WW 646 SEVERE TSTM CO UT WY 251920Z - 260200Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 646 NWS Storm Prediction Center Norman OK 120 PM MDT Sun Aug 25 2024 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Western Colorado Eastern Utah Southern Wyoming * Effective this Sunday afternoon and evening from 120 PM until 800 PM MDT. * Primary threats include... Scattered large hail and isolated very large hail events to 2 inches in diameter possible Scattered damaging wind gusts to 70 mph possible SUMMARY...Scattered storms, including some supercells, will continue to develop and increase across the region, with large hail and severe-caliber wind gusts possible through early/mid-evening. The severe thunderstorm watch area is approximately along and 80 statute miles east and west of a line from 50 miles north northeast of Rock Springs WY to 45 miles south southwest of Blanding UT. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU6). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. Severe thunderstorms can and occasionally do produce tornadoes. && AVIATION...A few severe thunderstorms with hail surface and aloft to 2 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 450. Mean storm motion vector 23030. ...Guyer Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0437 PM CDT Sun Aug 25 2024 Valid 271200Z - 021200Z A robust midlevel trough/low will advance eastward across the Northwest on Day 3/Tuesday. A related belt of strong deep-layer west-southwesterly flow will cross the Cascades, promoting strong downslope winds into the Columbia Basin. These winds, coupled with downslope-induced warming/drying, will favor elevated to locally critical fire-weather conditions during the afternoon and evening. 40-percent Critical probabilities have been maintained with this outlook, though if fuels trend drier than currently anticipated, a Critical area could eventually be needed. On Day 4/Wednesday, the midlevel low will continue eastward, with associated strong post-frontal surface winds overspreading the northern Rockies and adjacent High Plains. While this will favor some increase in fire-weather potential, preceding rainfall and a potentially limited overlap with low RH casts uncertainty on the overall risk -- precluding Critical probabilities at this time. Breezy post-frontal winds will continue across the northern High Plains into Day 5/Thursday, with similar uncertainties to the day prior. Thereafter, an expansive large-scale ridge will build over the West, resulting in a warming/drying trend and a fairly weak surface pressure gradient until around Day 8/Sunday. ..Weinman.. 08/25/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0437 PM CDT Sun Aug 25 2024 Valid 271200Z - 021200Z A robust midlevel trough/low will advance eastward across the Northwest on Day 3/Tuesday. A related belt of strong deep-layer west-southwesterly flow will cross the Cascades, promoting strong downslope winds into the Columbia Basin. These winds, coupled with downslope-induced warming/drying, will favor elevated to locally critical fire-weather conditions during the afternoon and evening. 40-percent Critical probabilities have been maintained with this outlook, though if fuels trend drier than currently anticipated, a Critical area could eventually be needed. On Day 4/Wednesday, the midlevel low will continue eastward, with associated strong post-frontal surface winds overspreading the northern Rockies and adjacent High Plains. While this will favor some increase in fire-weather potential, preceding rainfall and a potentially limited overlap with low RH casts uncertainty on the overall risk -- precluding Critical probabilities at this time. Breezy post-frontal winds will continue across the northern High Plains into Day 5/Thursday, with similar uncertainties to the day prior. Thereafter, an expansive large-scale ridge will build over the West, resulting in a warming/drying trend and a fairly weak surface pressure gradient until around Day 8/Sunday. ..Weinman.. 