SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1252 AM CDT Thu Aug 29 2024 Valid 301200Z - 311200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE LAKE HURON AND ERIE VICINITY WEST-SOUTHWESTWARD ACROSS THE MIDWEST... ...SUMMARY... Strong/locally severe storms will be possible from Lakes Huron and Erie southwestward into the Midwest Friday. ...Synopsis... An upper-level trough will continue moving slowly eastward out of the north-central U.S. across the Great Lakes and Midwest on Friday, with the more vigorous portion of the trough expected to eject northeastward across western Ontario into the Hudson Bay region. At the surface, a cold front is forecast to continue eastward across the Great Lakes, southeastward across the Midwest, and slowly southward across the southern Plains. By the end of the period, the front should extend from the Lower Great Lakes west-southwestward across the Ohio Valley, and into Oklahoma and northern Texas. ...Lower Michigan/northern Ohio/northwestern Pennsylvania across the Midwest... Moderate destabilization is expected in tandem with afternoon heating ahead of the cold front, from Lower Michigan west-southwestward across northern Illinois and Missouri, and southward across the warm sector. As the front slowly advances, scattered thunderstorm development is expected, initially across the lower Michigan and potentially into parts of Ohio, and then expanding southwestward across Indiana, Illinois, and into Missouri. Although the stronger deep-layer shear will largely remain to the cool side of the front, modest westerly mid-level flow of 20-25 kts will favor loosely organized storms, with some potential for upscale growth/clustering. Strong/isolated damaging gusts and perhaps severe hail will be possible. While risk should diminish after dark, convection -- and very limited risk with a couple of stronger storms -- may continue well into the overnight hours. ..Goss.. 08/29/2024 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1252 AM CDT Thu Aug 29 2024 Valid 301200Z - 311200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE LAKE HURON AND ERIE VICINITY WEST-SOUTHWESTWARD ACROSS THE MIDWEST... ...SUMMARY... Strong/locally severe storms will be possible from Lakes Huron and Erie southwestward into the Midwest Friday. ...Synopsis... An upper-level trough will continue moving slowly eastward out of the north-central U.S. across the Great Lakes and Midwest on Friday, with the more vigorous portion of the trough expected to eject northeastward across western Ontario into the Hudson Bay region. At the surface, a cold front is forecast to continue eastward across the Great Lakes, southeastward across the Midwest, and slowly southward across the southern Plains. By the end of the period, the front should extend from the Lower Great Lakes west-southwestward across the Ohio Valley, and into Oklahoma and northern Texas. ...Lower Michigan/northern Ohio/northwestern Pennsylvania across the Midwest... Moderate destabilization is expected in tandem with afternoon heating ahead of the cold front, from Lower Michigan west-southwestward across northern Illinois and Missouri, and southward across the warm sector. As the front slowly advances, scattered thunderstorm development is expected, initially across the lower Michigan and potentially into parts of Ohio, and then expanding southwestward across Indiana, Illinois, and into Missouri. Although the stronger deep-layer shear will largely remain to the cool side of the front, modest westerly mid-level flow of 20-25 kts will favor loosely organized storms, with some potential for upscale growth/clustering. Strong/isolated damaging gusts and perhaps severe hail will be possible. While risk should diminish after dark, convection -- and very limited risk with a couple of stronger storms -- may continue well into the overnight hours. ..Goss.. 08/29/2024 Read more

MD 2027 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR CENTRAL AND EASTERN NORTH DAKOTA
