Severe Storms

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0153 PM CDT Tue Sep 19 2023 Valid 201200Z - 211200Z An Elevated area was added for portions of northern CA (including the northern/northwestern Sacramento Valley), far south-central OR, and far northwest NV. The latest high-resolution guidance and CANSAC WRF runs have come into reasonably good agreement, depicting the development of around 15 mph sustained northerly surface winds (with gusts upwards of 25 mph) and 15-25 percent RH during the afternoon/evening hours -- along the southern periphery of the cooler conditions to the north. For the northern/northwestern Sacramento Valley, the best overlap of breezy winds and reduced RH is expected from the evening into the overnight hours, with some uncertainty regarding RH reductions during this time frame. Given modestly receptive fuels across the area and possibly a few holdover fires from recent lightning activity, elevated fire-weather conditions are expected. ..Weinman.. 09/19/2023 .PREV DISCUSSION... /ISSUED 0117 AM CDT Tue Sep 19 2023/ ...Synopsis... Fire weather concerns are expected to be minimal on Wednesday. A mid-level trough will amplify across the Northwest and bring cool and moist conditions to much of this region. Farther south, dry and breezy conditions are expected across the Great Basin and Southwest as mid-level flow strengthens in the well-mixed environment. However fuels remain green in this region, which should preclude the potential for new large fires. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No watches are valid as of Mon Sep 18 22:31:02 UTC 2023.

No Mesoscale Discussions are in effect as of Mon Sep 18 22:31:02 UTC 2023.