08/25/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0256 PM CDT Sun Aug 25 2024 Valid 252000Z - 261200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHERN PLAINS/UPPER MIDWEST AND CENTRAL ROCKIES... ...SUMMARY... Severe wind gusts and hail are most probable today over parts of the Four Corners to southwestern Wyoming, and this evening over portions of the eastern Dakotas and western Minnesota. ...Utah and Wyoming... Portions of the Marginal risk are were expanded westward across north-central UT and far western WY into extreme southeast ID to account for recent convective trends. While this region is on the fringe of the monsoonal moisture plume, cooler mid-level temperatures are compensatory and supporting convection with similar IR/cloud-top temperature presentations as convection further to the southeast. Thunderstorms should remain more isolated, but sporadic severe hail and/or wind gusts appear possible. ...Southeast MI/northeast OH... The Marginal risk area across southeast lower MI into OH has been removed. Large scale forcing for ascent should remain fairly weak as the mid-level impulse associated with early-morning convection exits the region. Low-level ascent along a surface confluence axis may support a storm or two across southeast lower MI, but confidence in the overall severe threat appears sufficiently low to warrant removal of risk probabilities. ..Moore.. 08/25/2024 .PREV DISCUSSION... /ISSUED 1138 AM CDT Sun Aug 25 2024/ ...Northern Plains/Upper Midwest... Scattered thunderstorms are expected to develop along/ahead of the cold front and near a South Dakota surface wave, primarily this evening after 00Z/7pm CDT, although enough moistening and heating may occur for isolated late-afternoon development. Some supercells and bowing lines/clusters are expected, with large hail and severe wind gusts possible. Intensifying thunderstorm development should occur as the front encounters what is left of a diurnally well-heated and still-unstable boundary-layer airmass. Forecast soundings indicate the moist layer should deepen through the day beneath strong capping and steep mid-level lapse rates, MLCAPE in the 3000-4000 J/kg range possible. This will occur with gradually strengthening west-southwesterly winds aloft with 30-45 kt effective shear. Additional severe storms may occur late this afternoon into evening within an evolving post-frontal environment across northeast Wyoming into northwest South Dakota/southwest North Dakota, with moderate buoyancy and very long/straight hodographs potentially supporting storms capable of hail and possibly severe-caliber wind gusts. ...Central/southern Rockies... Scattered thunderstorms are ongoing early today across eastern Utah and western Colorado in advance of an upper-level trough centered over Nevada. A greater coverage and intensity of storms should occur into the afternoon as the boundary layer further warms/destabilizes. Relatively strong mid/high-level southwesterlies will support ample deep-layer/effective shear, with supercells and bowing clusters possible in a corridor spanning portions of the Four Corners area to northern Colorado/southwest Wyoming. Elongated and semi-straight hodographs will support large-hail potential aside from a broader regional risk for severe-caliber wind gusts. ...South-central High Plains... Scattered slow-moving thunderstorms are expected this afternoon particularly across eastern Colorado and northeast New Mexico. Hot/well-mixed boundary layers within the pre-convective environment will support the possibility of strong to locally severe-caliber wind gusts through late afternoon until around sunset. Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0207 PM CDT Sun Aug 25 2024 Valid 271200Z - 281200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE GREAT LAKES... ...SUMMARY... Severe-weather potential is evident across the Great Lakes region on Tuesday. ...Great Lakes Vicinity... Only modest outlook changes have been made with the Day 3 update as overall pattern remains similar to prior thinking. An upper trough over the northern Plains will migrate east across the Great Lakes and southern Ontario. This will suppress the upper ridge over the Midwest while bringing a belt of enhanced westerly flow across the region. Convection will likely be ongoing across portions of WI/MI, though exact location of morning thunderstorms is a bit uncertain and will be driven by evolution of a possible MCS in the Day 2/Mon period. Nevertheless, a very moist boundary-layer is forecast, with surface dewpoints in the upper 60s to mid 70s F ahead of southeastward-advancing cold front. Strong to extreme instability is forecast, though some midlevel inhibition may persist across portions of the region. Nevertheless, this overall pattern continues to point toward severe thunderstorm potential, mainly in the form of severe/damaging gusts and large hail across the Great Lakes vicinity Tuesday into Tuesday evening. ...NE/IA vicinity... The western extent of the surface front will sag southward across the area. Strong differential heating along the boundary is forecast. A very moist boundary-layer will support strong instability, but warm midlevels leading to capping may preclude thunderstorm development. The Marginal risk (level 1 of 2) has been extended southwest along the forecast frontal zone for a conditional risk of severe storms during the afternoon into early evening as strong gusts and hail could occur if storms develop. ..Leitman.. 08/25/2024 Read more

