Severe Storms

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1020 AM CST Sat Dec 24 2022 Valid 241700Z - 251200Z ...NO CRITICAL AREAS... No changes. See previous discussion below. ..Bentley.. 12/24/2022 .PREV DISCUSSION... /ISSUED 1140 PM CST Fri Dec 23 2022/ ...Synopsis... Cold air will remain in place across much of the CONUS today as high pressure remains situated from the West into the Midwest. This, in combination with generally poor fuel receptiveness to fire, will keep fire weather concerns minimal. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0143 PM CST Fri Dec 23 2022 Valid 241200Z - 251200Z ...NO CRITICAL AREAS... No changes. See previous discussion below. ..Bentley.. 12/23/2022 .PREV DISCUSSION... /ISSUED 1132 PM CST Thu Dec 22 2022/ ...Synopsis... The strong high pressure in the Plains will shift slightly eastward on Saturday. Cold temperatures will continue to be present across a substantial portion of the U.S. Fire weather concerns will continue to be minimal. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No watches are valid as of Fri Dec 23 19:46:01 UTC 2022.

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1115 AM CST Fri Dec 23 2022 Valid 241200Z - 251200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are not expected over the contiguous United States on Saturday. ...Synopsis... An expansive upper-level trough will extend from eastern Canada south over much of the eastern U.S. on Saturday as upper-level ridging dominates across much of the western states. A low-amplitude shortwave trough will move onshore across the Pacific Northwest Saturday accompanied by rain showers. NAM forecast soundings depict minimal elevated instability (less than 200 J/kg) near the coast, and a sporadic lightning strike will be possible in this area as precipitation moves onshore. Overall, the risk remains too low to introduce thunder probabilities with this outlook. Elsewhere, surface high pressure and a very cold/stable air mass will preclude thunderstorm development across the CONUS on Saturday. ..Bunting.. 12/23/2022 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1022 AM CST Fri Dec 23 2022 Valid 231630Z - 241200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Isolated lightning flashes will be possible today across parts of New England and south Florida. ...Synopsis... A deepening cyclone will develop northward across southwestern ON and western QC, within the left exit region of a 170 kt jet streak that will rotate around the eastern periphery of a deep mid-upper low over the Great Lakes. South of the cyclone, an arctic cold front will continue to surge eastward across the Mid-Atlantic/New England today, and southeastward into south FL. Buoyancy rooted in the mid levels will remain limited across New England, with only isolated lightning flashes expected with embedded/elevated convection. A narrow/forced band of showers, and very isolated lightning flashes, will move quickly offshore of NJ prior to 17z. Otherwise, the primary pre-frontal band of convection has shifted southward into the FL Straits, and only isolated thunderstorms will be possible this afternoon along the cold front/wind shift. ..Thompson/Jewell.. 12/23/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0953 AM CST Fri Dec 23 2022 Valid 231700Z - 241200Z ...NO CRITICAL AREAS... No changes. See previous discussion below. ..Bentley.. 12/23/2022 .PREV DISCUSSION... /ISSUED 1131 PM CST Thu Dec 22 2022/ ...Synopsis... A strong high pressure system within the Plains into the Southeast will keep cold temperatures entrenched across much of the CONUS today. Fire weather concerns are expected to be minimal as a result. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

MD 2069 CONCERNING HEAVY SNOW FOR WESTERN NEW YORK STATE
Mesoscale Discussion 2069 NWS Storm Prediction Center Norman OK 0951 AM CST Fri Dec 23 2022 Areas affected...western New York State Concerning...Heavy snow Valid 231551Z - 232145Z SUMMARY...Heavy snow with lake-enhanced rates of 1-2+ in/hr and localized blizzard conditions possible through much of the afternoon. DISCUSSION...In the wake of a strong surface low and cold front moving across the northeastern US, snow is forecast to increase in intensity and persists across portions of western NY State through much of this afternoon. Over the last 90 min, snow has increased in intensity with below 1/4 mile visibility and heavy snow reported at several locations along the eastern shores of lake Erie. As the surface low is forecast to drift slowly northeastward, low and mid-level winds are expected to become more southwesterly with time, aligning more favorably with the lake axis. Significant lake-enhancement of ongoing snow is expected within the post-frontal arctic airmass. Rates of 1-2 in/hr with localized rates greater than 2+ in/hr are possible. In addition to the heavy snow, the strong fetch of low-level southwesterly flow will be enhanced by strong surface pressure gradients along the backside of the surface low. Numerous gusts greater than 50 mph have been noted across western NY State in the last 2 hours. Localized blizzard conditions are likely along the immediate lake shore, where heavy blowing snow and strong wind gusts to 50-60 mph will likely persist well into the afternoon. ..Lyons.. 12/23/2022 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BUF... LAT...LON 43397899 43457851 43427796 43387781 43277759 43097778 42927800 42757828 42607871 42527890 42447912 42387930 42377938 42457945 42637930 42807911 42937913 43117915 43397899 Read more

No watches are valid as of Thu Dec 22 19:46:02 UTC 2022.

