SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0223 PM CDT Sun Sep 01 2024 Valid 031200Z - 041200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF EASTERN IDAHO INTO SOUTHWEST MONTANA AND WESTERN WYOMING... ...SUMMARY... A few strong storms may produce hail and gusty winds over parts of eastern Idaho, southwest Montana, and western Wyoming on Tuesday. ...Synopsis... On Tuesday, an upper trough will move east across ID into MT and WY, weakening during that time. Cooling aloft will still accompany this wave, with 500 mb wind speeds around 30-35 kt. Meanwhile, a larger upper trough will quickly exit the Northeast, with height rises over the Great Lakes and upper MS Valley. At the surface, a prominent high will affect much of the eastern CONUS, providing relatively stable conditions. A trough will develop during the afternoon over the northern High Plains, with the primary cold front affecting parts of the northern Rockies in association with the a shortwave trough moving across ID, MT, and WY. ...ID into MT and WY... Cool temperatures aloft will support early/ongoing showers and a few thunderstorms on Tuesday, with increasing coverage as heating occurs into parts of eastern ID, southwest MT and western WY. As the trough progresses east, scattered strong to marginally severe storms may develop as instability increases with heating. Steeper lapse rates aloft as well as elongated hodographs with effective deep-layer shear around 40 kt will favor cellular storm mode with hail, perhaps to severe levels. Veering winds with height and perhaps 100 m2/s2 SRH may support a supercell or two as well. ..Jewell.. 09/01/2024 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1211 PM CDT Sun Sep 01 2024 Valid 021200Z - 031200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Minimal severe risk will exist across the USA on Monday, with thunderstorms most prevalent across parts of the Southeast and from the Great Basin into parts of the Northwest. ...Great Basin into eastern OR into ID... A compact upper low is forecast to move across northern CA and into central OR on Monday, while mid and high level winds increase ahead of it. Cooling aloft along with surface heating will result in very steep lapse rates over much of the area, with -10 C at 500 mb as far south as central NV. A surface trough will develop over eastern WA/OR into western ID and northern NV, providing a focus for scattered late-day storms. Forecast soundings indicate inverted-v profiles, with minimal overall CAPE values of a few hundred J/kg. This will support gusty outflow winds with the strongest storms, however, it is unclear whether enough downdraft material will be present to produce severe gusts. In addition, mean winds in the lowest few km will remain relatively weak while the stronger winds remain at or above 500 mb. That said, an isolated gust over 50 kt cannot be ruled out, and low severe wind probabilities may be considered in later outlooks as confidence increases. ...Southeast... A large upper trough will progress across the northeastern States on Monday, with weak but cyclonic flow aloft extending into the Southeast. Minimal cooling aloft will occur, while the air mass remains moist. High pressure north of the region will result in northerly winds which will tend to shunt the 70s F dewpoints toward the coastal Carolinas, while providing minimal convergence. Daytime heating should then result in scattered thunderstorms from parts of GA across SC and toward coastal NC, but weak shear and poor lapse rates suggest little severe risk. ..Jewell.. 09/01/2024 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1211 PM CDT Sun Sep 01 2024 Valid 021200Z - 031200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Minimal severe risk will exist across the USA on Monday, with thunderstorms most prevalent across parts of the Southeast and from the Great Basin into parts of the Northwest. ...Great Basin into eastern OR into ID... A compact upper low is forecast to move across northern CA and into central OR on Monday, while mid and high level winds increase ahead of it. Cooling aloft along with surface heating will result in very steep lapse rates over much of the area, with -10 C at 500 mb as far south as central NV. A surface trough will develop over eastern WA/OR into western ID and northern NV, providing a focus for scattered late-day storms. Forecast soundings indicate inverted-v profiles, with minimal overall CAPE values of a few hundred J/kg. This will support gusty outflow winds with the strongest storms, however, it is unclear whether enough downdraft material will be present to produce severe gusts. In addition, mean winds in the lowest few km will remain relatively weak while the stronger winds remain at or above 500 mb. That said, an