Severe Storms

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1155 AM CDT Wed Sep 07 2022 Valid 071700Z - 081200Z ...EXTREMELY CRITICAL FIRE WEATHER AREA FOR NORTH-CENTRAL MONTANA... ...CRITICAL FIRE WEATHER AREA FOR SOUTHEASTERN OREGON AND VICINITY... ...CRITICAL FIRE WEATHER AREA FOR PARTS OF WESTERN AND CENTRAL MONTANA... ...CRITICAL FIRE WEATHER AREA FOR SCATTERED DRY THUNDERSTORMS IN EAST-CENTRAL OREGON...CENTRAL IDAHO...SOUTHWEST MONTANA... The ongoing forecast remains on track with minimal changes to the isolated dry thunder area based on observations. A multi-faceted and high-impact fire weather day is still expected across the Northwest into the northern Great Basin and northern Rockies. In the short term, thunderstorm activity is most likely to occur from central into east-central Oregon as a weak disturbance moves north and east. Greater storm coverage can be expected as heating occurs through the afternoon and mid-level ascent increases late afternoon into the evening. Sustained winds and strong gusts will also increase across north-central Montana later today as the boundary layer deepens substantially. See the previous forecast for more details. ..Wendt.. 09/07/2022 .PREV DISCUSSION... /ISSUED 0104 AM CDT Wed Sep 07 2022/ ...Synopsis... A strong pattern shift is forecast across much of the western CONUS today and tonight as the prominent ridge of high pressure is broken down by a strengthening Pacific trough. Unseasonably strong winds aloft along with increasing forcing for ascent will overspread the Pacific Northwest and Northern Rockies, while a cold front sweeps out of southern Canada. Ahead of the front, an unstable atmosphere along with very warm temperatures and strong winds will support weather conditions favorable for dry thunderstorms as well as extreme fire behavior. ...Northern Rockies and adjacent plains... Across portions of northern ID and MT, westerly winds are forecast to increase early this morning and through much of the day ahead of the approaching cold front. Enhanced by strong surface pressure gradients from the deepening lee low across the southern Canadian Rockies, west-southwest surface winds of 25-35 mph are likely by early afternoon. Deep vertical mixing to 600 mb evident on regional model soundings also shows potential for stronger surface gusts (40-50+ mph) as 50-65 kt of flow aloft approaches. Coincident with peak heating, the well-mixed boundary layer, very warm surface temperatures, and downsloping westerly flow will support low teens to single digit RH values. The combination of hot, dry and windy conditions within very dry fuels lends high confidence to widespread critical and extremely critical fire weather conditions across portions of northern and central MT. Extreme fire weather conditions should continue through the afternoon ahead of the fast-moving cold front arriving after dark. While cooler temperatures and increasing humidity will accompany the frontal passage, a rapid wind direction change to northerly flow is also expected. Fire weather concerns may linger for a few hours overnight before winds gradually decrease and surface humidity recovers. ...Dry Thunderstorms... Ahead of the cold front, dynamic ascent and modest mid-level moisture associated with the approaching upper trough will support isolated to scattered thunderstorms from northern CA, through portions of the northern Great Basin, into the northern Rockies. Forecast sounding show generally 0.5 to 0.75 in PWAT values with 100-500 J/kg of MUCAPE. Below the unstable layers, high LCLs (2-3 km AGL) and with fast storm motions will favor poor precipitation efficiency and the potential for strong outflow winds over much of the West. Recent fire activity indicates that fuels remain highly receptive across the region and will support critical lightning-driven fire weather concerns. Storm coverage is expected to be greatest along the cold front from portions of eastern OR, central ID, into western MT. HREF lightning probabilities show high confidence in the potential for scattered strike coverage atop highly receptive fuels in this area. Additionally, the risk for convective outflow gusts greater than 60 mph also suggests a high probability of critical fire weather concerns across this region given the expected storm potential. A Scattered dry thunderstorm area was introduced, and additional information related to the severe weather risk is available in the Day1 Convective Outlook. ...Cascades and northern Great Basin... Across the Cascades and Great Basin westerly flow will remain strong in the wake of the cold front farther east. Bolstered by increasing flow aloft from the upper trough, widespread 15-25 mph surface winds are expected along with low humidity. Widespread elevated fire weather conditions are expected within dry fuels. Critical fire weather conditions will also be possible across portions of the northern Great Basin across southern OR, and far northern CA/NV. Here, higher confidence in winds greater than 25 mph exists along with afternoon humidity values below 15%. ...