SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0253 PM CDT Sat Aug 31 2024 Valid 312000Z - 011200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE CENTRAL APPALACHIANS AND UPPER OHIO VALLEY... ...SUMMARY... Severe thunderstorms capable of producing mainly damaging winds remain possible this afternoon and evening from parts of the central Appalachians into the Ohio and Tennessee Valleys. Isolated severe wind gusts may also occur across parts of the northern Great Lakes. ...20Z Update... Some minor adjustments have been made to the Marginal and Slight Risks based on observational trends, but no major changes have been made to the outlook. Scattered damaging winds remain possible through late afternoon and perhaps into early evening from parts of WV into western/central PA and western MD/VA. See MCD 2040 regarding the short-term threat in this area. Also, see the previous discussion below for more information. ..Dean.. 08/31/2024 .PREV DISCUSSION... /ISSUED 1129 AM CDT Sat Aug 31 2024/ ...Mid-Atlantic into the Ohio and Tennessee Valleys... A mid/upper-level trough will move eastward across Ontario/Quebec and the Great Lakes today while undergoing some amplification. Ahead of this feature, a surface front will move eastward over parts of the Northeast/Mid-Atlantic, and southeastward over the OH Valley before eventually stalling. A warm front will lift north through the period across the mid-Atlantic and northeast states. Late morning visible satellite imagery shows substantial low cloud cover over much of the Northeast and Mid-Atlantic. This will reduce daytime heating and delay destabilization, especially east of the Blue Ridge Mountains. However, with a moist low-level air mass in place, even modest diurnal heating will result in sufficient destabilization to support some risk for strong/severe storms. The stronger mid-level flow associated with the upper trough is expected to remain generally displaced to the north/west of the surface warm sector. Even so, modestly increasing west-southwesterly winds with height through mid levels should support around 20-30 kt of deep-layer shear across parts of the central Appalachians and upper OH Valley vicinity. This shear will be sufficient for loosely organized multicell clusters to develop or intensify and subsequently spread east-southeastward through this afternoon. Isolated to scattered damaging winds should be the main threat with this convection, although some hail may also occur with the strongest cells. Storms should gradually weaken with eastward extent by this evening across the Mid-Atlantic while encountering a less unstable air mass. Weaker deep-layer shear with southward extent into the lower OH Valley and TN Valley will likely limit overall thunderstorm organization. However, occasional damaging winds may still occur with thunderstorms along/south of the front as low-level lapse rates steepen. ...Northern Great Lakes... Strong west-northwesterly mid-level flow will exist over the Upper Midwest and northern Great Lakes in association with a shortwave trough embedded within a broader cyclonic flow. While low-level moisture and related instability are both expected to remain limited, large-scale ascent and strong deep-layer shear may support the development of low-topped thunderstorms this afternoon. If these thunderstorms can be sustained, then isolated strong to severe winds may occur given the forecast strength of the low to mid-level flow in the presence of steepened low-level lapse rates. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0224 PM CDT Sat Aug 31 2024 Valid 011200Z - 021200Z No changes are needed to the D2 Fire Weather Outlook. See previous discussion below for more information. ..Thornton.. 08/31/2024 .PREV DISCUSSION... /ISSUED 0121 AM CDT Sat Aug 31 2024/ ...Synopsis... Dry thunderstorms will remain the primary fire weather concern on Sunday across parts of the Great Basin and Pacific Northwest. An upper-level low is evident in early-morning water-vapor imagery off the northern CA coast. This feature is expected to begin moving onshore Sunday afternoon into the overnight hours. Broadscale ascent ahead of this feature will overspread northern CA/southern OR and the northern Great Basin, resulting in slightly stronger surface winds compared to previous days (though generally at or below 15 mph) and isolated thunderstorm chances. Forecast soundings from across the region suggest buoyancy will be adequate for convection on the northern fringe of a modest monsoonal moisture plume, but mixed-layer LCLs between 3 to 3.5 km (indicative of a deep, dry boundary-layer) will promote little rain accumulation. As such, dry lightning appears likely and will pose a fire weather threat given regional ERC values between the 80th to 90th percentiles. Stronger forcing for ascent may result in higher thunderstorm coverage across the Great Basin compared to previous days, and recent CAM solutions hint that central to northeast NV may see the greatest potential for dry lightning strikes. ...