Severe Storms

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1156 AM CDT Tue Aug 16 2022 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE SOUTHEAST... ...SUMMARY... Isolated strong to severe thunderstorms capable of producing mainly wind damage appear possible Wednesday across parts of the Southeast. ...Southeast... An upper low over the Northeast and its attendant trough extending across much of the eastern half of the CONUS will persist on Wednesday. At the surface, a cold front will slowly develop southward across the southern Plains and much of the Deep South. The cold front will be a focus for thunderstorm development through the afternoon/evening. Some of these storms may be strong to severe, mainly posing a threat for damaging gusts. West/northwesterly deep-layer flow will remain modest on the southern periphery of the upper trough, though 20-35 kt of flow above 750 mb will support sufficient effective shear magnitudes for some storm organization. Weaker low-level winds and PW values near 2 inches amid 1500-2500 J/kg MLCAPE will support water loaded downdrafts capable of producing strong/isolated severe gusts. The overall severe threat should diminish after sunset with loss of daytime heating and increasing boundary-layering inhibition. ..Leitman.. 08/16/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1148 AM CDT Tue Aug 16 2022 Valid 161700Z - 171200Z ...NO CRITICAL AREAS... ...Northern Sierra and southern Cascades Dry Thunder... Confidence in thunderstorm development along the higher terrain has decreased further this morning as much of the monsoon moisture plume remains farther south. With only weak ascent moving inland and scant buoyancy available, the risk for dry lightning appears very low. A lightning flash or two may still be possible with weak convection anchored to the terrain, but coverage will be too low to maintain probabilities for dry thunder. As such, the IsoDryT area has been removed. See the prior discussion for additional information. ..Lyons.. 08/16/2022 .PREV DISCUSSION... /ISSUED 0153 AM CDT Tue Aug 16 2022/ ...Synopsis... Upper ridging will prevail across the western and central CONUS today, with weak forcing/surface wind fields limiting significant wildfire-spread concerns across most of the CONUS. The primary exception would be portions of the Pacific Northwest, where richer monsoonal moisture should begin to impinge on the Pacific Northwest. By late afternoon/early evening, a thunderstorm or two could develop across the southern Cascades. Despite the very low probability of thunderstorm development, isolated dry thunderstorm highlights were maintained for the Day 1 Fire Weather Outlook given the presence of very dry fuels across the region. ...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 1126 AM CDT Tue Aug 16 2022 Valid 161630Z - 171200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON/EVENING FROM THE LOWER MS VALLEY TO THE OZARKS AND SOUTHERN HIGH PLAINS...AND ACROSS NORTHERN MN AND VICINITY... ...SUMMARY... Isolated damaging winds and marginally severe hail will be possible this afternoon/evening for parts of the Ozarks, lower Mississippi Valley, southern High Plains, and northern Minnesota vicinity. ...Ozarks/lower MS Valley/southern Plains through this evening... A diffuse MCV over northern MO will move southeastward today, within a band of 30-40 kt midlevel flow (per regional VWPs). Elevated convection has persisted from overnight into this morning in a zone of warm advection over southern MO, and clouds/differential heating will reinforce a baroclinic zone across southern/western AR into southwestern MO. This baroclinic zone will serve to focus additional thunderstorm development later this afternoon near the MO/AR/OK border intersection, and storms will subsequently move southeastward through the evening. There will be a narrow corridor of overlap of moderate buoyancy and somewhat stronger vertical shear along the surface boundary where some low-end supercell potential will exist (at the northeast edge of the stronger surface heating and deeper mixing). Isolated wind damage and marginally severe hail will be possible with any supercells that form. Otherwise, a few cells/clusters may form along the slow-moving front farther southeast toward central MS, where MLCAPE of 2500-3000 J/kg and DCAPE near 1000 J/kg will support the potential for isolated strong/damaging downbursts. Buoyancy will be weaker in the warm sector farther west along the cold front in OK/eastern TX Panhandle and storm coverage is in question. If storms do form, deep inverted-v profiles and large DCAPE (> 1500 J/kg) will support the threat for isolated microbursts. ...Southeast CO/northeast NM vicinity this afternoon/evening... Low-level flow is expected to become weak upslope in a post-frontal environment from southeast CO into northeast NM by later this afternoon. Though midlevel lapse rates will not be particularly steep within the lingering monsoonal moisture plume, boundary-layer dewpoints in the upper 50s to lower 60s and surface heating will result in MLCAPE of 500-1000 J/kg with minimal convective inhibition. Scattered thunderstorm development is expected by mid afternoon along and just east of the higher terrain, and convection will spread east-southeastward onto the High Plains. Steepening low-level lapse rates and clustering/upscale growth may support isolated strong outflow gusts. ...Northern MN and vicinity this afternoon/evening... A convectively-enhanced shortwave trough near the MN/ON/MB border intersection will move slowly east-southeastward near the international border through the afternoon. An associated wind shift/weak cold front extends west-southwestward from northwest MN into eastern ND. Ascent along the wind shift, in combination with pockets of surface heating and boundary-layer dewpoints in the 60s, will support scattered thunderstorm development this afternoon/evening. MLCAPE of 1000-2000 J/kg and modest vertical shear will support isolated marginally severe hail and strong/damaging outflow gusts. ..Thompson/Wendt.. 08/16/2022 Read more

