MD 2047 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF SOUTHERN WY...NORTHWESTERN CO...NORTHEASTERN UT...AND FAR WESTERN NE
Mesoscale Discussion 2047 NWS Storm Prediction Center Norman OK 0106 PM CDT Wed Sep 04 2024 Areas affected...portions of southern WY...northwestern CO...northeastern UT...and far western NE Concerning...Severe potential...Watch unlikely Valid 041806Z - 042000Z Probability of Watch Issuance...20 percent SUMMARY...Scattered thunderstorm development is expected this afternoon across southern WY, northern CO, and portions of northeastern UT and far western NE. The strongest storms may pose a threat for local severe wind gusts and small hail. DISCUSSION...Deeper updraft development is underway across the region, predominantly in advance of a mid-level wave progressing eastward through the region. Associated upper-level ventilation is supporting storm maturation across southeastern WY. Convective development is also occurring in northeastern UT, aided by enhanced westerlies aloft and diurnal heating amidst the Uinta Mountains. Continued updraft intensification is expected through the afternoon as the wave propagates eastward through the area and diurnal heating continues to ramp up. Surface conditions are relatively cool across the area in the wake of a cold frontal passage. As such, MLCAPE values are relatively low (around 250-500 J/kg) and some convective inhibition remains. However, diurnal heating will support continued updraft development across the area. Updrafts will be relatively high-based, but steep mid-level lapse rates -- owing to synoptic-scale ascent ahead of the mid-level wave -- could yield MLCAPE around 500-1000 J/kg in some areas. Lengthening, relatively straight hodographs, characterized by bulk shear around 30-40 kts, could support a few more persistent, supercellular structures. Some severe wind gusts and small hail will be the primary threat with these storms through the afternoon. The threat is expected to remain rather localized in nature, and watch issuance is not anticipated at this time. ..Flournoy/Squitieri/Mosier.. 09/04/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BOU...CYS...RIW...GJT...SLC... LAT...LON 40041022 40911053 42051009 43190817 43250573 42610421 41640359 40310366 39440567 39450839 40041022 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1218 PM CDT Wed Sep 04 2024 Valid 051200Z - 061200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF NORTHEAST NEW MEXICO.... ...SUMMARY... A few strong to severe storms are possible across portions of northeast New Mexico Thursday afternoon/evening. ...Synopsis... An upper-level trough is forecast to amplify and move southeastward across the Canadian Prairies into the upper Midwest/Great Lakes on Thursday. To the southwest of this amplifying trough, a weakening shortwave is forecast to move southeastward across the central/southern Rockies into the southern High Plains. At the surface, a cold front is forecast to extend southwestward from the Great Lakes into parts of the Midwest and central/southern Plains during the afternoon. ...Southern Rockies and High Plains... A concentrated area of thunderstorms are forecast across northeast New Mexico on Thursday as a sharp mid-level shortwave trough advances southeast across the central/southern Rockies and interacts with a pocket of instability in the post-frontal airmass across northeast New Mexico. Some increasing mid-level flow associated with this trough will overspread the region and provide 20 to 25 knots of deep layer shear. This may be sufficient for some storm organization and the potential for severe-wind gusts. Some small hail is also possible, but relatively modest instability/shear may limit the potential for large hail. ...Parts of the Upper Midwest... Thunderstorms will likely be ongoing at the beginning of the period along the frontal zone in northwest Wisconsin. Expect this activity to wane by mid-morning as the low-level jet weakens. Strong height falls will overspread the cold front by mid to late afternoon which should support additional thunderstorm development along the cold front during the afternoon/early evening. Forecast soundings show limited moisture/instability (less than 1000 J/kg MLCAPE) and modest effective shear (25-30 kts). This could support a few strong to severe storms, but overall, expect the severe-weather threat to remain limited/isolated. ..Bentley.. 09/04/2024 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1218 PM CDT Wed Sep 04 2024 Valid 051200Z - 061200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF NORTHEAST NEW MEXICO.... ...SUMMARY... A few strong to severe storms are possible across portions of northeast New Mexico Thursday afternoon/evening. ...Synopsis... An upper-level trough is forecast to amplify and move southeastward across the Canadian Prairies into the upper Midwest/Great Lakes on Thursday. To the southwest of this amplifying trough, a weakening shortwave is forecast to move southeastward across the central/southern Rockies into the southern High Plains. At the surface, a cold front is forecast to extend southwestward from the Great Lakes into parts of the Midwest and central/southern Plains