Severe Storms

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1122 AM CDT Fri Aug 19 2022 Valid 191630Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SOUTHEAST IA...NORTHERN MO...AND FAR NORTHWEST IL... ...SUMMARY... The most favorable area for isolated to perhaps scattered severe hail and wind is across parts of southern/eastern Iowa, northern Missouri, and far northwest Illinois from late afternoon through mid-evening. ...IA/MO/IL vicinity... To the south and southeast of a vertically stacked low over southwest MN, pockets of greater boundary-layer heating are evident across parts of IA into MO and IL. Amid cool mid-level temperatures around -12 C at 500 mb, moderate buoyancy with MLCAPE of 1000-2000 J/kg should become common by late afternoon. A scattering of thunderstorms is expected during this time frame into the evening, focused along the primary surface cold front and confluence bands ahead of it. While stronger deep-layer shear will be found in the southwest quadrant of the broader cyclone, a swath of moderate mid-level westerlies should extend east towards the IA/MO/IL border area yielding effective bulk shear of 25-35 kts. This area should be most favored for a few lower-end supercells and small multicell clusters mainly producing isolated severe hail and damaging wind until convection wanes later this evening. ...KS... In the wake of ongoing elevated convection, a corridor of destabilization is expected near and behind the surface cold front drifting south from southern NE/northwest KS. Buoyancy will remain limited and mid-level lapse rates were relatively modest in upstream 12Z soundings from North Platte and Rapid City. Nevertheless, the presence of 30-40 kt mid-level west-northwesterlies to the southwest of the vertically stacked low in southern MN will support a threat for a few cells producing isolated severe hail and wind during the late afternoon to early evening. ...Eastern GA/coastal Carolinas... Generally stratiform rain with isolated deeper convection has been slowly drifting east over southern NC and far eastern SC. This has convectively reinforced a weak baroclinic zone across the region with a 1017-mb mesolow over eastern SC. This minor cyclone should drift north towards central NC through tonight. A rather localized corridor of enhanced low-level SRH near the track of this low conditionally supports a threat for a brief tornado. Otherwise, locally damaging winds will be possible with scattered multicell clusters that emanate out of GA later this afternoon. ...Central/western AZ... A few strong storms with locally gusty winds may materialize during the late afternoon and early evening across the region within a very moist air mass. Potential for organized severe storms appears limited owing to weak deep-layer shear/mid-level lapse rates. ..Grams/Wendt.. 08/19/2022 Read more

No watches are valid as of Thu Aug 18 18:01:01 UTC 2022.

No Mesoscale Discussions are in effect as of Thu Aug 18 18:01:01 UTC 2022.