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0108 PM CST Thu Dec 22 2022 Valid 231200Z - 241200Z ...NO CRITICAL AREAS... No changes. See previous discussion below. ..Bentley.. 12/22/2022 .PREV DISCUSSION... /ISSUED 0145 AM CST Thu Dec 22 2022/ ...Synopsis... An arctic airmass will encompass much of the CONUS on Friday, while a cold front moves southward across South FL into the evening hours. While this pattern will generally limit fire-weather concerns, a brief period of dry/breezy conditions is possible across north-central FL behind the cold front during the afternoon. However, the brief nature of these conditions, coupled with marginally receptive fuels, should generally temper the fire-weather threat. ...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 1114 AM CST Thu Dec 22 2022 Valid 231200Z - 241200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms are not forecast on Friday. ...Synopsis and Discussion... An intense mid/upper-level cyclone will progress east-northeastward from the OH Valley/Great Lakes across the Mid-Atlantic and Northeast on Friday. A strong cold front will sweep quickly eastward off the Atlantic Coast Friday morning, and southeastward over FL through the period. Isolated thunderstorms may occur early in the period across parts of New England with weak instability and pronounced forcing for ascent associated with a strong low-level warm advection regime, and over parts of south FL before the front arrives. Organized severe thunderstorms are not anticipated across either area. ..Gleason.. 12/22/2022 Read more

MD 2062 CONCERNING SNOW SQUALL FOR EASTERN MISSOURI TO WESTERN ILLINOIS
Mesoscale Discussion 2062 NWS Storm Prediction Center Norman OK 1059 AM CST Thu Dec 22 2022 Areas affected...Eastern Missouri to western Illinois Concerning...Snow Squall Valid 221659Z - 222100Z SUMMARY...Sporadic, short-lived blizzard/snow squall conditions will be possible under a mesoscale snow band as it tracks east across parts of eastern Missouri and western Illinois through early/mid afternoon. DISCUSSION...Recent surface observations from far eastern IA show visibility reductions down to 1/4 mile at times under a persistent, though loosely organized, snow band. Based on latest RAP mesoanalysis, this band is primarily being driven by broad scale ascent ahead of a deepening upper low over the central Plains, augmented by more focused frontogenetical lift within the 850-700 mb layer. Forecast soundings indicate that much of this lift coincides with a 100-150 mb deep dendritic growth zone, which is likely yielding moderate, to at times heavy, snowfall rates up to 1 inch/hour. Concurrently, strong cold advection behind the surface front is supporting frequent wind gusts between 25-35 knots from eastern IA to central MO. The combination of these winds and moderate snowfall rates will likely result in periods of blizzard/snow squall conditions with visibility reductions briefly falling to 1/4 mile under the snow band as it continues moving east through early/mid afternoon. ..Moore.. 