isolated gust over 50 kt cannot be ruled out, and low severe wind probabilities may be considered in later outlooks as confidence increases. ...Southeast... A large upper trough will progress across the northeastern States on Monday, with weak but cyclonic flow aloft extending into the Southeast. Minimal cooling aloft will occur, while the air mass remains moist. High pressure north of the region will result in northerly winds which will tend to shunt the 70s F dewpoints toward the coastal Carolinas, while providing minimal convergence. Daytime heating should then result in scattered thunderstorms from parts of GA across SC and toward coastal NC, but weak shear and poor lapse rates suggest little severe risk. ..Jewell.. 09/01/2024 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1155 AM CDT Sun Sep 01 2024 Valid 011700Z - 021200Z No changes are needed to the current D1 Fire Weather Outlook. See previous discussion below for more information. ..Thornton.. 09/01/2024 .PREV DISCUSSION... /ISSUED 0151 AM CDT Sun Sep 01 2024/ ...Synopsis... Dry thunderstorms will be the primary fire weather concern for today. Isolated dry thunderstorms were observed yesterday (Saturday) across portions of central NV on the fringe of a modest monsoonal moisture plume. This air mass is currently advecting northward into north-central NV and adjacent portions of OR/ID per latest water-vapor imagery. 00z soundings along the West Coast have already begun to sample this mid-level moisture as well as cool mid-level temperatures, which should support MUCAPE values between 100-250 J/kg this afternoon. Concurrently, an upper wave off the northern CA coast is forecast to move onshore over the next 24-48 hours. Lift ahead of this wave will overspread the moisture plume, resulting in isolated to widely scattered thunderstorms from central OR into eastern NV/far western UT. Dry boundary layer conditions (as well as fast storm motions across OR) will limit rainfall accumulation and favor dry lightning strikes. Given regional ERCs at or above the 80th percentile, dry lightning will pose a fire weather concern. Elsewhere across the West, dry conditions will prevail with another day of afternoon RH minimums in the teens expected. Strengthening southerly mid-level winds may support areas of dry/windy conditions in the immediate lee of the central and northern Sierra Nevada, but such conditions should remain too limited to warrant highlights. ...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 1155 AM CDT Sun Sep 01 2024 Valid 011700Z - 021200Z No changes are needed to the current D1 Fire Weather Outlook. See previous discussion below for more information. ..Thornton.. 09/01/2024 .PREV DISCUSSION... /ISSUED 0151 AM CDT Sun Sep 01 2024/ ...Synopsis... Dry thunderstorms will be the primary fire weather concern for today. Isolated dry thunderstorms were observed yesterday (Saturday) across portions of central NV on the fringe of a modest monsoonal moisture plume. This air mass is currently advecting northward into north-central NV and adjacent portions of OR/ID per latest water-vapor imagery. 00z soundings along the West Coast have already begun to sample this mid-level moisture as well as cool mid-level temperatures, which should support MUCAPE values between 100-250 J/kg this afternoon. Concurrently, an upper wave off the northern CA coast is forecast to move onshore over the next 24-48 hours. Lift ahead of this wave will overspread the moisture plume, resulting in isolated to widely scattered thunderstorms from central OR into eastern NV/far western UT. Dry boundary layer conditions (as well as fast storm motions across OR) will limit rainfall accumulation and favor dry lightning strikes. Given regional ERCs at or above the 80th percentile, dry lightning will pose a fire weather concern. Elsewhere across the West, dry conditions will prevail with another day of afternoon RH minimums in the teens expected. Strengthening southerly mid-level winds may support areas of dry/windy conditions in the immediate lee of the central and northern Sierra Nevada, but such conditions should remain too limited to warrant highlights. ...