Severe Storms

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1214 PM CDT Tue Aug 02 2022 Valid 031200Z - 041200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF LOWER MI AND THE MID MS VALLEY... ...SUMMARY... Scattered storms, some severe, are most likely from Lower Michigan into the Mid Mississippi Valley Wednesday, with at least isolated severe possible extending southwestward across Missouri and into eastern Kansas. ...Synopsis... Upper ridging is forecast to persist across the southern half of the CONUS throughout the period, keeping any stronger westerly flow aloft confined to the northern CONUS. A shortwave trough is expected to move through this western flow, beginning the period extended from western Ontario through the Upper Midwest. This shortwave should then progress eastward through the remainder of Ontario and the adjacent Upper Great Lakes, and into Quebec. Surface low attendant to this shortwave will take a similar track, moving just ahead of the parent shortwave, as associated cold front pushes southeastward through the Upper/Middle MS Valley and Upper Great Lakes. This cold front will interact with the warm and moist air mass covering the MS Valley, Upper Great Lakes, and OH Valley, triggering scattered to widespread thunderstorms across the region. ...Upper Great Lakes into the Lower MO Valley... Showers and thunderstorms will likely be ongoing within the warm-air advection regime preceding the front over northern Lower MI and adjacent portions of far eastern Upper MI. Stable low-levels will limit surface-based storms, but cold mid-level temperatures and low to mid-level moisture advection will support elevated thunderstorms, a few of which could be strong enough produce hail. The low-level stable layer will be relatively shallow, so a few downbursts could be strong enough to reach the surface. These storms should move east into northeastern Ontario throughout the morning, allowing for destabilization in their wake across northern Lower MI. Additional destabilization is anticipated ahead the front within the warm and very moist air mass through the Mid MS Valley and into the Ozark Plateau. By the afternoon, strong to very strong instability (i.e. MLCAPE from 2000-4000 J/kg) will likely be in place over this region, with little to no convective inhibition. Rapid thunderstorm development is expected as the front interacts with this airmass. The strongest mid-level flow is expected over Lower MI, decreasing with southward/southwestward extent. As a result, the highest potential for supercells is over Lower MI, with greater shear/outflow balance possible here as well. A more outflow-dominant, multicellular mode is likely farther south, from the Mid MS Valley to the Lower MO Valley. Damaging wind gusts will be the primary severe threat across the entire region, but potential for supercells and stronger low-level hodograph curvature suggests a tornado or two is possible across northern Lower MI. ...Southern AZ... Deep easterly flow is expected over the region, as the upper ridge shifts slightly northward towards the Four Corners vicinity. Thunderstorm development is anticipated over the higher terrain, with the deep easterly flow then favoring motion off the terrain in the well-mixing boundary layer of adjacent desert. Thermodynamic conditions favor strong outflow, and the potential for a few severe wind gusts. ..Mosier.. 08/02/2022 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1117 AM CDT Tue Aug 02 2022 Valid 021630Z - 031200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS NORTHERN UPPER MIDWEST... ...SUMMARY... Scattered large hail and damaging winds are possible across a portion of the northern Upper Midwest this evening into tonight. ...Northeast ND to northern WI/Upper MI... A vigorous shortwave trough will progress east across the southern Prairie Provinces into northwest ON through 12Z tomorrow. A deep surface cyclone will similarly track from southern SK to far northwest ON. A cold front arcing southwest from this cyclone will sweep into the Red River Valley by evening and likely reach western Lake Superior in the early morning. Initial severe potential should be focused near this boundary in the northeast ND vicinity during the early evening. Here, the trailing portion of supercell development may spread across the international border (more likely in eastern MB) as MLCIN wanes on the western periphery of upper 60s boundary-layer dew points. This activity may occur within a confined corridor of large buoyancy (MLCAPE of 2500-3000 J/kg), steep mid-level lapse rates (8-8.5 C/km from 700-500 mb), and an elongated/straight-line hodograph. These will conditionally favor a discrete supercell or two capable of producing very large hail and locally damaging wind gusts into northwest MN during the evening. Farther east, a leading mid-level perturbation near the MB/ND border in conjunction with low-level warm theta-e advection should support a separate corridor of severe potential from the St. Croix Valley to western Upper MI this evening into tonight. The environment along the northwest/southeast-oriented warm front will be conditionally favorable for intense