No watches are valid as of Mon Aug 15 18:01:02 UTC 2022.

No Mesoscale Discussions are in effect as of Mon Aug 15 18:01:02 UTC 2022.

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1211 PM CDT Mon Aug 15 2022 Valid 161200Z - 171200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE OZARK PLATEAU INTO THE LOWER MS VALLEY... ...SUMMARY... Isolated strong to severe thunderstorms appear possible Tuesday across parts of the Ozarks into the lower Mississippi Valley and central Gulf Coast. Occasional damaging winds should be the main threat, but some hail may also occur. ...Synopsis... A corridor of modest northwesterly flow aloft is expected to be in place from the northern Plains through the Mid-South on Tuesday morning, situated between upper ridging from the southern Plains into the Great Basin and upper troughing from the Northeast into FL. This western ridge/eastern trough upper pattern is forecast to persist throughout the period as a shortwave trough moves through the corridor of northwesterly flow from the Lower MO Valley through the TN Valley into the Carolinas. Surface pattern early Tuesday morning will likely feature a low over southeast KS, with a diffuse stationary boundary extending southeastward from this low to another low near the southern GA/SC border. Boundary over the Southeast is expected to remain largely in place, while a cold front progresses southward through OK and the TX Panhandle. ...Ozark Plateau into the Lower MS Valley... Numerous showers and thunderstorms are forecast to be ongoing at the beginning of the period over MO, within the warm-air advection to the northeast of the surface low mentioned in the synopsis. This early morning activity should persist into the early afternoon before diminishing in tandem with weakening low to mid-level westerly flow. Addition storm development is anticipated during the afternoon in the vicinity of the stationary front, where low-level convergence will combine with ample low-level moisture and strong daytime heating to foster convective initiation. These storms will be displaced south of the stronger mid-level flow, but veering wind profiles will still support moderate vertical shear and the potential for a few stronger, more organized storm structures, particularly across northern and central AR. A mix of multicells and marginal supercells is possible, with isolated strong to damaging winds and some hail both possible. Farther south, a more buoyant but less sheared air mass is anticipated, supporting the threat for a few water-loaded downbursts with any stronger, more persistent storms. ..Mosier.. 08/15/2022 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1127 AM CDT Mon Aug 15 2022 Valid 151630Z - 161200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON/EVENING ACROSS PARTS OF THE CAROLINAS... ...SUMMARY... Isolated severe thunderstorms may occur today across parts of the Carolinas. An isolated severe wind/hail threat may also develop across parts of the central and northern Plains this afternoon and evening. ...Central Carolinas this afternoon/evening... Pockets of surface heating and boundary-layer dewpoints in the mid 60s will contribute to some destabilization this afternoon across the Piedmont, with thunderstorm development expected to focus along a weak surface front/trough. Midlevel lapse rates will remain poor over this area, but the daytime heating will still boost MLCAPE to near 1000 J/kg. Embedded speed maxima rotating around the southwest periphery of a midlevel trough over the Northeast will combine with weak low-level winds (veering with height) to result in sufficient deep-layer vertical shear for organized/supercell storms. A few damaging gusts appear to be the main threat with these storms later this afternoon into this evening. Scattered thunderstorms will along be possible farther west along the wind shift across GA/AL, where vertical shear will be weaker. Primarily multicell storms will be capable of producing isolated wind damage in this corridor later this afternoon. ...Northern Plains later this afternoon/evening... A surface cold front has been reinforced by outflow with morning convection across ND, and surface heating will be slowed some by lingering clouds along the boundary into early afternoon. Still, pockets of stronger surface heating and steep midlevel lapse rates noted in the 12z BIS sounding will support MLCAPE of 1500-2000 J/kg by late afternoon along the front/outflow. Vertical shear will be relatively weak, but afternoon/evening storms along the boundary will be capable of producing isolated large hail and damaging outflow gusts. ...Central Plains later this afternoon into early tonight... In the wake of overnight convection, an MCV is moving eastward over northeast NE. The MCV is located well north of the surface warm sector, and outflow from the overnight storms reinforced a boundary from northeast CO to near the KS/NE border. Clouds to the cool side of the boundary and stronger surface heating to the south will tend to reinforce the boundary through the afternoon, which should serve as a focus for thunderstorm later this afternoon through late evening. Midlevel lapse rates are not particularly steep within the monsoonal moisture plume emanating from the central Rockies, but there will be steep low-level lapse rates in the stronger surface heating/deeper mixing across northern KS. A cluster or two of storms on the cool side of the boundary could have modest organization in association with the belt of 25-30 kt midlevel westerlies atop surface easterly winds, and isolated high-based storms may form this afternoon across northern KS. Isolated strong/damaging gusts may occur with the strongest storms late this afternoon into early tonight. ...Rio Grande Valley of TX this afternoon... A well-defined tropical low is moving slowly west-northwestward and is located just west of Eagle Pass as of 16z. Some supercell structures have been noted this morning within convective banding to the east of the center over South TX, coincident with a belt of 30-40 kt low-midlevel flow and modestly enhanced effective SRH (100-150 m2/s2). The overlap of the somewhat stronger wind profiles and low-level hodograph curvature with northwest edge of the surface temperatures in the 80s and dewpoints in the mid-upper 70s will continue to support the potential for isolated supercells and a weak tornado or two through the afternoon. ..Thompson/Wendt.. 08/15/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1131 AM CDT Mon Aug 15 2022 Valid 151700Z - 161200Z ...NO CRITICAL AREAS... Fire weather concerns are limited today due to the lack of stronger flow aloft. Brief locally gusty winds may develop across portions of the southern Plains near a lee low this afternoon, but gusts should not exceed 15-20 mph. Elsewhere, hot and dry conditions will persist beneath the upper ridge, but the absence of strong winds will keep fire weather conditions localized and minimal. ..Lyons.. 08/15/2022 .PREV DISCUSSION... /ISSUED 0152 AM CDT Mon Aug 15 2022/ ...Synopsis... An upper ridge will persist over the western and central CONUS today as multiple mid-level impulses crest the ridge. Overall weak flow aloft and associated forcing around the ridge should limit widespread significant wildfire spread concerns. However, locally dry and breezy surface conditions may occur in terrain-favoring areas with dry fuel beds across portions of the Pacific Northwest into the northern Rockies and perhaps the southern Plains. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No watches are valid as of Sun Aug 14 17:56:02 UTC 2022.

No Mesoscale Discussions are in effect as of Sun Aug 14 17:56:02 UTC 2022.

