Severe Storms

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1141 AM CDT Thu Aug 25 2022 Valid 251700Z - 261200Z ...NO CRITICAL AREAS... There are no changes to the forecast. For details, see the previous discussion below. ..Weinman.. 08/25/2022 .PREV DISCUSSION... /ISSUED 0125 AM CDT Thu Aug 25 2022/ ...Synopsis... Broad cyclonic upper flow will prevail across the eastern U.S. while multiple mid-level impulses will traverse the Northwest into the central Plains today. Scattered thunderstorms are expected to develop amid a modestly buoyant airmass across portions of the northern Rockies. A few of the thunderstorms may be dry initially, before becoming a more wet/dry mix. Fuels, however, are receptive to wildfire spread on a spotty basis. As such, sparse dry strikes into patchy receptive fuels or gusty, erratic winds emanating from storms may support very localized wildfire-spread potential. Locally dry and windy conditions are also possible across parts of the northern Great Basin in association with the passage of a mid-level impulse. ...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 1120 AM CDT Thu Aug 25 2022 Valid 251630Z - 261200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER WESTERN MONTANA AND ACROSS PORTIONS OF THE NORTH-CENTRAL HIGH PLAINS... ...SUMMARY... Isolated severe hail and thunderstorm gusts will be possible across portions of western Montana and the north-central High Plains today. ...Western MT... Slow-moving closed upper low over near the international border in the vicinity of northern ID will begin to move slowly east late today. Diurnal heating of initially 50s surface dew points will result in a deep mixed layer, and steep midlevel lapse rates will contribute to 1000-1500 J/kg MLCAPE this afternoon. Although winds throughout the cloud-bearing layer will be generally modest (30 kts or less), veering low/midlevel flow will contribute to 30-35 kts of effective shear. Widely scattered to scattered thunderstorm development is expected this afternoon across western MT, with multicell/supercell modes possible. Deep mixed layer will result in a risk for isolated severe wind gusts, and large hail will be possible with a few stronger updrafts/supercell structures. ...North-Central High Plains... Midlevel perturbation currently over western WY will continue east, with a region of ascent favorably timed to develop over the Big Horn/Black Hills region during the mid/late afternoon. Despite ongoing cloud cover, heating of mid/upper 50s surface dew points beneath reasonably steep midlevel lapse rates should result in pockets of MLCAPE of 1000-1500 J/kg. Modest midlevel west/northwest flow will contribute to around 30 kts of effective shear which will favor a mixed multicell/transient supercell mode. Isolated stronger storms will be capable of strong/damaging gusts and hail through early evening. ..Bunting/Wendt.. 08/25/2022 Read more

No watches are valid as of Wed Aug 24 17:48:02 UTC 2022.

No Mesoscale Discussions are in effect as of Wed Aug 24 17:48:02 UTC 2022.