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 0159 PM CDT Sat Aug 31 2024 Valid 021200Z - 031200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorm potential remains quite limited across the U.S. on Monday. ...Synopsis... Upper ridging will build over much of the central CONUS as a mid-level trough ejects into the Atlantic, and a second mid-level trough traverses the Pacific Northwest on Day 3/Monday. WAA, driven by surface lee troughing across the Plains, as well as the heating of a moist boundary layer across the southeast quadrant of the U.S., will foster isolated to scattered thunderstorm development from eastern NM to the central/southern Atlantic Seaboard. At least isolated thunderstorm development is also likely across much of the Interior West as the West Coast mid-level trough approaches. ...Pacific Northwest... Isolated to scattered thunderstorms may form near a weak surface low to the lee of the Cascades late Monday afternoon into early evening. These storms should be high based as they develop atop a boundary layer that may mix up to 600-500 mb. Steep low and mid-level lapse rates exceeding 9 C/km amid stronger unidirectional southwesterly flow above 500 mb (hence elongated hodographs) may encourage storm organization to some degree, with gusty winds possible. A Category 1/Marginal Risk for severe gusts may be needed over the Harney Basin in eastern OR in future outlooks if greater storm coverage by afternoon peak heating becomes apparent. ..Squitieri.. 08/31/2024 Read more

WW 0666 Status Updates
STATUS FOR WATCH 0666 HAS NOT BEEN ISSUED YET Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1217 PM CDT Sat Aug 31 2024 Valid 011200Z - 021200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF SOUTHERN NEW ENGLAND INTO THE SOUTHERN APPALACHIANS... ...SUMMARY... Strong thunderstorms capable of producing damaging gusts still appear possible from southern New England into the southern Appalachians on Sunday. ...Synopsis... A mid-level trough will progress across the northeastern U.S. as an upper ridge builds across the Plains and a second mid-level trough impinges on the West Coast tomorrow (Sunday). A surface cold front accompanying the eastern upper trough will sweep across much of the central, northern U.S. east of the Rockies through the period, serving as a lifting mechanism for at least scattered thunderstorms from New England down to the Southern Plains. The best chance for isolated strong to perhaps severe thunderstorms will be from southern New England into the central Appalachians, where modest mid-level flow will overspread a mixing boundary layer by afternoon. ...Southern New England into the central Appalachians... At least scattered clusters of thunderstorms should develop ahead of the cold front from southern New England into the central Appalachians by late morning or early afternoon, when convective temperatures in the mid 80s F are reached. With surface dewpoints in the mid 60s to just over 70 F, MLCAPE will exceed 1000 J/kg in most spots, with parts of the Carolinas seeing up to 2000 J/kg MLCAPE, driven primarily by low-level lapse rates. Stronger mid-level flow and accompanying vertical wind shear is expected to lag the surface cold front, with effective bulk shear values likely remaining under 30 kts over most locales. As such, pulse-cellular and perhaps briefly multicellular convection will be the dominant storm modes. Given a heated, mixed boundary layer, storms from southern New England into the central Appalachians may produce a few strong, damaging wind gusts. ..Squitieri.. 08/31/2024 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1217 PM CDT Sat Aug 31 2024 Valid 011200Z - 021200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF SOUTHERN NEW ENGLAND INTO THE SOUTHERN APPALACHIANS... ...SUMMARY... Strong thunderstorms capable of producing damaging gusts still appear possible from southern New England into the southern Appalachians on Sunday. ...Synopsis... A mid-level trough will progress across the northeastern U.S. as an upper ridge builds across the Plains and a second mid-level trough impinges on the West Coast tomorrow (Sunday). A surface cold front accompanying the eastern upper trough will sweep across much of the central, northern U.S. east of the Rockies through the period, serving as a lifting mechanism for at least scattered thunderstorms from New England down to the Southern Plains. The best chance for isolated strong to perhaps severe thunderstorms will be from southern New England into the central Appalachians, where modest mid-level flow will overspread a mixing boundary layer by afternoon. ...Southern New England into the central Appalachians... At least scattered clusters of thunderstorms should develop ahead of the cold front from southern New England into the central Appalachians by late morning or early afternoon, when convective temperatures in the mid 80s F are reached. With surface dewpoints in the mid 60s to just over 70 F, MLCAPE will exceed 1000 J/kg in most spots, with parts of the Carolinas seeing up to 2000 J/kg MLCAPE, driven primarily by low-level lapse rates. Stronger mid-level flow and accompanying vertical wind shear is expected to lag the surface cold front, with effective bulk shear values likely remaining under 30 kts over most locales. As such, pulse-cellular and perhaps briefly multicellular convection will be the dominant storm modes. Given a heated, mixed boundary layer, storms from southern New England into the central Appalachians may produce a few strong, damaging wind gusts. ..Squitieri.. 