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 1134 AM CDT Wed Sep 07 2022 Valid 071630Z - 081200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE INTERIOR NORTHWEST/NORTHERN ROCKIES... ...SUMMARY... Scattered thunderstorms may yield scattered severe wind gusts, a few of which could be significant, across portions of the interior Northwest and northern Rockies, centered on mid-afternoon through early evening. ...Interior Northwest/northern Rockies... A high-impact to extreme fire weather day is anticipated this afternoon into the evening. Please see the latest Day 1 Fire Weather Outlook for details on all hazards. Upper ridge will break down over the region as a vigorous shortwave trough over British Columbia amplifies and shifts east-southeastward toward the Canadian Rockies. Mid-level height falls accompanying this wave will overspread the interior Northwest as a belt of 50-kt 500-mb westerlies becomes centered from northeast Oregon/eastern Washington across northern Montana into southern Saskatchewan. Modest moisture along with record warmth will yield very deeply mixed boundary layers, especially east of the Rockies in Montana and across the Idaho Snake River Valley into southeast Oregon. Dry thunderstorms will increase in coverage this afternoon as both the boundary layer deepens and large-scale forcing for ascent strengthens. While buoyancy will be quite meager with MLCAPE of 300 J/kg or less, the extreme lapse rate profiles to 500 mb will support dry downbursts mixing to the surface from high-based/low-topped convection. Latest convection-allowing guidance are consistent in suggesting severe wind gusts will be prevalent within this fast-moving, skeletal activity. The eastern extent of this threat may include amalgamating convective outflows which could maintain severe gusts into eastern Montana despite diminishing lightning flashes this evening. ...Southeast/south-central Texas and southwest Louisiana... A minor mid-level impulse evident in water vapor imagery over the Ark-La-Tex will gradually move south-southwest into south Texas by this evening. A pocket of relatively cooler mid-level temperatures and steeper lapse rates attendant to this impulse should support a plume of moderate to large MLCAPE of 1500-3000 J/kg. While deep-layer shear will be modest and generally offset west of the greater instability/buoyancy, isolated marginally severe hail and strong to localized severe wind gusts will be possible as scattered thunderstorms develop this afternoon. ..Guyer/Bentley.. 09/07/2022 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1229 PM CDT Tue Sep 06 2022 Valid 071200Z - 081200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF EASTERN OREGON...CENTRAL IDAHO...WESTERN/CENTRAL MONTANA... ...SUMMARY... Thunderstorms capable of isolated severe wind gusts will be possible from eastern Oregon into central Idaho and western and central Montana, mainly Wednesday afternoon and evening. ...Interior Northwest into the northern Rockies/High Plains... A partial breakdown of the highly amplified western upper ridge is expected across the Northwest and northern Rockies on Wednesday, as a vigorous midlevel shortwave trough moves across British Columbia and Alberta through the day. Moisture will generally remain rather limited across the Northwest, but may become sufficient to support convection within a hot and well-mixed environment across the interior Northwest into parts of Montana. Very limited buoyancy will tend to limit storm intensity, but the thermodynamic environment will be quite favorable for isolated downburst winds with any sustained storms. There will also be some potential for outflows to consolidate and move east-northeastward with a threat for gusty winds, even if convection attendant to the outflow remains relatively disorganized. A Marginal Risk was added in a corridor from eastern OR through central ID into western/central MT, where there appears to be the greatest potential for possibly multiple rounds of convection with strong/locally severe gusts from late afternoon into the evening. ...Central/east TX... A low-amplitude midlevel shortwave trough is forecast to move southward into parts of central/east TX on Wednesday, around the eastern periphery of the western upper ridge. While this shortwave may tend to weaken and not be ideally timed with the diurnal cycle, it may still aid in the development of scattered thunderstorms during the afternoon. While northerly midlevel flow may support the potential for weakly organized cells/clusters, the severe potential remains uncertain, with generally weak midlevel lapse rates and low-level flow expected. Storms capable of isolated strong gusts and/or marginal hail cannot be ruled out, but confidence is too low to add probabilities at this time. ..Dean.. 09/06/2022 Read more

