increase to 15-20 mph (with locally stronger winds in the lee of terrain features). However, fuels across both regions appear to be only modestly receptive per recent ERC analyses. Transient elevated conditions are possible along the lee trough in northwest TX/southwest OK within the dry thunderstorm risk area, but low ensemble probability for sustained winds over 15 mph limits confidence in this potential. ..Moore.. 09/06/2023 .PREV DISCUSSION... /ISSUED 1234 AM CDT Wed Sep 06 2023/ ...Synopsis... The upper-level ridge will remain within the Southwest on Thursday. At the surface, a weak low will develop in the southern High Plains along the stalled surface front. High surface pressure will be situated within the Four Corners region. ...Southern High Plains... With the increase in the surface pressure gradient, some areas of locally elevated fire weather are possible from northeast New Mexico into parts of the Texas Panhandle and South Plains. Fuels will remain quite dry, particularly into the Rolling Plains/Permian Basin. However, the impact of precipitation from Tuesday evening will have to be assessed. Overall, the duration and coverage of these elevated conditions are short and limited, respectively. No highlights will be added this outlook. Another conditional concern will be a dry thunderstorm or two within the surface low in the Texas Panhandle/South Plains. The probability of this occurring is less than 5%. ...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 Wed Sep 06 2023 Valid 071200Z - 081200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHEAST AND MID-ATLANTIC REGION... ...SUMMARY... Potential for locally damaging wind gusts and marginal hail will be possible across the Northeast, and southwestward into the Southeast. Gusty winds and hail may also occur locally over parts of the central and southern Plains and Arklatex area. ...Parts of the Northeast and Mid-Atlantic region, and into the Southeast... Showers and isolated thunderstorms may be ongoing across the central Appalachians vicinity at the start of the period, ahead of a weak cold front moving eastward across the mountains and southeastward across the Southeast. As the warm sector heats/destabilizes through the day, additional/isolated storm development is expected along the entire extent of this front, from the lower Great Lakes and New England, to the Gulf Coast. At this time, somewhat more concentrated convective development is expected to evolve from the Mid-Atlantic States into New England, associated with a compact vort max progged to shift northeastward across this region during the afternoon and evening, in advance of the main short-wave trough to the west. Slightly stronger flow aloft and moderate instability may result in bands/clusters of storms capable of producing locally damaging winds, and marginally severe hail. Activity should peak in intensity through late afternoon/early evening, before diminishing nocturnally. ...Parts of Oklahoma southeastward across the Arklatex... Isolated afternoon thunderstorms may develop across parts of Oklahoma/East Texas/Arkansas/Louisiana, in the vicinity of a surface baroclinic zone expected to lie across the area. A deep mixed layer may support potential for locally strong wind gusts across the Oklahoma portion of the outlook, through early evening. During the evening, southwesterly low-level jet development may support some increase in convective development, possibly clustering into a loosely organized MCS over the Arkansas vicinity, that would then shift southward toward Louisiana, possibly accompanied by limited/local wind/hail near severe levels. ...Central and eastern Nebraska vicinity... Afternoon heating/destabilization across the central Plains vicinity should support isolated convective development, ahead of weak mid-level short-wave troughing forecast to crest the ridge and shift east-southeastward across the area during the afternoon and evening. With a belt of 40 kt west-northwesterly flow around the periphery of the ridge possibly contributing to evolution of a couple of stronger/organized storms, limited local risk for gusty winds and marginal hail remains evident during the late afternoon and evening hours. ..Goss.. 09/06/2023 Read more

WW 0671 Status Updates
STATUS FOR WATCH 0671 HAS NOT BEEN ISSUED YET Read more