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1222 PM CDT Wed Aug 24 2022 Valid 251200Z - 261200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms are not forecast across the contiguous United States on Thursday. ...Northern Rockies/Northern High Plains... A slow-moving and weakening mid-level low will move east across the northern Rockies into the northern High Plains. Widely scattered to scattered diurnal thunderstorms are forecast to develop during the afternoon over the higher terrain of western into southern MT and near the Big Horns/Black Hills. Models continue to indicate that heating will be tempered in some areas due to partial cloud cover. However, steepening low-level lapse rates and large directional shear contributing to modest deep-layer shear, will support intermittently organized multicells. Given the marginal character of the potential storm intensity, will defer the highlighting of low wind probabilities for the time being. ..Mid MS Valley... A cold front, associated with a shortwave trough moving through the Upper Great Lakes, is expected to move southward through the Mid MS Valley Thursday afternoon and evening. Dewpoints will likely be in the upper 60s and temperatures in the mid 80s ahead of the front, resulting in moderate buoyancy. Isolated to widely scattered thunderstorms are anticipated across the region near the front. A few stronger updrafts could develop, but weak vertical shear will limit storm intensity. ...Elsewhere... Thunderstorms are also possible within the monsoonal moisture still in place across the Southwest and central Rockies, and in the vicinity of subtle upper low and associated surface low over the Southeast and FL. In each of these regions, weak vertical shear should keep the severe threat low. ..Smith.. 08/24/2022 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1129 AM CDT Wed Aug 24 2022 Valid 251200Z - 261200Z ...NO CRITICAL AREAS... The forecast remains on track, and no changes were made with this update. For details, see the previous discussion below. ..Weinman.. 08/24/2022 .PREV DISCUSSION... /ISSUED 0153 AM CDT Wed Aug 24 2022/ ...Synopsis... A mid-level trough will meander across the northern Rockies tomorrow/Thursday, supporting another day of scattered thunderstorms (a couple of which may be dry) by afternoon. Similar to Day 1, fuels are expected to remain receptive to fire spread on a spotty basis. Given recent rainfall accumulations as well as the potential for appreciable accumulations on Day 1, fuel receptiveness to wildfire spread will likely remain modest, precluding dry thunderstorm highlights this outlook. Also like Day 1, locally Elevated dry and windy conditions may occur in terrain-favoring areas of the northern Great Basin by afternoon. ...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 1126 AM CDT Wed Aug 24 2022 Valid 241700Z - 251200Z ...NO CRITICAL AREAS... The previous forecast reasoning (see below) remains the same, and no changes were needed with this update. ..Weinman.. 08/24/2022 .PREV DISCUSSION... /ISSUED 0153 AM CDT Wed Aug 24 2022/ ...Synopsis... A mid-level trough will traverse the Northwest U.S. as broad but weak cyclonic upper flow remains in place east of the Rockies today. Ahead of the mid-level trough, adequate lift and buoyancy will support scattered thunderstorm development, with at least isolated thunderstorms capable of producing strong to severe wind gusts. Fuel beds are receptive to wildfire spread on a spotty basis. However, the combination of dry strikes away from precipitation cores into dry fuel beds, and strong wind gusts exacerbating ongoing fires suggests that at least localized wildfire-spread concerns exist, especially along the Idaho/Montana border. Farther south across the northern Great Basin, locally Elevated dry and windy conditions are possible by afternoon peak heating. Please see the Day 1 Convective Outlook for more details on the severe threat. ...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 1121 AM CDT Wed Aug 24 2022 Valid 241630Z - 251200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE NORTHERN ROCKIES TO UPPER THE MISSISSIPPI VALLEY... ...SUMMARY... Marginally severe gusts and/or hail will be possible in a corridor from portions of the northern Rockies to the upper Mississippi Valley. ...Northern Rockies to upper Mississippi Valley... Modest west-northwest mid-level flow will prevail from the Northern Rockies into the upper Great Lakes through tonight. An upper low over WA will drift east, while a low-amplitude impulse over western MN moves slowly southeast. A surface front, extending from the MI Upper Peninsula west/southwest through western NE and southern MT, will serve as a focus for isolated severe potential as thunderstorms develop/intensify this afternoon. Two areas with potentially greater thunderstorm coverage remain evident, over portions of southeast MN/northern IA/southern WI associated with a weak surface low along the front over southern MN, and over western MT in association with the eastward-migrating upper low. Relatively greater boundary-layer moisture exists over IA/southern MN late this morning (surface dew points mid 60s), and this will contribute to pockets of moderate MLCAPE where heating can be maximized. Generally weak low/mid-level wind fields will result in effective shear below 30 kts, though this may support organized multicell structures capable of isolated damaging gusts and hail late this afternoon through early evening. Across western MT, steeper mid-level lapse rates will contribute moderate buoyancy, and effective shear values will average 30-40 kts. Scattered thunderstorms should develop this afternoon, aided by post-frontal upslope flow and ascent with the approaching upper low. A mix of multicell and transient supercell storm modes is possible with a risk for isolated severe wind and hail with the strongest storms. A focused Slight Risk was considered over portions of western MT, however with existing cloud cover some uncertainty remains regarding the degree of destabilization and spatial extent of any greater severe threat. Elsewhere along the front, storm coverage is expected to be more isolated overall, though with perhaps slightly greater coverage in the upslope region of the Black Hills in western SD. A well-mixed boundary layer and marginal low-level moisture will support at least some risk for strong wind gusts. ..Bunting/Wendt.. 08/24/2022 Read more

No watches are valid as of Tue Aug 23 17:41:01 UTC 2022.