12/22/2022 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LOT...ILX...LSX...DVN...SGF...EAX... LAT...LON 39969175 41699077 42249007 42128917 41658861 40958810 40208837 38978904 38298989 37559125 37559200 38439313 38789294 39259244 39969175 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1029 AM CST Thu Dec 22 2022 Valid 221630Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS WESTERN PART OF CENTRAL/SOUTH FL AND EASTERN NC... ...SUMMARY... A severe thunderstorm remains possible this afternoon across far eastern North Carolina. A few severe thunderstorms are possible this evening into tonight, mainly over western portions of central to south Florida. ...Central to south FL... Isolated to scattered thunderstorms are developing over the Loop Current in the east-central Gulf within a modest low-level warm advection regime. This regime will gradually shift east towards the west coast of FL through this evening and across the peninsula tonight. Typically, this setup would yield convection weakening as it approaches the relatively cooler waters along the west coast. But a strengthening mid-level jetlet, separate yet influenced by amplification of the longwave trough centered over the north-central states, could support offshore supercells reaching the coast. Low-level flow will modestly amplify, stronger north and weaker south, while gradually veering from southwest to west overnight. This could yield a marginal severe threat spreading somewhat inland before weakening towards dawn. ...Eastern NC... A 1011-mb surface low near the NC/SC coastal border should deepen somewhat as it tracks northeast over eastern NC this afternoon. The corridor of surface-based instability near this cyclone will remain quite narrow inland of the shelf waters as abundant elevated showers and thunderstorms persist in the warm conveyor downstream. This process will likely mitigate diabatic destabilization until after convection passes by, but mid-level subsidence will ensue with substantial drying and weak warming aloft. This setup suggests that the environment conditionally favorable for surface-based supercells may remain storm-free, which is largely supported by morning CAM guidance. The southern Outer Banks should have the relatively greatest potential for a supercell to brush the region during the afternoon, with a brief severe wind gust or weak tornado possible. ..Grams/Moore.. 12/22/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1028 AM CST Thu Dec 22 2022 Valid 221700Z - 231200Z ...NO CRITICAL AREAS... Winds of 15-20 mph and relative humidity around 20-25 percent is currently being observed locally across portions of southwest Texas. However, these conditions will be brief as an arctic cold front continues to move southwestward into the area. In addition, fuels are mostly moist across this region which also precludes significant fire weather concern. ..Bentley.. 12/22/2022 .PREV DISCUSSION... /ISSUED 0144 AM CST Thu Dec 22 2022/ ...Synopsis... Anomalously cold surface temperatures accompanying an arctic airmass across the central CONUS will generally limit fire-weather concerns on Thursday. The one exception will be over parts of southwest TX, where a brief period of dry/breezy conditions is possible ahead of a southward-advancing cold front. However, these conditions should be too marginal/brief for any appreciable fire-weather threat. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0133 PM CST Wed Dec 21 2022 Valid 221200Z - 231200Z ...NO CRITICAL AREAS... The previous forecast (see below) remains on track. ..Squitieri.. 12/21/2022 .PREV DISCUSSION... /ISSUED 0142 AM CST Wed Dec 21 2022/ ...Synopsis... An arctic airmass will infiltrate much of the central CONUS along/east of the Rockies, generally limiting fire-weather concerns on Thursday. While a brief period of dry/breezy conditions is possible over southwest TX ahead of the southward-advancing cold front, these conditions should be too brief/marginal for any appreciable fire-weather threat. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No watches are valid as of Wed Dec 21 19:35:02 UTC 2022.