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 1125 AM CDT Sun Sep 01 2024 Valid 011630Z - 021200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE SOUTHERN APPALACHIANS INTO THE MID-ATLANTIC AND SOUTHERN NEW ENGLAND... ...SUMMARY... Strong to severe thunderstorms capable of producing isolated damaging winds may occur this afternoon across parts of the southern Appalachians into the Mid-Atlantic and southern New England. ...Southern Appalachians into the Mid-Atlantic and Southern New England... Thunderstorms should gradually increase in coverage this afternoon along/south of a diffuse front that extends from the Mid-South/lower OH Valley into the Mid-Atlantic. Late morning visible satellite imagery shows substantial cloud cover in the vicinity of the boundary. Nevertheless, daytime heating of a moist low-level air mass should allow at least weak/pockets of moderate instability to develop by early to mid afternoon along and south/east of the front. Modest ascent with an upper trough over eastern Canada and adjacent Great Lakes/Northeast U.S., in combination with orographic ascent, will likely contribute to thunderstorm development through the afternoon and early evening. Mid-level flow and related deep-layer shear will remain fairly modest, especially with southward extent across the Mid-Atlantic into the Carolinas and southern Appalachians. Mid-level flow should still prove sufficient to support modest thunderstorm organization. Multiple loosely organized multicell clusters may eventually develop and consolidate by late afternoon and early evening, posing some threat for isolated strong to damaging winds while moving generally eastward. The greatest concentration of thunderstorms should exist across parts of southern VA into NC and upstate SC where greater instability (MLCAPE on the order of 2000-2500 J/kg) is forecast this afternoon. ...Western/Northern New York into Northern New England... The upper-level trough and associated surface cold front will move east today across Ontario/Quebec provinces and Northeast U.S., with weak surface-based instability possibly developing in advance of the front. This may result in a narrow, low-topped line of convection (possibly with little lightning) moving east and accompanied by some risk for strong/locally damaging gusts. ..Bunting/Bentley.. 09/01/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1125 AM CDT Sun Sep 01 2024 Valid 011630Z - 021200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE SOUTHERN APPALACHIANS INTO THE MID-ATLANTIC AND SOUTHERN NEW ENGLAND... ...SUMMARY... Strong to severe thunderstorms capable of producing isolated damaging winds may occur this afternoon across parts of the southern Appalachians into the Mid-Atlantic and southern New England. ...Southern Appalachians into the Mid-Atlantic and Southern New England... Thunderstorms should gradually increase in coverage this afternoon along/south of a diffuse front that extends from the Mid-South/lower OH Valley into the Mid-Atlantic. Late morning visible satellite imagery shows substantial cloud cover in the vicinity of the boundary. Nevertheless, daytime heating of a moist low-level air mass should allow at least weak/pockets of moderate instability to develop by early to mid afternoon along and south/east of the front. Modest ascent with an upper trough over eastern Canada and adjacent Great Lakes/Northeast U.S., in combination with orographic ascent, will likely contribute to thunderstorm development through the afternoon and early evening. Mid-level flow and related deep-layer shear will remain fairly modest, especially with southward extent across the Mid-Atlantic into the Carolinas and southern Appalachians. Mid-level flow should still prove sufficient to support modest thunderstorm organization. Multiple loosely organized multicell clusters may eventually develop and consolidate by late afternoon and early evening, posing some threat for isolated strong to damaging winds while moving generally eastward. The greatest concentration of thunderstorms should exist across parts of southern VA into NC and upstate SC where greater instability (MLCAPE on the order of 2000-2500 J/kg) is forecast this afternoon. ...Western/Northern New York into Northern New England... The upper-level trough and associated surface cold front will move east today across Ontario/Quebec provinces and Northeast U.S., with weak surface-based instability possibly developing in advance of the front. This may result in a narrow, low-topped line of convection (possibly with little lightning) moving east and accompanied by some risk for strong/locally damaging gusts. ..Bunting/Bentley.. 09/01/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0748 AM CDT Sun Sep 01 2024 Valid 011300Z - 021200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE SOUTHERN APPALACHIANS INTO THE MID-ATLANTIC AND SOUTHERN NEW ENGLAND... ...SUMMARY... Strong thunderstorms capable of producing isolated damaging winds may occur this afternoon across parts of the southern Appalachians into the Mid-Atlantic and southern New England. ...Southern Appalachians into the Mid-Atlantic and Southern New England... Thunderstorms should gradually increase in coverage this afternoon along/south of a weak front that extends from the Mid-South/lower OH Valley into the Mid-Atlantic. Morning visible satellite imagery shows plentiful cloud cover near this boundary, and downstream