Mesoscale Discussion 2027 NWS Storm Prediction Center Norman OK 1247 AM CDT Thu Aug 29 2024 Areas affected...central and eastern North Dakota Concerning...Severe potential...Watch unlikely Valid 290547Z - 290715Z Probability of Watch Issuance...20 percent SUMMARY...A few supercells across central North Dakota are expected to persist into eastern North Dakota early this morning with a threat or isolated large hail and severe wind gusts. DISCUSSION...Regional radar composite shows a decaying MCS across southeast North Dakota as this cluster moves east of the better instability. Across western and central North Dakota, a significant increase in convection has occurred during the last hour within the post-frontal airmass due to a combination of strengthening isentropic ascent and DCVA ahead of the approaching mid-level trough. Between this post-frontal convection and the decaying MCS a locally favorable environment exists. MUCAPE around 2000 to 3000 J/kg on the apex of a strengthening low-level jet and strong shear (50-60 knots per BIS VWP) will support strong to severe supercells. While this environment will be quite favorable for the next 1 to 2 hours, expect storms to quickly outpace this better environment and thus weaken across eastern/northeast North Dakota. Due to the limited temporal nature of the threat, no severe thunderstorm watch is justified. ..Bentley/Edwards.. 08/29/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...FGF...BIS... LAT...LON 46279930 46950013 47950026 48579988 48869896 48729772 47839716 46819762 46319806 46279930 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1245 AM CDT Thu Aug 29 2024 Valid 291200Z - 301200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE UPPER/MIDDLE MISSISSIPPI VALLEY... ...SUMMARY... Severe thunderstorms are expected across the Upper/Middle Mississippi Valley to the central Plains. A few severe storms also will be possible over portions of the mid-Atlantic region. ...Upper/Middle Mississippi Valley... Southern portions of a strong upper trough, currently located over the northern Rockies, will eject across the Dakotas this afternoon. As 70-80kt 500mb speed max translates through the base of the trough across ND, primary upper low will track across southern AB into northwestern ON during the latter half of the period. Latest model guidance suggests very strong 12hr mid-level height falls just north of the international border, with more modest falls into the upper Mississippi Valley by 29/00z. Strong low-level warm advection will likely prove instrumental in one or more thunderstorm clusters over eastern ND/northwestern MN at the start of the period. LLJ responsible for this activity will shift into northwestern ON during the day, and this warm-advection activity should lift north of the border as well. However, strong boundary-layer heating will occur across eastern NE into extreme southwest MN by early afternoon. This will aid instability, and CINH will begin to weaken along the front, as surface temperatures rise into the mid 80s across central MN. NAM forecast sounding for KLJF at 22z is thermodynamically impressive with MLCAPE around 5400 J/kg and 0-6km shear approaching 30kt. 30-35kt deep-layer shear is expected along the northern extent of the stronger buoyancy. As a result, supercells are expected to develop along/ahead of the cold front, supported aloft by the upstream short wave. Large hail, severe gusts, and a few tornadoes are the expected hazards with these storms. Scattered convection, with a more-isolated severe threat, is forecast along the trailing cold front across the central Plains as readings breach convective temperatures later in the afternoon. Wind profiles at lower latitudes are not very strong, so this activity will be multicellular and less organized. Even so, some risk for hail/wind can be expected into the evening hours. ...Middle Atlantic Region... Dominant surface anticyclone over southeastern Canada will shift across ON/QC, which will allow a synoptic front to drape itself across the Middle Atlantic during the afternoon. This boundary will focus scattered thunderstorms as convective temperatures are breached by mid afternoon. Wind profiles favor mostly disorganized pulse-multicell updrafts. These storms will move slowly southeast with an attendant risk for wind and perhaps some hail. Robust updrafts will be strongly diurnally driven. ..Darrow/Jirak.. 08/29/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1245 AM CDT Thu Aug 29 2024 Valid 291200Z - 301200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE UPPER/MIDDLE MISSISSIPPI VALLEY... ...SUMMARY... Severe thunderstorms are expected across the Upper/Middle Mississippi Valley to the central Plains. A few severe storms also will be possible over portions of the mid-Atlantic region. ...Upper/Middle Mississippi Valley... Southern portions of a strong upper trough, currently located over the northern Rockies, will eject across the Dakotas this afternoon. As 70-80kt 500mb speed max translates through the base of the trough across ND, primary upper low will track across southern AB into northwestern ON during the latter half of the period. Latest model guidance