WW 671 SEVERE TSTM KS MO 052230Z - 060500Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 671 NWS Storm Prediction Center Norman OK 530 PM CDT Tue Sep 5 2023 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Far southeast Kansas Southwest to central Missouri * Effective this Tuesday afternoon from 530 PM until Midnight CDT. * Primary threats include... Scattered damaging winds and isolated significant gusts to 75 mph possible Isolated large hail events to 1.5 inches in diameter possible SUMMARY...Multicell clusters should develop along a cold front and spread east-southeast this evening with a primary threat of damaging winds. The severe thunderstorm watch area is approximately along and 65 statute miles east and west of a line from 65 miles north northwest of Columbia MO to 15 miles south southwest of Monett MO. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU1). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for 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. Severe thunderstorms can and occasionally do produce tornadoes. && OTHER WATCH INFORMATION...CONTINUE...WW 669...WW 670... AVIATION...A few severe thunderstorms with hail surface and aloft to 1.5 inches. Extreme turbulence and surface wind gusts to 65 knots. A few cumulonimbi with maximum tops to 550. Mean storm motion vector 29030. ...Grams Read more

WW 0669 Status Updates
STATUS REPORT ON WW 669 THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA. ..LYONS..09/05/23 ATTN...WFO...DLH...MPX...ARX... STATUS REPORT FOR WS 669 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS MNC001-003-009-013-017-019-021-025-031-035-037-039-043-045-047- 049-053-055-059-061-065-075-079-085-093-095-097-099-103-109-115- 123-131-137-139-141-143-145-147-157-161-163-169-171-052340- MN . MINNESOTA COUNTIES INCLUDED ARE AITKIN ANOKA BENTON BLUE EARTH CARLTON CARVER CASS CHISAGO COOK CROW WING DAKOTA DODGE FARIBAULT FILLMORE FREEBORN GOODHUE HENNEPIN HOUSTON ISANTI ITASCA KANABEC LAKE LE SUEUR MCLEOD MEEKER MILLE LACS MORRISON MOWER NICOLLET OLMSTED PINE RAMSEY RICE ST. LOUIS SCOTT SHERBURNE SIBLEY STEARNS STEELE WABASHA WASECA WASHINGTON WINONA WRIGHT WIC003-005-007-011-013-031-033-051-091-093-095-107-109-113-129- 052340- Read more

WW 669 SEVERE TSTM MN WI LS 052055Z - 060400Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 669 NWS Storm Prediction Center Norman OK 355 PM CDT Tue Sep 5 2023 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Central and Eastern Minnesota Western Wisconsin Lake Superior * Effective this Tuesday afternoon and evening from 355 PM until 1100 PM CDT. * Primary threats include... Scattered damaging wind gusts to 70 mph possible Scattered large hail events to 1.5 inches in diameter possible A tornado or two possible SUMMARY...Strong to severe thunderstorms are expected to develop through late afternoon and early evening, initially across the eastern half of Minnesota, with large hail and damaging winds as the primary hazards. Storms are expected to develop into western Wisconsin by early/mid-evening. The severe thunderstorm watch area is approximately along and 75 statute miles east and west of a line from 10 miles north of Ely MN to 40 miles southwest of Rochester MN. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU9). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for 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. Severe thunderstorms can and occasionally do produce tornadoes. && AVIATION...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 550. Mean storm motion vector 23025. ...Guyer Read more

WW 0670 Status Updates
STATUS FOR WATCH 0670 HAS NOT BEEN ISSUED YET Read more

WW 670 SEVERE TSTM AR OK 052200Z - 060500Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 670 NWS Storm Prediction Center Norman OK 500 PM CDT Tue Sep 5 2023 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Northwest Arkansas Southwest to northeast Oklahoma * Effective this Tuesday afternoon from 500 PM until Midnight CDT. * Primary threats include... Scattered damaging winds and isolated significant gusts to 80 mph possible Isolated large hail events to 1 inch in diameter possible SUMMARY...Isolated to scattered thunderstorms will develop along a northeast to southwest-oriented front in Oklahoma and should grow upscale into multicell clusters, especially over eastern Oklahoma into northwest Arkansas. Damaging winds will be the main threat. The severe thunderstorm watch area is approximately along and 70 statute miles east and west of a line from 30 miles northeast of Grove OK to 40 miles southeast of Chickasha OK. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU0). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for 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. Severe thunderstorms can and occasionally do produce tornadoes. && OTHER WATCH INFORMATION...CONTINUE...WW 669... AVIATION...A few severe thunderstorms with hail surface and aloft to 1 inch. Extreme turbulence and surface wind gusts to 70 knots. A few cumulonimbi with maximum tops to 550. Mean storm motion vector 32025. ...Grams Read more