across parts of NC and the Mid-Atlantic into southern New England. Still, filtered daytime heating of a moist low-level airmass should allow at least weak instability to develop by early to mid afternoon along and south/east of the front, even though mid-level lapse rates will remain poor. The glancing influence/ascent of an upper trough over eastern Canada, along with weak orographic lift, will likely encourage convection development through the afternoon and early evening. Mid-level flow and related deep-layer shear are forecast to remain fairly modest, especially with southward extent across the Mid-Atlantic into the Carolinas and southern Appalachians. Still, enough flow and related shear may be present to support modest thunderstorm organization. Multiple loosely organized multicell clusters may eventually develop and consolidate by late afternoon and early evening, while posing some threat for isolated strong to damaging winds as they move generally eastward. The greatest concentration of thunderstorms should exist across parts of southern VA into NC and upstate SC where greater instability is forecast this afternoon. But, confidence in a more organized wind threat remains too low to include greater severe wind probabilities. ...Western/Northern New York into Northern New England... As the primary upper trough and related surface cold front continue eastward across Ontario/Quebec today, daytime heating of a modestly moist low-level airmass will occur over parts of western/northern NY. Although poor mid-level lapse rates will likely hinder the development of any more than weak instability across this area (MLCAPE generally 500 J/kg of less), low/mid-level winds and related shear in the cloud-bearing layer is expected to strengthen through this afternoon with the approach of the upper trough. Some high-resolution/convection-allowing model guidance shows a low-topped line of thunderstorms developing this afternoon along or just ahead of the cold front. As low-level lapse rates steepen with daytime heating, some of this convection could produce isolated strong to severe wind gusts given the strengthening low/mid-level flow expected. The area impacted should remain fairly small across western/northern NY (generally downstream of Lake Ontario) due to more even more limited instability farther east across central NY into northern New England. ..Gleason/Leitman.. 09/01/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0748 AM CDT Sun Sep 01 2024 Valid 011300Z - 021200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE SOUTHERN APPALACHIANS INTO THE MID-ATLANTIC AND SOUTHERN NEW ENGLAND... ...SUMMARY... Strong thunderstorms capable of producing isolated damaging winds may occur this afternoon across parts of the southern Appalachians into the Mid-Atlantic and southern New England. ...Southern Appalachians into the Mid-Atlantic and Southern New England... Thunderstorms should gradually increase in coverage this afternoon along/south of a weak front that extends from the Mid-South/lower OH Valley into the Mid-Atlantic. Morning visible satellite imagery shows plentiful cloud cover near this boundary, and downstream across parts of NC and the Mid-Atlantic into southern New England. Still, filtered daytime heating of a moist low-level airmass should allow at least weak instability to develop by early to mid afternoon along and south/east of the front, even though mid-level lapse rates will remain poor. The glancing influence/ascent of an upper trough over eastern Canada, along with weak orographic lift, will likely encourage convection development through the afternoon and early evening. Mid-level flow and related deep-layer shear are forecast to remain fairly modest, especially with southward extent across the Mid-Atlantic into the Carolinas and southern Appalachians. Still, enough flow and related shear may be present to support modest thunderstorm organization. Multiple loosely organized multicell clusters may eventually develop and consolidate by late afternoon and early evening, while posing some threat for isolated strong to damaging winds as they move generally eastward. The greatest concentration of thunderstorms should exist across parts of southern VA into NC and upstate SC where greater instability is forecast this afternoon. But, confidence in a more organized wind threat remains too low to include greater severe wind probabilities. ...Western/Northern New York into Northern New England... As the primary upper trough and related surface cold front continue eastward across Ontario/Quebec today, daytime heating of a modestly moist low-level airmass will occur over parts of western/northern NY. Although poor mid-level lapse rates will likely hinder the development of any more than weak instability across this