supercells. However, confidence is low in whether surface-based supercells will develop and be sustained given the presence of the upstream elevated mixed-layer and warming 700-mb temperatures (near 14 C this evening over the Twin Cities). The more probable scenario is for elevated convection later this evening into the overnight. With ample upstream buoyancy and effective bulk shear, organized clusters with embedded supercell structures should pose a threat for both severe hail and damaging winds. ...Lower OH Valley/Mid-South... Thunderstorm clusters are ongoing but largely decaying in southern IL. Broader convective outflow has spread out well ahead of these clusters near the confluence of the MS/OH rivers and should be a limiting factor to a more robust threat. But strong boundary-layer heating to the south and west of this outflow could support resurgence of convective remnants into the Mid-South region later this afternoon amid modest mid to upper-level north-northwesterlies. Morning guidance such as the 12Z NAM and HRRR runs have terribly simulated ongoing convection, lowering confidence in areal extent of the isolated damaging wind threat today. ...Northern ME... Scattered showers are ongoing along and just ahead of a surface cold front shifting east from the St. Lawrence Valley. This activity should deepen somewhat as it impinges on the warming boundary layer across northern New England. Weak mid-level lapse rates will limit updraft intensity, although a modest combination of buoyancy/shear could favor some threat for isolated damaging winds. ...Central/southern FL Peninsula... Numerous thunderstorms will develop along the sea breezes and should eventually coalesce over the interior peninsula as they slowly spread inland later this afternoon. Light winds through 400 mb will limit potential for storm-scale organization with ambient effective bulk shear expected to only reach 8-15 kts. But large buoyancy and storm-scale mergers should support a threat for sporadic wet microbursts and localized strong gusts. ..Grams/Lyons.. 08/02/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1041 AM CDT Tue Aug 02 2022 Valid 021700Z - 031200Z ...CRITICAL FIRE WEATHER AREA FOR CENTRAL MONTANA INTO THE WESTERN DAKOTAS... The main adjustment for this update is to expand the Elevated risk area into portions of northwest South Dakota and to introduce an isolated dry-thunderstorm risk to portions of central/northern NE. The 12 UTC UNR sounding sampled very dry boundary-layer conditions atop a shallow nocturnal inversion. Latest surface observations show temperatures quickly warming into the mid 80s as the inversion begins to mix out. Relative humidity should quickly fall through the afternoon as mixing continues (though this may be hindered to a degree by increasing cloud cover). As pressure gradient winds increase this afternoon, elevated conditions appear probable. To the south across NE, richer moisture content is noted in morning soundings, which will help support adequate instability for high-based thunderstorms later this afternoon. Forecast soundings suggest a deep, well-mixed boundary layer will be in place as temperatures warm into the upper 90s and low 100s. A 2-3 km deep sub-cloud layer coupled with steep low-level lapse rates should be supportive of a few dry thunderstorms as well as gusty outflow winds. With ERCs across the region near the 90th percentile and 10-hour fuel moisture between 5-8%, a lightning-driven fire weather threat appears probable. ..Moore.. 08/02/2022 .PREV DISCUSSION... /ISSUED 0201 AM CDT Tue Aug 02 2022/ ...Synopsis... Along the northern periphery of a large-scale ridge centered over the western CONUS, a belt of deep/enhanced westerly flow will extend from the Pacific Northwest into the northern Rockies and adjacent High Plains. Multiple shortwave troughs will move through the westerly flow aloft during the day, with the strongest midlevel flow expected across parts of northern MT into northwest ND. ...Wind/RH... Deep boundary-layer mixing into the belt of strong flow aloft will result in a swath of 20-25 mph sustained westerly surface winds amid 15-20 percent RH across portions of MT into far western ND this afternoon. Given highly receptive fuels over this area, critical conditions are expected. Farther west, westerly downslope flow will favor warming/drying in the lee of the Cascades in WA into northern OR. Here, 15-20 mph sustained westerly surface winds coupled with 15-20 percent minimum RH will yield elevated to locally critical conditions. ...Dry Thunderstorms... Large-scale ascent accompanying the shortwave troughs and sufficient midlevel moisture/instability will support high-based thunderstorm development along and east of the Cascades in OR into northern CA and farther east in the northern Rockies. While many of these storms will be associated with accumulating rainfall given 1.0-1.2 in PW, isolated lightning-induced ignitions will still be possible on the periphery of precipitation cores. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No watches are valid as of Mon Aug 1 17:39:02 UTC 2022.

No Mesoscale Discussions are in effect as of Mon Aug 1 17:39:02 UTC 2022.