MD 2085 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PORTIONS OF MO...SOUTHEAST KS...NORTHEAST/CENTRAL OK...AND FAR NORTHWEST AR
Mesoscale Discussion 2085 NWS Storm Prediction Center Norman OK 0404 PM CDT Tue Sep 05 2023 Areas affected...Portions of MO...southeast KS...northeast/central OK...and far northwest AR Concerning...Severe potential...Watch possible Valid 052104Z - 052330Z Probability of Watch Issuance...60 percent SUMMARY...The severe-storm risk should increase during the next few hours. Severe gusts and isolated hail are both possible. A watch issuance is possible this afternoon. DISCUSSION...Latest surface analysis shows a northeast/southwest- oriented cold front extending from northwest MO into parts of central OK this afternoon -- where shallow boundary-layer cumulus is beginning to develop. Continued diurnal heating amid rich boundary-layer moisture (lower 70s surface dewpoints) along/immediately ahead of the east-southeastward-moving front should support convective initiation in the next few hours. Steep low/mid-level lapse rates and 20-30-kt midlevel west-southwesterly flow oriented oblique to the surface front (strongest across MO) will initially support semi-discrete storms capable of marginally severe hail and locally severe gusts. However, a fairly quick transition from cells to an organized line of storms is expected as storms maintain residence time in the frontal circulation amid increasing outflow generation. This mode transition will favor an increasing severe-wind threat as the front continues slowly east-southeastward into the evening hours. Currently, the potential for an organized QLCS appears greatest over parts of MO -- where deep-layer shear and large-scale ascent will be stronger compared to areas farther southwest. However, 100 deg surface temperatures and related steep low-level lapse rates will still support severe-thunderstorm gusts into central OK. A watch issuance is possible this afternoon for parts of the area. ..Weinman/Guyer.. 09/05/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LSX...SGF...EAX...TSA...ICT...OUN... LAT...LON 36569631 37239540 38389426 39019377 39809340 40159304 40189255 39939190 39489136 38849125 37679171 36929252 36239377 35159582 35069665 35229703 35569727 35839723 36569631 Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0253 PM CDT Tue Sep 05 2023 Valid 052000Z - 061200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE UPPER MISSISSIPPI VALLEY/WESTERN UPPER GREAT LAKES REGION...AND FROM MISSOURI AND VICINITY SOUTHWESTWARD INTO NORTHEASTERN OKLAHOMA... ...SUMMARY... Severe thunderstorms are expected this afternoon and evening over parts of the upper Mississippi Valley/Lake Superior region, and across the Ozarks and parts of Oklahoma. Severe wind gusts and isolated large hail are possible. ...Discussion... Along with minor line tweaks in a few areas, including some eastward expansion of thunder into parts of Wyoming for the overnight period, the only other substantive change at this time is the northward expansion of SLGT risk/15% wind into parts of northern Missouri. Here, a similar thermodynamic pre-frontal environment is indicated as compared to areas a bit farther south, and several CAM runs are indicating development along the front may extend a bit farther north than previously hinted at in the outlook. Otherwise, expectations remain similar to those in prior outlooks. ..Goss.. 09/05/2023 .PREV DISCUSSION... /ISSUED 1131 AM CDT Tue Sep 05 2023/ ...Upper Mississippi Valley... A shortwave trough over the Dakotas this morning will continue eastward toward the upper Mississippi Valley through tonight. A slight cooling of mid-level temperatures (-10C at 500 mb) will accompany this trough, while only a modest strengthening of trough-preceding winds aloft is expected, given that the trough is somewhat removed from the stronger westerlies over the Canadian prairies. While some warm-sector cloud cover persists early today