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0352 PM CDT Mon Sep 18 2023 Valid 201200Z - 261200Z A midlevel cut-off low will evolve southward from the Pacific Northwest into parts of the Great Basin on Days 3-4/ Wednesday-Thursday, as a substantial mid/upper-level jet streak advances southward along the Pacific Northwest coast. On the backside of the midlevel low, breezy northerly surface winds will develop over portions of OR, northern CA, and northwest NV on Day 3/Wednesday (and to a lesser extent on Day 4/Thursday). While the strengthening winds may influence any ongoing fires across the region, cool surface temperatures and limited RH reductions should generally limit the fire-weather threat. Along the southern and eastern peripheries of the midlevel low, strong deep-layer southwesterly flow will overspread parts of the Great Basin, the Southwest, the central/southern Rockies, and the central High Plains on Days 3-5/Wednesday-Friday. Deep boundary-layer mixing into the strong flow aloft will yield dry/breezy conditions across these areas. While these meteorological conditions would typically warrant Critical probabilities, above-average rainfall and generally unreceptive fuels cast uncertainty on the overall fire-weather risk. ..Weinman.. 09/18/2023 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0251 PM CDT Mon Sep 18 2023 Valid 182000Z - 191200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE TEXAS PANHANDLE AND SOUTH PLAINS...AND ADJACENT PORTIONS OF SOUTHEASTERN NEW MEXICO AND WESTERN OKLAHOMA... ...SUMMARY... Isolated, marginal severe wind and hail will be possible across the Texas Panhandle vicinity from about 5 to 9 PM CDT. ...Discussion... Aside from minor line adjustments, the reasoning regarding, and the areal extent of, the potential/isolated severe-weather threat for this afternoon and early evening across the Texas Panhandle/South Plains and vicinity remains consistent with prior outlooks. Thus, no major changes appear necessary at this time. ..Goss.. 09/18/2023 .PREV DISCUSSION... /ISSUED 1059 AM CDT Mon Sep 18 2023/ ...TX Panhandle... Clear skies are currently present across the TX Panhandle and western OK, where dewpoints are in the 50s to lower 60s and afternoon temperatures will approach 90F. The result will be a deeply mixed boundary layer with steep low-level lapse rates. A weak surface boundary will stretch across the region by late afternoon. Roughly half of the morning CAM solutions suggest widely scattered high-based thunderstorms will form along this boundary. Winds aloft are rather weak, so those cells that form will likely be rather disorganized and transient in intensity. However, the strongest cells could produce locally gusty winds and hail for a few hours early this evening. ...Elsewhere... Elsewhere, another mesoscale area of modest concern for strong storms would be over parts of eastern NE. If a storm or two can form in this area, gusty winds might be possible for a couple of hours. Finally, scattered high-based showers and thunderstorms may occur across much of the intermountain west today from MT/UT into the Four Corners region. Any cell in this area could produce a locally intense wind gust, but the overall coverage is expected to be low. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0201 PM CDT Mon Sep 18 2023 Valid 191200Z - 201200Z Minor adjustments were made to the northern Plains Elevated highlights based on the latest guidance consensus. Farther west, locally elevated conditions are possible across portions of southeast Oregon, the northern Cascade gaps, and the Columbia Basin. However, the overlap of breezy winds and low RH is generally limited for these areas -- precluding highlights. For additional details, see the previous discussion below. ..Weinman.. 