suggests very strong 12hr mid-level height falls just north of the international border, with more modest falls into the upper Mississippi Valley by 29/00z. Strong low-level warm advection will likely prove instrumental in one or more thunderstorm clusters over eastern ND/northwestern MN at the start of the period. LLJ responsible for this activity will shift into northwestern ON during the day, and this warm-advection activity should lift north of the border as well. However, strong boundary-layer heating will occur across eastern NE into extreme southwest MN by early afternoon. This will aid instability, and CINH will begin to weaken along the front, as surface temperatures rise into the mid 80s across central MN. NAM forecast sounding for KLJF at 22z is thermodynamically impressive with MLCAPE around 5400 J/kg and 0-6km shear approaching 30kt. 30-35kt deep-layer shear is expected along the northern extent of the stronger buoyancy. As a result, supercells are expected to develop along/ahead of the cold front, supported aloft by the upstream short wave. Large hail, severe gusts, and a few tornadoes are the expected hazards with these storms. Scattered convection, with a more-isolated severe threat, is forecast along the trailing cold front across the central Plains as readings breach convective temperatures later in the afternoon. Wind profiles at lower latitudes are not very strong, so this activity will be multicellular and less organized. Even so, some risk for hail/wind can be expected into the evening hours. ...Middle Atlantic Region... Dominant surface anticyclone over southeastern Canada will shift across ON/QC, which will allow a synoptic front to drape itself across the Middle Atlantic during the afternoon. This boundary will focus scattered thunderstorms as convective temperatures are breached by mid afternoon. Wind profiles favor mostly disorganized pulse-multicell updrafts. These storms will move slowly southeast with an attendant risk for wind and perhaps some hail. Robust updrafts will be strongly diurnally driven. ..Darrow/Jirak.. 08/29/2024 Read more

MD 2026 CONCERNING TORNADO WATCH 661... FOR PARTS OF NORTH CENTRAL SOUTH DAKOTA AND SOUTH CENTRAL NORTH DAKOTA
Mesoscale Discussion 2026 NWS Storm Prediction Center Norman OK 0941 PM CDT Wed Aug 28 2024 Areas affected...parts of north central South Dakota and south central North Dakota Concerning...Tornado Watch 661... Valid 290241Z - 290445Z The severe weather threat for Tornado Watch 661 continues. SUMMARY...Thunderstorm development, in general, is beginning to weaken, with the risk for tornadoes likely to become increasingly negligible through 10-11 PM CDT. Some risk for severe hail and, perhaps, localized strong wind gusts may persist into the overnight hours across parts of the central and eastern Dakotas. However, a new severe weather watch is not currently anticipated. DISCUSSION...Ongoing convection appears to be undergoing notable weakening trends, including the the isolated supercell just south of the state border vicinity, across eastern Campbell county South Dakota. This has occurred as the loss of daytime heating has resulted in increasing inhibition for the seasonably moist boundary parcels near the surface trough across the central Dakotas. However, forcing associated with strong low-level warm advection may maintain at least a severe hail threat with the Campbell county storm as it accelerates north-northeastward, and becomes increasingly rooted above the boundary layer during the next hour or two. Strongest potential instability remains focused near a weak surface low, centered within the surface trough to the north-northwest of Pierre SD. However, as the slow moving upstream low, now centered over southern Saskatchewan just to the north of the international border, continues east-northeastward, models suggest that warming elevated mixed-layer air will gradually advect across the central North and South Dakota state border area through 04-05Z. As this occurs, the potential for renewed thunderstorm development rooted within the unstable boundary layer is expected to diminish. ..Kerr.. 08/29/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...ABR...BIS... LAT...LON 45960044 47149937 46599839 45019952 45030058 45960044 Read more

WW 0661 Status Updates