No watches are valid as of Sun Aug 25 18:31:01 UTC 2024.

No Mesoscale Discussions are in effect as of Sun Aug 25 18:31:01 UTC 2024.

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1225 PM CDT Sun Aug 25 2024 Valid 261200Z - 271200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF FAR NORTHERN NEBRASKA...EXTREME NORTHWEST IOWA...EASTERN SOUTH DAKOTA...SOUTHERN/CENTRAL MINNESOTA...AND FAR WESTERN WISCONSIN... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF SOUTHERN NEW ENGLAND... ...SUMMARY... Severe storms are expected to evolve within a zone extending from the northern/central High Plains eastward to Wisconsin Monday afternoon into the nighttime hours. Large to very large hail, and swaths of severe, potentially damaging, gusts are expected, especially across South Dakota into Minnesota. A few severe storms producing strong gusts and hail are also expected across southern New England. ...South Dakota into MN/WI and vicinity... An upper shortwave trough will develop east/northeast from the Intermountain West to the Dakotas on Monday. This will flatten the upper ridge over the Upper Midwest and a belt of enhanced southwesterly mid/upper flow (50-60 kt at 500 mb) will overspread the region. By late afternoon, 700 mb flow is expected to increase to around 40-50 kt. Vertical wind profiles, and effective shear magnitudes increasing to greater than 40 kt, will support supercell thunderstorms. At the surface, a cold front will extend from northern MN southwestward into western SD during the morning. The front will develop southeast through the day and into the evening, becoming positioned from western WI/IA to the NE/KS border by Tuesday morning. Ahead of the front, a very moist airmass (upper 60s to mid 70s F dewpoints) will be in place across portions of MN/WI/IA and eastern SD, while a dryslot will be oriented over NE nosing into far southeast SD/western IA. With increasing ascent through the day, and persistent low-level warm advection, MLCIN should gradually erode. MLCAPE values across warm/moist sector are forecast as high as 3000-5000 J/kg, decreasing with southwest extent into the drier airmass. Steep midlevel lapse rates will within the strong to extremely unstable airmass will support robust updrafts, and initial supercell thunderstorms are expected to develop along the cold front from SD into MN. Large to very large (isolated stones greater than 2 inches diameter) will be possible. While damaging gusts will also be possible with cellular activity, one or more bowing segments/MCSs are expected to develop into the evening hours as convection shifts northeast across eastern SD/MN and eventually WI. As this occurs, potential for severe/damaging wind swaths will increase and a few gusts greater than 65 kt/75 mph are possible. Tornado potential is a bit more uncertain, but would likely be locally increased near and east of the surface low where low-level flow will remain more southeasterly. This will enhance low-level SRH and frontal convergence and a few tornadoes are possible with either supercells or within mesovortex formation along bowing segments. ...Northern/Central High Plains... Within the drier boundary-layer across southeast MT/eastern WY southward into eastern CO/western KS/western NE, scattered thunderstorms are expected to develop as the main upper trough overspreads the area during the afternoon. High-based thunderstorms amid steep low-level lapse rates will pose a risk for strong/isolated severe outflow winds. Isolated large hail also is possible, mainly from eastern WY into western SD/NE. ...New England and portions of the Upper OH Valley/Mid-Atlantic... Modestly enhanced deep-layer northwesterly flow on the back side of an upper trough will overspread the region. Pockets of 60 F dewpoints and cool temperatures aloft will support modest destabilization during the afternoon and thunderstorm bands/clusters are expected. Locally strong gusts will be possible with the activity. Isolated large hail also may be possible, especially over southern New England where forecast hodographs show more favorable vertical shear and elongated/straight hodographs. ..Leitman.. 08/25/2024 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1211 PM CDT Sun Aug 25 2024 Valid 261200Z - 271200Z ...NO CRITICAL AREAS... The previous forecast reasoning (see below) remains the same, and no changes were needed with this update. ..Weinman.. 