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SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0213 PM CDT Fri Oct 04 2024 Valid 042000Z - 051200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected through tonight. Little was changed to the existing outlook for the 20Z outlook except to remove the 10% general thunderstorm area from IL as the activity has diminished. Otherwise, general storms will remain possible from the TX Coast into much of the Southeast, south of the Great Lakes high and within the relatively moist easterly flow regime. ..Jewell.. 10/04/2024 .PREV DISCUSSION... /ISSUED 1122 AM CDT Fri Oct 04 2024/ ...Synopsis... A mid-level shortwave trough over the western Great Lakes will continue to quickly move east through the afternoon and a lingering thunderstorm cluster over west-central IL late this morning will gradually diminish as this disturbance becomes displaced. Farther south, isolated to widely scattered thunderstorms will be possible from parts of the Mid-Atlantic southwestward to the Gulf Coast/Southeast. Weak flow will limit storm intensity in these regions. A vigorous shortwave trough will move across the Pacific Northwest and northern Rockies/Plains through tonight. While large-scale forcing and mid-level flow associated with the upper trough passage will be strong, thunderstorm coverage is expected to remain sparse due to a rather dry airmass present across these areas. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0212 PM CDT Fri Oct 04 2024 Valid 051200Z - 061200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE CENTRAL ROCKIES ONTO THE CENTRAL/NORTHERN PLAINS... The previous forecast remains on track as widespread elevated to critical conditions are expected from eastern Montana, North Dakota, and western Montana southward through much of Wyoming, Colorado, and Kansas into northern New Mexico and the Oklahoma/Texas Panhandles. The Elevated and Critical areas were both expanded based on the latest high-resolution forecast guidance. Of note, elevated and critical fire weather conditions are likely to continue from Day 1/Friday night into Day 2/Saturday AM in portions of southeast Wyoming, western Nebraska, and northeast Colorado, with elevated/critical conditions beginning by late morning in the vicinity of the Critical area. There remains uncertainty on the northern/eastern borders of the Elevated area, and post-frontal dry/breezy elevated conditions are possible in portions of the Great Basin. ..Nauslar.. 10/04/2024 .PREV DISCUSSION... /ISSUED 0137 AM CDT Fri Oct 04 2024/ ...Synopsis... A pronounced mid-level trough and associated surface lee trough will progress over the Plains states and quickly eject into the Upper Mississippi Valley tomorrow (Saturday). Strong southerly flow will precede the surface lee trough, with a strong northwesterly surface wind shift noted behind a cold front that is poised to sweep across the northern Plains tomorrow afternoon. Widespread Elevated highlights have been introduced where sustained surface winds should exceed 15 mph amid 15-25 percent RH and very dry fuels. Critical highlights are in place along the Colorado/Wyoming border into portions of the Central Plains, where 25+ mph sustained northwesterly surface winds and 15 percent RH is expected immediately behind the cold front. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0203 PM CDT Fri Oct 04 2024 Valid 061200Z - 071200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS WESTERN NEW YORK AND PENNSYLVANIA INTO PARTS OF WEST VIRGINIA... ...SUMMARY... Isolated strong to severe thunderstorms are possible Sunday afternoon and evening across parts of the western New York and Pennsylvania into West Virginia. ...Upper Ohio Valley/Lower Great Lakes vicinity... A negatively tilted upper trough will shift east from the Upper Great Lakes into the Northeast on Sunday. A belt of strong westerly deep-layer flow will accompany this system and overspread the Upper OH Valley into NY/PA during the afternoon and evening. A narrow warm sector will bring upper 50s to low 60s F dewpoints northward across the region ahead of an eastward-advancing cold front. Meanwhile, cooling aloft will result in steep midlevel lapse rates around 6.5-7.5 C/km. This will contribute to modest destabilization across western NY/PA into WV and eastern KY (MUCAPE 1000-1500 J/kg). Effective shear magnitudes greater than 35 kt (somewhat less with southward extent) suggest organized storms will be possible along the cold front. Elongated and somewhat straight hodographs amid other favorable parameters indicate isolated large hail will be possible with the strongest cells. Strong gusts also may occur with this activity as convection quickly tracks east during the late afternoon/early evening. ..Leitman.. 