08/31/2024 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1140 AM CDT Sat Aug 31 2024 Valid 311700Z - 011200Z No changes are needed to the D1 Fire Weather Outlook. See previous discussion below for more information. ..Thornton.. 08/31/2024 .PREV DISCUSSION... /ISSUED 1242 AM CDT Sat Aug 31 2024/ ...Synopsis... Dry thunderstorms will be the primary fire weather concern for today across portions of southern/eastern Nevada into far southwest Utah. A modest monsoonal moisture plume has been slowly spreading northwestward from southern/central AZ into southern NV over the past 12 hours per GOES water-vapor and PWAT imagery. Increasing mid-level moisture has also been noted in recent VEF soundings with PWAT values increasing to 0.85 inches as recently as 00 UTC Saturday. This moisture, combined with cool mid-level temperatures, will support isolated thunderstorms by late afternoon as ascent associated with a weak mid-level perturbation overspreads the southern Great Basin. Slow storm motions around 10 knots should promote very narrow swaths of rainfall, but very dry boundary layer conditions (similar in nature to the 00 UTC VEF sounding) will likely be in place by peak heating and should promote limited rain accumulation away from the primary downdraft cores. While thunderstorm coverage is expected to be fairly isolated, dry lightning strikes are likely with any storm that can develop and will pose a fire weather concern considering ERCs are at or above the 80th percentile. Elsewhere, very dry conditions will persist across the remainder of the Great Basin with afternoon RH values in the single digits to teens. Surface gradient winds are forecast to generally remain below 15 mph for most locations, which limits confidence in additional fire weather concerns. The general consensus among recent high-res guidance is that the strongest winds will likely be associated with thunderstorm outflows across southern NV/southwest UT and into central AZ. ...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 1129 AM CDT Sat Aug 31 2024 Valid 311630Z - 011200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE CENTRAL APPALACHIANS AND UPPER OHIO VALLEY... ...SUMMARY... Severe thunderstorms capable of producing mainly damaging winds will be possible today from parts of the central Appalachians into the Ohio and Tennessee Valleys. Isolated severe wind gusts may also occur across parts of the northern Great Lakes. ...Mid-Atlantic into the Ohio and Tennessee Valleys... A mid/upper-level trough will move eastward across Ontario/Quebec and the Great Lakes today while undergoing some amplification. Ahead of this feature, a surface front will move eastward over parts of the Northeast/Mid-Atlantic, and southeastward over the OH Valley before eventually stalling. A warm front will lift north through the period across the mid-Atlantic and northeast states. Late morning visible satellite imagery shows substantial low cloud cover over much of the Northeast and Mid-Atlantic. This will reduce daytime heating and delay destabilization, especially east of the Blue Ridge Mountains. However, with a moist low-level air mass in place, even modest diurnal heating will result in sufficient destabilization to support some risk for strong/severe storms. The stronger mid-level flow associated with the upper trough is expected to remain generally displaced to the north/west of the surface warm sector. Even so, modestly increasing west-southwesterly winds with height through mid levels should support around 20-30 kt of deep-layer shear across parts of the central Appalachians and upper OH Valley vicinity. This shear will be sufficient for loosely organized multicell clusters to develop or intensify and subsequently spread east-southeastward through this afternoon. Isolated to scattered damaging winds should be the main threat with this convection, although some hail may also occur with the strongest cells. Storms should gradually weaken with eastward extent by this evening across the Mid-Atlantic while encountering a less unstable air mass. Weaker deep-layer shear with southward extent into the lower OH Valley and TN Valley will likely limit overall thunderstorm organization. However, occasional damaging winds may still occur with thunderstorms along/south of the front as low-level lapse rates steepen. ...Northern Great Lakes... Strong west-northwesterly mid-level flow will exist over the Upper Midwest and northern Great Lakes in association with a shortwave trough embedded within a broader cyclonic flow. While low-level moisture and related instability are both expected to remain limited, large-scale ascent and strong deep-layer shear may support the development of low-topped thunderstorms this afternoon. If these thunderstorms can be sustained, then isolated strong to severe winds may occur given the forecast strength of the low to mid-level flow in the presence of steepened low-level lapse rates. ..Bunting/Jewell.. 08/31/2024 Read more

No watches are valid as of Sat Aug 31 13:37:01 UTC 2024.