regionally, the boundary layer ahead of an eastward-moving cold front should become minimally inhibited by early into mid-afternoon, with MLCAPE reaching 2500+ J/kg especially across the eastern halves of Minnesota and Iowa, as well as much of western Wisconsin and far northwest Illinois. Initial thunderstorm intensification is expected this afternoon across northern/central Minnesota, potentially with an ongoing band of storms across northern Minnesota, and more so near the aforementioned front and surface wave, with subsequent scattered development southward into southeast Minnesota/eastern Iowa and western Wisconsin through late afternoon and early evening. Severe wind gusts and hail will be possible with a mixed mode of storms including multicells and some transient supercells. Some tornado risk may exist as well, mainly across northeast Minnesota/northwest Wisconsin. ...Middle Mississippi Valley/Ozarks/southern Plains... Widely scattered mid-level convection across the region trails a shortwave trough centered generally near the confluence of the Mississippi/Ohio Rivers. This convection is atop a warm-sector boundary layer that will heat and become strongly unstable by peak heating, particularly across eastern Oklahoma into Missouri western/northern Arkansas ahead of an east/southeastward-moving front. Isolated to widely scattered thunderstorms are expected to develop by mid/late afternoon near the front, and somewhat across the warm sector, potentially influenced by lingering cloud cover/zones of differential heating. While tropospheric winds will only be modest strength (effective shear less than 30 kt), strong heating, steep lapse rates, and ample buoyancy will support the potential for severe-caliber wind gusts, especially with the aforementioned corridor of greatest destabilization. Some severe hail may occur as well. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0253 PM CDT Tue Sep 05 2023 Valid 052000Z - 061200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE UPPER MISSISSIPPI VALLEY/WESTERN UPPER GREAT LAKES REGION...AND FROM MISSOURI AND VICINITY SOUTHWESTWARD INTO NORTHEASTERN OKLAHOMA... ...SUMMARY... Severe thunderstorms are expected this afternoon and evening over parts of the upper Mississippi Valley/Lake Superior region, and across the Ozarks and parts of Oklahoma. Severe wind gusts and isolated large hail are possible. ...Discussion... Along with minor line tweaks in a few areas, including some eastward expansion of thunder into parts of Wyoming for the overnight period, the only other substantive change at this time is the northward expansion of SLGT risk/15% wind into parts of northern Missouri. Here, a similar thermodynamic pre-frontal environment is indicated as compared to areas a bit farther south, and several CAM runs are indicating development along the front may extend a bit farther north than previously hinted at in the outlook. Otherwise, expectations remain similar to those in prior outlooks. ..Goss.. 09/05/2023 .PREV DISCUSSION... /ISSUED 1131 AM CDT Tue Sep 05 2023/ ...Upper Mississippi Valley... A shortwave trough over the Dakotas this morning will continue eastward toward the upper Mississippi Valley through tonight. A slight cooling of mid-level temperatures (-10C at 500 mb) will accompany this trough, while only a modest strengthening of trough-preceding winds aloft is expected, given that the trough is somewhat removed from the stronger westerlies over the Canadian prairies. While some warm-sector cloud cover persists early today regionally, the boundary layer ahead of an eastward-moving cold front should become minimally inhibited by early into mid-afternoon, with MLCAPE reaching 2500+ J/kg especially across the eastern halves of Minnesota and Iowa, as well as much of western Wisconsin and far northwest Illinois. Initial thunderstorm intensification is expected this afternoon across northern/central Minnesota, potentially with an ongoing band of storms across northern Minnesota, and more so near the aforementioned front and surface wave, with subsequent scattered development southward into southeast Minnesota/eastern Iowa and western Wisconsin through late afternoon and early evening. Severe wind gusts and hail will be possible with a mixed mode of storms including multicells and some transient supercells. Some tornado risk may exist as well, mainly across northeast Minnesota/northwest Wisconsin. ...Middle Mississippi Valley/Ozarks/southern