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1228 PM CDT Sun Aug 14 2022 Valid 151200Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF GEORGIA INTO THE CAROLINAS AND SOUTHERN VIRGINIA...AND PORTIONS OF THE NORTHERN AND CENTRAL PLAINS... ...SUMMARY... Isolated strong to severe thunderstorms may occur Monday across parts of Georgia into the Carolinas and southern Virginia, and for portions of the northern and central Plains. Occasional damaging winds and hail should be the main threats. ...Synopsis... Upper ridging, centered over the southern High Plains, is forecast to cover much of the southern Plains, Southwest, and Great Basin Monday morning. Some dampening is anticipated along the northeastern periphery of this ridge as a shortwave trough progresses from the central High Plains towards the Lower MO Valley. Upper troughing is expected to persist over the eastern CONUS, with a corridor of enhanced northwesterly flow between this troughing and the ridging to the west (i.e. from the Upper Midwest to the Carolinas). One or more convectively induced shortwave troughs may be moving through this corridor of enhanced flow, including one that may move through the southern Appalachians and into the Carolinas Monday afternoon. ...Georgia into the Carolinas and Southern Virginia... The surface pattern early Monday morning is forecast to feature a low over eastern KY, with a weak frontal boundary extending westward trough southern MO This surface low should develop towards the Carolinas through the day, with a trailing cold front slowly moving east-southeastward across the TN Valley into the central Appalachians and Southeast through the period. Air mass downstream of this front will likely feature temperatures in the upper 80s and dewpoints in the mid 60s, contributing to moderate buoyancy by the early afternoon. Thunderstorms are expected to develop along the front as it interacts with this warm and moist air mass, with some supporting large-scale ascent attendant to the shortwave trough mentioned in the synopsis. A predominantly multicellular storm mode is anticipated, with outflow-dominant storms contributing to bowing line segments. However, effective bulk shear is forecast to be around 25 to 35 kt, which could support a few supercells. Damaging wind gusts will be the primary severe risk, but hail is also possible, particularly if any supercells develop. ...Northern/Central Plains... A stationary front is expected to extend from southern MO back northwestward to a low near the western KS/NE border. This central Plains low will likely be the southernmost in a series of weak lows along a surface trough across the western Dakotas. The western KS/NE low should consolidate over KS and vicinity through the day while deepening slightly, with a narrow corridor of rich low-level moisture extending from parts of NE into eastern KS and MO. Low-level convergence near this deepening low, as well as along the trough extending southward from this low and the sharpening stationary boundary, may result in convective initiation. Uncertainty regarding the thermodynamic conditions, largely resulting from uncertainty regarding cloud cover and the coverage/extent of antecedent precipitation, currently limits predictability. A few strong to severe storms are possible if updrafts are able to mature. Additional thunderstorms are possible along the surface trough across the western Dakotas. However, like areas farther south, antecedent precipitation and resulting cloud cover result in uncertainty regarding afternoon/evening air mass destabilization. Additionally, modest height rises are possible across the region. Despite these negative factors, recent guidance shows storm development across the region and at least a low potential for a few severe storms. ..Mosier.. 08/14/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1138 AM CDT Sun Aug 14 2022 Valid 141700Z - 151200Z ...NO CRITICAL AREAS... No changes have been made to the ongoing forecast. Localized dry and breezy conditions may develop across the Plains and Pacific Northwest where fuels are dry. Please see the prior discussion for additional information. ..Lyons.. 