10/04/2024 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1207 PM CDT Fri Oct 04 2024 Valid 051200Z - 061200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF NORTHERN WI INTO THE UPPER PENINSULA OF MI... ...SUMMARY... Isolated strong to severe thunderstorms may produce hail and gusty winds across parts of northern Wisconsin into the Upper Peninsula of Michigan Saturday evening. ...Great Lakes... A potent upper shortwave trough over the northern High Plains will shift east on Saturday, becoming positioned over the Great Lakes by Sunday morning. A strong 70+ kt southwesterly 500 mb jet will overspread the Upper Midwest as the trough shifts east. Meanwhile, cooling aloft will lead to a plume of steep midlevel lapse rates across WI/MI by late afternoon/evening. Low-level inhibition will limit surface-based instability, but cool temperatures aloft and increasing midlevel moisture will support MUCAPE values around 1500-2000 J/kg. A cold front extending south from a deepening low over Manitoba and western Ontario will shift east across the Upper Midwest during the day and into the evening, becoming oriented from central Lower MI to northern OK by 12z Sunday. A warm advection regime ahead of the upper trough, coupled with increasing instability and moderate vertical shear will support thunderstorm development near the front by late afternoon/early evening. A few organized cells may produce strong gusts and marginal hail across parts of northern WI into the U.P. of MI during the evening, and a Marginal risk (level 1 of 5) has been included with the Day 2 update. ...Gulf Coast... East to northeast low-level flow will persist over the Gulf, where a very moist airmass (70s F dewpoints) will be in place along the coastal regions from TX eastward across Florida. Sufficient instability will support thunderstorm potential, especially along any sea breeze boundaries where low-level convergence will be enhanced. Overall instability will remain modest, with poor lapse rates forecast and limited vertical shear, precluding severe thunderstorm concerns. ..Leitman.. 10/04/2024 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1207 PM CDT Fri Oct 04 2024 Valid 051200Z - 061200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF NORTHERN WI INTO THE UPPER PENINSULA OF MI... ...SUMMARY... Isolated strong to severe thunderstorms may produce hail and gusty winds across parts of northern Wisconsin into the Upper Peninsula of Michigan Saturday evening. ...Great Lakes... A potent upper shortwave trough over the northern High Plains will shift east on Saturday, becoming positioned over the Great Lakes by Sunday morning. A strong 70+ kt southwesterly 500 mb jet will overspread the Upper Midwest as the trough shifts east. Meanwhile, cooling aloft will lead to a plume of steep midlevel lapse rates across WI/MI by late afternoon/evening. Low-level inhibition will limit surface-based instability, but cool temperatures aloft and increasing midlevel moisture will support MUCAPE values around 1500-2000 J/kg. A cold front extending south from a deepening low over Manitoba and western Ontario will shift east across the Upper Midwest during the day and into the evening, becoming oriented from central Lower MI to northern OK by 12z Sunday. A warm advection regime ahead of the upper trough, coupled with increasing instability and moderate vertical shear will support thunderstorm development near the front by late afternoon/early evening. A few organized cells may produce strong gusts and marginal hail across parts of northern WI into the U.P. of MI during the evening, and a Marginal risk (level 1 of 5) has been included with the Day 2 update. ...Gulf Coast... East to northeast low-level flow will persist over the Gulf, where a very moist airmass (70s F dewpoints) will be in place along the coastal regions from TX eastward across Florida. Sufficient instability will support thunderstorm potential, especially along any sea breeze boundaries where low-level convergence will be enhanced. Overall instability will remain modest, with poor lapse rates forecast and limited vertical shear, precluding severe thunderstorm concerns. ..Leitman.. 