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0740 AM CDT Sat Aug 31 2024 Valid 311300Z - 011200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL APPALACHIANS AND UPPER OHIO VALLEY... ...SUMMARY... Severe thunderstorms capable of producing mainly damaging winds will be possible today from parts of the central Appalachians into the Ohio and Tennessee Valleys. Isolated severe wind gusts may also occur across parts of the northern Great Lakes. ...Mid-Atlantic into the Ohio and Tennessee Valleys... A mid/upper-level trough will make slow eastward progress today across Ontario/Quebec and the Great Lakes while amplifying further. Ahead of this feature, a surface front should continue to lose definition and weaken through the day as it moves eastward over parts of the Northeast/Mid-Atlantic, and southeastward over the OH Valley before eventually stalling. Recent visible satellite imagery shows cloud cover remains prevalent over much of the Northeast and Mid-Atlantic. This will hinder daytime heating and delay destabilization, especially east of the Blue Ridge Mountains. Still, area 12Z soundings and recent surface observations indicate a moist low-level airmass remains in place ahead of the weak cold front. Generally less cloud cover with westward and southward extent into the upper OH Valley and TN Valley should allow for greater instability to develop this afternoon across these regions. The stronger mid-level flow associated the upper trough is expected to remain generally displaced to the north/west of the surface warm sector. Even so, modestly increasing west-southwesterly winds with height through mid levels should support around 20-30 kt of deep-layer shear across parts of the central Appalachians and upper OH Valley vicinity. This shear will be sufficient for loosely organized multicell clusters to develop and subsequently spread east-southeastward through this afternoon. Isolated to scattered damaging winds should be the main threat with this convection, although some hail may also occur with the strongest cores. Activity should weaken with eastward extent late this afternoon and evening across the Mid-Atlantic as it encounters a less unstable airmass. Weaker deep-layer shear with southward extent into the lower OH Valley and TN Valley will likely limit overall thunderstorm organization. But, occasional damaging winds may still occur with thunderstorms along/south of the front as low-level lapse rates steepen with diurnal heating. ...Northern Great Lakes... Strong west-northwesterly mid-level flow will be present today over the Upper Midwest and northern Great Lakes, in association with a shortwave trough embedded within a larger upper trough moving east-southeastward across these regions. While low-level moisture and related instability are both expected to remain limited, large-scale ascent and strong deep-layer shear may support the development low-topped convection this afternoon. If these thunderstorms can form and be sustained, then isolated strong to severe winds may occur given the forecast strength of the low to mid-level flow amid steepened low-level lapse rates. ..Gleason/Leitman.. 08/31/2024 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0333 AM CDT Sat Aug 31 2024 Valid 031200Z - 081200Z ...DISCUSSION... Global models are in reasonable agreement with handling of large-scale features through about Day 5/Wednesday, after which divergent tendencies become apparent -- particularly with the handling of a weak short-wave feature moving across the northwestern U.S. early in the period. Models depict this feature partially phasing with a more substantial trough moving across western Canada within the faster belt of westerlies to the north Day 4/Tuesday, and then emerging into the north-central U.S. Day 5. Afterward, evolution of this trough begins to differ substantially amongst the models. The GFS depicts this trough evolving into cut-off low over the Upper Mississippi Valley/Upper Great Lakes region Day 6/Thursday, which then lingers in place through Day 8 and beyond. Meanwhile, the ECMWF remains slowly progressive with the trough into eastern North America through the period. Given these substantial differences, convective/severe potential cannot be reasonably assessed beyond Day 5. In the Day 4-5 time frame, a cold-frontal advance out of the western U.S. into the northern Plains -- and eventually the Great Lakes region -- is expected, in tandem with the progression of the aforementioned upper trough. However, with a surface high still firmly in place from the eastern U.S. westward into the central/southern Plains, Gulf moisture will remain suppressed, and thus the likelihood for only meager destabilization across the pre-frontal warm sector. Therefore, severe risk is expected to remain limited, thus not requiring a 15% areal outline associated with this system through Day 5. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0215 AM CDT Sat Aug 31 2024 Valid 021200Z - 031200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe-weather potential is forecast to remain quite limited, and isolated at best, across the U.S. on Monday. ...Discussion... As a long-wave upper trough continues to shift across eastern Canada and the eastern U.S. Monday, a cold front -- already off the New England and Mid-Atlantic Coasts early in the day -- is forecast to linger from the southeastern U.S. Atlantic Coast westward across the Gulf Coast region. This front will represent the southern/eastern bounds of a cool/dry continental airmass from Canada -- represented by large area of surface high pressure to encompass much of the central and eastern CONUS. Showers and thunderstorms are forecast across the Southeast, Gulf Coast States, and Southern Plains area, but with stronger flow aloft well to the north, severe-weather potential should remain minimal. In the West, an upper trough will shift east-northeastward across the northwestern states, impinging on a persistent upper ridge. Showers and scattered to isolated thunderstorms are expected across portions of the West ahead of this system, but with little in the way of severe potential evident due to meager instability forecast across the area. ..Goss.. 08/31/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0215 AM CDT Sat Aug 31 2024 Valid 021200Z - 031200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe-weather potential is forecast to remain quite limited, and isolated at best, across the U.S. on Monday. ...Discussion... As a long-wave upper trough continues to shift across eastern Canada and the eastern U.S. Monday, a cold front -- already off the New England and Mid-Atlantic Coasts early in the day -- is forecast to linger from the southeastern U.S. Atlantic Coast westward across the Gulf Coast region. This front will represent the southern/eastern bounds of a cool/dry continental airmass from Canada -- represented by large area of surface high pressure to encompass much of the central and eastern CONUS. Showers and thunderstorms are forecast across the Southeast, Gulf Coast States, and Southern Plains area, but with stronger flow aloft well to the north, severe-weather potential should remain minimal. In the West, an upper trough will shift east-northeastward across the northwestern states, impinging on a persistent upper ridge. Showers and scattered to isolated thunderstorms are expected across portions of the West ahead of this system, but with little in the way of severe potential evident due to meager instability forecast across the area. ..Goss.. 08/31/2024 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0121 AM CDT Sat Aug 31 2024 Valid 011200Z - 021200Z ...Synopsis... Dry thunderstorms will remain the primary fire weather concern on Sunday across parts of the Great Basin and Pacific Northwest. An upper-level low is evident in early-morning water-vapor imagery off the northern CA coast. This feature is expected to begin moving onshore Sunday afternoon into the overnight hours. Broadscale ascent ahead of this feature will overspread northern CA/southern OR and the northern Great Basin, resulting in slightly stronger surface winds compared to previous days (though generally at or below 15 mph) and isolated thunderstorm chances. Forecast soundings from across the region suggest buoyancy will be adequate for convection on the northern fringe of a modest monsoonal moisture plume, but mixed-layer LCLs between 3 to 3.5 km (indicative of a deep, dry boundary-layer) will promote little rain accumulation. As such, dry lightning appears likely and will pose a fire weather threat given regional ERC values between the 80th to 90th percentiles. Stronger forcing for ascent may result in higher thunderstorm coverage across the Great Basin compared to previous days, and recent CAM solutions hint that central to northeast NV may see the greatest potential for dry lightning strikes. ..Moore.. 08/31/2024 ...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 1258 AM CDT Sat Aug 31 2024 Valid 011200Z - 021200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHEAST AND MID-ATLANTIC REGIONS...AND SOUTHWESTWARD TO THE SOUTHERN APPALACHIANS... ...SUMMARY... Strong/isolated severe storms capable of producing gusty/damaging winds will be possible from the Mid-Atlantic region to the central and southern Appalachians, and possibly parts of New England on Sunday. ...Synopsis... An upper trough advancing initially across Ontario and the Upper Great Lakes region will progress steadily eastward eastern Canada and the northeastern U.S. through the period. Upstream, ridging will prevail over the West, though an eastern Pacific upper low will approach the Oregon/northern California Coasts late in the period. At the surface, an initial/weakening cold front lingering across New England and the Atlantic Coast states during the first half of the period will be gradually overtaken by a second/stronger front shifting across the Great Lakes/Midwest early in the period. By Monday morning, the front will likely have reached/moved off the New England and Mid-Atlantic Coasts, trailing southwestward across the southeast and Gulf Coast regions. ...Parts