No watches are valid as of Tue Sep 6 17:34:02 UTC 2022.

No Mesoscale Discussions are in effect as of Tue Sep 6 17:34:02 UTC 2022.

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Tue Sep 06 2022 Valid 061630Z - 071200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms are not expected through tonight. ...Mid-Atlantic States... This morning's isolated severe/brief tornado potential should continue to diminish across the New Jersey coastal vicinity as MCV-related forcing for ascent and moderately strong low-level shear/SRH likewise shift eastward offshore ahead of the eastward-moving surface low. Elsewhere, a few stronger storms with gusty winds could occur this afternoon in areas such as far eastern North Carolina. However, the potential for severe-caliber storms should be tempered by weak mid-level lapse rates/vertical shear. ..Guyer/Bentley.. 09/06/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1107 AM CDT Tue Sep 06 2022 Valid 061700Z - 071200Z No changes to the ongoing forecast. ..Wendt.. 09/06/2022 .PREV DISCUSSION... /ISSUED 1233 AM CDT Tue Sep 06 2022/ ...Synopsis... Fire weather concerns will persist across parts of the Great Basin and northern/central Rockies today as a dominant upper high maintains hot and dry conditions across the western CONUS. Pockets of elevated fire weather conditions are possible across much of the Great Basin and northern Rockies, but are expected to be fairly transient in nature. A more robust fire weather threat will likely emerge across parts of the northern Sierra Nevada and southern Cascades under a belt of stronger mid-level flow. ...Northern Sierra Nevada/southern Cascades... An open trough moving into the northeast Pacific will bolster mid-level gradient winds across the Pacific Northwest this afternoon. This will likely coincide with peak diurnal heating/boundary-layer mixing, which will aid in downward transfer of stronger gusts - especially in the lee of terrain features. Latest ensemble guidance maintains reasonably high probability for 15-20 mph winds with gusts near 25 mph by late afternoon. Combined with afternoon RH minimums in the low teens, a few hours of sustained elevated fire weather conditions remain likely. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No watches are valid as of Mon Sep 5 17:40:02 UTC 2022.

No Mesoscale Discussions are in effect as of Mon Sep 5 17:40:02 UTC 2022.