during the afternoon. ...Southern Rockies and High Plains... A concentrated area of thunderstorms are forecast across northeast New Mexico on Thursday as a sharp mid-level shortwave trough advances southeast across the central/southern Rockies and interacts with a pocket of instability in the post-frontal airmass across northeast New Mexico. Some increasing mid-level flow associated with this trough will overspread the region and provide 20 to 25 knots of deep layer shear. This may be sufficient for some storm organization and the potential for severe-wind gusts. Some small hail is also possible, but relatively modest instability/shear may limit the potential for large hail. ...Parts of the Upper Midwest... Thunderstorms will likely be ongoing at the beginning of the period along the frontal zone in northwest Wisconsin. Expect this activity to wane by mid-morning as the low-level jet weakens. Strong height falls will overspread the cold front by mid to late afternoon which should support additional thunderstorm development along the cold front during the afternoon/early evening. Forecast soundings show limited moisture/instability (less than 1000 J/kg MLCAPE) and modest effective shear (25-30 kts). This could support a few strong to severe storms, but overall, expect the severe-weather threat to remain limited/isolated. ..Bentley.. 09/04/2024 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1207 PM CDT Wed Sep 04 2024 Valid 041700Z - 051200Z ...NO CRITICAL AREAS... No changes are needed to the D1 Fire Weather Outlook. See previous discussion below for more information. ..Thornton.. 09/04/2024 .PREV DISCUSSION... /ISSUED 0108 AM CDT Wed Sep 04 2024/ ...Synopsis... Fire weather concerns appear limited for today across the country. Breezy conditions will persist across the central Plains ahead of a migratory surface trough. Low-level moisture has begun to advect northward based on early-morning surface observations, and this trend should continue through the day and modulate afternoon RH minimums over the Plains. Areas of elevated fire weather conditions are possible across central to southern UT as a cold front pushes across the region, but confidence in prolonged/widespread elevated conditions is limited and should occur over fuels that are only modestly receptive. Dry conditions will persist across the Great Basin and West Coast, but a building ridge over the western CONUS will promote weak surface winds and limited fire concerns. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1207 PM CDT Wed Sep 04 2024 Valid 041700Z - 051200Z ...NO CRITICAL AREAS... No changes are needed to the D1 Fire Weather Outlook. See previous discussion below for more information. ..Thornton.. 09/04/2024 .PREV DISCUSSION... /ISSUED 0108 AM CDT Wed Sep 04 2024/ ...Synopsis... Fire weather concerns appear limited for today across the country. Breezy conditions will persist across the central Plains ahead of a migratory surface trough. Low-level moisture has begun to advect northward based on early-morning surface observations, and this trend should continue through the day and modulate afternoon RH minimums over the Plains. Areas of elevated fire weather conditions are possible across central to southern UT as a cold front pushes across the region, but confidence in prolonged/widespread elevated conditions is limited and should occur over fuels that are only modestly receptive. Dry conditions will persist across the Great Basin and West Coast, but a building ridge over the western CONUS will promote weak surface winds and limited fire concerns. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1124 AM CDT Wed Sep 04 2024 Valid 041630Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL ROCKIES INTO THE NORTHERN/CENTRAL PLAINS AND UPPER MISSISSIPPI VALLEY... ...SUMMARY... Isolated strong to severe thunderstorms capable of gusty winds and hail may occur this afternoon and evening across parts of the central Rockies into the northern/central Plains and upper Mississippi Valley. ...Central Rockies into the central High Plains... Recent satellite imagery reveals a broad shortwave trough currently moving through southern ID and northern NV/UT. This shortwave trough and accompanying cold mid-level temperatures are forecast to continue eastward throughout the day, progressing across WY and northern CO. Modest buoyancy, fostered mainly by cooling mid-level temperatures, is anticipated across WY and adjacent parts of northern CO as the shortwave trough progresses through. Thunderstorm development is expected as the large-scale ascent attendant to the shortwave trough interacts with this buoyancy during the afternoon. Moderate mid-level westerlies will accompany this shortwave trough as well, with the resulting increase in vertical shear supporting the potential for a few more organized/persistent storms. Initially more cellular development across the higher terrain could pose a risk for isolated hail, particularly across south-central WY and north-central CO where the best overlap between the stronger shear and cold mid-level temperatures is expected. Damaging wind gusts are possible as well, particularly as the storms reach the lower elevations