Severe Storms

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1134 AM CDT Sat Aug 20 2022 Valid 201700Z - 211200Z ...NO CRITICAL AREAS... The forecast remains on track, and no changes were made with this update. For details, see the previous discussion below. ..Weinman.. 08/20/2022 .PREV DISCUSSION... /ISSUED 1218 AM CDT Sat Aug 20 2022/ ...Synopsis... A mid-upper-level trough will move east slowly across the Great Lakes and Ohio Valley and the western ridge will continue to build north into southwest Canada. Much of the contiguous United States will be seasonably cool, moist, or both. Additionally, absent any strong mid-upper-level height gradients or surface-pressure gradients, large-scale winds will remain generally light. Thunderstorms are likely atop dry fuels in Idaho and Montana, but overall high coverage and sufficiently moist precipitable water values should support wetting rains. Thus, large-scale fire weather concerns should be minimal on Saturday. ...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 1132 AM CDT Sat Aug 20 2022 Valid 201630Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF CENTRAL ILLINOIS AND FROM SOUTHEAST INDIANA ACROSS WESTERN OHIO... ...SUMMARY... Scattered severe storms with damaging winds and large hail will be possible this afternoon and evening across central Illinois and from eastern Indiana into western Ohio. ..Midwest/Ohio Valley/Ozarks... A weak surface low over central IA will move slowly southeast through tonight as an associated cold front also moves east, extending from west-central IL into central MO and southern KS by 00z. Despite ongoing precipitation/cloud cover over portions of IL/IN, pockets of more substantial destabilization are expected by afternoon, especially from southern/eastern IN into southwest OH where slightly higher boundary layer moisture exists and stronger heating is expected. With minimal CINH by early/mid afternoon, more concentrated thunderstorm development or re-intensification is expected near the cold front/upper low across eastern IA/central IL, with a second area over eastern IN/western OH. Elsewhere, more isolated strong/severe storms will be possible within the Marginal Risk area near and in advance of the front with severe winds the primary hazard. Southwesterly mid-level flow will contribute to effective shear ranging from 30-35 kts this afternoon which will support multicells and a few transient supercell structures. Damaging winds will be the primary severe hazard, with instances of large hail also possible primarily over eastern IA/central IL where cooler mid-level temperatures will exist. Some potential for low-level rotation may exist with supercell structures east of the surface low this afternoon, and have retained the low tornado probabilities in this area. ...South Texas... A low over the western Gulf of Mexico is expected to move northwestward toward Deep South Texas. Refer to the latest National Hurricane Center advisory for additional forecast details regarding Potential Tropical Cyclone Four. While a modest strengthening of southeasterly low-level winds may occur, present indications are that the low/mid-level wind field will likely remain sufficiently weak to preclude a tornado risk. ..Bunting/Dean.. 08/20/2022 Read more

No watches are valid as of Fri Aug 19 18:03:01 UTC 2022.

No Mesoscale Discussions are in effect as of Fri Aug 19 18:03:01 UTC 2022.

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1202 PM CDT Fri Aug 19 2022 Valid 201200Z - 211200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE OZARKS INTO THE MID MISSISSIPPI VALLEY...MIDWEST/OHIO VALLEY...AND GREAT LAKES...... ...SUMMARY... Isolated strong to severe thunderstorms may occur Saturday across parts of the Ozarks into the mid Mississippi Valley, Midwest/Ohio Valley, and Great Lakes. Occasional damaging winds and marginally severe hail should be the main threats. ...Ozarks...Mid-MS and OH Valleys...Great Lakes... An upper low/trough will migrate east across the Midwest/Great Lakes vicinity on Saturday. Deep-layer west/southwesterly flow associated with this system will remain moderate, with around 25-40 kt midlevel flow forecast. At the surface, a weak low over eastern IA Saturday morning will drift east/southeast across northern IL. Meanwhile, a cold front will develop east/southeast across IL/MO/KS/OK. A seasonally moist boundary-layer will exist ahead of the surface low/cold front with dewpoints in the mid 60s likely. Midlevel lapse rates are forecast to remain modest (around 6.5 C/km), but pockets of stronger heating of the moist boundary-layer will contribute to MLCAPE values around 1000-2000 J/kg. Effective shear magnitudes to around 35 kt will result in at least transient supercells and briefly organized clusters. Some consideration was given to an upgrade to a Slight risk across parts of MO/IL. However, uncertainty due to possible morning convection and cloud cover, along with decreasing large-scale ascent with southward extent will preclude an upgrade at this time. Isolated strong to severe gusts and hail will be the main concern with this activity as bands and clusters of storms shift east through the evening. ..Leitman.. 08/19/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1126 AM CDT Fri Aug 19 2022 Valid 191700Z - 201200Z The forecast remains on track, and no changes were made with this update. See the previous discussion below for details. ..Weinman.. 08/19/2022 .PREV DISCUSSION... /ISSUED 0141 AM CDT Fri Aug 19 2022/ ...Synopsis... An upper-level shortwave trough evident on water vapor imagery this morning near the California-Oregon-Nevada border is forecast to shift slowly eastward and weaken throughout the day. Concurrently, an axis of monsoonal moisture (PW values around 1") extending northward from Arizona will also shift eastward into western Utah and southern Idaho. Consequently, clouds and precipitation are likely early in the day along this axis. On the northeastern periphery of this moisture axis across portions of central Idaho and southwestern Montana, sufficient heating and destabilization will likely lead to scattered thunderstorm development in the afternoon over the higher terrain. Despite borderline environmental characteristics for dry thunderstorms (i.e., PW values around 0.75" and surface RH values around 30%), numerous CG lightning flashes are expected over dry fuels with limited rainfall accumulation expected outside of thunderstorm cores. Thus, an isolated dry thunderstorm area has been delineated to highlight this fire-weather concern. ...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 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.