area (MLCAPE generally 500 J/kg of less), low/mid-level winds and related shear in the cloud-bearing layer is expected to strengthen through this afternoon with the approach of the upper trough. Some high-resolution/convection-allowing model guidance shows a low-topped line of thunderstorms developing this afternoon along or just ahead of the cold front. As low-level lapse rates steepen with daytime heating, some of this convection could produce isolated strong to severe wind gusts given the strengthening low/mid-level flow expected. The area impacted should remain fairly small across western/northern NY (generally downstream of Lake Ontario) due to more even more limited instability farther east across central NY into northern New England. ..Gleason/Leitman.. 09/01/2024 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0349 AM CDT Sun Sep 01 2024 Valid 041200Z - 091200Z ...DISCUSSION... Similar to 24 hours prior, global model solutions with respect to the large-scale pattern evolution over the U.S. begin substantial divergence relatively early in the medium-range period. This deviation in solutions becomes readily apparent by Friday (Day 6), and the differences preclude any meaningful assessment of severe risk beyond Thursday (Day 5). Through Day 5, severe-weather risk appears likely to remain minimal. Though a cold front is forecast to cross the northern Plains Wednesday (Day 4) and the Upper Mississippi Valley/Upper Great Lakes region Thursday (Day 5), low-level moisture -- and thus potential for destabilization -- is forecast to remain limited ahead of the front. As such, appreciable severe risk appears unlikely at this time. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0219 AM CDT Sun Sep 01 2024 Valid 031200Z - 041200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe weather risk should remain local/limited at best on Tuesday. ...Discussion... As a long-wave upper trough gradually vacates the northeastern U.S. Tuesday, an upstream short-wave trough is forecast to move slowly eastward across the northern Intermountain region. At the surface, a baroclinic zone should linger in the vicinity of the Gulf Coast through the period, while farther north, a cold front is forecast to emerge into the north-central states through the second half of the period, in tandem with the advance of the western U.S. upper system. As this upper system and associated front cross the northern Intermountain region Tuesday, weak destabilization is expected to support showers and isolated thunderstorms. Though CAPE will remain quite limited, a dry/mixed boundary layer may support locally strong wind gusts with a couple of the stronger storms. At this time however, risk appears too isolated to warrant MRGL risk inclusion. Elsewhere, showers and scattered thunderstorms are expected across portions of the south-central and southeastern states, near the remnant front. However, weak shear suggests storms will remain disorganized and generally sub-severe through the period. ..Goss.. 09/01/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0219 AM CDT Sun Sep 01 2024 Valid 031200Z - 041200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe weather risk should remain local/limited at best on Tuesday. ...Discussion... As a long-wave upper trough gradually vacates the northeastern U.S. Tuesday, an upstream short-wave trough is forecast to move slowly eastward across the northern Intermountain region. At the surface, a baroclinic zone should linger in the vicinity of the Gulf Coast through the period, while farther north, a cold front is forecast to emerge into the north-central states through the second half of the period, in tandem with the advance of the western U.S. upper system. As this upper system and associated front cross the northern Intermountain region Tuesday, weak destabilization is expected to support showers and isolated thunderstorms. Though CAPE will remain quite limited, a dry/mixed boundary layer may support locally strong wind gusts with a couple of the stronger storms. At this time however, risk appears too isolated to warrant MRGL risk inclusion. Elsewhere, showers and scattered thunderstorms are expected across portions of the south-central and southeastern states, near the remnant front. However, weak shear suggests storms will remain disorganized and generally sub-severe through the period. ..Goss.. 09/01/2024 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0210 AM CDT Sun Sep 01 2024 Valid 021200Z - 031200Z ...CRITICAL FIRE WEATHER AREA FOR NORTHEAST CALIFORNIA INTO SOUTHERN OREGON AND NORTHWEST NEVADA... ...Synopsis... Fire weather concerns are expected across parts of the Pacific Northwest/Great Basin as well as central to northern High Plains on Monday afternoon. ...Pacific Northwest/Great