of central High Plains where a deeply mixed boundary layer will be in place. ...Central Plains into the Upper MS Valley... Recent surface analysis places a low over southeast ND, with weak troughing extending southwestward from this low in east-central CO. The primary cold front is west of this surface trough, extending from the low over southeast ND into more of northwest SD and adjacent northeast WY. The surface low is forecast to progress east-southeastward throughout the day, reaching south-central MN by late tonight. The attendant cold front is expected to push southward during the same period, progressing through much of NE by early Thursday morning. Warm mid-level temperatures should preclude thunderstorm development along the surface trough during the afternoon and evening. A few isolated storms are possible during the evening behind the front as the shortwave trough ejects out into the central Plains. Additional thunderstorm development is expected overnight/early Thursday morning across the Upper MS Valley, with some isolated hail possible within the strongest storms. ..Mosier/Flournoy.. 09/04/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0716 AM CDT Wed Sep 04 2024 Valid 041300Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL ROCKIES INTO THE NORTHERN/CENTRAL PLAINS AND UPPER MISSISSIPPI VALLEY... ...SUMMARY... Isolated strong to severe thunderstorms capable of gusty winds and hail may occur this afternoon and evening across parts of the central Rockies into the northern/central Plains and upper Mississippi Valley. ...Central Rockies into the Northern/Central Plains and Upper Mississippi Valley... A weak shortwave trough over the northern Rockies and adjacent Great Basin this morning will become absorbed later today into an amplifying upper trough over the Canadian Prairie provinces and northern Plains. At the surface, a cold front related to the upper trough will continue southward over the northern Plains, and southeastward across the Upper MS Valley through the period. Modest low-level moisture is forecast to be in place ahead of this boundary across the northern Plains and upper MS Valley, with more limited moisture expected farther west across the central Rockies and adjacent High Plains. Relatively cool mid-level temperatures associated with the weak shortwave trough and the presence of steep mid-level lapse rates should aid in the development of weak instability across parts of WY, northern CO, and vicinity this afternoon. Sufficient deep-layer shear (generally 25-35 kt) should support some updraft organization with convection that initially forms over the higher terrain before subsequently spreading eastward. Isolated instances of marginally severe hail and strong/gusty winds may occur with the more cellular development. But, some increase in strong to severe wind potential may be realized as thunderstorms move into an area of steeper low-level lapse rates across the central High Plains by late this afternoon and early evening, especially if any small clusters can form. The severe potential along much of the length of the front in the northern Plains and upper MS Valley appears rather conditional. While large-scale ascent associated with the approaching upper trough should gradually overspread the warm sector by late afternoon/early evening, most guidance continues to suggest that a cap and substantial MLCIN will hinder robust convection from developing through much of the day. Even so, sufficient instability and shear should be in place along/ahead of the front to support an isolated hail/wind threat if thunderstorms can form and be sustained through the evening and early overnight period. The post-frontal regime across much of MT into ND and western SD appears unlikely to support severe convection. Accordingly, the Marginal Risk has been trimmed southward to account for recent guidance and observational trends. ..Gleason/Leitman.. 09/04/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0716 AM CDT Wed Sep 04 2024 Valid 041300Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL ROCKIES INTO THE NORTHERN/CENTRAL PLAINS AND UPPER MISSISSIPPI VALLEY... ...SUMMARY... Isolated strong to severe thunderstorms capable of gusty winds and hail may occur this afternoon and evening across parts of the central Rockies into the northern/central Plains and upper Mississippi Valley. ...Central Rockies into the Northern/Central Plains and Upper Mississippi Valley... A weak shortwave trough over the northern Rockies and adjacent Great Basin this morning will become absorbed later today into an amplifying upper trough over the Canadian Prairie provinces and northern Plains. At the surface, a cold front related to the upper trough will continue southward over the northern Plains, and southeastward across the Upper MS Valley through the period. Modest low-level moisture is forecast to be in place ahead of this boundary across the northern Plains and upper MS Valley, with more limited moisture expected farther west across the central Rockies and adjacent High Plains. Relatively cool mid-level temperatures associated with the weak shortwave trough and the presence of steep mid-level lapse rates should aid