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1227 PM CDT Mon Aug 01 2022 Valid 021200Z - 031200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE UPPER MIDWEST NEAR THE INTERNATIONAL BORDER AND LAKE SUPERIOR... ...SUMMARY... Large hail and damaging to severe thunderstorm gusts are most likely Tuesday evening and night over parts of the Upper Midwest near the international border and Lake Superior. ...Synopsis... The large-scale pattern will continue to be characterized by an anticyclone over AZ/NM and vicinity, with ridging eastward over the southern Plains and Gulf Coast States. Mean troughing will persist over the Lower Great Lakes and central Appalachians, south of a strong synoptic cyclone moving erratically over the northern Hudson Bay region. However, that troughing should deamplify as heights fall in the upstream west-northwest flow belt, across the northwestern/north-central CONUS and adjoining Canada. Those height falls will be related largely to two strong shortwave troughs, the trailing one forecast to move from AK into BC. The leading shortwave trough, and most relevant for this forecast, is apparent in moisture-channel imagery from northwestern NC southward off the coast of Vancouver Island. This perturbation is forecast to move east-southeastward to the northern Rockies by the start of the period (02/12Z), penetrate a low-amplitude mean ridge during the day, followed by entering the confluent-flow belt south of the Hudson Bay cyclone. By 03/12Z, the trough should reach the southern part of the MB/ON provincial border, southward over western MN. There it should phase with an initially separate/weaker perturbation currently evident over parts of central CA and southern NV, that will be entrained into the northern-stream westerlies early day 2. At the surface, a cold front -- initially located over Lake Michigan, northern IL and southern IA -- should move eastward into the Lower Great Lakes and Northeast early day-2. The western segment of this frontal zone should become a warm front by the start of the period, extending from central IL northwestward to a frontal- wave low over eastern/southeastern ND, then northwestward to a primary low over southern SK. By 03/00Z, the latter low should move eastward to southern MB, with warm front over northwestern MN, southeastern MN/western WI, and central IL. A cold front will extend from the low across parts of northeastern ND, northwestern SD and central/southern WY. By 12Z, the warm front should reach the western U.P., central Lake Michigan, southwestern Lower MI, near the IN/OH line, to central KY. ...Upper Midwest... During the afternoon, a corridor of strong buoyancy will develop in the warm sector over southern/eastern MN, with strong diurnal heating and rich low-level moisture fostering MLCAPE in the 3000-4000 J/kg range. Still-favorable but lower values will extend northwestward toward the main surface low, with 1500-2500 J/kg possible over northeastern ND. However, strong MLCINH and nebulous deep-layer forcing cast great uncertainty on diurnal development near the warm front, over the eastern MN/WI area. Thunderstorms may develop during the afternoon and evening over northeastern ND and northwestern MN, as well as the Boundary Waters, MN Arrowhead and western Lake Superior region. Activity northeast of the warm front will be elevated, but still pose a threat for severe hail and isolated damaging gusts. Development over the warm sector is more uncertain in timing/coverage due to strong EML-related capping, but the potential for at least isolated to widely scattered surface-based thunderstorms will increase as the mid/upper trough approaches and associated mass response strengthens overnight. That mass response also will include strengthening of the associated zone of low-level warm advection, moisture transport and isentropic lift to LFC over the warm-frontal zone. The entire convective regime is expected to shift eastward or east- southeastward across the lake, and perhaps northern/eastern parts of the Upper Peninsula, through the period. Forecast soundings early in the episode suggest very steep low/ middle level lapse rates above the warm-frontal surface, supporting MLCAPE and elevated MUCAPE increasing to the 2500-3500 J/kg range, amidst effective-shear magnitudes of 40-50 kt (perhaps higher). This will support supercell and large-hail potential, especially early in the convective cycle and along the inflow (south to southwest sides) of any resulting complex, where relatively unimpeded access persists to the 45-55-kt nocturnal LLJ. The track of this convective regime remains somewhat uncertain, but it should outpace the advance of the warm front and become more elevated with time. Unconditional probabilities are being extended eastward over more of the U.P. to accommodate the threat from this activity. ...Northeastern Plains... A conditional threat exists for strong-severe gusts with thunderstorms that may form during the evening and overnight, ahead of the cold front over eastern parts of SD and northeastern NE. While moisture/buoyancy will be less than areas farther northeast near the warm front, increasing large-scale ascent and cooling aloft will occur ahead of the southern/phased branch of the shortwave trough. A residual very warm and deeply mixed boundary layer from prior diurnal heating will foster the potential for strong-severe gusts with any convection that can develop; however, storm coverage appears too uncertain for more than marginal unconditional probabilities at this time. ...Lower Ohio Valley to Ozarks... Scattered showers and thunderstorms may be ongoing over northern and/or eastern parts of this region from prior/overnight MCS activity discussed in more detail in the day-1 outlook. This convection should leave outflow/differential-heating boundaries to focus additional, diurnal development. Though deep-layer shear will be weak, strong diabatic heating away from any persistent cloud cover, combined with very rich low-level moisture (dewpoints commonly in the 70s F) will underlie moderately steep midlevel lapse rates of around 6.5 deg C/km, within a deep troposphere. The result should be areas of 3000-4000 J/kg MLCAPE. MLCINH will be weak east of the EML, supporting diurnal development and perhaps upscale growth into one or more wind-producing clusters. Any more-focused area of potential within the broader outlook will be very dependent on mesoscale processes yet to evolve, and this outlook area may shift or change shape substantially as time gets closer. ..Edwards.. 