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1200 PM CDT Mon Sep 05 2022 Valid 061200Z - 071200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for severe thunderstorms is expected to be relatively low on Tuesday. ...Synopsis... An upper ridge is forecast to amplify further across the western CONUS on Tuesday. A broad, positively tilted mid/upper-level trough will persist over the East, as several embedded vorticity maxima move through the mean trough position. A weak surface low is forecast to develop near a remnant baroclinic zone over the Mid Atlantic during the morning and then move offshore by the end of the period. Scattered to widespread convection is expected within a seasonably moist environment from the ArkLaTex into the Mid South, though weak deep-layer shear is expected to limit the organized severe-thunderstorm threat. Extensive convection is also expected from coastal NC into the Mid Atlantic within a slightly stronger flow regime, though any severe potential across quite uncertain across that region. ...Mid Atlantic... Guidance varies somewhat regarding the timing and intensity of surface cyclone development across the Mid Atlantic Tuesday morning. The stronger solutions depict a modest increase in low-level flow/shear during the first part of the day near the cyclone track and surface boundary, which could potentially support a threat of locally damaging wind gusts and/or a brief tornado as substantial convection moves through the region. However, given the uncertainty regarding this scenario and the relatively limited areal extent of any potential threat before convection moves offshore, no probabilities have been introduced at this time. ..Dean.. 09/05/2022 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1127 AM CDT Mon Sep 05 2022 Valid 051630Z - 061200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS CENTRAL TEXAS... ...SUMMARY... Isolated marginally severe thunderstorms are possible across a portion of central Texas centered on 3 to 7 PM CDT. ...Central Texas... A mid-level low will drift southwestward across far southeast Oklahoma and northeast Texas through tonight. The western fringe of relatively cooler mid-level temperatures in conjunction with a belt of 15-25 kt mid-level northerlies should overlap a confined corridor of low to mid 60s surface dew points near the intersection of a diffuse surface front and dryline. Within this regime, isolated to scattered thunderstorms should develop in the mid to late afternoon. Marginally severe hail and localized strong to severe gusts will be possible until convection begins to weaken by around sunset. ...Midwest to Appalachians... Cloud breaks and a moist air mass (near 70F dewpoints) will be conducive for moderate destabilization across the Lower Ohio Valley, although weak wind profiles should keep any stronger storms of a pulse-type character with limited severe potential. Farther east, modestly stronger low/mid-level southwesterly winds will reside near and in the windward side of the Appalachians through tonight. However, insolation will be limited by the generally prevalent nature of existing cloud cover and precipitation. A bit more insolation/destabilization could occur across northern/eastern Georgia into South Carolina/western North Carolina this afternoon. A few stronger storms could occur in this region, but organized severe potential is currently expected to remain low. ..Guyer/Bentley.. 09/05/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Mon Sep 05 2022 Valid 051700Z - 061200Z No changes to the ongoing forecast. ..Wendt.. 09/05/2022 .PREV DISCUSSION... /ISSUED 0105 AM CDT Mon Sep 05 2022/ ...Synopsis... Fire weather concerns will linger across the northern Rockies for today as a winds increase within a hot/dry boundary layer. A belt of strong mid-level flow is expected to shift from the Pacific Northwest into the northern Rockies over the next 24 hours as a low-amplitude upper wave shifts into western Canada. This will support a breezy and dry downslope wind regime across parts of ID into central/northern MT where fuels continue to cure after several days of hot conditions. ...Northern Montana to North Dakota... Elevated fire weather conditions are expected from north-central MT into far western ND this afternoon. A surface low/lee trough is evident across the northern High Plains and Canadian Prairies in early-morning surface observations/analyses. This feature will shift east through the day in tandem with the upper disturbance, establishing a westerly downslope wind regime across much of MT. Diurnal heating/boundary-layer mixing will help downward transfer of strengthening mid-level flow as RH values fall into the teens and low 20s. Sustained winds near 15 mph will be accompanied by frequent gusts between 20-30 mph. Brief periods of critical conditions are possible, but confidence in the duration/coverage of 20+ mph winds remains low. Recent fire activity across the region indicates that fuels remain receptive and will support the fire weather threat. A cold front is expected to push across north/northeast MT during the overnight hours, bringing a wind shift to the north/northwest. ...Idaho... The 00 UTC BOI sounding sampled a very dry boundary layer with 0-1 km mean RH near 12%. With little moisture flux into the region expected over the next 24 hours, similar low-level thermodynamic conditions are anticipated for this afternoon. Strong diurnal heating through the Snake River Plain will support deep boundary-layer mixing and RH reductions into the low teens (and possibly single digits) by mid afternoon. Sustained winds near 15-20 mph may occasionally gust to 25 mph. Elevated conditions appear likely, and brief/localized periods of critical conditions are possible. ...Northwest NV into southern OR... Localized elevated conditions are possible this afternoon from far northeast CA/northwest NV into southern OR. Widespread RH reductions below 15% are likely with pockets of breezy winds between 15-20 mph. With the stronger synoptic pressure gradients shifting to the east away from the region through the day, such winds will most likely be confined to the vicinity of terrain features, limiting confidence in a more widespread fire weather concern. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No watches are valid as of Sun Sep 4 17:38:02 UTC 2022.

No Mesoscale Discussions are in effect as of Sun Sep 4 17:38:02 UTC 2022.