STATUS REPORT ON WW 661 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 25 SW ABR TO 35 NNE PIR TO 50 SW MBG TO 10 NNW MBG TO 20 NE BIS TO 50 SE MOT. ..KERR..08/29/24 ATTN...WFO...BIS...ABR... STATUS REPORT FOR WT 661 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS NDC029-043-047-051-093-103-290340- ND . NORTH DAKOTA COUNTIES INCLUDED ARE EMMONS KIDDER LOGAN MCINTOSH STUTSMAN WELLS SDC021-031-041-045-049-089-107-129-290340- SD . SOUTH DAKOTA COUNTIES INCLUDED ARE CAMPBELL CORSON DEWEY EDMUNDS FAULK MCPHERSON POTTER WALWORTH 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 661 TORNADO ND SD 282140Z - 290400Z
URGENT - IMMEDIATE BROADCAST REQUESTED Tornado Watch Number 661 NWS Storm Prediction Center Norman OK 440 PM CDT Wed Aug 28 2024 The NWS Storm Prediction Center has issued a * Tornado Watch for portions of South central North Dakota North central South Dakota * Effective this Wednesday afternoon and evening from 440 PM until 1100 PM CDT. * Primary threats include... A few tornadoes possible Scattered large hail and isolated very large hail events to 3 inches in diameter likely Scattered damaging wind gusts to 70 mph possible SUMMARY...Supercell development is expected soon near the central North Dakota/South Dakota border, with additional storm development in the next 1-3 hours farther north and south in the watch area. The storm environment initially favors supercells with tornadoes and very large hail (up to 3 inches in diameter), while some clustering of storms later this evening will lead to some increase in the potential for damaging winds of 60-70 mph. The tornado watch area is approximately along and 60 statute miles east and west of a line from 40 miles east northeast of Garrison ND to 80 miles south southeast of Mobridge SD. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU1). 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 3 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 600. Mean storm motion vector 25015. ...Thompson Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0744 PM CDT Wed Aug 28 2024 Valid 290100Z - 291200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE DAKOTAS... ...SUMMARY... Severe thunderstorm threat continues across parts of the Dakotas this evening. ...01z Update... Strong mid-level short-wave trough is well evident in satellite imagery, extending from the AB/SK border, south into eastern ID. This feature will shift into eastern MT/WY by the end of the period as a 70kt+ 500mb speed max translates across western ND into southwest MB. Scattered supercells have developed ahead of this short wave from near Minot ND to just north of Mobridge SD. Latest model guidance suggests a weak surface low, or at least a wave, will track northeast along the surface front into southeast ND by 29/12z. Over the next few hours, LLJ will increase across the eastern Dakotas and this should encourage eastward propagation of convection within a concentrated zone of low-level warm advection. Latest diagnostic data suggests ongoing storms are rooted within the main corridor of instability, and peak updraft intensity may linger through 03-04z before a more hostile environment is encountered downstream. Very large hail may be noted for the next hour or two, along with some risk for a tornado, then hail/wind threat will linger into the late-evening hours. ..Darrow.. 08/29/2024 Read more

No Mesoscale Discussions are in effect as of Wed Aug 28 23:16:17 UTC 2024.

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0459 PM CDT Wed Aug 28 2024 Valid 301200Z - 051200Z On Days 3-4/Friday-Saturday, a large-scale ridge will remain in place across much of the West, resulting in continued boundary-layer warming and drying of fuels (most notably across the Northwest into the northern Rockies). Late on Day 4/Saturday, weak midlevel height falls will impinge on the Pacific Northwest, as a midlevel low approaches the region. Increasing PW and the weak ascent may support an isolated thunderstorm risk across coastal OR/WA, though confidence in this scenario is low. Thereafter, the midlevel low will continue east-northeastward across northern CA/southern OR on Day 5/Sunday, with strengthening ascent overspreading increasing midlevel moisture. This will support isolated dry thunderstorms, with the greatest confidence over portions of south/central OR during the late afternoon into overnight hours. On Day 6/Monday, more substantial midlevel height falls/ascent accompanying the upper trough/low will overspread OR, as PW continues to gradually increase. This will favor another day of isolated thunderstorms, some of which could be a mix of wet/dry. Given gradually drying fuels preceding this potential thunderstorm event, 10-percent Isolated Dry Thunderstorm probabilities have been added for both days. The thunderstorm risk will spread east-northeastward into the northern Rockies on Day 7/Tuesday -- in tandem with the midlevel trough -- though the details are unclear at this time. ..Weinman.. 