08/14/2022 .PREV DISCUSSION... /ISSUED 0142 AM CDT Sun Aug 14 2022/ ...Synopsis... Upper ridging will generally prevail across the western and central U.S. today, though some de-amplification of the ridge is expected as multiple mid-level impulses pivot anticyclonically around the ridge. Given overall weak large-scale forcing with this upper-air pattern, only localized bouts of Elevated surface wind/RH conditions are likely by afternoon peak heating, mainly in terrain-favoring locations of the Pacific Northwest, northern Rockies, and Plains states. Otherwise, monsoonal moisture will continue to impinge on the northern Rockies, supporting thunderstorm development by afternoon peak heating. Localized wildfire start or spread concerns may exist wherever lightning can strike away from precipitation cores into dry fuel beds, or where gusty surface winds can develop. ...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 1130 AM CDT Sun Aug 14 2022 Valid 141630Z - 151200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON/EVENING ACROSS THE CENTRAL HIGH PLAINS...NORTHWEST ND...AND EASTERN KY AND VICINITY... ...SUMMARY... Scattered convection capable of isolated/marginally severe hail and wind will spread across portions of the central High Plains, northwest North Dakota, and eastern Kentucky and vicinity this afternoon and evening. ...Central High Plains this afternoon/evening... Embedded perturbations will move eastward toward the central High Plains, around the north-northwest periphery of the persistent midlevel high over the central/southern Plains. Low-level upslope flow will help maintain boundary-layer dewpoints in the mid 50s to lower 60s as low-level lapse rates steepen with afternoon heating/mixing. Midlevel lapse rates will not be particularly steep within the monsoonal moisture plume, but steepening low-level lapse rates and modest deep-layer shear will support the potential for a few storm clusters capable of producing strong/isolated severe outflow winds this afternoon/evening. ...Northwest ND late this afternoon/evening... A diffuse surface cyclone/lee trough will persist through the afternoon near the MT/ND border, near the southern edge of the main belt of mid-upper westerlies over the southern Prairie Provinces. Boundary-layer dewpoints in the mid 60s across western ND, near the east edge of the deeper mixing across MT, will support moderate buoyancy (MLCAPE of 1500-2000 J/kg) and the potential for isolated thunderstorm development near the international border by late afternoon. Assuming a storm or two forms and moves southeastward into ND, the environment will conditionally favor some potential for supercells/small clusters capable of producing isolated large hail and damaging winds for a few hours late this afternoon through late evening. ...Southern IN to eastern KY/western VA this afternoon/evening... A weak surface cyclone will move southeastward from IN toward eastern KY, in advance of an embedded speed max digging southeastward over IL/IN. Though clouds will slow surface heating some and midlevel lapse rates will not be particularly steep, boundary-layer dewpoints well into the 60s and surface heating in cloud breaks will support MLCAPE of 500-1000 J/kg. Deep-layer northwesterly shear of 35-40 kt will be sufficient for organized/supercell storms capable of producing marginally severe hail and isolated wind damage. ...South TX this afternoon... A tropical low is moving inland over south TX as of late morning, with some banded convective structures to the east of the center. Since the low is already inland and is not expected to intensify, wind profiles/vertical shear are likewise not expected to strengthen. A weakly rotating storm or two may occur near the lower TX coast as the convective bands spread westward/inland, but the threat for tornadoes is too marginal to warrant the addition of an outlook area. ..Thompson/Bentley.. 08/14/2022 Read more