MD 2055 CONCERNING SNOW SQUALL FOR WYOMING TO SOUTHWEST SOUTH DAKOTA AND NORTHWEST NEBRASKA
Mesoscale Discussion 2055 NWS Storm Prediction Center Norman OK 1205 PM CST Wed Dec 21 2022 Areas affected...Wyoming to southwest South Dakota and northwest Nebraska Concerning...Snow Squall Valid 211805Z - 212100Z SUMMARY...Snow squalls will remain possible across northern and central Wyoming into portions southwest South Dakota and northwest Nebraska through the mid-afternoon hours as an arctic front continues to push south. DISCUSSION...Latest surface observations continue to show reduced visibility at or below one-quarter mile across much of central and northern WY where post-frontal winds are gusting to 45 mph amid light to moderate snow showers. Across western SD, snow has begun to increase in coverage as lift along the frontal surface increases. The combination of light falling snow, sustained winds near 20 mph (gusting to 30-40 mph), and a pre-existing snow pack are resulting in sporadic visibility reductions - particularly in open country. The expectation through mid-afternoon is for a continuation of persistent snow squalls across central WY where stronger winds and heavier snow rates (bolstered by embedded convective elements) will yield visibility reductions near/below one-quarter mile. Across SD/WY, more localized/sporadic post-frontal snow squalls are expected as strong cold advection continues over the next few hours and supports deeper downward mixing of 30-45 mph winds. Impacts will be most notable across open country where blowing snow model output suggests visibility reductions to one-quarter mile will become more likely as sustained wind speeds reach the 25-30 mph range. ..Moore.. 12/21/2022 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...ABR...LBF...UNR...CYS...BYZ...RIW... LAT...LON 42570014 42210042 41980121 41790214 41620336 41630436 41770582 42090734 42500850 42850944 43181000 43511003 44210994 44690945 44780465 45280259 45040175 44410097 42570014 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1128 AM CST Wed Dec 21 2022 Valid 221200Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF EASTERN NORTH CAROLINA...SOUTHEASTERN VIRGINIA...AND PORTIONS OF THE FLORIDA PENINSULA... ...SUMMARY... Isolated strong to severe thunderstorms may occur Thursday over eastern North Carolina and southeastern Virginia, as well as parts of the Florida Peninsula. ...Eastern North Carolina and Southeastern Virginia... A pronounced upper trough will continue eastward Thursday across the central/eastern CONUS. A strong cold front will sweep east- southeastward over these regions in tandem with the upper trough. A secondary surface low over coastal SC Thursday morning is forecast to develop northeastward across central/eastern NC and southeastern VA through the day. The inland return of low-level moisture across coastal/eastern NC should be limited owing to residual surface ridging over the Mid-Atlantic/Northeast that should be slow to erode. Still, it appears that upper 50s to low 60s surface dewpoints should be present in a narrow corridor over eastern NC and far southeastern VA as the surface low develops northeastward. Poor lapse rates and only modest daytime heating will likely keep instability weak, even though low-level and deep-layer shear are forecast to be quite strong. Given the strength of the low-level flow, isolated strong/damaging winds may occur with low-topped convection spreading quickly northeastward through the morning and afternoon. Better tornado potential should remain offshore where greater low-level moisture is present, but a brief tornado appears possible along the immediate NC Coast and Outer Banks. ...Florida Peninsula... Rich low-level moisture will likely remain confined along/south of a residual front across the FL Peninsula on Thursday. This region will remain mostly displaced to the south of ascent associated with the upper trough over the central/eastern CONUS. However, a strong west-southwesterly mid-level jet will spread over much of FL through the day. Low-level convergence along the surface boundary should remain weak. But, any convection that can develop along/south of this boundary could become organized in the presence of weak instability and strong deep-layer shear. Isolated damaging winds appear to be the main threat if any thunderstorm can be sustained. ..Gleason.. 12/21/2022 Read more

MD 2054 CONCERNING HEAVY SNOW FOR SOUTHEAST SOUTH DAKOTA...FAR NORTHWEST IOWA...SOUTHERN MINNESOTA INTO FAR NORTHWEST WISCONSIN