of New England to the Mid-Atlantic region, and into the central/southern Appalachians... The remnant surface cold front -- gradually being overtaken by the stronger/reinforcing front -- will serve as a focus for convective activity Sunday. As the upper trough steadily advances, increasingly strong flow aloft will overspread the Northeast/New England. With that said however, substantial questions persist across the Northeast -- particularly into New England -- given likelihood for ongoing convection/cloud cover in the vicinity of the initial/weakening front. Thus, despite increasingly favorable deep-layer shear that would otherwise support well-organized convection, afternoon destabilization potential may be sufficiently hampered so as to substantially limit severe potential. Farther to the south -- across portions of the Mid-Atlantic region and west-southwestward across the Appalachians, somewhat greater destabilization potential is expected, but with weaker flow aloft as compared to areas farther north. Still, shear may prove sufficient when combined with the anticipated/modest afternoon destabilization to support stronger storms locally, and associated risk for gusty outflow winds and local/minor wind damage during the afternoon and early evening hours. ..Goss.. 08/31/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0101 AM CDT Sat Aug 31 2024 Valid 311200Z - 011200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL APPALACHIANS AND UPPER OHIO VALLEY... ...SUMMARY... Severe thunderstorms, associated with severe wind gusts and hail, will be possible today from parts of the central Appalachians into the Ohio and Tennessee Valleys. Isolated severe wind gusts will be possible in parts of the northern Great Lakes. ...Central Appalachians/Ohio and Tennessee Valleys... An upper-level trough will move through the Great Lakes region, with the southern end of the trough located in the mid Mississippi Valley. An associated cold front will advance southeastward through the mid Mississippi Valley and southern Great Lakes. Ahead of the front, a moist airmass will be in place with surface dewpoints in the upper 60s and lower 70s F. Moderate instability is expected to develop by midday ahead of much of the front. Further to the east, a pre-frontal trough will be located from western New York and western Pennsylvania southwestward into eastern Kentucky. Scattered thunderstorms will form from near the front eastward to near the pre-frontal trough. By early to mid afternoon, RAP forecast soundings have MLCAPE peaking in the 1500 to 2000 J/kg range from western New York southwestward into West Virginia. Along this portion of the instability corridor, 0-6 km shear is forecast to be in the 20 to 30 knot range. This, along with 0-3 km lapse rates near 7.5 C/km will support severe wind gusts with the more organized bowing line segments. Hail will also be possible. Further to the southwest into parts of the lower Ohio and Tennessee Valleys, the models suggest that deep-layer shear will generally be below 20 knots. Although steep low-level lapse rates could be enough for a marginal wind-damage threat, the weakness in shear should keep any threat isolated. ...Northern Great Lakes... A cyclonic mid-level flow pattern will be in place today across much of southern Canada and over the Great Lakes. Within this flow, a shortwave trough and an associated cold front is forecast to move southeastward toward the northern Great Lakes. Ahead of the front, surface dewpoints in the 50s F will contribute to weak destabilization by afternoon. Thunderstorms are expected to form along and ahead of the front as instability peaks during the mid to late afternoon. In spite of the weak instability, large-scale ascent and strong deep-layer shear, associated with the shortwave trough, could be enough for isolated severe wind gusts. ..Broyles/Moore.. 08/31/2024 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1242 AM CDT Sat Aug 31 2024 Valid 311200Z - 011200Z ...Synopsis... Dry thunderstorms will be the primary fire weather concern for today across portions of southern/eastern Nevada into far southwest Utah. A modest monsoonal moisture plume has been slowly spreading northwestward from southern/central AZ into southern NV over the past 12 hours per GOES water-vapor and PWAT imagery. Increasing mid-level moisture has also been noted in recent VEF soundings with PWAT values increasing to 0.85 inches as recently as 00 UTC Saturday. This moisture, combined with cool mid-level temperatures, will support isolated thunderstorms by late afternoon as ascent associated with a weak mid-level perturbation overspreads the southern Great Basin. Slow storm motions around 10 knots should promote very narrow swaths of rainfall, but very dry boundary layer conditions (similar in nature to the 00 UTC VEF sounding) will likely be in place by peak heating and should promote limited rain accumulation away from the primary downdraft cores. While thunderstorm coverage is expected to be fairly isolated, dry lightning strikes are likely with any storm that can develop and will pose a fire weather concern considering ERCs are at or above the 80th percentile. Elsewhere, very dry conditions will persist across the remainder of the Great Basin with afternoon RH values in the single digits to teens. Surface gradient winds are forecast to generally remain below 15 mph for most locations, which limits confidence in additional fire weather concerns. The general consensus among recent high-res guidance is that the strongest winds will likely be associated with thunderstorm outflows across southern NV/southwest UT and into central AZ. ..Moore.. 