Basin... South/southwest mid-level flow along the West Coast will gradually increase over the next 24-48 hours with the approach of an upper wave currently off the northern CA coast. This will act to strengthen downslope flow off the northern Sierra Nevada with most deterministic and ensemble solutions indicating that winds between 15-25 mph will be common by peak heating Monday afternoon when RH values will fall into the teens. Elevated to critical fire weather conditions appear likely - especially across the CA/NV/OR tri-state region where the strongest winds are expected under the mid-level jet max. A warming trend over the past week (featuring multiple days of sub-20% RH minimums) has maintained ERC values well within the 80-90th percentiles across much of the Pacific Northwest and Great Basin. While thunderstorms are anticipated across parts of the region today (Sunday), little rain accumulation is expected, and holdover fires from dry-lightning starts may become more active Monday as winds increase. Dry thunderstorms will also be a concern across much of NV, central to eastern OR, and western ID. A plume of mid-level moisture (noted in 00z soundings and water-vapor imagery across NV into southern OR) is expected to continue spreading north through Monday afternoon. Lift associated with the wave should support another day of isolated thunderstorms. Dry boundary-layer conditions will promote limited rainfall and an attendant threat of dry lightning. While thunderstorms are possible across a broader swath of the region, the dry-lightning risk area was confined to areas with receptive fuels and low probability for wetting rainfall per ensemble guidance. ...High Plains... A surface high currently building across the northern Plains in the wake of a cold front is forecast to shift east towards the Midwest by Monday afternoon. Modest lee troughing juxtaposed with the nearby surface high will bolster southerly pressure gradient winds across northeast CO and western NE/SD. The displacement of richer low-level moisture to the south across the southern Plains will promote a dry return flow regime with afternoon RH values falling to near 20%. When combined with 15-20 mph winds and very dry fuels (ERCs are currently estimated to be above the 90th percentile), elevated to locally critical fire weather conditions appear probable. ..Moore.. 09/01/2024 ...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 0210 AM CDT Sun Sep 01 2024 Valid 021200Z - 031200Z ...CRITICAL FIRE WEATHER AREA FOR NORTHEAST CALIFORNIA INTO SOUTHERN OREGON AND NORTHWEST NEVADA... ...Synopsis... Fire weather concerns are expected across parts of the Pacific Northwest/Great Basin as well as central to northern High Plains on Monday afternoon. ...Pacific Northwest/Great Basin... South/southwest mid-level flow along the West Coast will gradually increase over the next 24-48 hours with the approach of an upper wave currently off the northern CA coast. This will act to strengthen downslope flow off the northern Sierra Nevada with most deterministic and ensemble solutions indicating that winds between 15-25 mph will be common by peak heating Monday afternoon when RH values will fall into the teens. Elevated to critical fire weather conditions appear likely - especially across the CA/NV/OR tri-state region where the strongest winds are expected under the mid-level jet max. A warming trend over the past week (featuring multiple days of sub-20% RH minimums) has maintained ERC values well within the 80-90th percentiles across much of the Pacific Northwest and Great Basin. While thunderstorms are anticipated across parts of the region today (Sunday), little rain accumulation is expected, and holdover fires from dry-lightning starts may become more active Monday as winds increase. Dry thunderstorms will also be a concern across much of NV, central to eastern OR, and western ID. A plume of mid-level moisture (noted in 00z soundings and water-vapor imagery across NV into southern OR) is expected to continue spreading north through Monday afternoon. Lift associated with the wave should support another day of isolated thunderstorms. Dry boundary-layer conditions will promote limited rainfall and an attendant threat of dry lightning. While thunderstorms are possible across a broader swath of the region, the dry-lightning risk area was confined to areas with receptive fuels and low probability for wetting rainfall per ensemble guidance. ...High Plains... A surface high currently building across the northern Plains in the wake of a cold front is forecast to shift east towards the Midwest by Monday afternoon. Modest lee troughing juxtaposed with the nearby surface high will bolster southerly pressure gradient winds across northeast CO and western NE/SD. The displacement of richer low-level moisture to the south across the southern Plains will promote a dry return flow regime with afternoon RH values falling to near 20%. When combined with 15-20 mph winds and very dry fuels (ERCs are currently estimated to be above the 90th percentile), elevated to locally critical fire weather conditions appear probable. ..Moore.. 