No watches are valid as of Sat Aug 13 17:53:02 UTC 2022.

No Mesoscale Discussions are in effect as of Sat Aug 13 17:53:02 UTC 2022.

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1221 PM CDT Sat Aug 13 2022 Valid 141200Z - 151200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE CENTRAL HIGH PLAINS... ...SUMMARY... Isolated severe thunderstorms are possible across portions of the central High Plains on Sunday. ...Synopsis... Upper ridging is forecast to remain centered over the central CONUS from Sunday morning into Monday morning. Weak upper troughing will persist over the eastern CONUS during the same period, with modestly enhanced northwesterly flow aloft within the corridor between this trough and the central CONUS ridge (from the northern Plains/Upper Midwest into the central Appalachians). A pair of shortwave troughs are expected to traverse the corridor on Sunday, with the lead wave moving through the central Appalachians, and the following wave moving through the Upper Midwest. At the surface, a weak low is forecast to move across the OH Valley into the central Appalachians. This low is expected to be centered over central IL early Sunday morning, with an associated frontal boundary extending westward across MO into central KS, and then back northwestward through the NE Panhandle. Some southward progression of this front is anticipated across MO and portions of the Lower OH Valley, while the western portion of the frontal over the Plains remains largely stationary. ...Central High Plains... Thunderstorm are expected to develop across eastern WY Sunday afternoon, ahead of a convectively enhanced shortwave trough cresting the upper ridge. Moderate westerly flow aloft atop southeasterly low-level will support moderate vertical shear, and the potential for a few more organized storms. Isolated damaging wind gusts are possible as these storms move into the well-mixed environment south of the stationary front. A few instances of hail could also occur, particularly along and north of the stationary front, as storms interact with this boundary. ...South TX... A weak tropical disturbance may move inland from parts of the lower TX Coast into deep south TX on Sunday. Most guidance currently shows modest low-level wind fields with this feature, with minimal severe potential anticipated at this time. ...AZ... Scattered to numerous thunderstorms are expected to develop during the afternoon across the high terrain/Mogollon Rim, within the moist, Monsoonal air mass over the region. Low to mid-level flow will be very weak, but a strong gust or two is possible as these storms move into the steep low-level lapse rate environment over the desert. ...Upper OH/Central Appalachians... Showers and thunderstorms will likely be ongoing across the middle OH Valley ahead the lead shortwave and attendant surface low. This early morning development should weaken, with additional development anticipated during the afternoon across the central Appalachians. Vertical shear is strong enough to support a few persistent updrafts, but buoyancy will be limited but weak lapse rates, likely keeping the overall severe potential limited. ..Mosier.. 08/13/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1152 AM CDT Sat Aug 13 2022 Valid 131700Z - 141200Z ...NO CRITICAL AREAS... No changes to the ongoing forecast, see the previous discussion for more information. ..Lyons.. 08/13/2022 .PREV DISCUSSION... /ISSUED 0142 AM CDT Sat Aug 13 2022/ ...Synopsis... Upper ridging will prevail across the central U.S., with some breakdown of the ridge/modest mid-level troughing likely across the Northwest today. Deep-layer flow/forcing beneath and to the periphery of the upper ridge is expected to be too modest to support a significant wildfire-spread threat anywhere across the CONUS. Locally though, a few exceptions may exist. While the sustained surface wind field is expected to remain under 15 mph on a widespread basis, pockets of 15+ mph surface winds may overlap 15-20 percent RH all along the periphery of the ridge, spanning from northern California into the Northern Rockies and the Plains states. Monsoonal moisture meandering northward along the upper ridge axis will aid in thunderstorm development across the central and northern Rockies. A mix of wet and dry thunderstorms is likely, and a localized wildfire-start threat may accompany strikes away from storm cores into dry fuel beds, with gusty thunderstorm winds potentially exacerbating ongoing fires. ...