08/01/2022 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1121 AM CDT Mon Aug 01 2022 Valid 011630Z - 021200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OH VALLEY AND MID-MO VALLEY... ...SUMMARY... Scattered severe thunderstorms, mainly in the form of damaging gusts and a tornado or two, will be possible, centered on this evening into early tonight across the Ohio Valley. A swath of mainly severe wind gusts and some hail is also possible across parts of northern Nebraska to western Iowa this evening. ...OH Valley... Decayed remnants of an early morning MCS have spread into southwest OH and northern KY. Subsidence in its wake and the southern progression of outflow render uncertainty on when/where redevelopment will occur later today. Large buoyancy will develop from the Mid-MO to Lower OH Valleys amid an elevated mixed layer extending southeast from the north-central Great Plains with peak MLCAPE approaching 4000 J/kg centered on southern IL. Weak low-level warm advection atop the residual convective outflow/baroclinic zone will likely be the primary driver for redevelopment. This will become more likely into the early to mid-evening, especially with eastern extent where mid-level lapse rates are weaker. Adequate low-level veering of the wind profile with height but backing of mid to upper flow should support predominantly cluster with embedded supercell modes. Damaging winds and marginally severe hail will be the main threats, though a tornado or two could occur with embedded supercells based on rich low-level moisture (70-74 F boundary-layer dew points) and hodograph curvature (effective SRH near 200 m2/s2). Overnight, severe potential should wane as convective outflows spread southeast away from the instability axis. ...North-central/northeast NE to the Mid-MS Valley... At least isolated thunderstorm development is expected near the intersection of the dryline, lee trough, and western flank of the Mid-MO Valley buoyancy plume. Steep low to mid-level lapse rates and boundary-layer dew points in the 60s will yield a pronounced gradient in MLCAPE, nearing 3000 J/kg over the Mid-MO Valley. Weak southerly low-level flow beneath northwesterlies that strengthen with height from the mid to upper levels will support a couple supercells initially developing with a threat for isolated large hail and severe wind gusts. With time this evening, a small cluster may spread east across the MO River into IA as warm advection intensifies. Guidance is quite varied in how this evolution will take place, likely owing to the modest large-scale ascent, robust MLCIN south of the baroclinic zone, and tight MLCAPE gradient to the north. It is plausible that a corridor of severe wind gust and hail potential may be maintained into the overnight to the east of the Mid-MS Valley. ..Grams/Lyons.. 08/01/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1036 AM CDT Mon Aug 01 2022 Valid 011700Z - 021200Z Expanded the IsoDryT slightly farther west to cover areas near the Mckinney and China2 fires where some thunderstorms are possible. These thunderstorms are expected along the moisture gradient and have the potential to be both wet and dry. Given the presence of large fire in the area, decided it would be best to expand the IsoDryT area slightly to cover this region. Also expanded the critical delineation across southeast Montana, northeast Wyoming, and far northwest South Dakota. Some of the strongest winds may actually occur in this region given the presence of a low-level jet and a passing mid-level jet maximum. ..Bentley.. 08/01/2022 .PREV DISCUSSION... /ISSUED 0200 AM CDT Mon Aug 01 2022/ ...Synopsis... A large-scale ridge will remain centered over the western CONUS, while a belt of enhanced west-northwesterly midlevel flow extends from the Pacific Northwest into the northern/central Plains along the northern periphery of the ridge. Within the west-northwesterly flow, an embedded shortwave trough and accompanying strong flow aloft will cross the northern Rockies, while a surface low deepens over eastern MT. ...Northern Rockies into the adjacent High Plains... As the belt of enhanced west-northwesterly flow overspreads the Rockies and adjacent High Plains, downslope warming/drying and deep boundary-layer mixing will result in a broad area of elevated fire-weather conditions. Along the periphery of the deepening surface low, a corridor of stronger sustained west-northwesterly surface winds near 20 mph will overlap 10-15 percent minimum RH across portions of central into eastern MT -- where critical fire-weather conditions are forecast. ...Lee of the Cascades in WA and northern OR... The enhanced west-northwesterly downslope flow will support elevated to locally critical conditions in the lee of the northern Cascades, where 15-20 mph westerly surface winds will overlap 10-15 percent RH. ...Dry Thunderstorms... Along the northern periphery of the ridge, a series of subtle midlevel impulses coupled with sufficient midlevel moisture/instability will favor high-based thunderstorms from the Cascades eastward into the northern Rockies. While many of these storms will be a hybrid wet/dry mode, any lightning strikes away from precipitation cores could lead to new fire starts owing to highly receptive fuels over the area. ...