No Mesoscale Discussions are in effect as of Tue Aug 23 17:41:01 UTC 2022.

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1235 PM CDT Tue Aug 23 2022 Valid 241200Z - 251200Z ...NO CRITICAL AREAS... The previous forecast (see below) remains on track, and no changes were needed with this update. Isolated dry thunderstorms will also be possible over parts of central into eastern NV during the afternoon, though current indications are that fuels are generally not receptive to wildfire spread over this area. ..Weinman.. 08/23/2022 .PREV DISCUSSION... /ISSUED 0151 AM CDT Tue Aug 23 2022/ ...Synopsis... Broad cyclonic flow will prevail across the eastern U.S., while the western CONUS will remain under the influence of weak upper ridging tomorrow/Wednesday. A weak mid-level cutoff low will also meander around the northern Rockies to the north of the upper ridge. South of this upper low, locally dry and breezy conditions may occur across portions of far southeast Oregon into northern and central Nevada around afternoon peak heating. A greater concentration of dry thunderstorms is also likely across portions of the northern Rockies (particularly central into eastern Idaho) compared to Day 1. As in Day 1 though, dry thunderstorm highlights were withheld given questionable fuel receptiveness to fire spread. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1222 PM CDT Tue Aug 23 2022 Valid 241200Z - 251200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms are not currently forecast for Wednesday across the contiguous United States. ...Synopsis... A flattened mid- to upper-level ridge will reside over the Four Corners while a weak upper low remains over the Pacific Northwest. A subtle shortwave trough is expected to move northeastward in the corridor between the upper ridging and upper low, moving across northern NV/southern ID into southwest MT. ...Northern Rockies/High Plains into the Upper Midwest... A weak area of low pressure will gradually move east across southern MN during the day while an attendant cool front becomes draped from NE and becoming more diffuse over parts of the northern Rockies. Isolated thunderstorms are anticipated across southern MN, northern/central IA, and eastern NE along the cold front. Weak vertical shear will limit storm intensity. Some additional thunderstorm development is possible over eastern WY, where low-level convergence between the post-frontal easterly flow and the lee trough is maximized. Vertical shear will be slightly stronger here compared to areas farther east, largely as a result of low-level easterly flow veering to northwesterly aloft. Model guidance continues to indicate instability will be modest, thereby tempering the risk for strong/locally severe thunderstorms. Perhaps the area with the highest relative concern for a stronger thunderstorm will be over parts of western MT. Strong gusty winds may accompany the more intense thunderstorms during the early evening. ...Southeast... A convectively augmented shortwave trough and attendant surface low will continue to slowly drift eastward across the Southeast states, with numerous thunderstorms expected over the region throughout the day. Uncertainty remains high whether mesoscale enhancement to the wind profile will occur in a very moist airmass. ..Smith.. 08/23/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1120 AM CDT Tue Aug 23 2022 Valid 231700Z - 241200Z ...NO CRITICAL AREAS... The forecast remains on track, and no changes were made with this update. For details, see the previous discussion below. ..Weinman.. 08/23/2022 .PREV DISCUSSION... /ISSUED 0151 AM CDT Tue Aug 23 2022/ ...Synopsis... While broad cyclonic upper flow will prevail east of the Rockies, and a mid-level shortwave trough impinges on the West Coast today, deep-layer winds/forcing should be weak, with dry and windy conditions expected to remain constrained to terrain-favoring areas. While isolated to scattered thunderstorms are possible across parts of the Pacific Northwest into the northern Rockies, several of the storms are expected to be wet. Spotty fuel beds may support isolated lightning-induced ignitions. However, many earlier fire starts have yet to grow rapidly, suggesting that fuels are modestly receptive at best to significant wildfire spread. As such, dry thunderstorm highlights have been withheld this outlook. ...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 1113 AM CDT Tue Aug 23 2022 Valid 231630Z - 241200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS CENTERED ON PARTS OF AZ...ND...AND SOUTHERN NEW ENGLAND... ...SUMMARY... Isolated severe thunderstorms are possible into this evening, centered on portions of Arizona, North Dakota, and southern New England. ...Lower CO Valley to south-central AZ... Full insolation this morning in conjunction with steep mid-level lapse rates of 7-7.5 C/km will yield a moderately unstable air mass with MLCAPE of 1500-2500 J/kg south of the Mogollon Rim by late afternoon. Scattered thunderstorms are expected to develop off the Rim and drift to the south-southwest within a belt of 10-15 kt 500-600 mb flow. Localized severe gusts will be possible as convection spreads into the lower deserts including the greater Phoenix metro area. The lack of stronger shear should limit potential for a more organized severe wind event. ...Central/northern ND... 16Z surface analysis placed a couple of 1013-mb lows near the MT/ND border and the SK/MB/ND border along a weak quasi-stationary front. A minor mid-level vort max attendant to the latter wave should drift southeast, aiding in scattered thunderstorm development later this afternoon across northern to central ND. A compact belt of enhanced upper-level flow may be adequate for a couple stronger cells given moderate mid-level lapse rates sampled by the 12Z Bismarck sounding. These cells will be capable of marginally severe hail and localized strong to marginally severe gusts. ...Southern New England... Scattered thunderstorms are underway across the Hudson Valley downstream of a mid-level trough centered on the Upper St. Lawrence Valley, with more isolated activity farther south. Boundary-layer heating has been more robust across the Tri-State area in the NYC vicinity, with stratus still holding across most of MA/RI. This should result in a confined corridor having a modest combination of buoyancy and mid-level flow over southern New England. In this area, a few wet microbursts capable of locally damaging winds are possible through the rest of the afternoon. ..Grams/Wendt.. 08/23/2022 Read more