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1157 AM CDT Thu Aug 18 2022 Valid 191200Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE CENTRAL PLAINS INTO THE UPPER MIDWEST...AND ACROSS PARTS OF GEORGIA AND SOUTH CAROLINA... ...SUMMARY... Isolated severe thunderstorms appear possible Friday across parts of the central Plains into the Upper Midwest. Occasional hail and damaging winds should be the main threats. Sporadic strong gusts also may accompany thunderstorms across parts of Georgia and South Carolina Friday afternoon. ...KS/MO/IA... A mid/upper level low/trough will develop east/southeast across the Upper Midwest on Friday. 25-40 kt mid/upper level northwesterly flow will overspread portions of the northern/central Plains into the lower MO Valley and Upper Midwest. At the surface, weak low pressure will meander east/southeast across the southern MN/IA vicinity. A cold front will extend southwest from the low and slowly shift east across the central Plains to the lower MO Valley. Modest boundary-layer moisture will be in place ahead of the front as afternoon temperatures climb into the 80s. Midlevel lapse rates around 7 C/km above the modest boundary-layer moisture will contribute to moderate instability (1000-2000 J/kg MLCAPE). Effective shear magnitudes around 25-35 kt will support some organized multicell clusters and transient supercells. Isolated strong to severe gusts and marginally severe hail will be possible with the strongest cells during the afternoon and evening. ...GA/SC... Deep-layer flow will remain modest across the region, on the southern periphery of the eastern U.S. upper trough. However, some weak speed shear and 25-35 kt midlevel flow will result in marginal effective shear magnitudes around 25 kt. This may support some transient/briefly organized multicell clusters in the vicinity of a weak surface low and stationary front draped across central GA into SC. Midlevel lapse rates will remain poor, but surface dewpoints in the 70s will contribute to MLCAPE as high as 1500 J/kg. Low-level flow will remain weak, generally less than 10-15 kt through 1 km. However, steepening low-level lapse rates and PW values near 2 inches will support water-loaded downdrafts capable of sporadic strong gusts and wind damage through the afternoon. ..Leitman.. 08/18/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1142 AM CDT Thu Aug 18 2022 Valid 181700Z - 191200Z ...Northwest Dry Thunder... Early morning observations show widespread clouds and stratiform precipitation ongoing across portions of central/southern OR, and extending north into the WA Cascades. This cloud cover appears likely to limit solar heating and subsequent destabilization across portions of the eastern Cascades this afternoon. Hi-res model guidance is in good agreement showing very limited buoyancy and strong capping. Thus, the IsoDryT has been removed this area. Farther west, marine influence was noted across the windward slopes of the OR Cascades. While some heating is likely, the stable marine layer suggests storm coverage will be very isolated and tied to local orographic effects. While some risk for isolated dry lightning strikes remains, the highest confidence in afternoon storms has shifted to portions of the northern Great Basin and southwestern ID. Here, clearing and warming will support the greatest potential for dry thunderstorms with the potential for lightning in dry fuels. ..Lyons.. 08/18/2022 .PREV DISCUSSION... /ISSUED 0132 AM CDT Thu Aug 18 2022/ ...Synopsis... Broad mid-level troughing will dominate the Plains states eastward while weak upper ridging persists across the Interior West today. A mid-level shortwave trough is expected to pivot around the upper ridge and lift a monsoonal airmass, promoting high-based thunderstorm development across portions of the Pacific Northwest by afternoon. Isolated dry thunderstorm highlights were added to account for the potential of several strikes occurring away from storm cores into dry fuel beds. Otherwise, locally Elevated conditions may accompany the post-cold frontal environment across the central Plains, supporting localized potential for fire growth wherever dry/occasionally breezy conditions overlap with patchy dry fuels. ...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 1051 AM CDT Thu Aug 18 2022 Valid 181630Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SOUTH-CENTRAL NE TO THE MID-MO VALLEY... ...SUMMARY... Isolated large hail and localized severe wind gusts are most likely from south-central Nebraska to the Mid-Missouri Valley during the late afternoon and early evening. ...KS/NE to southwest MN... A shortwave trough will gradually amplify as it drifts southeast across the Upper Midwest through tonight. An initially weak surface cyclone over the Upper Red River Valley will deepen as it slowly moves east across northern MN. Trailing cold front to its southwest will sharpen towards late afternoon across the Mid-MO Valley. Boundary-layer moisture will be relatively modest by mid-August standards, but a confined plume of steep mid-level lapse rates sampled by the 12Z Aberdeen sounding should support a narrow corridor of moderate buoyancy with MLCAPE of 1000-2000 J/kg. A belt of enhanced mid-level northwesterlies will overspread much of the Great Plains to the west and southwest of the shortwave trough. This will strengthen deep-layer shear, mainly across the central Great Plains portion of the front, yielding elongation of the hodograph atop weak low-level SRH. This should support potential for a few discrete supercells with mid-level rotation centered on the IA/NE/SD border area southwest into south-central NE. Isolated large hail and localized severe gusts should be the primary hazards before convection wanes rapidly after dusk. With northeast extent into MN, slower-moving storms and more prominent multicell clustering should serve to marginalize wind/hail intensities. ...Central TX to southern LA and north FL to southeast GA... While deep-layer shear will be lacking to the south of a convectively reinforced surface front, very rich boundary-layer moisture characterized by observed PW values around 2 inches will support a threat for localized wet microbursts, peaking in the late afternoon. Extensive pulse to weakly organized multicells are anticipated before convection decays this evening. ..Grams/Wendt.. 08/18/2022 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1216 PM CDT Wed Aug 17 2022 Valid 181200Z - 191200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE CENTRAL PLAINS...AND FROM CENTRAL/EASTERN TX INTO THE SOUTHEAST... ...SUMMARY... Isolated strong to severe thunderstorms may occur Thursday over parts of central/eastern Texas into the Southeast, and portions of the central Plains. Damaging gusts will be the main hazard with this activity. ...Central Plains... Moderate mid/upper level northwesterly flow will be in position across the central/northern Plains on the western periphery of the eastern US upper trough. A shortwave perturbation is forecast to develop southward from the Canadian Prairies into the Plains during the forecast period. At the surface, modest boundary-layer moisture will reside ahead of a south/southeastward-advancing cold front. A lack of better quality moisture will limit instability some, but heating into the 80s and modestly steep midlevel lapse rates will support MLCAPE values around 500-1500 J/kg. Effective shear magnitudes greater than 30 kt will support at least transient supercells and organized clusters by afternoon along/ahead of the front. Strong to severe gusts and marginally severe hail will be possible with the strongest cells through early evening. ...Central TX through the Southeast... A reservoir of rich boundary-layer moisture will reside ahead of the west to east oriented surface front. Surface dewpoints in the upper 60s to low 70s F and areas of strong heating will result in moderate to strong instability, with MLCAPE values around 2000-3000 J/kg likely. PW values also will be quite high, nearing 2 inches. Vertical shear will remain weak, with mostly unidirectional/westerly deep-layer flow over the region. This combination of strong instability and weak shear in the presence of a surface boundary will mainly support initially intense updrafts with limited organization. As a result, the main severe threat with thunderstorm clusters through the afternoon will be limited to damaging gusts in water loaded downdrafts. ..Leitman.. 08/17/2022 Read more

No watches are valid as of Wed Aug 17 17:21:01 UTC 2022.