08/28/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0459 PM CDT Wed Aug 28 2024 Valid 301200Z - 051200Z On Days 3-4/Friday-Saturday, a large-scale ridge will remain in place across much of the West, resulting in continued boundary-layer warming and drying of fuels (most notably across the Northwest into the northern Rockies). Late on Day 4/Saturday, weak midlevel height falls will impinge on the Pacific Northwest, as a midlevel low approaches the region. Increasing PW and the weak ascent may support an isolated thunderstorm risk across coastal OR/WA, though confidence in this scenario is low. Thereafter, the midlevel low will continue east-northeastward across northern CA/southern OR on Day 5/Sunday, with strengthening ascent overspreading increasing midlevel moisture. This will support isolated dry thunderstorms, with the greatest confidence over portions of south/central OR during the late afternoon into overnight hours. On Day 6/Monday, more substantial midlevel height falls/ascent accompanying the upper trough/low will overspread OR, as PW continues to gradually increase. This will favor another day of isolated thunderstorms, some of which could be a mix of wet/dry. Given gradually drying fuels preceding this potential thunderstorm event, 10-percent Isolated Dry Thunderstorm probabilities have been added for both days. The thunderstorm risk will spread east-northeastward into the northern Rockies on Day 7/Tuesday -- in tandem with the midlevel trough -- though the details are unclear at this time. ..Weinman.. 08/28/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

WW 0661 Status Updates
STATUS FOR WATCH 0661 HAS NOT BEEN ISSUED YET Read more

WW 661 TORNADO ND SD 282140Z - 290400Z
URGENT - IMMEDIATE BROADCAST REQUESTED Tornado Watch Number 661 NWS Storm Prediction Center Norman OK 440 PM CDT Wed Aug 28 2024 The NWS Storm Prediction Center has issued a * Tornado Watch for portions of South central North Dakota North central South Dakota * Effective this Wednesday afternoon and evening from 440 PM until 1100 PM CDT. * Primary threats include... A few tornadoes possible Scattered large hail and isolated very large hail events to 3 inches in diameter likely Scattered damaging wind gusts to 70 mph possible SUMMARY...Supercell development is expected soon near the central North Dakota/South Dakota border, with additional storm development in the next 1-3 hours farther north and south in the watch area. The storm environment initially favors supercells with tornadoes and very large hail (up to 3 inches in diameter), while some clustering of storms later this evening will lead to some increase in the potential for damaging winds of 60-70 mph. The tornado watch area is approximately along and 60 statute miles east and west of a line from 40 miles east northeast of Garrison ND to 80 miles south southeast of Mobridge SD. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU1). 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 3 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 600. Mean storm motion vector 25015. ...Thompson Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0249 PM CDT Wed Aug 28 2024 Valid 282000Z - 291200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ALONG THE NORTH DAKOTA SOUTH DAKOTA BORDER... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN PLAINS AND THE OHIO VALLEY INTO THE MID ATLANTIC... ...SUMMARY... Severe thunderstorms are expected across parts of the Dakotas and from the Ohio Valley to the Mid-Atlantic Coast this afternoon through this evening. ...20z Update... No substantial changes have been made to the prior outlook. Storm coverage should gradually increase over parts of the OH Valley and Mid Atlantic through this afternoon. Damaging gusts will be possible with the stronger clusters of storms, potentially focused from eastern OH into WV and PA. To the west, supercell development is expected near the surface low and along the trialing surface trough/wind shift across western SD/ND late this afternoon. Moderate mid-level ascent overspreading a warming and moistening air mass across the Dakotas will allow for rapid storm development and intensification as CINH is removed. Large hail remains the primary threat, along with damaging gusts, given strong buoyancy and robust supercell wind profiles. However, strong low-level turning may support a risk for a couple of tornadoes with the more discrete supercells, especially near the warm front. Most short-term guidance does show gradual upscale growth this evening and into the early overnight period across the eastern Dakotas. Should this occur, the risk for damaging winds may increase with the greater organized/persistent clusters before they move into more stable air across parts of western MN. See the prior discussion for additional information. ..Lyons.. 