08/25/2024 .PREV DISCUSSION... /ISSUED 0142 AM CDT Sun Aug 25 2024/ ...Synopsis... A mid/upper-level trough is forecast to shift from the Northern Rockies into the Northern Plains Day 2/Monday. As this occurs, enhanced deep-layer flow is forecast to overspread portions of Wyoming near the base of the aforementioned trough, which will promote dry and breezy conditions. While locally elevated fire weather conditions are probable -- mainly during the afternoon with boundary-layer mixing -- fire weather conditions appear too spotty/brief to introduce an Elevated area at this time. ...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 1156 AM CDT Sun Aug 25 2024 Valid 251700Z - 261200Z Based on the latest observational data and high-resolution guidance, an Elevated area was added over portions of southwest/central Utah with this update. Here, breezy southwesterly surface winds (sustained 20-25 mph) will overlap 15-20 percent RH ahead of a cold front this afternoon. Despite slightly cooler temperatures and higher RH than previous days, the breezy/gusty winds amid a couple ongoing fire incidents warrant the highlights. Elsewhere, the previous forecast (see below) remains on track. ..Weinman.. 08/25/2024 .PREV DISCUSSION... /ISSUED 0138 AM CDT Sun Aug 25 2024/ ...Synopsis... A mid/upper-level trough is forecast to gradually shift from the Northern Great Basin into the Northern Rockies through tonight. Ascent associated with the trough should foster isolated to widely scattered thunderstorms this afternoon/evening across portions of Idaho, Wyoming, Montana, and Nevada. While a mix of wet/dry thunderstorms is expected, fast-moving thunderstorms atop receptive fuels may promote new ignitions, especially along the periphery of any heavier thunderstorm precipitation cores. In addition, gusty and erratic outflow winds are possible with the strongest storms. Please see the SPC Day 1 Convective Outlook for more information on the nearby severe thunderstorm risk across portions of Wyoming. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook CORR 1 NWS Storm Prediction Center Norman OK 1138 AM CDT Sun Aug 25 2024 Valid 251630Z - 261200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHERN PLAINS/UPPER MIDWEST AND CENTRAL ROCKIES... CORRECTED FOR NDFD THUNDER ...SUMMARY... Severe wind gusts and hail are most probable today over parts of the Four Corners to southwestern Wyoming, and this evening over portions of the eastern Dakotas and western Minnesota. ...Northern Plains/Upper Midwest... Scattered thunderstorms are expected to develop along/ahead of the cold front and near a South Dakota surface wave, primarily this evening after 00Z/7pm CDT, although enough moistening and heating may occur for isolated late-afternoon development. Some supercells and bowing lines/clusters are expected, with large hail and severe wind gusts possible. Intensifying thunderstorm development should occur as the front encounters what is left of a diurnally well-heated and still-unstable boundary-layer airmass. Forecast soundings indicate the moist layer should deepen through the day beneath strong capping and steep mid-level lapse rates, MLCAPE in the 3000-4000 J/kg range possible. This will occur with gradually strengthening west-southwesterly winds aloft with 30-45 kt effective shear. Additional severe storms may occur late this afternoon into evening within an evolving post-frontal environment across northeast Wyoming into northwest South Dakota/southwest North Dakota, with moderate buoyancy and very long/straight hodographs potentially supporting storms capable of hail and possibly severe-caliber wind gusts. ...Central/southern Rockies... Scattered thunderstorms are ongoing early today across eastern Utah and western Colorado in advance of an upper-level trough centered over Nevada. A greater coverage and intensity of storms should occur into the afternoon as the boundary layer further warms/destabilizes. Relatively strong mid/high-level southwesterlies will support ample deep-layer/effective shear, with supercells and bowing clusters possible in a corridor spanning portions of the Four Corners area to northern Colorado/southwest Wyoming. Elongated and semi-straight hodographs will support large-hail potential aside from a broader regional risk for severe-caliber wind gusts. ...South-central High Plains... Scattered slow-moving thunderstorms are expected this afternoon particularly across eastern Colorado and northeast New Mexico. Hot/well-mixed boundary layers within the pre-convective environment will support the possibility of strong to locally severe-caliber wind gusts through late afternoon until around sunset. ..Guyer/Wendt.. 