09/18/2023 .PREV DISCUSSION... /ISSUED 0151 AM CDT Mon Sep 18 2023/ ...Synopsis... Some elevated fire weather concerns are possible on Tuesday across northeast Montana and northwest North Dakota. The mid-level shortwave trough, currently over the northeast Pacific which will traverse the Pacific Northwest today, will move into the northern Plains on Tuesday. As this occurs, the surface front/low-pressure center will start to accelerate east. As it departs, some strong westerly/northwesterly winds are expected to the west of the surface low. There is still considerable spread within guidance regarding how dry/breezy conditions will be in this region. RH ranges from 15 percent to 40 percent and winds range from 10 to 15 mph all the way to 25 to 30 mph. An Elevated delineation should cover this threat and its associated uncertainties for the time being with additional refinement likely needed in later outlooks as the forecast evolution becomes more clear. Elsewhere, no significant fire weather concerns are anticipated on Tuesday. ...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 1232 PM CDT Mon Sep 18 2023 Valid 191200Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF OKLAHOMA AND ADJACENT NORTH TEXAS... ...SUMMARY... Scattered severe thunderstorms are possible Tuesday and Tuesday night across portions of the southern Great Plains. Large to very large hail and severe wind gusts are the primary hazards. ...Synopsis... Relatively zonal mid-level flow is expected across much of the U.S. Tuesday, though an upper trough is progged to dig southward across British Columbia toward -- and eventually into -- the Pacific Northwest. Otherwise, multiple mid-level perturbations embedded within the quasi-zonal flow will cross central portions of the country. At the surface, lee troughing is generally progged across the Plains, as a result of the background upper-level westerlies across the interior West. Some northward transport of low-level moisture will support diurnally maximized destabilization, which -- combined with ascent provided by the aforementioned mid-level perturbations -- will support rounds of scattered strong to severe thunderstorms over the southern Plains during the period. ...Portions of the Southern Plains... Northward advection of low-level moisture, combined with diurnal heating beneath steepening mid-level lapse rates accompanying the short-wave troughing aloft will support moderate destabilization. By late afternoon, 1500 to 2000 J/kg mixed-layer CAPE is expected across much of Oklahoma and adjacent portions of western and central Texas. Meanwhile, with around 30 kt southwesterly 850 mb flow beneath 30-40 kt 500 mb westerlies, shear will support organized/rotating storms with initial convective development, with later, upscale growth into an MCS possible, that would shift across central Oklahoma and possibly adjacent portions of Texas. Other, more isolated storms may also develop southwestward along the trough/dryline, as far southwestward as roughly the Concho Valley area, where a few storms with mid-level rotation may evolve. Given the likelihood for supercells within the moderately unstable environment, large to very large hail will be possible with the initial convection, though locally damaging wind gusts may also occur given the deep mixed layer, and resulting sub-cloud evaporative effects. Damaging wind potential may continue into the overnight hours, particularly if storms grow upscale as anticipated. Additionally, redevelopment of smaller clusters of storms should occur near convective outflows as a nocturnal low-level jet strengthens, resulting in multiple rounds of storms in some areas. ...Southern Florida Peninsula... Latest guidance indicates that scattered thunderstorm development will occur Tuesday afternoon, initially focused near the southeastern FL coast but drifting inland with time in tandem with sea-breeze boundary advance. Model soundings depict 1000-1500 J/kg, though with relatively weak lapse rates aloft. Shear should remain rather modest, suggesting weakly organized storms at best. Still, potential for a damaging gust or two cannot be completely ruled out during the afternoon. ..Goss.. 09/18/2023 Read more

No watches are valid as of Sun Sep 17 22:29:01 UTC 2023.