09/01/2024 ...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 0151 AM CDT Sun Sep 01 2024 Valid 011200Z - 021200Z ...Synopsis... Dry thunderstorms will be the primary fire weather concern for today. Isolated dry thunderstorms were observed yesterday (Saturday) across portions of central NV on the fringe of a modest monsoonal moisture plume. This air mass is currently advecting northward into north-central NV and adjacent portions of OR/ID per latest water-vapor imagery. 00z soundings along the West Coast have already begun to sample this mid-level moisture as well as cool mid-level temperatures, which should support MUCAPE values between 100-250 J/kg this afternoon. Concurrently, an upper wave off the northern CA coast is forecast to move onshore over the next 24-48 hours. Lift ahead of this wave will overspread the moisture plume, resulting in isolated to widely scattered thunderstorms from central OR into eastern NV/far western UT. Dry boundary layer conditions (as well as fast storm motions across OR) will limit rainfall accumulation and favor dry lightning strikes. Given regional ERCs at or above the 80th percentile, dry lightning will pose a fire weather concern. Elsewhere across the West, dry conditions will prevail with another day of afternoon RH minimums in the teens expected. Strengthening southerly mid-level winds may support areas of dry/windy conditions in the immediate lee of the central and northern Sierra Nevada, but such conditions should remain too limited to warrant highlights. ..Moore.. 09/01/2024 ...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 0151 AM CDT Sun Sep 01 2024 Valid 011200Z - 021200Z ...Synopsis... Dry thunderstorms will be the primary fire weather concern for today. Isolated dry thunderstorms were observed yesterday (Saturday) across portions of central NV on the fringe of a modest monsoonal moisture plume. This air mass is currently advecting northward into north-central NV and adjacent portions of OR/ID per latest water-vapor imagery. 00z soundings along the West Coast have already begun to sample this mid-level moisture as well as cool mid-level temperatures, which should support MUCAPE values between 100-250 J/kg this afternoon. Concurrently, an upper wave off the northern CA coast is forecast to move onshore over the next 24-48 hours. Lift ahead of this wave will overspread the moisture plume, resulting in isolated to widely scattered thunderstorms from central OR into eastern NV/far western UT. Dry boundary layer conditions (as well as fast storm motions across OR) will limit rainfall accumulation and favor dry lightning strikes. Given regional ERCs at or above the 80th percentile, dry lightning will pose a fire weather concern. Elsewhere across the West, dry conditions will prevail with another day of afternoon RH minimums in the teens expected. Strengthening southerly mid-level winds may support areas of dry/windy conditions in the immediate lee of the central and northern Sierra Nevada, but such conditions should remain too limited to warrant highlights. ..Moore.. 09/01/2024 ...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 1238 AM CDT Sun Sep 01 2024 Valid 021200Z - 031200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorm potential remains quite limited across the U.S. on Monday. ...Discussion... A progressive long-wave upper trough will continue shifting across eastern NOAM on Monday, while large-scale ridging expands across the central and eastern U.S. in its wake. Farther west, an upper low near the southwestern Oregon/northwestern California coastal area will shift inland/eastward with time, devolving into an open wave with time. At the surface, a cold front will likely have cleared the New England and Mid-Atlantic Coasts by Monday morning, and should linger from the vicinity of the Southern Atlantic Coast westward across the Gulf Coast area and into Texas. Meanwhile, high pressure will prevail east of the Rockies, in the wake of the surface front. Showers and thunderstorms are expected across parts of the southern U.S. near and ahead of the stalling surface front. While a couple of stronger storms may occur during the day in the vicinity of the Carolinas, the overall risk for severe weather appears limited at best over the entire southern CONUS. In the West, meager mixed-layer CAPE atop a deep mixed layer can be expected across portions of the Oregon/Idaho/western Montana vicinity and into