08/25/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0756 AM CDT Sun Aug 25 2024 Valid 251300Z - 261200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE FOUR CORNERS TO SOUTHWESTERN WYOMING...AND OVER PORTIONS OF WESTERN MINNESOTA AND THE EASTERN DAKOTAS... ...SUMMARY... Severe gusts and hail are most probable today over parts of the Four Corners to southwestern Wyoming, and this evening over portions of western Minnesota and the eastern Dakotas. ...Synopsis... A seasonally well-amplified mid/upper-level pattern will persist over the CONUS, but with some important changes due to the progression of embedded synoptic- to subsynoptic-scale features. An intermittently closed cyclone now over north-central NV will eject slowly northeastward to southeastern ID through the period, while devolving to an open-wave trough. By 12Z tomorrow, the full trough should extend from the MT Rockies southward through the remnant low's vorticity max, then southwestward to southern NV. Meanwhile, a broad anticyclone -- initially centered over northern OK/southern KS -- will move northeastward, with the 500-mb high over central MO by 12Z, and ridging north-northeastward across Lake Superior. The northward component of this shift should occur partly in response to a well-defined low/trough in the subtropical easterlies, now evident over the north-central to southwestern Gulf. This feature should move ashore on the lower/middle TX Coast around the end of the period. Northeast of the high, a strong shortwave trough now over northwestern QC will dig south-southeastward through tonight, reaching the St. Lawrence Valley and approaching northern NY by 12Z. At the surface, 11Z analysis showed a persistent, very slowly frontolytic, quasistationary boundary from just offshore of the Carolinas to the north-central Gulf Coast, becoming a diffuse warm front over astern parts of TX/OK. Rich low-level moisture has returned northward near this boundary in OK/AR and farther north across parts of the central/northern Plains. A low was drawn north of MIB, with cold front southwestward across the northwestern corner area of SD, into north-central WY. By 00Z, the front should reach from near the MN/ND/MB border confluence across the eastern Dakotas, parts of north-central/southwestern NE and near CYS. The front should proceed overnight to a 12Z position from northeastern MN to the FSD/SUX vicinity, central NE and eastern CO. ...Northern Plains/Upper Midwest... Scattered thunderstorms are expected to develop along/ahead of the cold front -- predominantly after 00Z, though enough moistening/ heating may occur for isolated late-afternoon development. Supercells and bowing lines/clusters will be possible, offering large hail and severe gusts. Activity should occur as the front encounters what is left of a diurnally well-heated and still-unstable boundary-layer airmass, with only minimal diabatic cooling, due to the presence of rich moisture near the surface, Surface dewpoints already are commonly in the 70s F in a swath of the warm sector with 11Z axis from north-central ND south-southeastward across eastern portions of SD/NE/KS and the Arklatex region. Forecast soundings indicate the moist layer should deepen through the day beneath strong capping, and steep midlevel lapse rates. With a deep troposphere still present over this area, atop the favorably unstable boundary layer, MLCAPE in the 3000-4000 J/kg range will be possible. This will be collocated with slowly strengthening flow aloft, such that 30-45-kt effective-shear magnitudes will be possible from late afternoon through the evening. ...Central/southern Rockies and vicinity, south-central Plains... Scattered showers and thunderstorms, with at least isolated strong-severe gust potential, should become common by this afternoon in a vast, roughly triangular area in and near the outlook, from western NM and eastern AZ to parts of southeastern MT and southern KS. Within that area, the greatest potential for severe should be on the western fringes, with supercells and bowing clusters possible in a corridor spanning portions of the Four Corners area to southwestern WY. In that region, the greatest diurnal destabilization will overlap the most favorable deep-layer lapse rates, and strengthening vertical shear ahead of the progressive western trough. Mid/upper-level moisture-channel imagery, available GPS PW data, and surface analysis show a persistent plume of deep-layer monsoonal moisture, maintaining some continuity from the ITCZ well south of mainland MX, across parts of west-central MX and Chihuahua, to NM, CO, WY and western NE. Enough low-level moisture (PW above 1 inch in some areas) to support organized convective potential extends farther westward over the Four Corners area, especially into northeastern AZ, eastern UT and western CO. Forecast