No Mesoscale Discussions are in effect as of Sun Sep 17 22:29:01 UTC 2023.

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0358 PM CDT Sun Sep 17 2023 Valid 191200Z - 251200Z ...Day 3/Tuesday... Within the base of a large-scale trough over western Canada, a belt of enhanced low/mid-level westerly flow will persist from the Pacific Northwest into the northern Plains. Breezy post-frontal surface winds are expected across portions of the Northwest and northern Plains on Day 3/Tuesday, though limited boundary-layer heating/mixing will temper RH reductions and the potential for the stronger flow aloft to mix to the surface. While elevated fire-weather conditions are possible for both areas, confidence in the development of critical conditions is currently low. ...Days 4-8/Wednesday-Sunday... A substantial mid/upper-level jet streak will advance southward along the West Coast, supporting the development of a midlevel cut-off low over the western CONUS. On Day 4/Wednesday, a related surface low will deepen over the Great Basin, with a tightening surface pressure gradient along its northwestern periphery. As a result, northerly surface winds will strengthen across portions of Oregon, though generally cool surface temperatures should limit RH reductions. While this may still support some increase in fire-weather concerns, the limited overlap of strong winds and low RH casts uncertainty on the overall threat -- precluding Critical probabilities at this time. Along the southern/eastern peripheries of the cut-off low, a prolonged period of dry/breezy conditions are expected across portions of the Southwest into the southern/central Rockies. While this will lead to increasing fire-weather concerns on a localized basis, much of this area has experienced appreciable rainfall -- limiting confidence in where the fire-weather threat will be maximized. ..Weinman.. 09/17/2023 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0247 PM CDT Sun Sep 17 2023 Valid 172000Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF NORTHEASTERN FLORIDA AND SOUTHEASTERN GEORGIA TO FAR SOUTHEASTERN NORTH CAROLINA... ...SUMMARY... Isolated damaging winds and a tornado or two remain possible across portions of the southeast Atlantic coastal region through early tonight. ...Discussion... Aside from minor line adjustments, including a decrease of the western extent of the southeastern U.S. MRGL risk area to reflect convective advance/evolution, no appreciable changes to outlook areas or forecast reasoning appear necessary at this time. ..Goss.. 09/17/2023 .PREV DISCUSSION... /ISSUED 1106 AM CDT Sun Sep 17 2023/ ...Southeast Coastal Plain... A large and deepening upper trough is present today over much of the eastern US, with its associated surface cold front moving into the southeast states. Along and ahead of the front, ample low level moisture and moderate CAPE values are present from southeast NC into parts of SC/GA and FL. Visible satellite imagery shows considerable clouds across much of this region, which will limit daytime heating to the 70s and 80s. However, greater heating will be associated with a region of more clear skies over southern GA and eventually over southeast SC. Several morning CAM solutions focus on this area for robust afternoon thunderstorms. Forecast soundings in this area show rather weak mid-level lapse rates, a lack of persistent mid-level dry air, and winds below 3km mainly less than 20kt. This suggests a risk of locally gusty winds, but only a marginal threat of severe gusts. A brief tornado or two is also possible early this evening over northeast SC and southeast NC where low-level shear will be slightly stronger. Therefore will maintain ongoing MRGL risk category. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0155 PM CDT Sun Sep 17 2023 Valid 181200Z - 191200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF CENTRAL AND EASTERN MONTANA... ...Montana... A Critical area was added over portions of central and eastern Montana, where confidence in the overlap of 15-20 percent RH and sustained westerly surface winds near 20 mph has increased based on the latest guidance consensus. Given very dry fuels over this area, critical fire-weather conditions are expected. ...Dry Thunderstorms... Upon collaboration with fire-weather partners and local forecast offices, the Isolated Dry Thunderstorm highlights were trimmed over much of the Sierra -- where fuels remain too wet for an appreciable fire-weather risk. ...Northern Cascades/Columbia Basin... Locally critical conditions are possible primarily within gap-flow areas of the northern Cascades. However, these conditions appear too localized for Critical highlights. For additional details, see the previous discussion below. ..Weinman.. 09/17/2023 .PREV DISCUSSION... /ISSUED 0117 AM CDT Sun Sep 17 2023/ ...Synopsis... A surface cyclone will move across southern Alberta on Monday with a cold front extending into the northern Plains. In the wake of this cold front, dry and breezy conditions are expected across Montana and western North Dakota with winds of 15 to 20 mph and relative humidity of 13 to 18 percent. Fuels in this region, are critically dry, particularly across northeast Montana and northwest North Dakota where less than an inch of precipitation has fallen in the last 30 days. Farther west, stronger mid-level flow will overspread the Columbia Basin as the next shortwave trough approaches. Some of this stronger flow may mix to the surface amid a deepening boundary layer Monday afternoon/evening. Thunderstorms are expected to develop across the central/northern Sierra and the Klamath mountains Monday afternoon/evening. These storms will form in an environment with PWAT around 0.5 inches. Therefore, storms are expected to be mostly dry with LCLs around 10kft. An IsoDryT delineation has been added across this area to address this threat. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No Mesoscale Discussions are in effect as of Sat Sep 16 21:31:02 UTC 2023.