08/28/2024 .PREV DISCUSSION... /ISSUED 1136 AM CDT Wed Aug 28 2024/ ...Dakotas... Have upgraded portions of south-central North Dakota/north-central South Dakota to a categorical Enhanced Risk for what should be a relatively greater likelihood and concentration of severe storms late this afternoon through early/mid-evening. A prominent upper-level trough centered over western Montana and southern Alberta will continue generally eastward over the Canadian Prairies and toward the northern High Plains, with a trough-preceding/basal upper-level jet resulting in considerably strengthening southwesterly winds aloft by peak heating into tonight. This will be atop an increasingly moist boundary layer (dewpoints increasing through the 60s F) ahead of a surface low across South Dakota and a front extending northward into North Dakota. Thunderstorms should develop near the front by late afternoon/early evening, perhaps initially across North Dakota where overall forcing will be greater, and subsequently southward into South Dakota where richer low-level moisture and greater buoyancy will reside. Given steep lapse rates and the reservoir of instability, these initial storms should be supercells capable of very large hail amidst strengthening flow aloft. Large to very large hail and severe wind gusts will be the most common hazards, although a tornado risk may also exist particularly across north-central South Dakota/far south-central North Dakota near the surface low/warm front-related triple point where moisture/low-level SRH will be maximized. Over time, relatively weak mid-level flow may encourage a transition to messier, quasi-linear modes with embedded LEWP/bow formations for a few hours. Activity should weaken overnight as it moves into stabilizing boundary-layer air, though a 45-55-kt low-level jet may encourage persistence of a cluster or two tonight into the eastern Dakotas. ...Midwest/Ohio Valley to Mid-Atlantic States... Widely scattered to scattered thunderstorms will pose a risk for damaging winds particularly mid/late afternoon through early/mid-evening regionally. Some hail may also occur on a more marginal and isolated basis. This severe risk will primarily span parts of Indiana/Ohio eastward to the coastal Mid-Atlantic/Delmarva vicinity, although the overall extent and magnitude of today's risk is still a bit uncertain. The boundary layer will not be overly moist by late-summer standards, particularly across the middle Ohio River Valley, but a relatively richer moist axis (through the lowest 2-3 km AGL) extends this morning from the upper Ohio Valley eastward toward the coastal Mid-Atlantic/Northeast. The boundary layer will also not be overly unstable later today, with severe-adequate MLCAPE generally limited to 2000 J/kg MLCAPE. Aside from differential heating related to last night's convection across the Midwest, several impetuses for thunderstorm development to the south of the primary Great Lakes front may include the eastward transitions of MCVs across southeast Lower Michigan and north-central Illinois, which should be influential into the Lake Ontario/New York/northern Pennsylvania and lower/middle Ohio Valley vicinities, respectively, later this afternoon and evening. Effective shear will tend to be limited to 20-25 kt, but slowly-increasing-with-height deep-layer westerlies will support multicell-related damaging wind/some hail potential as low-level lapse rates steepen and the boundary layer moderately destabilizes this afternoon. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0249 PM CDT Wed Aug 28 2024 Valid 282000Z - 291200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ALONG THE NORTH DAKOTA SOUTH DAKOTA BORDER... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN PLAINS AND THE OHIO VALLEY INTO THE MID ATLANTIC... ...SUMMARY... Severe thunderstorms are expected across parts of the Dakotas and from the Ohio Valley to the Mid-Atlantic Coast this afternoon through this evening. ...20z Update... No substantial changes have been made to the prior outlook. Storm coverage should gradually increase over parts of the OH Valley and Mid Atlantic through this afternoon. Damaging gusts will be possible with the stronger clusters of storms, potentially focused from eastern OH into WV and PA. To the west, supercell development is expected near the surface low and along the trialing surface trough/wind shift across western SD/ND late this afternoon. Moderate mid-level ascent overspreading a warming and moistening air mass across the Dakotas will allow for rapid storm development and intensification as CINH is removed. Large hail remains the primary threat, along with damaging gusts, given strong buoyancy and robust supercell wind profiles. However, strong low-level turning may support a risk for a couple of tornadoes with the more discrete supercells, especially near the warm front. Most short-term guidance does show gradual upscale growth this evening and into the early overnight period across the eastern Dakotas. Should this occur, the risk for damaging winds may increase with the greater organized/persistent clusters before they move into more stable air across parts of western MN. See the prior discussion for additional information. ..Lyons.. 08/28/2024 .PREV DISCUSSION... /ISSUED 1136 AM CDT Wed Aug 28 2024/ ...Dakotas... Have upgraded portions of south-central North Dakota/north-central South Dakota to a categorical Enhanced Risk for what should be a relatively greater likelihood and concentration of severe storms late this afternoon through early/mid-evening. A prominent upper-level trough centered over western Montana and southern Alberta will continue generally eastward over the Canadian Prairies and toward the northern High Plains, with a trough-preceding/basal upper-level jet resulting in considerably strengthening southwesterly winds aloft by peak heating into tonight. This will be atop an increasingly moist boundary layer (dewpoints increasing through the 60s F) ahead of a surface low across South Dakota and a front extending northward into North Dakota. Thunderstorms should develop near the front by late afternoon/early evening, perhaps initially across North Dakota where overall forcing will be greater, and subsequently southward into South Dakota where richer low-level moisture and greater buoyancy will reside. Given steep lapse rates and the reservoir of instability, these initial storms should be supercells capable of very large hail amidst strengthening flow aloft. Large to very large hail and severe wind gusts will be the most common hazards, although a tornado risk may also exist particularly across north-central South Dakota/far south-central North Dakota near the surface low/warm front-related triple point where moisture/low-level SRH will be maximized. Over time, relatively weak mid-level flow may encourage a transition to messier, quasi-linear modes with embedded LEWP/bow formations for a few hours. Activity should weaken overnight as it moves into stabilizing boundary-layer air, though a 45-55-kt low-level jet may encourage persistence of a cluster or two tonight into the eastern Dakotas. ...Midwest/Ohio Valley to Mid-Atlantic States... Widely scattered to scattered thunderstorms will pose a risk for damaging winds particularly mid/late afternoon through early/mid-evening regionally. Some hail may also occur on a more marginal and isolated basis. This severe risk will primarily span parts of Indiana/Ohio eastward to the coastal Mid-Atlantic/Delmarva vicinity, although the overall extent and magnitude of today's risk is still a bit uncertain. The boundary layer will not be overly moist by late-summer standards, particularly across the middle Ohio River Valley, but a relatively richer moist axis (through the lowest 2-3 km AGL) extends this morning from the upper Ohio Valley eastward toward the coastal Mid-Atlantic/Northeast. The boundary layer will also not be overly unstable later today, with severe-adequate MLCAPE generally limited to 2000 J/kg MLCAPE. Aside from differential heating related to last night's convection across the Midwest, several impetuses for thunderstorm development to the south of the primary Great Lakes front may include the eastward transitions of MCVs across southeast Lower Michigan and north-central Illinois, which should be influential into the Lake Ontario/New York/northern Pennsylvania and lower/middle Ohio Valley vicinities, respectively, later this afternoon and evening. Effective shear will tend to be limited to 20-25 kt, but slowly-increasing-with-height deep-layer westerlies will support multicell-related damaging wind/some hail potential as low-level lapse rates steepen and the boundary layer moderately destabilizes this afternoon. Read more

No watches are valid as of Wed Aug 28 19:54:02 UTC 2024.