soundings in that corridor show favorable deep shear for supercells, with effective-shear magnitudes in the 40-55-kt range, and elongated, rather straight low/middle-level hodographs favoring a large-hail threat, in addition to the broader severe-gust potential. Farther east, much of the higher terrain across the "marginal" area will reach convective temperature relatively early in the diurnal-heating cycle, with little CINH, resulting in abundant development, slowing the pace of additional destabilization. Still, isolated strong/briefly severe gusts may occur, especially where north-northeastward moving clusters of convection encounter pockets of well-mixed boundary layer suitable for intense downdrafts. Farther east onto the High Plains, more-favorable heating/mixing will occur, but with weak shear nearer to the mid/upper high. ..Edwards/Bentley.. 08/25/2024 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0359 AM CDT Sun Aug 25 2024 Valid 281200Z - 021200Z ...DISCUSSION... Potential for severe weather may spread across parts of the Northeast/New England Day 4/Wednesday. However non-trivial uncertainty is evident -- regarding both details with respect to how the short-wave trough crossing Ontario interacts with the more pronounced trough shifting eastward across Quebec into the Canadian Maritimes, as well as evolution/progression of ongoing Day-3 convection. Therefore, despite potential for severe weather that is evident in a broad/general sense, no areas will be highlighted at this time. Upstream, models forecast the advance of an upper low across the Canadian Prairie, with troughing south of the low to cross the northern Intermountain Region and eventually reach the northern Plains. As this system advances, a cold front is progged to move into/across the Dakotas and western Nebraska diurnally. Amply strong flow should accompany this trough, along with the likelihood for sufficient warm-sector destabilization to support storm development. This suggests some potential for severe weather across portions of the northern Plains, but -- similar to the potential for severe weather over the Northeast -- will refrain from any areal highlights at this time. Beyond Day 4/Wednesday, model differences steadily increase with respect to the large-scale features, and thus will refrain from attempts to assess risk through the remainder of the medium-range period. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0227 AM CDT Sun Aug 25 2024 Valid 271200Z - 281200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF THE GREAT LAKES REGION... ...SUMMARY... Severe-weather potential is evident across the Great Lakes region on Tuesday. ...Synopsis... While upper ridging/weak flow aloft prevails across most of the southern 2/3 of the country, an active northern stream will persist Tuesday. Within this stream, and upper trough will continue moving eastward across western Canada and the northwest CONUS. Meanwhile, a weaker/lower amplitude downstream trough will nonetheless be the more substantial feature with respect to convective/severe potential. This trough, initially over the north-central U.S., is forecast to shift eastward across the Upper Great Lakes and southern Ontario through Wednesday morning. At the surface, low pressure initially near the Upper Mississippi Valley will accompany the eastward advance of the upper system, moving eastward across the Great Lakes region through the period. ...Great Lakes region... Thunderstorms -- and accompanying risk for large hail and damaging winds -- are expected to be ongoing across parts of the Upper Mississippi Valley/western Upper Great Lakes region at the start of the period, in advance of the eastward-moving upper disturbance. Questions regarding initial location, and speed of advance, of this convection cast substantial uncertainties with respect to evolution of the severe threat into Tuesday afternoon and beyond. Still, as the upper system and associated surface low track eastward across the Great Lakes, and a moist boundary layer heats/strongly destabilizes through the afternoon in areas away from ongoing convection/clouds, severe threat should persist/shift eastward with time. With a belt of moderately strong deep-layer westerlies shifting across the Great Lakes in tandem with the upper system, potential for organized, rather fast-moving storms is indicated. While capping may limit convective coverage with southward extent, Wisconsin and Michigan appear likely to be the centroid of the risk. As storms spread eastward through the evening and into the overnight hours, the eastern extent of the risk is difficult to delineate at this time. At least some risk may reach as far east as