No watches are valid as of Mon Aug 22 17:51:01 UTC 2022.

No Mesoscale Discussions are in effect as of Mon Aug 22 17:51:01 UTC 2022.

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1227 PM CDT Mon Aug 22 2022 Valid 231200Z - 241200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... A few strong thunderstorms will be possible across parts of Arizona, the northern Rockies and northern Plains, and parts of New England on Tuesday, but the organized severe-thunderstorm threat appears relatively low at this time. ...Arizona... Substantial convective overturning occurred across parts of AZ and adjacent portions of southern CA/NV on Sunday. This may tend to suppress convection somewhat on D1/Monday, which in turn may allow for more substantial recovery by D2/Tuesday. If this scenario occurs, then some threat for strong/locally severe wind gusts (and perhaps some hail across higher elevations) may materialize on Tuesday along the Mogollon Rim into portions of the lower deserts. Severe probabilities may need to be added sometime during the Day 1 outlook cycle, depending on shorter-term trends regarding destabilization and the strength of midlevel steering flow. ...Northern Rockies/Great Plains... A few strong storms will be possible Tuesday across parts of the northern Rockies, near and east of a midlevel low moving slowly from southern BC into eastern WA and northern ID. With only modest instability and generally weak deep-layer shear, the severe threat still appears too low to include probabilities. Farther east into the northern Great Plains, isolated to widely scattered storms will be possible during the afternoon and evening, as a midlevel shortwave trough moves eastward and interacts with a weak surface boundary. Moderate instability could support some stronger updrafts, but rather weak deep-layer flow/shear may limit the threat for organized severe storms. ...New England... A weakening mid/upper-level low and associated trough are forecast to move across New England on Tuesday. Modestly enhanced midlevel southwesterly flow could support some occasional storm organization as convection redevelops during the afternoon, though weak midlevel lapse rates will tend to limit updraft intensity to some extent. Any severe threat will likely be dependent on the extent of diurnal heating and destabilization, which remains uncertain at this time due to the potential for widespread early-day cloudiness. ..Dean.. 08/22/2022 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1131 AM CDT Mon Aug 22 2022 Valid 221630Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE MID-ATLANTIC/CAROLINAS AND FROM CENTRAL TEXAS EAST THROUGH CENTRAL LOUISIANA AND SOUTHWEST MISSISSIPPI... ...SUMMARY... A few severe thunderstorms will be possible across parts of central/east Texas to Louisiana/southwest Mississippi, with additional locally severe storms possible across parts of the Mid-Atlantic states and Carolinas. ..Central/east Texas Louisiana/southern Mississippi... Widespread/persistent convection across North Texas this morning should result in a slow southward movement of an east-west baroclinic zone into central TX east to northern/central LA this afternoon as a broad/weak surface low near the DFW area moves slowly east. Diurnal heating of a very moist air mass characterized by PW values of 2-2.4 inches will contribute to moderate destabilization within a largely uncapped environment, and a few stronger storms will be capable of damaging downburst winds. Some potential for transient low-level rotation will continue east of the surface low near an effective warm front across east TX into central LA, where subtle low-level veering in forecast wind profiles will exist. ...Mid-Atlantic States/Carolinas... Variable cloud cover across the area has led to steady