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 1245 PM CDT Sun Jul 31 2022 Valid 011200Z - 021200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE OHIO VALLEY... ...SUMMARY... At least isolated severe storms are expected mainly across parts of the Midwest and Ohio Valley Monday afternoon and evening. ...Midwest/Ohio Valley including Indiana/Ohio/Kentucky... Have introduced a categorical Slight Risk for parts of the region, including portions of Indiana/Ohio/Kentucky. Moderate to strong destabilization is expected into Monday afternoon especially across the lower/middle Ohio River Valley, northward across eastern Indiana and western/central Ohio. This will be near/ahead of a southeastward-advancing front, and to the south-southwest of possible residual overnight convection and cloud cover that may be located over Michigan/northern Indiana vicinity Monday morning. An amplifying belt of moderately strong westerlies (30-50 kt at 500 mb) will influence forcing for ascent and probable storm development/longevity Monday afternoon and evening. This could potentially include some supercells aside from more prevalent multicells and southeastward-moving bands/linear segments. Wind damage will be the primary risk overall. ...Central Plains/Lower Missouri Valley... An initially southward-settling front will decelerate/stall and begin to return northward late Monday afternoon and Monday night. Moderately strong northwesterly winds will overlie the front. The potential for deep convective development should remain limited south of the front owing to strong capping, however isolated storm development may occur late Monday afternoon and night near/north of the boundary, particularly across portions of Nebraska where a near-boundary zone of moderate to strong destabilization should be maximized across much of central Nebraska to southeast Nebraska. Where storms do form, a few supercells could occur, along with the potential for storm organization and upscale growth near/northeast of the boundary. Large hail and damaging winds may occur, with damaging winds a viable possibility on the cool side of the front owing to the steep lapse rate environment/dry air above the more stable boundary layer. Portions of central and possibly east-central/northeast Nebraska could ultimately warrant an upgrade to a Slight Risk pending higher confidence in convective initiation/deep convective development within an otherwise severe-favorable environment. ...North Dakota... The main thunderstorm potential should be relegated to the morning and/or activity potentially crossing the international border later in the day near/north-northeast of a front across the region. A few strong to severe storms could occur given the strong wind profiles and moderate surface-based buoyancy near the front and elevated buoyancy to its east-northeast. ..Guyer.. 07/31/2022 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1245 PM CDT Sun Jul 31 2022 Valid 011200Z - 021200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE OHIO VALLEY... ...SUMMARY... At least isolated severe storms are expected mainly across parts of the Midwest and Ohio Valley Monday afternoon and evening. ...Midwest/Ohio Valley including Indiana/Ohio/Kentucky... Have introduced a categorical Slight Risk for parts of the region, including portions of Indiana/Ohio/Kentucky. Moderate to strong destabilization is expected into Monday afternoon especially across the lower/middle Ohio River Valley, northward across eastern Indiana and western/central Ohio. This will be near/ahead of a southeastward-advancing front, and to the south-southwest of possible residual overnight convection and cloud cover that may be located over Michigan/northern Indiana vicinity Monday morning. An amplifying belt of moderately strong westerlies (30-50 kt at 500 mb) will influence forcing for ascent and probable storm development/longevity Monday afternoon and evening. This could potentially include some supercells aside from more prevalent multicells and southeastward-moving bands/linear segments. Wind damage will be the primary risk overall. ...Central Plains/Lower Missouri Valley... An initially southward-settling front will decelerate/stall and begin to return northward late Monday afternoon and Monday night. Moderately strong northwesterly winds will overlie the front. The potential for deep convective development should remain limited south of the front owing to strong capping, however isolated storm development may occur late Monday afternoon and night near/north of the boundary, particularly across portions of Nebraska where a near-boundary zone of moderate to strong destabilization should be maximized across much of central Nebraska to southeast Nebraska. Where storms do form, a few supercells could occur, along with the potential for storm organization and upscale growth near/northeast of the boundary. Large hail and damaging winds may occur, with damaging winds a viable possibility on the cool side of the front owing to the steep lapse rate environment/dry air above the more stable boundary layer. Portions of central and possibly east-central/northeast Nebraska could ultimately warrant an upgrade to a Slight Risk pending higher confidence in convective initiation/deep convective development within an otherwise severe-favorable environment. ...North Dakota... The main thunderstorm potential should be relegated to the morning and/or activity potentially crossing the international border later in the day near/north-northeast of a front across the region. A few strong to severe storms could occur given the strong wind profiles and moderate surface-based buoyancy near the front and elevated buoyancy to its east-northeast. ..Guyer.. 07/31/2022 Read more

No watches are valid as of Sun Jul 31 17:50:02 UTC 2022.