portions of the Great Basin. With enhanced flow aloft ahead of the aforementioned upper short-wave trough, a stronger storm or two may evolve, with some enhancement convective downdrafts provided by evaporative potential in the deep surface-based mixed layer. However, with only very isolated thunderstorms anticipated -- coverage of stronger convection appears insufficient to warrant inclusion of a 5% wind/MRGL risk area at this time. ..Goss.. 09/01/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1234 AM CDT Sun Sep 01 2024 Valid 011200Z - 021200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE SOUTHERN APPALACHIANS INTO THE MID-ATLANTIC AND PARTS OF NEW ENGLAND.... ...SUMMARY... Strong thunderstorms capable of producing damaging wind gusts are probable this afternoon across the southern Appalachians and Mid-Atlantic region, as well as across parts of southern New England. ...Synopsis... Latest water-vapor imagery depicts a deepening upper trough over the Great Lakes region with an attendant cold front noted in surface observations extending from the Great Lakes region into the central Plains. The northern portion of the cold front will continue to surge to the east in tandem with the upper trough; to the south, the front will begin to slow as it becomes increasingly frontolytic over the TN Valley and Ozark Plateau later today. Thunderstorm development will mainly be focused along this front as it impinges on a moist, weakly capped air mass currently in place from the Mid-MS River Valley into the Mid-Atlantic. More isolated thunderstorm chances are anticipated across the southern U.S. and over portions of the Southwest/Great Basin. ...Southern Appalachians/Mid-Atlantic... Initially isolated thunderstorm development is expected along the cold front as it approaches the TN Valley/southern Appalachians, but the weakly capped environment will favor additional development along convective outflows as well as orographically-initiated convection within the higher terrain of the southern Appalachians. As such, convective coverage should increase through mid-afternoon as storms propagate east into the Mid-Atlantic region. Mid-level flow on the southern periphery of the upper trough will be strong enough to support around 20 knots of effective bulk shear, which should support loosely organized convective clusters/multi-cells with an attendant risk for damaging wind gusts. Recent CAM guidance suggests central NC/VA may see the best potential for such clusters, and consequently could have a relatively higher potential for damaging winds. Further to the northeast into parts of southern New England, thunderstorm coverage is expected to be much more isolated and tied primarily to a deepening surface trough during the mid/late afternoon hours. While buoyancy will remain somewhat meager due to poor mid-level lapse rates, stronger mid-level flow in closer proximity to the upper trough may support an organized storm or two. ...Northwest New York... Consideration for a small Marginal risk area was made across far northwest NY. Forcing along the cold front will be much stronger along the international border with several CAM solutions hinting that shallow convection may accompany the front with an attendant damaging wind risk (as was observed Saturday evening across the upper Great Lakes region). However, warmer mid-level temperatures further over the Northeast should limit overall buoyancy values and casts uncertainty onto convective depth and intensity. Additionally, most CAM solutions hint that this potential will remain fairly confined to along the NY international border. Due to these concerns risk probabilities were withheld, but trends will continue to be monitored. ..Moore.. 09/01/2024 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0738 PM CDT Sat Aug 31 2024 Valid 010100Z - 011200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN GREAT LAKES... ...SUMMARY... Isolated severe wind gusts will be possible this evening across parts of the northern Great Lakes. ...Northern Great Lakes... Water vapor imagery shows a low-amplitude shortwave trough over southern Ontario extending into northern Minnesota. Ahead of the shortwave trough, a band of large-scale ascent appears to be moving through the vicinity of Lake Superior, where a broken line of thunderstorms is ongoing. Ahead of this line, surface dewpoints are in the mid 50s F, and the RAP has SBCAPE of 250 to 500 J/kg. RAP forecast soundings over upper Michigan have strong deep-layer shear exceeding 60 knots, and steep low to mid-level lapse rates. This may be enough for an isolated threat of severe wind gusts. This threat may persist for another hour or two. ..Broyles.. 09/01/2024 Read more

No Mesoscale Discussions are in effect as of Sat Aug 31 21:54:11 UTC 2024.