in the development of weak instability across parts of WY, northern CO, and vicinity this afternoon. Sufficient deep-layer shear (generally 25-35 kt) should support some updraft organization with convection that initially forms over the higher terrain before subsequently spreading eastward. Isolated instances of marginally severe hail and strong/gusty winds may occur with the more cellular development. But, some increase in strong to severe wind potential may be realized as thunderstorms move into an area of steeper low-level lapse rates across the central High Plains by late this afternoon and early evening, especially if any small clusters can form. The severe potential along much of the length of the front in the northern Plains and upper MS Valley appears rather conditional. While large-scale ascent associated with the approaching upper trough should gradually overspread the warm sector by late afternoon/early evening, most guidance continues to suggest that a cap and substantial MLCIN will hinder robust convection from developing through much of the day. Even so, sufficient instability and shear should be in place along/ahead of the front to support an isolated hail/wind threat if thunderstorms can form and be sustained through the evening and early overnight period. The post-frontal regime across much of MT into ND and western SD appears unlikely to support severe convection. Accordingly, the Marginal Risk has been trimmed southward to account for recent guidance and observational trends. ..Gleason/Leitman.. 09/04/2024 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0310 AM CDT Wed Sep 04 2024 Valid 071200Z - 121200Z ...DISCUSSION... ...D4/Saturday - D5/Sunday: Northeast/Mid Atlantic... An amplifying trough is forecast to evolve into a rather deep mid/upper-level cyclone over parts of Ontario into the eastern Great Lakes region on Saturday, and then begin moving eastward on Sunday. Uncertainty remains regarding the intensity/location of related surface cyclogenesis, and the timing of an attendant cold front into parts of the Northeast and Mid Atlantic. There will be some potential for low-level moisture to be drawn northward in advance of the cold front, though instability will likely remain weak. If adequate buoyancy can develop, then increasing flow fields could support some increase in severe potential across parts of the Mid Atlantic and Northeast on D4/Saturday. Uncertainty regarding frontal position increases into D5/Sunday, though some guidance suggests potential for frontal convection to develop across parts of New England before moving offshore. ...D6/Monday - D8/Wednesday... The deep trough over the eastern CONUS is generally forecast to weaken and move offshore early next week. Farther west, an upper ridge is forecast to amplify over the Southwest, while an upper trough deepens over the eastern Pacific and eventually begins to impinge upon the Pacific Coast. A persistent surface ridge over the East is expected to keep richer low-level moisture confined to near the Gulf Coast, which will tend to limit moisture return and severe-thunderstorm potential across much of the CONUS. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0310 AM CDT Wed Sep 04 2024 Valid 071200Z - 121200Z ...DISCUSSION... ...D4/Saturday - D5/Sunday: Northeast/Mid Atlantic... An amplifying trough is forecast to evolve into a rather deep mid/upper-level cyclone over parts of Ontario into the eastern Great Lakes region on Saturday, and then begin moving eastward on Sunday. Uncertainty remains regarding the intensity/location of related surface cyclogenesis, and the timing of an attendant cold front into parts of the Northeast and Mid Atlantic. There will be some potential for low-level moisture to be drawn northward in advance of the cold front, though instability will likely remain weak. If adequate buoyancy can develop, then increasing flow fields could support some increase in severe potential across parts of the Mid Atlantic and Northeast on D4/Saturday. Uncertainty regarding frontal position increases into D5/Sunday, though some guidance suggests potential for frontal convection to develop across parts of New England before moving offshore. ...D6/Monday - D8/Wednesday... The deep trough over the eastern CONUS is generally forecast to weaken and move offshore early next week. Farther west, an upper ridge is forecast to amplify over the Southwest, while an upper trough deepens over the eastern Pacific and eventually begins to impinge upon the Pacific Coast. A persistent surface ridge over the East is expected to keep richer low-level moisture confined to near the Gulf Coast, which will tend to limit moisture return and severe-thunderstorm potential across much of the CONUS. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 AM CDT Wed Sep 04 2024 Valid 061200Z - 071200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe-thunderstorm potential appears relatively low for Friday, though a few strong storms will be possible from near Lake Erie into parts of the Ohio Valley. ...Synopsis... An upper-level trough is forecast to amplify as it digs southeastward across the Great Lakes and Ohio Valley regions on Friday. A mid/upper-level cyclone is forecast to develop with time, as a strong embedded shortwave moves southeastward into the base of the trough by Friday evening. A leading cold front is forecast to slow down and weaken across parts of the Ohio Valley, as a reinforcing front moves through parts of the Great Lakes and Midwest. ...Lake Erie/Ohio Valley vicinity... With richer low-level moisture expected to remain confined near the Gulf Coast, guidance varies regarding the extent of prefrontal moistening and destabilization across parts of the Ohio Valley into the lower Great Lakes on Friday. Development of at least modest buoyancy appears plausible, which will aid in the development of convection near the frontal zone during the afternoon and evening. Gradually increasing deep-layer flow/shear associated with the digging upper-level trough could support a few relatively organized storms, and localized damaging gusts cannot be ruled out if adequate destabilization can occur. Depending on trends regarding destabilization and the timing of stronger ascent and deep-layer flow attendant to the digging trough, severe probabilities may eventually be needed from near Lake Erie into parts of the Ohio Valley. ..Dean.. 09/04/2024 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0109 AM CDT Wed Sep 04 2024 Valid 051200Z - 061200Z ...NO CRITICAL AREAS... ...Synopsis... Fire weather concerns will remain limited through Thursday across the country. A strong upper trough is forecast to push southward out of the Canadian Prairies into the northern U.S. through the day Thursday. As this occurs, a cool continental air mass will push southward into the Plains, reinforcing a surface trough/cold front as it pushes further south into the Midwest and southern Plains. While breezy conditions are possible behind the front, the cooler temperatures and cloud cover will limit RH reductions. An upper-level ridge will remain over the western CONUS, promoting mostly clear skies and dry conditions (RH values in the teens to 20s), but relatively weak surface winds. ..Moore.. 09/04/2024 ...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 0109 AM CDT Wed Sep 04 2024 Valid 051200Z - 061200Z ...NO CRITICAL AREAS... ...Synopsis... Fire weather concerns will remain limited through Thursday across the country. A strong upper trough is forecast to push southward out of the Canadian Prairies into the northern U.S. through the day Thursday. As this occurs, a cool continental air mass will push southward into the Plains, reinforcing a surface trough/cold front as it pushes further south into the Midwest and southern Plains. While breezy conditions are possible behind the front, the cooler temperatures and cloud cover will limit RH reductions. An upper-level ridge will remain over the western CONUS, promoting mostly clear skies and dry conditions (RH values in the teens to 20s), but relatively weak surface winds. ..Moore.. 09/04/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0108 AM CDT Wed Sep 04 2024 Valid 041200Z - 051200Z ...NO CRITICAL AREAS... ...Synopsis... Fire weather concerns appear limited for today across the country. Breezy conditions will persist across the central Plains ahead of a migratory surface trough. Low-level moisture has begun to advect northward based on early-morning surface observations, and this trend should continue through the day and modulate afternoon RH minimums over the Plains. Areas of elevated fire weather conditions are possible across central to southern UT as a cold front pushes across the region, but confidence in prolonged/widespread elevated conditions is limited and should occur over fuels that are only modestly receptive. Dry conditions will persist across the Great Basin and West Coast, but a building ridge over the western CONUS will promote weak surface winds and limited fire concerns. ..Moore.. 09/04/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0108 AM CDT Wed Sep 04 2024 Valid 041200Z - 051200Z ...NO CRITICAL AREAS... ...Synopsis... Fire weather concerns appear limited for today across the country. Breezy conditions will persist across the central Plains ahead of a migratory surface trough. Low-level moisture has begun to advect northward based on early-morning surface observations, and this trend should continue through the day and modulate afternoon RH minimums over the Plains. Areas of elevated fire weather conditions are possible across central to southern UT as a cold front pushes across the region, but confidence in prolonged/widespread elevated conditions is limited and should occur over fuels that are only modestly receptive. Dry conditions will persist across the Great Basin and West Coast, but a building ridge over the western CONUS will promote weak surface winds and limited fire concerns. ..Moore.. 