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0225 PM CDT Wed Aug 28 2024 Valid 301200Z - 311200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE LOWER GREAT LAKES AND MIDWEST... ...SUMMARY... Strong/locally severe storms will be posible from Lakes Huron and Erie southwestward into the Midwest Friday. ...Synopsis... An upper-level trough will continue moving slowly eastward out of the north-central U.S. across the Great Lakes and Midwest on Friday, with the more vigorous portion of the trough expected to eject northeastward across Ontario into the Hudson Bay region. At the surface, a cold front is forecast to continue eastward across the Great Lakes, southeastward across the Midwest, and southward across the Plains. By the end of the period, the front should extend from the Lower Great Lakes west-southwestward across the Ohio Valley, and into Oklahoma and northern Texas. ...Lower Michigan/northern Ohio/northwestern Pennsylvania across the Midwest... Destabilization is expected ahead of the cold front, with moderate/pockets of strong MLCAPE by afternoon. With minimal CINH, thunderstorm development is likely from lower MI southwest to IL. Although the stronger deep-layer shear will lag towards the cool side of the front, modest westerly mid-level flow of 20-25 kts will favor loosely-organized storms that should tend to cluster over time. Strong/isolated damaging gusts and perhaps severe hail will be possible. ..Bunting.. 08/28/2024 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0225 PM CDT Wed Aug 28 2024 Valid 301200Z - 311200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE LOWER GREAT LAKES AND MIDWEST... ...SUMMARY... Strong/locally severe storms will be posible from Lakes Huron and Erie southwestward into the Midwest Friday. ...Synopsis... An upper-level trough will continue moving slowly eastward out of the north-central U.S. across the Great Lakes and Midwest on Friday, with the more vigorous portion of the trough expected to eject northeastward across Ontario into the Hudson Bay region. At the surface, a cold front is forecast to continue eastward across the Great Lakes, southeastward across the Midwest, and southward across the Plains. By the end of the period, the front should extend from the Lower Great Lakes west-southwestward across the Ohio Valley, and into Oklahoma and northern Texas. ...Lower Michigan/northern Ohio/northwestern Pennsylvania across the Midwest... Destabilization is expected ahead of the cold front, with moderate/pockets of strong MLCAPE by afternoon. With minimal CINH, thunderstorm development is likely from lower MI southwest to IL. Although the stronger deep-layer shear will lag towards the cool side of the front, modest westerly mid-level flow of 20-25 kts will favor loosely-organized storms that should tend to cluster over time. Strong/isolated damaging gusts and perhaps severe hail will be possible. ..Bunting.. 08/28/2024 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1229 PM CDT Wed Aug 28 2024 Valid 291200Z - 301200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF MINNESOTA...WESTERN WISCONSIN AND NORTHERN IOWA... ...SUMMARY... Severe thunderstorms are possible on Thursday from portions of the Upper/Middle Mississippi Valley to the central Plains. A few severe storms also will be possible over portions of the mid-Atlantic region. ...Synopsis... A weak upper-level short-wave trough will shift east across the Northeast on Thursday, as a much stronger trough/low will continue to advance into/across the north-central states. At the surface, a cold front is forecast to sag southward across the Mid-Atlantic region in lee of the Appalachians, while a more prominent cold front shifts eastward/southeastward across the central and northern Plains. ...Mid and Upper Mississippi Valley area to the central Plains... Large scale ascent with the upper low/trough will increase in the vicinity of the eastward-advancing cold front over MN/northern IA, augmented by the right-entrance region of a 250-mb jet lifting north during the day. Substantial instability should be in place by afternoon, with afternoon MLCAPE in excess of 3000 J/kg expected. Strengthening mid-level flow with the approach of the upper trough will contribute to deep-layer shear of 35-45 kts, supporting organized storms including the potential for supercell structures. Thunderstorms should increase in coverage through the afternoon and evening, becoming more linear with time along the cold front. Damaging winds and large hail will be the primary severe hazards, with the severe risk continuing into the evening hours. Some tornado risk may also develop with embedded QLCS circulations as low-level shear appears supportive, especially within the Slight Risk area. Both instability and shear will diminish with southward extent across eastern NE/northern KS, however afternoon thunderstorm development is expected along the front within a largely uncapped environment. Isolated damaging winds will be the primary risk as strong boundary-layer heating will steepen low-level lapse rates, and storms begin to cluster during the late afternoon/evening. Instances of large hail will also be possible. ...Mid-Atlantic Region... A southward-moving cold front will move across the mid-Atlantic in the lee of the Appalachians Thursday within a moderately unstable though weakly sheared environment. With minimal afternoon CINH, thunderstorms should develop over the higher terrain and along the front and tend to cluster with time. This will result in a risk for damaging gusts, and perhaps hail with the stronger updrafts. ..Bunting.. 08/28/2024 Read more