10/04/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1122 AM CDT Fri Oct 04 2024 Valid 041630Z - 051200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected through tonight. ...Synopsis... A mid-level shortwave trough over the western Great Lakes will continue to quickly move east through the afternoon and a lingering thunderstorm cluster over west-central IL late this morning will gradually diminish as this disturbance becomes displaced. Farther south, isolated to widely scattered thunderstorms will be possible from parts of the Mid-Atlantic southwestward to the Gulf Coast/Southeast. Weak flow will limit storm intensity in these regions. A vigorous shortwave trough will move across the Pacific Northwest and northern Rockies/Plains through tonight. While large-scale forcing and mid-level flow associated with the upper trough passage will be strong, thunderstorm coverage is expected to remain sparse due to a rather dry airmass present across these areas. ..Smith/Lyons.. 10/04/2024 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1049 AM CDT Fri Oct 04 2024 Valid 041700Z - 051200Z ...CRITICAL FIRE WEATHER AREA FOR NORTHWEST GREAT BASIN AND SOUTHERN IDAHO INTO SOUTHWEST MONTANA... ...CRITICAL FIRE WEATHER AREA FOR NORTHEAST UTAH AND SOUTHERN/CENTRAL WYOMING... The overall forecast for widespread elevated to critical conditions across the northern Intermountain West onto the northern Plains ahead of an approaching cold front remains on track. However, based on the latest observations and high-resolution guidance, the Elevated area was expanded south/east in portions of Nevada, Utah, and Colorado. Additionally, both Critical areas were expanded. Elevated/locally critical conditions will continue overnight from southeast Montana through eastern Wyoming. Elevated conditions are likely to linger into the overnight in portions of the Great Basin, especially at mid/upper slopes due to remaining in the pre-frontal environment, with poor RH recovery and gusty winds aloft. ..Nauslar.. 10/04/2024 .PREV DISCUSSION... /ISSUED 0135 AM CDT Fri Oct 04 2024/ ...Synopsis... A mid-level trough will rapidly traverse the northwestern CONUS while supporting the development of a pronounced surface cyclone across southern Saskatchewan today. As the surface cyclone quickly translates eastward through the period, a wide corridor of strong surface gradient winds will overlap with a dry boundary layer and overspread very dry fuels across portions of the northwestern to north-central U.S. Elevated highlights are in place across the Great Basin toward the Northern Plains. Widespread 15 mph sustained westerly surface winds are expected from eastern Oregon to central Wyoming, with the wind direction shifting to more southerly across the Plains states (given surface lee troughing). RH will drop to 15 percent over portions of the Intermountain West, with RH dipping to 20-25 percent in the Northern Plains. Sustained surface wind speeds are expected to reach 20-25 mph over portions of the Harney Basin into the northern Great Basin, as well as central Wyoming by afternoon peak heating, where Critical highlights have been introduced. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0748 AM CDT Fri Oct 04 2024 Valid 041300Z - 051200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected today and tonight. ...Synopsis and Discussion... Elevated thunderstorms ongoing across west-central IL should continue for a few more hours this morning, aided by modest warm advection in the 850-700 mb layer and ascent on the southern periphery of a shortwave trough over the Upper Midwest. With a mainly linear mode now dominant, severe hail appears unlikely. This activity should gradually diminish in coverage and intensity through the remainder of the morning. Isolated to scattered thunderstorms will be possible today from parts of the Mid-Atlantic southwestward to the Gulf Coast/Southeast. Weak flow and related deep-layer shear will limit the overall severe threat with any convection that develops across these regions. A pronounced shortwave trough will move across the Pacific Northwest and northern Rockies/Plains through tonight. While large-scale forcing and mid-level flow associated with the upper trough passage will be strong, thunderstorm coverage is expected to remain sparse due to a rather dry airmass present across these areas. ..Gleason/Dean.. 10/04/2024 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0334 AM CDT Fri Oct 04 2024 Valid 071200Z - 121200Z ...DISCUSSION... Medium-range guidance continues to show cyclonic flow aloft persisting over the northeast CONUS from D4/Monday into D6/Wednesday before extensive upper ridging over the western and central CONUS builds eastward and displaces the cyclone. Even with this cyclonic flow persisting early next week, much of the low-level moisture will likely be off the Northeast coast by early D4/Monday. Modest low-level moisture will likely linger across much of the Southeast and Gulf Coast for much of the week, with some thunderstorm threat persisting, predominately across the FL Peninsula. Dry and stable conditions are currently expected elsewhere across the CONUS as upper ridging builds eastward and the continental airmass remains in place. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0334 AM CDT Fri Oct 04 2024 Valid 071200Z - 121200Z ...DISCUSSION... Medium-range guidance continues to show cyclonic flow aloft persisting over the northeast CONUS from D4/Monday into D6/Wednesday before extensive upper ridging over the western and central CONUS builds eastward and displaces the cyclone. Even with this cyclonic flow persisting early next week, much of the low-level moisture will likely be off the Northeast coast by early D4/Monday. Modest low-level moisture will likely linger across much of the Southeast and Gulf Coast for much of the week, with some thunderstorm threat persisting, predominately across the FL Peninsula. Dry and stable conditions are currently expected elsewhere across the CONUS as upper ridging builds eastward and the continental airmass remains in place. Read more

MD 2129 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR SOUTH-CENTRAL/SOUTHEAST IA INTO FAR NORTHEAST MO/NORTHWEST IL
Mesoscale Discussion 2129 NWS Storm Prediction Center Norman OK 0211 AM CDT Fri Oct 04 2024 Areas affected...South-central/southeast IA into far northeast MO/northwest IL Concerning...Severe potential...Watch unlikely Valid 040711Z - 040915Z Probability of Watch Issuance...20 percent SUMMARY...Isolated hail is possible overnight. DISCUSSION...Elevated convection has increased in coverage and intensity over the last 1-2 hours across parts of Iowa, within a low-level warm advection regime. Recent intensification has occurred with a cell south of Des Moines, with other semi-discrete cells noted along the southwest periphery of the ongoing convection. These storms have developed within the northern periphery of a gradually expanding elevated buoyancy plume, with MUCAPE generally around 500-1000 J/kg. Moderate west-southwesterly flow aloft is supporting effective shear of 25-35 kt for convection rooted within the 800-700 mb layer, sufficient for some storm organization. Relatively steep midlevel lapse rates and cool temperatures aloft will continue to support an isolated severe-hail threat with any stronger storms that can remain semi-discrete overnight. ..Dean/Gleason.. 10/04/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...DVN...DMX...EAX... LAT...LON 41319410 41749247 41839148 41729101 41309081 40589084 40369141 40669330 40709354 41319410 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0216 AM CDT Fri Oct 04 2024 Valid 061200Z - 071200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Isolated thunderstorms are possible across the middle and upper Ohio Valley as well across the Gulf Coast Sunday. Severe thunderstorms are not currently anticipated. ...Middle/Upper OH Valley... A maturing mid-latitude cyclone will likely be over northwest Ontario early Sunday morning. A pair of fast-moving, low-amplitude shortwave troughs will move through the base of this cyclone during the period, helping induce a more negative tilt while also pulling the cyclone eastward. Primary surface low associated with this system will remain occluded over Ontario throughout the period. However, a secondary triple-point low will likely be over central Ontario early Sunday, with its associated cold front extending southwestward through the Mid MS Valley. This low is forecast to push eastward across eastern Ontario during the day, with the cold front progressing eastward/southeastward as well. Some low-level moisture return is anticipated ahead of this front across the middle/upper OH Valley, although the best moisture will be confined to a narrow axis just ahead of the front. This buoyancy, coupled with increasing large-scale forcing for ascent, could contribute to enough buoyancy for thunderstorm development along and just ahead of the front. However, the quality of this moisture return and associated buoyancy remain uncertain, with the veered low-level flow ahead of the front and narrow character of the warm sector also limiting factors. Low predictability within this scenario merits precluding introducing low severe probabilities with this outlook. ...Gulf Coast into the Coastal GA and FL Peninsula... Easterly/northeasterly low-level flow will persist for another day across the northern Gulf of Mexico, as a broad area of low pressure remains in place. Showers and thunderstorms are possible within the moist airmass, but weak shear should keep storm severity low. ..Mosier.. 