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1200 PM CDT Sun Sep 04 2022 Valid 051200Z - 061200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms potential appears low on Monday. ...Synopsis and Discussion... An upper anticyclone will persist over much of the western CONUS on Monday. Compared to prior days, weak large-scale ascent should limit overall convective potential to mainly terrain-driven circulations across the Four Corners region to the Mogollon Rim, and parts of the Sierra Mountains into the Coastal Ranges of southern CA. While strong/gusty winds may occur with any convection that can develop, overall sparse thunderstorm coverage precludes any severe wind probabilities. Thunderstorms will be possible across a broad portion of the central and eastern states extending from parts of the southern Plains to the Northeast, mainly Monday afternoon and evening. Weak upper troughing should extend from the ArkLaTex region northeastward to the OH Valley and Great Lakes. Generally weak mid-level flow and related deep-layer shear is anticipated east of this feature across the warm sector, which should limit thunderstorm organization. Poor mid-level lapse rates should also temper instability across much of these regions, with moderate to perhaps strong instability developing along/south of a weak front that should be draped across parts of north/central TX. While occasional strong/gusty winds may occur with any convection that develops, the threat for organized severe thunderstorms still appears low. ..Gleason.. 09/04/2022 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sun Sep 04 2022 Valid 041630Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE DESERT SOUTHWEST AND THE SOUTHERN GREAT PLAINS... ...SUMMARY... Isolated severe wind gusts are possible during the late afternoon to early evening over parts of the Desert Southwest along with southeast Oklahoma and North Texas. ...Desert Southwest... With a moist air mass remaining across the region, strong boundary layer heating and orographic influences will again yield isolated thunderstorm development late this afternoon into evening. This will include a corridor from northwest Arizona, far southern Nevada into interior southern California. A belt of moderately strong easterly winds will persist on the southern periphery of the Great Basin-centered upper ridge, which will support a west-southwestward movement of some potentially semi-organized storms. A well-mixed boundary layer will support a threat for isolated severe wind gusts from the late afternoon into early/mid-evening. ...Southeast Oklahoma and North Texas... A southward-sagging front along with different heating/outflow will focus renewed thunderstorm development this afternoon. With 15-25 kt mid-level north/northwesterly winds, weakly organized clusters may congeal and spread south in north Texas with a threat for locally strong to severe wind gusts given surface temperatures in the 90s F. Storms will weaken towards/after sunset as the boundary layer cools and MLCIN increases. ..Guyer/Bentley.. 09/04/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1104 AM CDT Sun Sep 04 2022 Valid 041700Z - 051200Z ...CRITICAL FIRE WEATHER AREA FOR FAR NORTHWESTERN GREAT BASIN... No changes to the ongoing forecast. ..Wendt.. 09/04/2022 .PREV DISCUSSION... /ISSUED 0153 AM CDT Sun Sep 04 2022/ ...Synopsis... Two upper-level shortwave troughs are forecast to move over the ridge centered in the Great Basin today, acting to deamplify the upper-level high pressure. The first small and compact shortwave over northwestern Montana this morning is forecast to weaken and move eastward across northern Montana and North Dakota throughout the day. The second shortwave, currently off the Pacific Northwest coast, is forecast to move into British Columbia and Washington state by the end of the day. In response at the surface, a low-pressure trough is forecast to develop over the northern High Plains. Ahead of these shortwave troughs, a broad area of elevated fire weather conditions is expected from northeastern California east-northeastward across Montana. The environment across this region will be characterized by hot, dry, and well-mixed boundary layers yielding critical RH values in the presence of enhanced flow aloft. The best overlap of strong winds (>20 mph) and critical RH values is in the vicinity of the California/Nevada/Oregon border, so a focused critical area has been delineated across that region. Farther east ahead of the surface pressure trough, critical south-southeasterly winds are likely across the western Dakotas, but RH values may be a limiting factor with surface dewpoints only mixing into the mid-to-upper 40s F. Nevertheless, this different fire-weather regime compared to areas farther west should also lead to elevated fire-weather concerns. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No watches are valid as of Sat Sep 3 17:40:02 UTC 2022.

No Mesoscale Discussions are in effect as of Sat Sep 3 17:40:02 UTC 2022.

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1222 PM CDT Sat Sep 03 2022 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF THE DESERT SOUTHWEST... ...SUMMARY... There is a Marginal Risk of severe thunderstorms across portions of the Desert Southwest Sunday afternoon/evening. ...Synopsis... The upper-level ridge across the western CONUS will deamplify somewhat tomorrow as a mid-level shortwave traverses the northern Rockies and northern Plains. Farther east, a slow-moving upper-level low will continue to slowly drift east through the Ohio Valley. Thunderstorms are expected in much of the moist sector, extending from most of Texas and the Southeast through the Ohio Valley and into the Northeast. An even greater concentration of thunderstorms is likely near and east of the upper-level low across the Ohio Valley. However, wind shear will remain weak across the warm sector. Therefore, storm organization should be minimal. ...Portions of the Desert Southwest... Some thunderstorms will likely develop and move off the higher terrain across portions of Northwest Arizona Sunday afternoon/evening. Weak to moderate instability amid 30 knots of mid-level easterly flow should provide an environment favorable for a few strong to severe storms. The primary threat will be damaging winds, particularly with any clusters which may develop and move across the Colorado River Valley. ...Northern/Central Texas... There is some signal in convective allowing guidance for a potential cluster/southward moving line of storms across central Texas. A cold front will be moving south through this region which could provide the focus for more concentrated convection, and forecast MLCAPE will be around 2000-2500 J/kg. However, wind shear will be very weak and therefore, organized severe convection is not anticipated. ..Bentley.. 09/03/2022 Read more