MD 1619 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR CENTRAL/EAST NC...FAR SOUTH-CENTRAL/SOUTHEAST VA
Mesoscale Discussion 1619 NWS Storm Prediction Center Norman OK 1138 AM CDT Sun Jul 31 2022 Areas affected...Central/East NC...Far South-Central/Southeast VA Concerning...Severe potential...Watch unlikely Valid 311638Z - 311915Z Probability of Watch Issuance...20 percent SUMMARY...Multicell thunderstorms capable of damaging wind gusts will persist across the region through the afternoon. Additionally, a supercell or two is possible later this afternoon, with an attendant risk of damaging wind gust and/or a brief tornado. DISCUSSION...The air mass across north-central/northeast NC and adjacent portions of far south-central/southeast VA has quickly destabilized amid filtered diurnal heating and ample low-level moisture. Thunderstorm coverage is expected to gradually increase over the next few hours, as modest low-level convergence persists near and south of the wavy warm front extending from south-central VA into far northeast NC. Much of this thunderstorm activity will occur south of the stronger mid-level flow, limiting the deep-layer vertical shear and likely leading to a predominantly multicellular, outflow-dominant storm mode. Primary severe risk with any of these storms is water-loaded downbursts. Later this afternoon, ascent may be augmented slightly by the shortwave trough moving through the Upper OH Valley. This shortwave will also contribute to a modest increase in the mid-level flow. While still favorable mostly multicells, these condition could also support a supercell or two. Primary risk would continue to be damaging wind gust, although a brief tornado or two could also occur. ..Mosier/Grams.. 07/31/2022 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...AKQ...MHX...RAH...ILM...RNK... LAT...LON 34637776 35357923 35767997 36437998 36927923 36867767 36677674 36367582 35607564 34697624 34637776 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1126 AM CDT Sun Jul 31 2022 Valid 311700Z - 011200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN OREGON INTO EXTREME NORTHERN CALIFORNIA... Only minor modifications were made to the ongoing IsoDryT delineation, primarily to trim the western edge where fuels are not as favorable. ..Bentley.. 07/31/2022 .PREV DISCUSSION... /ISSUED 0222 AM CDT Sun Jul 31 2022/ ...Synopsis... Upper ridging will remain in place across the western U.S. today while a mid-level trough ejects into the Plains states during the afternoon. Downslope flow along the higher terrain in western Montana and modest surface lee troughing across the northern Plains may support at least locally dry and windy conditions for a few hours. The bigger concern for wildfire-spread potential today exists across the Pacific Northwest. Modest deep-layer ascent with passing subtle mid-level impulses will work in tandem with afternoon peak heating to support the initiation of scattered high-based thunderstorms across portions of the Pacific Northwest, where fuels have recently become highly receptive to fire spread (based on the latest observations). The previous day's storms may have slightly dampened fuels locally. However, the relatively higher number of thunderstorm expected today, combined with the critically dry fuels (especially in lower-terrain areas) necessitates the addition of scattered dry thunderstorm highlights. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1126 AM CDT Sun Jul 31 2022 Valid 311700Z - 011200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN OREGON INTO EXTREME NORTHERN CALIFORNIA... Only minor modifications were made to the ongoing IsoDryT delineation, primarily to trim the western edge where fuels are not as favorable. ..Bentley.. 07/31/2022 .PREV DISCUSSION... /ISSUED 0222 AM CDT Sun Jul 31 2022/ ...Synopsis... Upper ridging will remain in place across the western U.S. today while a mid-level trough ejects into the Plains states during the afternoon. Downslope flow along the higher terrain in western Montana and modest surface lee troughing across the northern Plains may support at least locally dry and windy conditions for a few hours. The bigger concern for wildfire-spread potential today exists across the Pacific Northwest. Modest deep-layer ascent with passing subtle mid-level impulses will work in tandem with afternoon peak heating to support the initiation of scattered high-based thunderstorms across portions of the Pacific Northwest, where fuels have recently become highly receptive to fire spread (based on the latest observations). The previous day's storms may have slightly dampened fuels locally. However, the relatively higher number of thunderstorm expected today, combined with the critically dry fuels (especially in lower-terrain areas) necessitates the addition of scattered dry thunderstorm highlights. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1116 AM CDT Sun Jul 31 2022 Valid 311630Z - 011200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS EAST-CENTRAL/SOUTHEAST MN INTO WEST-CENTRAL WI... ...SUMMARY... A tornado or two, scattered damaging winds, and isolated severe hail are most likely across a portion of the Upper Mississippi Valley between about 5 to 9 PM CDT. ...Synopsis... A low-amplitude shortwave trough centered on the MB/ND border area will progress east-southeast into the western Great Lakes region tonight. Associated surface cold front over the eastern Dakotas will similarly push east-southeast across the Upper MS Valley through this evening. ...Upper MS Valley... Low-level warm-advection-driven convection is ongoing across south-central MN to northwest IA, but decaying ahead of the cold front. Stronger surface heating and greater boundary-layer moisture in the wake of this activity will support a confined plume of moderate buoyancy with MLCAPE increasing to 1500-2000 J/kg by 21-00Z. Initial surface-based thunderstorm development is expected along the northern periphery of the buoyancy gradient in northwest to north-central MN. Convection will likely build south along the front through central to east-central MN during the early evening, with lower confidence in southern extent towards the IA border. Surface temperature-dew point spreads will be marginally large initially, but favorable low-level hodograph curvature/SRH will be sufficient for a threat of a tornado or two. Otherwise, around 30-35 kt effective bulk shear should yield a mixed cluster/embedded supercell mode, with the latter tending to be favored farther south where shear is slightly stronger and convection should be more semi-discrete. Damaging winds should be somewhat more favored in terms of coverage, but isolated severe hail is anticipated as well. Convection will likely diminish tonight as it spreads east of the confined surface-based buoyancy plume deeper into WI. ...NE/IA... A conditional supercell threat will exist across portions of northern to western IA along the surface cold front centered on early evening, in the wake of decaying elevated activity approaching the region. Isolated thunderstorms are more probable into the southwest NE area where MLCIN will be minimal at peak heating, along the western extent of the central Great Plains buoyancy plume. Weaker deep-layer shear should tend to favor a more marginal intensity threat this far west. ...NC/southern VA... A weak and wavy surface warm front has drifted north into far southwest VA and northeast NC, in advance of a low-amplitude shortwave impulse over the Upper OH Valley. The southern fringe of modestly stronger mid-level westerlies (represented by effective bulk shear near 30 kt) will overlie the baroclinic zone, where there will be some enhancement to low-level hodograph curvature (0-1 km SRH around 100 m2/s2). Despite poor mid-level lapse rates, a mix of multicell clusters and transient supercells are expected across the baroclinic zone through about dusk. A brief weak tornado and isolated damaging wind gusts in water-loaded downdrafts will be possible. ...Southern AZ... The next perturbation within the monsoonal moisture plume is aiding morning thunderstorms over a portion of northwest Sonora and will likely yield a period of mid-level drying across southeast AZ in its wake. The midlevel drying and reduction in clouds will aid surface heating, but also casts some doubt on how widespread convection will be across the higher terrain in southeast AZ this afternoon. 15-20 kt southeasterly mid-level steering flow will support potential for isolated cells and small clusters to spread across the lower deserts of south-central AZ through about dusk with isolated severe wind gusts possible. ...Lower CO Valley to OR... Very isolated severe wind gusts are possible in pulse microbursts, but overall coverage is anticipated to be less than 5 percent over such a large swath around the Great Basin mid-level anticyclone. ..Grams/Lyons.. 07/31/2022 Read more

No watches are valid as of Sat Jul 30 17:42:01 UTC 2022.

No Mesoscale Discussions are in effect as of Sat Jul 30 17:42:01 UTC 2022.