10/04/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0216 AM CDT Fri Oct 04 2024 Valid 061200Z - 071200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Isolated thunderstorms are possible across the middle and upper Ohio Valley as well across the Gulf Coast Sunday. Severe thunderstorms are not currently anticipated. ...Middle/Upper OH Valley... A maturing mid-latitude cyclone will likely be over northwest Ontario early Sunday morning. A pair of fast-moving, low-amplitude shortwave troughs will move through the base of this cyclone during the period, helping induce a more negative tilt while also pulling the cyclone eastward. Primary surface low associated with this system will remain occluded over Ontario throughout the period. However, a secondary triple-point low will likely be over central Ontario early Sunday, with its associated cold front extending southwestward through the Mid MS Valley. This low is forecast to push eastward across eastern Ontario during the day, with the cold front progressing eastward/southeastward as well. Some low-level moisture return is anticipated ahead of this front across the middle/upper OH Valley, although the best moisture will be confined to a narrow axis just ahead of the front. This buoyancy, coupled with increasing large-scale forcing for ascent, could contribute to enough buoyancy for thunderstorm development along and just ahead of the front. However, the quality of this moisture return and associated buoyancy remain uncertain, with the veered low-level flow ahead of the front and narrow character of the warm sector also limiting factors. Low predictability within this scenario merits precluding introducing low severe probabilities with this outlook. ...Gulf Coast into the Coastal GA and FL Peninsula... Easterly/northeasterly low-level flow will persist for another day across the northern Gulf of Mexico, as a broad area of low pressure remains in place. Showers and thunderstorms are possible within the moist airmass, but weak shear should keep storm severity low. ..Mosier.. 10/04/2024 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0137 AM CDT Fri Oct 04 2024 Valid 051200Z - 061200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE CENTRAL ROCKIES INTO THE CENTRAL HIGH PLAINS... ...Synopsis... A pronounced mid-level trough and associated surface lee trough will progress over the Plains states and quickly eject into the Upper Mississippi Valley tomorrow (Saturday). Strong southerly flow will precede the surface lee trough, with a strong northwesterly surface wind shift noted behind a cold front that is poised to sweep across the northern Plains tomorrow afternoon. Widespread Elevated highlights have been introduced where sustained surface winds should exceed 15 mph amid 15-25 percent RH and very dry fuels. Critical highlights are in place along the Colorado/Wyoming border into portions of the Central Plains, where 25+ mph sustained northwesterly surface winds and 15 percent RH is expected immediately behind the cold front. ..Squitieri.. 10/04/2024 ...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 0135 AM CDT Fri Oct 04 2024 Valid 041200Z - 051200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE HARNEY BASIN INTO THE NORTHERN GREAT BASIN... ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF CENTRAL WYOMING... ...Synopsis... A mid-level trough will rapidly traverse the northwestern CONUS while supporting the development of a pronounced surface cyclone across southern Saskatchewan today. As the surface cyclone quickly translates eastward through the period, a wide corridor of strong surface gradient winds will overlap with a dry boundary layer and overspread very dry fuels across portions of the northwestern to north-central U.S. Elevated highlights are in place across the Great Basin toward the Northern Plains. Widespread 15 mph sustained westerly surface winds are expected from eastern Oregon to central Wyoming, with the wind direction shifting to more southerly across the Plains states (given surface lee troughing). RH will drop to 15 percent over portions of the Intermountain West, with RH dipping to 20-25 percent in the Northern Plains. Sustained surface wind speeds are expected to reach 20-25 mph over portions of the Harney Basin into the northern Great Basin, as well as central Wyoming by afternoon peak heating, where Critical highlights have been introduced. ..Squitieri.. 10/04/2024 ...