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 1124 AM CDT Sat Aug 13 2022 Valid 131630Z - 141200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATER THIS AFTERNOON/EVENING ACROSS PARTS OF MT/WESTERN ND...AND ACROSS EASTERN IA/SOUTHERN WI/NORTHERN IL... ...SUMMARY... Isolated severe thunderstorms are possible across portions of the northern High Plains and Midwest late this afternoon and evening. ...Eastern IA/southern WI/northern IL this afternoon/evening... A midlevel high persists over the central High Plains, with a downstream trough over the Northeast, and an upstream trough over the Pacific Northwest. Around the northeast periphery of the midlevel high, an embedded speed maximum will move southeastward from southeast MN toward southern WI/northeastern IL, in conjunction with a weak surface cyclone and cold front. The front is demarcated by persistent stratus spreading southward across IA, with a warm sector south of the front characterized by boundary-layer dewpoints in the mid 60s and surface temperatures warming into the 80s. Some elevated convection is ongoing over southwest WI in a zone of warm advection ahead of the midlevel speed max and weak surface cyclone. Continued warming/destabilization through the afternoon from west-to-east will result in MLCAPE of 1000-1500 J/kg in a narrow corridor ahead of the cold front across eastern IA/northwestern IL/southwestern WI. The stronger forcing for ascent will be in the warm advection zone just east of the surface warm sector, where a few elevated storms will pose a low-end hail threat. Low-level ascent near the surface cyclone and cold front, close to the northeast edge of the surface warm sector, could support isolated thunderstorm development this afternoon/evening. There will be a fairly narrow zone of overlapping buoyancy and hodograph length/curvature to support supercells, but confidence is low in storms forming and remaining in this favorable zone. Thus, will maintain 5% wind/hail (MRGL) probabilities. ...MT to western ND this afternoon/evening... Subtle speed maxima will rotate around the north/northwest periphery of the midlevel high over the central High Plains, within the monsoonal moisture plume from NV/UT into MT. Modest low-level moisture (boundary-layer dewpoints in the mid 50s to mid 60s now) will tend to mix some with strong afternoon heating, which will result in profiles with weak-moderate buoyancy (MLCAPE of 500-1000 J/kg) and inverted-v thermodynamic profiles. Aside from heating over the higher terrain of southwest/south central MT, the sources for storm initiation are nebulous this afternoon. Therefore, there are some questions about storm coverage, though deep-layer vertical shear will be sufficient for some storm organization. Overall, MRGL with 5% wind appears to be a reasonable reflection of the severe threat with high-based storms/small clusters that will spread east-northeastward from the higher terrain toward central/eastern MT later this afternoon into this evening. There will be a low-end threat for surface-based storm development this afternoon along a surface warm front across western ND. If a storm can form along this boundary, the environment will favor some potential for supercells. ..Thompson/Bentley.. 08/13/2022 Read more

No watches are valid as of Fri Aug 12 17:41:02 UTC 2022.

No Mesoscale Discussions are in effect as of Fri Aug 12 17:41:02 UTC 2022.