the Lake Ontario/Finger Lakes region of New York and adjacent north-central Pennsylvania. ..Goss.. 08/25/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0227 AM CDT Sun Aug 25 2024 Valid 271200Z - 281200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF THE GREAT LAKES REGION... ...SUMMARY... Severe-weather potential is evident across the Great Lakes region on Tuesday. ...Synopsis... While upper ridging/weak flow aloft prevails across most of the southern 2/3 of the country, an active northern stream will persist Tuesday. Within this stream, and upper trough will continue moving eastward across western Canada and the northwest CONUS. Meanwhile, a weaker/lower amplitude downstream trough will nonetheless be the more substantial feature with respect to convective/severe potential. This trough, initially over the north-central U.S., is forecast to shift eastward across the Upper Great Lakes and southern Ontario through Wednesday morning. At the surface, low pressure initially near the Upper Mississippi Valley will accompany the eastward advance of the upper system, moving eastward across the Great Lakes region through the period. ...Great Lakes region... Thunderstorms -- and accompanying risk for large hail and damaging winds -- are expected to be ongoing across parts of the Upper Mississippi Valley/western Upper Great Lakes region at the start of the period, in advance of the eastward-moving upper disturbance. Questions regarding initial location, and speed of advance, of this convection cast substantial uncertainties with respect to evolution of the severe threat into Tuesday afternoon and beyond. Still, as the upper system and associated surface low track eastward across the Great Lakes, and a moist boundary layer heats/strongly destabilizes through the afternoon in areas away from ongoing convection/clouds, severe threat should persist/shift eastward with time. With a belt of moderately strong deep-layer westerlies shifting across the Great Lakes in tandem with the upper system, potential for organized, rather fast-moving storms is indicated. While capping may limit convective coverage with southward extent, Wisconsin and Michigan appear likely to be the centroid of the risk. As storms spread eastward through the evening and into the overnight hours, the eastern extent of the risk is difficult to delineate at this time. At least some risk may reach as far east as the Lake Ontario/Finger Lakes region of New York and adjacent north-central Pennsylvania. ..Goss.. 08/25/2024 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0142 AM CDT Sun Aug 25 2024 Valid 261200Z - 271200Z ...NO CRITICAL AREAS... ...Synopsis... A mid/upper-level trough is forecast to shift from the Northern Rockies into the Northern Plains Day 2/Monday. As this occurs, enhanced deep-layer flow is forecast to overspread portions of Wyoming near the base of the aforementioned trough, which will promote dry and breezy conditions. While locally elevated fire weather conditions are probable -- mainly during the afternoon with boundary-layer mixing -- fire weather conditions appear too spotty/brief to introduce an Elevated area at this time. ..Elliott.. 08/25/2024 ...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 0142 AM CDT Sun Aug 25 2024 Valid 261200Z - 271200Z ...NO CRITICAL AREAS... ...Synopsis... A mid/upper-level trough is forecast to shift from the Northern Rockies into the Northern Plains Day 2/Monday. As this occurs, enhanced deep-layer flow is forecast to overspread portions of Wyoming near the base of the aforementioned trough, which will promote dry and breezy conditions. While locally elevated fire weather conditions are probable -- mainly during the afternoon with boundary-layer mixing -- fire weather conditions appear too spotty/brief to introduce an Elevated area at this time. ..Elliott.. 08/25/2024 ...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 0138 AM CDT Sun Aug 25 2024 Valid 251200Z - 261200Z ...NO CRITICAL AREAS... ...Synopsis... A mid/upper-level trough is forecast to gradually shift from the Northern Great Basin into the Northern Rockies through tonight. Ascent associated with the trough should foster isolated to widely scattered thunderstorms this afternoon/evening across portions of Idaho, Wyoming, Montana, and Nevada. While a mix of wet/dry thunderstorms is expected, fast-moving thunderstorms atop receptive fuels may promote new ignitions, especially along the periphery of any heavier thunderstorm precipitation cores. In addition, gusty and erratic outflow winds are possible with the strongest storms. Please see the SPC Day 1 Convective Outlook for more information on the nearby severe thunderstorm risk across portions of Wyoming. ..Elliott.. 