No Mesoscale Discussions are in effect as of Wed Aug 17 17:21:01 UTC 2022.

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1135 AM CDT Wed Aug 17 2022 Valid 171700Z - 181200Z No significant changes have been made to the current outlook. Isolated dry thunderstorms are expected to develop this afternoon and continue through this evening across portions of the Northwest. Please see the prior discussion for more information. ..Lyons.. 08/17/2022 .PREV DISCUSSION... /ISSUED 0150 AM CDT Wed Aug 17 2022/ ...Synopsis... An upper ridge will prevail across the western CONUS today as mid-level troughing gradually amplifies across the eastern two-thirds of the U.S. Multiple mid-level impulses will pivot around the upper ridge, with a relatively pronounced impulse traversing the Pacific Northwest Coastline. Deep-layer ascent across portions of the Pacific Northwest will lift a monsoonal airmass atop a dry boundary layer, encouraging high-based thunderstorm development by early evening. Isolated dry thunderstorm highlights were added to portions of northern California into southern Oregon and extreme northwest Nevada given the confidence in dry thunderstorms occurring atop very dry fuels. Otherwise, locally Elevated dry/windy surface conditions may accompany the passage of a cold front across portions of Montana and the northern High Plains through the day. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1129 AM CDT Wed Aug 17 2022 Valid 171630Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON/EVENING FROM EAST TX TO THE LOWER MS VALLEY AND NORTH FL...SOUTHERN AZ...AND THE WESTERN DAKOTAS... ...SUMMARY... Isolated damaging winds will be possible this afternoon/evening from east Texas across the lower Mississippi Valley to north Florida, southern Arizona, and the western Dakotas. ...Lower MS Valley to north FL this afternoon/evening... A remnant MCV will move east-southeastward from AR to MS/AL this afternoon, roughly along and just north of an outflow-reinforced front from the AR/LA border across central MS to southern AL. Strong surface heating and boundary-layer dewpoints well into the 70s will boost MLCAPE to near 3000 J/kg this afternoon along and south of the front/outflow, and additional thunderstorm development is expected by mid afternoon. The surface boundaries that will focus storm initiation will lie along the southwest fringe of the 20-30 kt midlevel flow, which will support multicell clusters. Precipitation loading with the strong buoyancy, in combination with DCAPE near or above 1000 J/kg, will support isolated wind damage with downbursts this afternoon/evening. Otherwise, isolated strong storms will also be possible across north FL, primarily with sea breeze and outflow interactions. ...Southern AZ this afternoon/evening... To the west of a remnant tropical low over northern Mexico, midlevel east-northeast flow will strengthen some through this evening over southern AZ. This will favor convective clusters moving southwestward from the higher terrain to the lower deserts, where strong surface heating and boundary-layer dewpoints in the 60s will contribute to moderate buoyancy and weakening convective inhibition. Typical steep low-level lapse rates and substantial precipitation loading will favor hybrid microbursts capable of producing isolated strong-severe outflow winds. ...Western Dakotas this afternoon/evening... Some convection is ongoing late this morning over the northern High Plains, in advance of a weak midlevel trough moving over northeast MT. The convection is expected to increase some later this afternoon as it encounters a deeper mixed boundary layer, when there will be the potential for isolated strong-severe outflow gusts. ..Thompson/Wendt.. 08/17/2022 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0755 AM CDT Wed Aug 17 2022 Valid 171300Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS EAST TEXAS/ARKLATEX TO THE GULF COAST... ...SUMMARY... A few storms may become severe this afternoon from eastern Texas across the Gulf Coast states, with locally damaging wind gusts possible. ...East Texas/Arklatex to Gulf Coast/northern Florida... Storms are ongoing this morning near and north of the front from Arkansas into northern Mississippi/central Alabama, with lift enhanced by modest warm advection from the west at 850 mb. Strong heating near/south of the front will result in a transition to surface-based storms into this afternoon. It appears that the composite front/outflow boundary will continually undercut the developing storms, and it is unclear how quickly new cells will regenerate for propagation. Regardless, at least isolated strong to severe gusts appear likely given afternoon-maximized steep low-level lapse rates and the expected storm aggregation. Small areas of storms may persist this evening, but any wind threat is expected to diminish after sunset. ...Western Dakota and far eastern Montana/northeast Wyoming... A few stronger storms may materialize this afternoon/early evening near a front/pre-frontal trough. Some thunderstorm-related strong/gusty winds could occur, but severe probabilities do not currently appear warranted given the relatively modest buoyancy by summertime standards. ...Southern Arizona... A west/northwestward-moving mid-level impulse and heating over the higher terrain will contribute to diurnally maximized thunderstorm development, some of which may propagate to the desert floor aided by a modest strengthening of mid-level easterlies. The region will be reevaluated in subsequent outlooks for a potential inclusion of wind-related probabilities. ..Guyer/Broyles.. 08/17/2022 Read more

No watches are valid as of Tue Aug 16 18:01:02 UTC 2022.

No Mesoscale Discussions are in effect as of Tue Aug 16 18:01:02 UTC 2022.

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