heating/destabilization through 16z, with moderate SBCAPE expected by afternoon within a largely uncapped environment. Scattered thunderstorm development is expected ahead of a cold front and over the higher terrain, with storms generally moving east through early evening. West/southwest mid-level flow of 20-30 kts will be sufficient for multicell storm structures capable of strong/locally severe gusts. ...Arizona/Lower Colorado River Valley... While a couple of stronger storms could materialize mainly along the Mogollon Rim late this afternoon through early evening, the overall convective potential across the region should be lower in the wake of Sunday night's MCS. ...Idaho/far western Montana... Upper trough and associated large-scale ascent over the Pacific Northwest/British Columbia will contribute to increasing (mostly dry) thunderstorms across the region this afternoon and evening. A warm and well-mixed boundary layer and modest strengthening of mid-level westerly flow may result in very isolated stronger wind gusts, although the potential for organized severe storms is currently expected to remain low. Please refer to the SPC Day 1 Fire Outlook for additional details. ..Bunting/Wendt.. 08/22/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1133 AM CDT Mon Aug 22 2022 Valid 221700Z - 231200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF CENTRAL IDAHO AND SOUTHWESTERN MONTANA... The forecast remains on track, and only minor adjustments were made to the ongoing Dry Thunderstorm highlights based on the latest observations and high-resolution guidance. In addition to the fire-weather concerns described below, 10-15 percent RH and breezy westerly surface winds could result in locally elevated conditions over portions of southeast OR, southwest ID, and north-central NV this afternoon. ..Weinman.. 08/22/2022 .PREV DISCUSSION... /ISSUED 0201 AM CDT Mon Aug 22 2022/ ...Synopsis... A shortwave trough evident in satellite imagery this morning near the Pacific Northwest coast is forecast to move eastward through the day. This trough will act to break down the upper-level ridge over the northern Intermountain West. Ahead of this trough, thunderstorms are expected to be ongoing early in the day across northeastern Oregon and southeastern Washington, where a mix of wet and dry thunderstorms are probable with PW values over 0.75". Farther east, strong heating will lead to warm, deeply mixed boundary layers across Idaho and southwestern Montana. By the afternoon, the shortwave trough will help to initiate scattered thunderstorms in an environment characterized by RH values below 20% and PW values less than 0.75". Given the dry fuels across the region, scattered coverage of dry thunderstorms warrants a critical fire-weather highlight. ...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 1256 PM CDT Sun Aug 21 2022 Valid 221200Z - 231200Z Only minor adjustments were made to the Dry Thunderstorm highlights based on the latest high-resolution guidance consensus. For details, see the previous discussion below. ..Weinman.. 08/21/2022 .PREV DISCUSSION... /ISSUED 0154 AM CDT Sun Aug 21 2022/ ...Synopsis... Upper ridging will weaken some across the Interior West as a mid-level trough traverses the Pacific Northwest and approaches the northern Rockies tomorrow/Monday. Ahead of the mid-level trough, lifting of mid-level monsoonal air across the northern Rockies will support at least isolated high-based thunderstorm development by late afternoon. Given the presence of patchy dry fuels, isolated dry thunderstorm highlights have been introduced. Locally Elevated dry and breezy conditions are also possible across the Harney Basin in southeast Oregon into southwest Idaho around afternoon peak heating. ...Please see www.spc.noaa.gov/fire for graphic product... Read more