08/31/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0750 PM CDT Fri Aug 30 2024 Valid 310100Z - 311200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE SOUTHERN GREAT LAKES SOUTHWESTWARD INTO THE MID MISSISSIPPI VALLEY... ...SUMMARY... Isolated severe storms, with marginally severe wind gusts and hail will be possible this evening from southeast Lower Michigan southwestward into the mid Mississippi Valley. ...Southern Great Lakes/Mid Mississippi Valley... The latest mosaic water vapor imagery shows an upper-level trough over the western Great Lakes extending southward into the mid Mississippi Valley. An associated cold front is analyzed from southeast Lower Michigan southwestward to near St. Louis, Missouri. Scattered thunderstorms are ongoing along and near the front. Surface dewpoints near and ahead of the front are in the upper 60s and lower 70s F, and the RAP has MLCAPE in the 1200 to 2500 J/k/g range. In addition, regional WSR-88D VWPs near the front have 0-6 km shear ranging from near 20 knot at St. Louis to around 30 knots at Detroit. This environment, combined with steep low-level lapse rates near 7 C/km, should be enough for a marginally severe wind gusts for a couple more hours this evening. Hail could also occur within the cores of the stronger multicells. ..Broyles.. 08/31/2024 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0750 PM CDT Fri Aug 30 2024 Valid 310100Z - 311200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE SOUTHERN GREAT LAKES SOUTHWESTWARD INTO THE MID MISSISSIPPI VALLEY... ...SUMMARY... Isolated severe storms, with marginally severe wind gusts and hail will be possible this evening from southeast Lower Michigan southwestward into the mid Mississippi Valley. ...Southern Great Lakes/Mid Mississippi Valley... The latest mosaic water vapor imagery shows an upper-level trough over the western Great Lakes extending southward into the mid Mississippi Valley. An associated cold front is analyzed from southeast Lower Michigan southwestward to near St. Louis, Missouri. Scattered thunderstorms are ongoing along and near the front. Surface dewpoints near and ahead of the front are in the upper 60s and lower 70s F, and the RAP has MLCAPE in the 1200 to 2500 J/k/g range. In addition, regional WSR-88D VWPs near the front have 0-6 km shear ranging from near 20 knot at St. Louis to around 30 knots at Detroit. This environment, combined with steep low-level lapse rates near 7 C/km, should be enough for a marginally severe wind gusts for a couple more hours this evening. Hail could also occur within the cores of the stronger multicells. ..Broyles.. 08/31/2024 Read more

MD 2038 CONCERNING SEVERE THUNDERSTORM WATCH 665... FOR SOUTHEAST LOWER MICHIGAN
Mesoscale Discussion 2038 NWS Storm Prediction Center Norman OK 0551 PM CDT Fri Aug 30 2024 Areas affected...Southeast lower Michigan Concerning...Severe Thunderstorm Watch 665... Valid 302251Z - 310045Z The severe weather threat for Severe Thunderstorm Watch 665 continues. SUMMARY...The threat for severe wind and hail should persist for the next 2 to 2.5 hours across southeastern Lower Michigan. The greatest severe wind risk may reside along and north of I-65 during this period. DISCUSSION...Convection continues to develop along a cold front across lower MI. Overall intensification has been somewhat gradual, likely owing to somewhat meager large-scale ascent over the region. However, KDTX VWP observations have shown a slight strengthening of mid-level flow over the past 30-60 minutes with 0-6 km bulk shear values increasing closer to 30 knots at times. Additionally, GOES 1-minute imagery shows several strong updraft pulses along the line, indicating that the potential for organized convection persists. Confidence in the coverage of robust convection remains limited given the aforementioned weak forcing for ascent and recent convective trends, but a few severe storms with an attendant hail/severe wind risk remain possible as the cold front continues to push east (especially along and north of I-65 where convection is comparatively more intense based on IR and lightning trends). Latest timing guidance suggests that this activity should exit southeastern lower MI within the next 2-3 hours. ..Moore.. 08/30/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...DTX...IWX...GRR... LAT...LON 41898480 42888362 43798304 44058279 44018259 43488235 42998239 42628252 42338274 42068302 41888326 41788357 41738396 41798454 41808474 41898480 Read more