09/04/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1252 AM CDT Wed Sep 04 2024 Valid 051200Z - 061200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The threat for organized severe thunderstorms currently appears low on Thursday, but a few strong storms cannot be ruled out across parts of the upper Midwest, New Mexico, and south-central Colorado. ...Synopsis... An upper-level trough is forecast to amplify and move southeastward across the Canadian Prairies into the upper Midwest/Great Lakes on Thursday. To the southwest of this amplifying trough, a weakening shortwave is forecast to move southeastward across the central/southern Rockies into the southern High Plains. At the surface, a cold front is forecast to extend southwestward from the Great Lakes into parts of the Midwest and central/southern Plains during the afternoon. ...Parts of the upper Midwest... Elevated convection will likely be ongoing Thursday morning across parts of WI and western upper MI. While this convection will likely tend to weaken with time, a strong storm or two cannot be ruled out early in the period. As the cold front moves south-southeastward through the day, isolated to widely scattered thunderstorm development will be possible in the vicinity of the frontal zone. Large-scale forcing and deep-layer flow are forecast to be somewhat stronger near the upper Midwest portion of the front, in response to the amplifying upper-level trough. Relatively substantial spread persists among guidance regarding the extent of moistening/destabilization, though in general, buoyancy is expected to remain relatively modest, rendering any organized-severe potential uncertain. With relatively limited low-level moisture, pockets of rather strong heating/mixing could develop, which may support localized gusty winds with any stronger storms. If stronger destabilization does evolve during the afternoon, then isolated hail cannot be ruled out. At this time, confidence in an organized severe threat remains too low for probabilities. ...South-central CO into NM... Scattered thunderstorms are expected from south-central CO into NM, as the weakening shortwave trough moves southeastward across the region during the afternoon/evening. Effective shear will become modestly supportive of organized convection (generally 25-30 kt), but buoyancy may remain rather weak. If adequate instability can be realized, then some threat for localized hail and strong/severe gusts could accompany the strongest storms. ..Dean.. 09/04/2024 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1252 AM CDT Wed Sep 04 2024 Valid 051200Z - 061200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The threat for organized severe thunderstorms currently appears low on Thursday, but a few strong storms cannot be ruled out across parts of the upper Midwest, New Mexico, and south-central Colorado. ...Synopsis... An upper-level trough is forecast to amplify and move southeastward across the Canadian Prairies into the upper Midwest/Great Lakes on Thursday. To the southwest of this amplifying trough, a weakening shortwave is forecast to move southeastward across the central/southern Rockies into the southern High Plains. At the surface, a cold front is forecast to extend southwestward from the Great Lakes into parts of the Midwest and central/southern Plains during the afternoon. ...Parts of the upper Midwest... Elevated convection will likely be ongoing Thursday morning across parts of WI and western upper MI. While this convection will likely tend to weaken with time, a strong storm or two cannot be ruled out early in the period. As the cold front moves south-southeastward through the day, isolated to widely scattered thunderstorm development will be possible in the vicinity of the frontal zone. Large-scale forcing and deep-layer flow are forecast to be somewhat stronger near the upper Midwest portion of the front, in response to the amplifying upper-level trough. Relatively substantial spread persists among guidance regarding the extent of moistening/destabilization, though in general, buoyancy is expected to remain relatively modest, rendering any organized-severe potential uncertain. With relatively limited low-level moisture, pockets of rather strong heating/mixing could develop, which may support localized gusty winds with any stronger storms. If stronger destabilization does evolve during the afternoon, then isolated hail cannot be ruled out. At this time, confidence in an organized severe threat remains too low for probabilities. ...South-central CO into NM... Scattered thunderstorms are expected from south-central CO into NM, as the weakening shortwave trough moves southeastward across the region during the afternoon/evening. Effective shear will become modestly supportive of organized convection (generally 25-30 kt), but buoyancy may remain rather weak. If adequate instability can be realized, then some threat for localized hail and strong/severe gusts could accompany the strongest storms. ..Dean.. 09/04/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1234 AM CDT Wed Sep 04 2024 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTH-CENTRAL ROCKIES...CENTRAL AND NORTHERN PLAINS...AND UPPER MISSISSIPPI VALLEY... ...SUMMARY... Isolated severe storms, capable of severe wind gusts and hail, will be possible this afternoon and evening across parts of the central and northern Rockies, and from the central and northern Plains into the upper Mississippi Valley. ...North-central Rockies/Central and Northern Plains/Upper Mississippi Valley... A positively-tilted upper-level trough will move