08/25/2024 ...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 0138 AM CDT Sun Aug 25 2024 Valid 251200Z - 261200Z ...NO CRITICAL AREAS... ...Synopsis... A mid/upper-level trough is forecast to gradually shift from the Northern Great Basin into the Northern Rockies through tonight. Ascent associated with the trough should foster isolated to widely scattered thunderstorms this afternoon/evening across portions of Idaho, Wyoming, Montana, and Nevada. While a mix of wet/dry thunderstorms is expected, fast-moving thunderstorms atop receptive fuels may promote new ignitions, especially along the periphery of any heavier thunderstorm precipitation cores. In addition, gusty and erratic outflow winds are possible with the strongest storms. Please see the SPC Day 1 Convective Outlook for more information on the nearby severe thunderstorm risk across portions of Wyoming. ..Elliott.. 08/25/2024 ...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 0107 AM CDT Sun Aug 25 2024 Valid 261200Z - 271200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF EASTERN SOUTH DAKOTA INTO SOUTHERN WISCONSIN...AND SMALL PORTIONS OF SURROUNDING STATES... ...SUMMARY... Severe storms are expected to evolve within a zone extending from the northern High Plains eastward to the Wisconsin vicinity during the afternoon and evening Monday. A few severe storms are also expected across the Northeast and Mid-Atlantic region. ...Synopsis... A weakening upper trough is forecast to remain across the central U.S. Monday. On the northwestern periphery of this ridge, and short-wave trough initially over the Intermountain West is forecast to advance northeastward across the northern High Plains into the Northern Plains through the period. Meanwhile, an upper low is forecast to shift southward out of the St. Lawrence Valley area across western/southern New England, before shifting offshore overnight. Finally, a Gulf of Alaska upper trough is forecast to advance into western Canada and the Pacific Northwest through Tuesday morning. At the surface, a northwest-to-southeast cold front is forecast to extend from the northeastern Minnesota vicinity southwestward across Nebraska early in the period. The front should move little through the day, as a frontal low lingers in the vicinity of the Mid-Missouri Valley area. Overnight, the low is forecast to shift northeastward, allowing the trailing portion of the cold front to progress southward across the central Plains through latter stages of the period. ...Northern High Plains east to parts of Wisconsin... Thunderstorms may be ongoing across portions of northern Minnesota early Monday morning, with limited severe risk potentially lingering through roughly midday. Meanwhile, as the moist low-level airmass heats near and south of the convectively reinforced front, mixed-layer CAPE in the 3000 to 5000 J/kg range is forecast to develop through the afternoon. This, combined with ascent near the front/convective outflows, should allow isolated storms to develop across the eastern South Dakota vicinity. The storms should rapidly become supercells, given the kinematic environment characterized by low-level flow veering/increasing with height to 40 to 50 kt southwesterlies at mid levels. Very large hail is expected, along with damaging wind gusts. Storms will continue into the evening, possibly growing upscale into an MCS overnight -- shifting northeastward into/across southern Minnesota. Along with continued risk for large hail, damaging winds would likely accompany this convection. In addition, a couple of tornadoes may also occur -- particularly just to the northeast of the anticipated position of the surface low where low-level flow will remain backed/southeasterly. Meanwhile farther west, into the High Plains, isolated afternoon convective development is expected, in closer proximity to the advancing upper system. A drier boundary layer and thus weaker CAPE across this region suggests less substantial severe risk. Still, hail and damaging gusts should accompany a few of the stronger storms, given the belt of 50 kt mid-level southwesterly flow accompanying the advancing short-wave trough. ...Portions of the Northeast/New England... As the upper low shifts southward across western New England through the day Monday, heating/destabilization is expected to support development of isolated to scattered thunderstorms. Enhanced northwesterly flow near and west of the low should support southeastward-moving bands/clusters of storms, which should prove locally capable of producing strong -- potentially damaging -- gusts from mid afternoon into the evening hours. ..Goss.. 08/25/2024 Read more