No watches are valid as of Sat Sep 16 21:31:02 UTC 2023.

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0356 PM CDT Sat Sep 16 2023 Valid 181200Z - 241200Z ...Days 3-4/Monday-Tuesday... Within the base of a large-scale trough over western Canada, several embedded midlevel perturbations accompanied by strong westerly flow aloft will overspread the northwestern CONUS on Days 3-4/Monday-Tuesday. Related downslope trajectories off the northern Cascades and northern Rockies will favor dry/breezy conditions across the Columbia Basin (on Day 3/Monday) and the northern Plains (on Days 3-4/Monday-Tuesday). Given dry fuels across both areas, elevated to locally critical fire-weather conditions are expected. ...Days 5-8/Wednesday-Saturday... A substantial mid/upper-level jet streak will advance southward along the West Coast, resulting in the development of a midlevel cut-off low over the western CONUS. Along the northwestern periphery of this feature, strong north-northeasterly surface winds will overspread Washington and Oregon. However, current indications are that increasing low/mid-level moisture and related cloud coverage may limit RH reductions and the overall fire-weather risk. Along the southern and eastern peripheries of the cut-off low, an expansive area of strong surface winds and low RH are expected across portions of the Southwest into the southern/central Rockies. While the dry/windy conditions will result in increasing fire-weather concerns, recent rainfall and generally unreceptive fuels cast uncertainty on the overall risk -- precluding Critical probabilities at this time. ..Weinman.. 09/16/2023 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0245 PM CDT Sat Sep 16 2023 Valid 162000Z - 171200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF SOUTHEASTERN TEXAS...AND OVER PORTIONS OF THE CENTRAL PLAINS AND MID-MISSISSIPPI VALLEY... ...SUMMARY... A few strong thunderstorms remain possible across a portion of southeastern Texas, and will continue over parts of the central Plains into the Mid-Mississippi Valley this afternoon and evening. ...Discussion... Few changes appear necessary to the ongoing outlook at this time, as current and anticipated evolution of convection remains in line with prior expectations. The primary changes in this outlook will trimming the MRGL risk area and removal of hail probability in southeastern Texas, in line with current convection evolution and motion, and also a slight northwestward expansion of MRGL risk over the southeastern Minnesota vicinity, where convection continues to develop just to the west of the existing outlook area. Otherwise, prior reasoning remains valid, across the CONUS. ..Goss.. 09/16/2023 .PREV DISCUSSION... /ISSUED 1101 AM CDT Sat Sep 16 2023/ ...TX... A long-lived MCS continues to track slowly southeastward across central TX. These storms produced occasional strong-severe wind gusts earlier this morning near/northwest of SJT. However, more recent trends have shown a general decreasing trend. At least remnants of the MCS are expected to persist through the day and track southeastward toward the coast. However, given the relatively weak winds aloft and lack of a more focused forcing mechanism, it is likely that the overall severe threat will remain rather marginal. Locally strong-damaging wind gusts will be the main risk. ...Central Plains into Mid MS Valley... A relatively strong upper trough and associated surface cold front is moving southeastward across parts of MN/WI/IA. By mid/late afternoon, this front will extend from near the KS/NE border into southern IA and southern WI. Scattered thunderstorm development will occur along/ahead of the front, in a moderately unstable air mass. Cool mid-level temperatures (-16 to -18C at 500mb) coupled with dewpoints in the 60s may result in sufficiently favorable thermodynamics for hail in the stronger updrafts. Steep low-level lapse rates could also promote gusty winds. However, the overall severe threat appears rather marginal at this time. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0149 PM CDT Sat Sep 16 2023 Valid 171200Z - 181200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF NORTH-CENTRAL MONTANA... The primary change with this update was to add an Isolated Dry Thunderstorm area over portions of northern California into south-central Oregon -- where fuels are modestly receptive. Similar to Day 1/Saturday, sufficient midlevel moisture and diurnal heating will support isolated thunderstorms over the higher terrain during the afternoon/evening hours -- aided by weak large-scale ascent preceding a mid/upper-level low off the California coast. Inverted-V thermodynamic profiles and 0.5-0.8 inch PW will favor a mix of dry/wet storms (mostly dry), with an attendant risk of isolated lightning-induced ignitions. Elsewhere, the previous forecast (see below) remains on track, with only minor changes made based on the latest high-resolution guidance. ..Weinman.. 09/16/2023 .PREV DISCUSSION... /ISSUED 0103 AM CDT Sat Sep 16 2023/ ...Synopsis... ...North-central Montana... A shortwave trough will move across southern Alberta on Sunday, this will overspread stronger mid-level flow across northern Montana and lead to lee cyclogenesis east of the Canadian Rockies with a tightening pressure gradient. The combination of deep mixing beneath this stronger mid-level flow, downslope flow, and a tightening surface pressure gradient, will lead to strong winds across northern Montana on Sunday. In addition, relative humidity will be very dry (9 to 16 percent). Much of this area has received less than half an inch of precipitation in the past 2 weeks. Therefore, given the weather conditions and dry fuels, there will be critical fire weather concerns across north-central Montana on Sunday. Farther west, some dry and breezy conditions are expected in the Columbia Basin as moderate mid-level flow remains in a region of deep boundary-layer mixing. Therefore, some elevated fire weather concerns are possible during the afternoon on Sunday. ...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 1232 PM CDT Sat Sep 16 2023 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF SOUTHEASTERN GEORGIA AND THE COASTAL CAROLINAS... ...SUMMARY... Isolated severe thunderstorms are possible Sunday afternoon and evening over parts of southeast Georgia and the Carolina Coastal Plain. A mid-level trough initially extending from the Upper Great Lakes south-southwestward to the central Gulf Coast area will advance steadily toward the Appalachians through Monday morning. Elsewhere, ridging aloft will prevail across much of the country. At the surface, a weak/diffuse front will progress eastward across the Appalachians, and then become a bit better-organized -- reaching the East Coast overnight. A weak frontal wave is forecast to evolve over southeastern Georgia during the day, and then move northeastward along the Carolina Coast through the second half of the period. ...Southeast... Daytime heating/weak destabilization is forecast over parts of Georgia and South Carolina Sunday, in the vicinity of the developing frontal wave. This should support development of showers and isolated thunderstorms, which would then spread northeastward in the vicinity of the North Carolina coast later in the period. With enhanced shear in the vicinity of the frontal wave, a few stronger storms/storm clusters may evolve with time, accompanied by risk for locally gusty winds. A brief tornado cannot be ruled out, particularly near or just off the Carolina coast through the second half of the period. ..Goss.. 09/16/2023 Read more

No watches are valid as of Fri Sep 15 22:16:02 UTC 2023.

No Mesoscale Discussions are in effect as of Fri Sep 15 22:16:02 UTC 2023.