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 1221 AM CDT Fri Oct 04 2024 Valid 051200Z - 061200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Potential for severe storms appears low on Saturday. ...Upper Midwest into the Upper Great Lakes... Northern-stream shortwave trough is forecast to move quickly eastward from the Canadian Prairies and adjacent northern High Plains through western Ontario and the Upper Midwest on Saturday. This shortwave is expected to mature as it progresses eastward, with the resulting closed mid-level cyclone over northwestern Ontario by early Sunday morning. An associated surface low will accompany this system, moving eastward across the central portion of Canadian Prairie Provinces and ending the period stacked beneath the mid-level low over northwestern Ontario. Cold front attendant to this surface low will push eastward across the northern and central Plains through the Upper Midwest. By 12Z Sunday, this front will likely extend from central Lower MI southwestward through central MO before then turning more westward and extending along the OK/KS border vicinity. Warm-air advection will gradually increase within the warm sector ahead of the front throughout the period. Low to mid-level moistening from this warm-air advection coupled with cooling mid-level temperatures will result in elevated buoyancy across the Upper Midwest and Upper Great Lakes from Saturday evening into Sunday morning. Isolated thunderstorms are possible within this region as a result. Enhanced mid-level flow associated with the shortwave trough will spread into the region during the evening as well, supporting moderate to strong deep-layer vertical shear. However, the cloud-bearing layer shear values will be more modest (i.e. around half of the bulk shear values), and the resulting combination of modest buoyancy and shear will likely result in predominantly sub-severe thunderstorms. ...Gulf Coast... Showers and thunderstorms are expected across the Gulf Coast and FL Peninsula throughout the period as low-level easterlies persist within a very moist airmass. Limited buoyancy and weak shear should keep the severe-thunderstorm potential low. ..Mosier.. 10/04/2024 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1221 AM CDT Fri Oct 04 2024 Valid 051200Z - 061200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Potential for severe storms appears low on Saturday. ...Upper Midwest into the Upper Great Lakes... Northern-stream shortwave trough is forecast to move quickly eastward from the Canadian Prairies and adjacent northern High Plains through western Ontario and the Upper Midwest on Saturday. This shortwave is expected to mature as it progresses eastward, with the resulting closed mid-level cyclone over northwestern Ontario by early Sunday morning. An associated surface low will accompany this system, moving eastward across the central portion of Canadian Prairie Provinces and ending the period stacked beneath the mid-level low over northwestern Ontario. Cold front attendant to this surface low will push eastward across the northern and central Plains through the Upper Midwest. By 12Z Sunday, this front will likely extend from central Lower MI southwestward through central MO before then turning more westward and extending along the OK/KS border vicinity. Warm-air advection will gradually increase within the warm sector ahead of the front throughout the period. Low to mid-level moistening from this warm-air advection coupled with cooling mid-level temperatures will result in elevated buoyancy across the Upper Midwest and Upper Great Lakes from Saturday evening into Sunday morning. Isolated thunderstorms are possible within this region as a result. Enhanced mid-level flow associated with the shortwave trough will spread into the region during the evening as well, supporting moderate to strong deep-layer vertical shear. However, the cloud-bearing layer shear values will be more modest (i.e. around half of the bulk shear values), and the resulting combination of modest buoyancy and shear will likely result in predominantly sub-severe thunderstorms. ...Gulf Coast... Showers and thunderstorms are expected across the Gulf Coast and FL Peninsula throughout the period as low-level easterlies persist within a very moist airmass. Limited buoyancy and weak shear should keep the severe-thunderstorm potential low. ..Mosier.. 