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Sat Jul 30 2022 Valid 311200Z - 011200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS MINNESOTA/WESTERN WISCONSIN... ...SUMMARY... Severe thunderstorms will be possible across parts of Minnesota and western Wisconsin Sunday afternoon and evening. Other more isolated severe storms could also occur across parts of the Carolinas and central Plains. ...Minnesota/western Wisconsin... Have introduced a categorical Slight Risk for parts of the region. A clipper-type shortwave trough will spread southeastward over the region amidst amplifying westerlies over the Dakotas/Upper Midwest through Sunday night. Scattered thunderstorm development seems probable near a southeastward-moving front across Minnesota Sunday afternoon. A favorable colocation of moderate buoyancy (2000+ J/kg MLCAPE) and effective shear (40 kt) is expected particularly across the southern half of Minnesota. This could support some initial supercells, with storms likely to subsequently merge and potentially grown upscale during the evening across southeast Minnesota toward western Wisconsin. Large hail and damaging winds should be the primary hazards. ...Nebraska/western Iowa... The region will be influenced by the southern periphery of the amplifying shortwave trough over the Dakotas/Upper Midwest. Heating/convergence near the southeastward-moving front (and pre-frontal trough) should be conducive for at least isolated thunderstorm development Sunday late afternoon/early evening, some of which could produce hail and/or severe-caliber wind gusts. ...Carolinas/southern Appalachians... The persistent/convectively reinforced front across the region may transition a bit northward into Sunday, with a moist airmass remaining near the boundary and to its south. Although the details of destabilization and preferred corridors of more appreciable thunderstorm development are a bit uncertain, it currently appears that destabilization will be regionally maximized across the Carolinas. This should coincide with a modestly enhanced belt of westerlies aloft. Some of the stronger updrafts/downdrafts could produce wet microbursts capable of localized wind damage Sunday afternoon through early evening. ...Southern Arizona/Lower Colorado River Valley... The southern CONUS upper ridge should build a bit westward toward the region on Sunday, with some potential for a further enhancement to east-southeasterly mid-level winds particularly across southern Arizona. Some questions exist regarding the lingering influence/cloud cover of thunderstorms from later today and tonight into Sunday. However, if confidence increases in boundary layer recovery/destabilization, microburst-related severe wind probabilities could be warranted in later outlooks. ..Guyer.. 07/30/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1138 AM CDT Sat Jul 30 2022 Valid 301700Z - 311200Z Expanded the IsoDryT delineation slightly farther north in Oregon and a bit farther south across northern California based on morning forecast soundings and CAM guidance. Otherwise, no changes were necessary. See previous discussion below. ..Bentley.. 07/30/2022 .PREV DISCUSSION... /ISSUED 0146 AM CDT Sat Jul 30 2022/ ...Synopsis... An upper ridge will persist across the western U.S. through the day today, with a mid-level impulse expected to pivot around the ridge over the northern Rockies. The mid-level impulse will support dry and breezy surface conditions across eastern Montana during the afternoon, where fuels are becoming receptive to wildfire spread, necessitating the addition of Elevated highlights. Meanwhile, upslope flow of a marginally unstable airmass along the southern Cascades may support isolated high-based thunderstorm development during the afternoon. Fuels continue to efficiently dry in this area, supporting lightning ignition potential and warranting the addition of isolated dry thunderstorm highlights. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1100 AM CDT Sat Jul 30 2022 Valid 301630Z - 311200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF NORTHEASTERN MONTANA AND THE DAKOTAS... ...SUMMARY... Isolated damaging gusts and large hail may occur this afternoon into tonight across northeastern Montana into central North/South Dakota. ...Northern Plains... A shortwave trough along the northern periphery of a western US mid-level anticyclone will move out of southern Canada across portions of northern MT and ND late this afternoon and evening. At the surface, a lee trough will develop ahead of the emerging shortwave, drawing low 60s F surface dewpoints north across the Dakotas. Strong heating and mixing of the airmass along the surface trough may support isolated storms this afternoon. While generally less than 25 kt, effective shear may favor organized multi-cell clusters with an isolated risk for damaging wind gusts and or hail. Overall confidence in severe coverage is low, but the highest likelihood of severe wind/hail within this regime will be from southern ND into central SD where hi-res guidance does show some convective signal. As the main shortwave emerges later in the evening, a cold front and associated surface low will move from southern SK into northeastern MT and far western ND. While poorly timed with the diurnal cycle, strong frontal convergence may still support isolated storms along and behind the front where low 60s F surface dewpoints should pool. 500-1000 J/kg of MUCAPE and 30-40kt of effective shear may allow some storm organization with the potential for damaging wind gusts and or severe hail. However, uncertainty on severe potential/coverage remains high given the poor timing of the main shortwave and the anafrontal nature of any convection that can develop. ...Southern US... Evident on morning visible imagery, a weak quasi stationary front will serve as a focus for another day of diurnal thunderstorms from the southern Plains into the southeastern US. Warm and moist through much of the lower atmosphere along and south of the boundary, the weakly sheared airmass will support scattered to numerous thunderstorms from eastern OK to the Carolinas. While an occasional gust may occur with any more concentrated storm clusters, overall predictability remains too low for the inclusion of severe probabilities. ..Lyons/Grams.. 07/30/2022 Read more