Mesoscale Discussion 2054 NWS Storm Prediction Center Norman OK 1033 AM CST Wed Dec 21 2022 Areas affected...Southeast South Dakota...far northwest Iowa...southern Minnesota into far northwest Wisconsin Concerning...Heavy snow Valid 211633Z - 212030Z SUMMARY...The potential for heavy snowfall rates between 1-2 inches per hour is expected to increase through the late morning and early afternoon from the mid Missouri River Valley to the upper Mississippi River Valley. DISCUSSION...Regional radar mosaics from the past 1-3 hours show an elongated zone of increasing reflectivity values from eastern SD to southern MN. This is likely in response to strengthening isentropic ascent in the 925-700 mb layer within a broad warm frontal zone draped across the region. This mesoscale ascent is augmenting more broad, synoptic lift ahead of an approaching shortwave trough over the northern Plains, and is supporting an increase in coverage of moderate, to at times heavy, snowfall rates per latest surface observations and regional web cams. Latest guidance suggests that this trend should continue through at least early afternoon as the synoptic low continues east/southeast and saturation of the lowest 1-2 km continues. Forecast soundings indicate that much of the low/mid-level ascent coincides with a ~100 mb deep dendritic growth zone, which will favor efficient snow production and the potential for heavy snowfall rates around 1 inch per hour. The current warm advection regime over eastern SD/southern MN will likely support periods of broken snow bands through the early afternoon (which appears probable based on latest reflectivity trends), and this may yield localized higher snowfall rates between 1-2 inches/hour. The approach of the mid-level cold front later this afternoon may maintain the potential for localized banding via frontogenetical processes. ..Moore.. 12/21/2022 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...DLH...ARX...MPX...DMX...FSD...ABR... LAT...LON 45649472 45919387 45959300 45809240 45299199 44759199 44179265 43729372 43059523 42879587 42899669 43129722 43519746 44169712 44959611 45649472 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1016 AM CST Wed Dec 21 2022 Valid 211700Z - 221200Z The previous forecast (see below) remains on track, with no changes or additions made. ..Squitieri.. 12/21/2022 .PREV DISCUSSION... /ISSUED 0142 AM CST Wed Dec 21 2022/ ...Synopsis... A large-scale trough will amplify over the central CONUS, as an intense mid/upper-level speed max overspreads the western states. The strong midlevel flow (60-75 kt at 500 mb) perpendicular to the central Rockies will support a deepening lee cyclone over eastern CO during the afternoon, before a strong cold front advances southward across the central/southern Rockies and adjacent Plains into the overnight hours. ...I-25 Corridor in south-central CO into northeast NM... As the aforementioned mid/upper-level speed max intercepts the central/southern Rockies, 15-25 mph sustained westerly surface winds (with 40-50 mph gusts) should develop in the immediate lee of the high terrain from south-central CO into northeast NM. Here, strong downslope warming/drying should yield 15-25 percent RH during the afternoon. The combination of strong/gusty winds and low RH atop receptive fuels will support elevated conditions, primarily along the I-25 corridor during the afternoon hours. While locally critical conditions are possible (especially through gap-flow areas), these conditions are too localized for Critical highlights. Strong/gusty winds and low RH are also expected north of the Elevated area along the Front Range foothills in north-central CO, though the localized nature of these conditions precludes highlights. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1013 AM CST Wed Dec 21 2022 Valid 211630Z - 221200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not forecast today and tonight. ...Synopsis... Mid-morning surface observations and satellite imagery reveal a cold front meandering southward along the FL peninsula with a weak, broad surface low off the FL east coast. Despite somewhat weak inhibition sampled in the MFL and KEY RAOBs, subsidence overspreading the region (evident in low-level water-vapor imagery) has stunted any convective development thus far. However, daytime heating should foster gradual destabilization through the day, and weak forcing along the front may be adequate for isolated convection across south FL. While strong mid to upper-level flow will continue to support nearly 50 knots of 0-6 km bulk shear, weak CAPE profiles of the most-unstable layer coupled with increasing mid-level dry air suggests updraft strengths will remain modest and will limit the potential for organized severe convection. The low off the FL coast is expected to shift north into the Carolinas during the overnight hours in response to increasing 850-700 mb warm advection. Warming, saturation, and lift within this layer will steepen mid-level lapse rates and support isolated to scattered thunderstorm development overnight across the Carolinas. Deeper, more robust convection appears most probable along the SC coast where warmer low-level temperatures will support deeper parcel trajectories and effective shear values near 30 knots. A few instances of small hail and/or strong wind gusts are possible, but the overall severe threat is expected to remain low. ..Moore/Grams.. 12/21/2022 Read more