Plains... Widely scattered mid-level convection across the region trails a shortwave trough centered generally near the confluence of the Mississippi/Ohio Rivers. This convection is atop a warm-sector boundary layer that will heat and become strongly unstable by peak heating, particularly across eastern Oklahoma into Missouri western/northern Arkansas ahead of an east/southeastward-moving front. Isolated to widely scattered thunderstorms are expected to develop by mid/late afternoon near the front, and somewhat across the warm sector, potentially influenced by lingering cloud cover/zones of differential heating. While tropospheric winds will only be modest strength (effective shear less than 30 kt), strong heating, steep lapse rates, and ample buoyancy will support the potential for severe-caliber wind gusts, especially with the aforementioned corridor of greatest destabilization. Some severe hail may occur as well. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0253 PM CDT Tue Sep 05 2023 Valid 052000Z - 061200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE UPPER MISSISSIPPI VALLEY/WESTERN UPPER GREAT LAKES REGION...AND FROM MISSOURI AND VICINITY SOUTHWESTWARD INTO NORTHEASTERN OKLAHOMA... ...SUMMARY... Severe thunderstorms are expected this afternoon and evening over parts of the upper Mississippi Valley/Lake Superior region, and across the Ozarks and parts of Oklahoma. Severe wind gusts and isolated large hail are possible. ...Discussion... Along with minor line tweaks in a few areas, including some eastward expansion of thunder into parts of Wyoming for the overnight period, the only other substantive change at this time is the northward expansion of SLGT risk/15% wind into parts of northern Missouri. Here, a similar thermodynamic pre-frontal environment is indicated as compared to areas a bit farther south, and several CAM runs are indicating development along the front may extend a bit farther north than previously hinted at in the outlook. Otherwise, expectations remain similar to those in prior outlooks. ..Goss.. 09/05/2023 .PREV DISCUSSION... /ISSUED 1131 AM CDT Tue Sep 05 2023/ ...Upper Mississippi Valley... A shortwave trough over the Dakotas this morning will continue eastward toward the upper Mississippi Valley through tonight. A slight cooling of mid-level temperatures (-10C at 500 mb) will accompany this trough, while only a modest strengthening of trough-preceding winds aloft is expected, given that the trough is somewhat removed from the stronger westerlies over the Canadian prairies. While some warm-sector cloud cover persists early today regionally, the boundary layer ahead of an eastward-moving cold front should become minimally inhibited by early into mid-afternoon, with MLCAPE reaching 2500+ J/kg especially across the eastern halves of Minnesota and Iowa, as well as much of western Wisconsin and far northwest Illinois. Initial thunderstorm intensification is expected this afternoon across northern/central Minnesota, potentially with an ongoing band of storms across northern Minnesota, and more so near the aforementioned front and surface wave, with subsequent scattered development southward into southeast Minnesota/eastern Iowa and western Wisconsin through late afternoon and early evening. Severe wind gusts and hail will be possible with a mixed mode of storms including multicells and some transient supercells. Some tornado risk may exist as well, mainly across northeast Minnesota/northwest Wisconsin. ...Middle Mississippi Valley/Ozarks/southern Plains... Widely scattered mid-level convection across the region trails a shortwave trough centered generally near the confluence of the Mississippi/Ohio Rivers. This convection is atop a warm-sector boundary layer that will heat and become strongly unstable by peak heating, particularly across eastern Oklahoma into Missouri western/northern Arkansas ahead of an east/southeastward-moving front. Isolated to widely scattered thunderstorms are expected to develop by mid/late afternoon near the front, and somewhat across the warm sector, potentially influenced by lingering cloud cover/zones of differential heating. While tropospheric winds will only be modest strength (effective shear less than 30 kt), strong heating, steep lapse rates, and ample buoyancy will support the potential for severe-caliber wind gusts, especially with the aforementioned corridor of greatest destabilization. Some severe hail may occur as well. Read more