10/04/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1133 PM CDT Thu Oct 03 2024 Valid 041200Z - 051200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for severe thunderstorms appears negligible across the U.S. today through tonight. ...Discussion... Seasonably high moisture content will generally remain confined to where the low-level easterlies prevail, across the southwestern Atlantic through the Gulf Basin during this period. The boundary layer does remain relatively moist across much of the southeastern U.S., but this region, and most areas east of the Mississippi Valley, are forecast to remain under the influence of surface high pressure. Still, weak to modest destabilization and orographic forcing with daytime heating may contribute to some thunderstorm development today across parts of the upper Tennessee Valley and Cumberland Plateau into the Blue Ridge. Otherwise, higher thunderstorm probabilities likely will remain focused across southern portions of the Florida Peninsula and immediate northwestern through north central Gulf coastal areas. An area of thunderstorm development, largely aided by ascent associated with lower/mid-tropospheric warm advection, may be ongoing at 12Z this morning across parts of southeastern Iowa and adjacent northeastern Missouri/west central Illinois. But this appears likely to gradually diminish while slowly spreading southeastward across west central/central Illinois through mid to late morning. The stronger westerlies remain confined to the northern mid-latitudes, with one rather vigorous embedded short wave trough forecast to rapidly accelerate inland of the Pacific Northwest coast and across the northern Rockies by 12Z Saturday. Models indicate that this will be accompanied by cyclogenesis to the lee of the Canadian Rockies, and strong pre- and post-frontal lower/mid-tropospheric wind fields across the northern U.S. Rockies into Great Plains. Despite rather dry initial conditions, strong mid/upper forcing for ascent may contribute to at least weak high-based convection, near or above/to the cool side of the surging cold front. While it is possible that this could coincide with strong/gusty surface conditions, forecast soundings suggest minimal potential for these gusts to be related to moist convective processes, and it still appears unlikely that this convection will be accompanied by much, if any, lightning. ..Kerr/Squitieri.. 10/04/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1133 PM CDT Thu Oct 03 2024 Valid 041200Z - 051200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for severe thunderstorms appears negligible across the U.S. today through tonight. ...Discussion... Seasonably high moisture content will generally remain confined to where the low-level easterlies prevail, across the southwestern Atlantic through the Gulf Basin during this period. The boundary layer does remain relatively moist across much of the southeastern U.S., but this region, and most areas east of the Mississippi Valley, are forecast to remain under the influence of surface high pressure. Still, weak to modest destabilization and orographic forcing with daytime heating may contribute to some thunderstorm development today across parts of the upper Tennessee Valley and Cumberland Plateau into the Blue Ridge. Otherwise, higher thunderstorm probabilities likely will remain focused across southern portions of the Florida Peninsula and immediate northwestern through north central Gulf coastal areas. An area of thunderstorm development, largely aided by ascent associated with lower/mid-tropospheric warm advection, may be ongoing at 12Z this morning across parts of southeastern Iowa and adjacent northeastern Missouri/west central Illinois. But this appears likely to gradually diminish while slowly spreading southeastward across west central/central Illinois through mid to late morning. The stronger westerlies remain confined to the northern mid-latitudes, with one rather vigorous embedded short wave trough forecast to rapidly accelerate inland of the Pacific Northwest coast and across the northern Rockies by 12Z Saturday. Models indicate that this will be accompanied by cyclogenesis to the lee of the Canadian Rockies, and strong pre- and post-frontal lower/mid-tropospheric wind fields across the northern U.S. Rockies into Great Plains. Despite rather dry initial conditions, strong mid/upper forcing for ascent may contribute to at least weak high-based convection, near or above/to the cool side of the surging cold front. While it is possible that this could coincide with strong/gusty surface conditions, forecast soundings suggest minimal potential for these gusts to be related to moist convective processes, and it still appears unlikely that this convection will be accompanied by much, if any, lightning. ..Kerr/Squitieri.. 10/04/2024 Read more