across the northern High Plains and north-central Rockies today. An associated cold front will move across the northern Plains and central High Plains. As surface temperatures warm, isolated to scattered thunderstorms are expected to develop in the higher terrain of the north-central Rockies in the post-frontal airmass. Additional storms are expected to form along and near the front across parts of the northern Plains. The storms will move east and southward across the region, affecting the central Plains and upper Mississippi during the mid to late evening. A chance for storms could persist into the overnight. Model forecasts suggest that the strongest instability will be located over the eastern Dakotas today, where the development of moderate instability will be possible. Weak instability is forecast to develop ahead of the front from the central Rockies and central High Plains northward into the post-frontal airmass as far north as eastern Montana. Due to the approaching upper-level trough, moderate deep-layer shear and steep mid-level lapse rates are forecast across much of the north-central U.S. The environment should be sufficient for an isolated severe threat during the afternoon and evening, especially in areas that sufficiently destabilize. Severe wind gusts and hail will be possible with the stronger multicells. An isolated supercell threat could develop in areas where parameters become most favorable, but location uncertainty is considerable. ..Broyles/Moore.. 09/04/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1234 AM CDT Wed Sep 04 2024 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTH-CENTRAL ROCKIES...CENTRAL AND NORTHERN PLAINS...AND UPPER MISSISSIPPI VALLEY... ...SUMMARY... Isolated severe storms, capable of severe wind gusts and hail, will be possible this afternoon and evening across parts of the central and northern Rockies, and from the central and northern Plains into the upper Mississippi Valley. ...North-central Rockies/Central and Northern Plains/Upper Mississippi Valley... A positively-tilted upper-level trough will move across the northern High Plains and north-central Rockies today. An associated cold front will move across the northern Plains and central High Plains. As surface temperatures warm, isolated to scattered thunderstorms are expected to develop in the higher terrain of the north-central Rockies in the post-frontal airmass. Additional storms are expected to form along and near the front across parts of the northern Plains. The storms will move east and southward across the region, affecting the central Plains and upper Mississippi during the mid to late evening. A chance for storms could persist into the overnight. Model forecasts suggest that the strongest instability will be located over the eastern Dakotas today, where the development of moderate instability will be possible. Weak instability is forecast to develop ahead of the front from the central Rockies and central High Plains northward into the post-frontal airmass as far north as eastern Montana. Due to the approaching upper-level trough, moderate deep-layer shear and steep mid-level lapse rates are forecast across much of the north-central U.S. The environment should be sufficient for an isolated severe threat during the afternoon and evening, especially in areas that sufficiently destabilize. Severe wind gusts and hail will be possible with the stronger multicells. An isolated supercell threat could develop in areas where parameters become most favorable, but location uncertainty is considerable. ..Broyles/Moore.. 09/04/2024 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0741 PM CDT Tue Sep 03 2024 Valid 040100Z - 041200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL AND NORTHERN ROCKIES INTO THE NORTHERN HIGH PLAINS... ...SUMMARY... Isolated severe storms, associated with marginally severe wind gusts, will be possible this evening across parts of the central and northern Rockies into the northern High Plains. ...Central and Northern Rockies/Northern High Plains... A positively-tilted upper-level trough is evident on water vapor imagery over the northern Rockies, with southwest mid-level flow from the Intermountain West into the northern High Plains. A weakly unstable airmass is located ahead of the trough from Wyoming northward into southern and central Montana, with scattered thunderstorms ongoing near the instability axis. RAP forecast soundings this evening from west of Billings, Montana southward to near Jackson, Wyoming have MLCAPE near 500 J/kg, 0-6 km shear around 40 knots and 700-500 mb lapse near 8 C/km. This environment should continue to support an isolated severe threat. Although instability is the limiting factor, the threat could continue for a few more hours this evening before surface temperatures cool significantly. The primary threat will be for marginally severe wind gusts. Hail will be possible from south-central Montana into northwest Wyoming, where large-scale ascent appears to be maximized ahead of the approaching upper-level trough. The severe threat could impact areas further to the east in the northern High Plains later this evening. ..Broyles.. 09/04/2024 Read more