Severe Storms

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0433 PM CDT Thu Aug 31 2023 Valid 021200Z - 081200Z A large upper-level trough will bring cool and wet conditions to much of the West Coast. Portions of the Inter-Mountain West will be breezy through the period, but these breezy conditions are expected where fuels are already moist and where additional monsoon moisture is expected with several days of wet thunderstorms expected to moisten fuels further. Therefore, the primary fire weather concerns will be across the central and northern Plains where several weeks of dry conditions have started to dry out fuels and across Texas where exceptional drought continues with very susceptible fuels. Lee troughing is expected across the Plains for much of the next week as the upper-level trough advances east and several mid-level shortwave troughs traverse the central Rockies. There is still a fair amount of uncertainty which days will have the strongest winds and where those winds will overlap low relative humidity which precludes critical probabilities at this time. However, drying fuels and an extended period of warm/dry conditions should result in critically dry fuels for much of the Plains by next week. Therefore, once the timing and location of dry and breezy conditions becomes more clear in later outlooks, critical probabilities or Day 1/2 Elevated/Critical areas may be needed. ..Bentley.. 08/31/2023 ...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 0248 PM CDT Thu Aug 31 2023 Valid 011200Z - 021200Z Fuels have dried across the plains the past few days amid a dry, continental airmass. Therefore, when dry and breezy conditions develop tomorrow, in response to lee troughing across western South Dakota, large fire concerns will be elevated from southwest Kansas into central Nebraska. Sustained winds could exceed 20 mph for a few hours in the afternoon with relative humidity in the upper teens. Therefore, despite fuels that may only be marginally dry, the strong winds should compensate. Otherwise, no changes were necessary. See previous discussion below. ..Bentley.. 08/31/2023 .PREV DISCUSSION... /ISSUED 1143 PM CDT Wed Aug 30 2023/ ...Synopsis... On Friday, the strongest winds will largely remain in regions where fuels do not support inclusion of highlights. A deepening trough across the West Coast will bring increasing moisture and shower and thunderstorm activity across northern California into the Great Basin. Windy and dry conditions will be possible across central Nevada into Utah, however recent rainfall has left fuels in this region well below seasonal normals which has tempered the fire threat. Lee troughing across the Central and Southern Plains will bring an increase in southerly flow, with potential for relative humidity dropping to around 20 percent. Overall, the strongest winds appear to be across the Oklahoma Panhandle northward into Colorado where fuels are too moist to include highlights at this time. ...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 0243 PM CDT Thu Aug 31 2023 Valid 312000Z - 011200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON AND EVENING ACROSS PARTS OF SOUTH CENTRAL THROUGH NORTHWESTERN ARIZONA...AND ADJACENT PORTIONS OF SOUTHEASTERN CALIFORNIA...SOUTHERN NEVADA AND SOUTHWESTERN UTAH... ...SUMMARY... Widely scattered thunderstorms with a few strong wind gusts are possible across Arizona and the Lower Colorado River Valley late this afternoon into evening. ...20Z Update... No changes were made to the severe probabilities, but there are some adjustments to the categorical (10 percent probability) thunder line to account for the progression of synoptic features, and current trends concerning destabilization. Particularly east of the Colorado Rockies into the northern Great Plains Red River Valley/Upper Midwest, stronger mid/upper support for convective development has shifted into the eastern Canadian Prairies, downstream of the significant mid-level low/troughing migrating north of the international border vicinity. A plume of rather modest moisture does exist ahead of associated lee surface troughing, extending south-southwestward across the eastern Dakotas toward the Raton Mesa vicinity. However, warm/dry layers in the lower/mid troposphere seem likely to suppress an appreciable risk for sustained thunderstorm development across much of this region. ..Kerr.. 08/31/2023 .PREV DISCUSSION... /ISSUED 1124 AM CDT Thu Aug 31 2023/ ...AZ/lower CO River Valley this afternoon through tonight... A midlevel high over NM this morning will shift east-northeastward toward the southern/central High Plains as an upstream shortwave trough evolves into a closed low over western OR and northern CA. A plume of 1.25-1.50 inch PW will be drawn northward from southwest AZ toward southeast NV and southwest UT through tonight around the northwest periphery of the NM high, as height gradients/flow gradually strengthen between the high and the developing Pacific coast low. This will result in some destabilization (when combined with daytime heating and deep mixing) and the potential for scattered high-based thunderstorms this afternoon into tonight from southern AZ into extreme southeast CA, southeast NV and extreme southwest UT. Thunderstorms are expected to develop over the Mogollon Rim and the higher terrain in southeast AZ, and subsequently spread westward/northwestward on convective outflows. MLCAPE up to 1000 J/kg with deep inverted-V profiles will support strong/isolated severe outflow gusts from later this afternoon into early tonight as thunderstorm clusters spread across AZ toward southeast NV/southwest UT. Read more

MD 2067 CONCERNING TORNADO WATCH 662... FOR PORTIONS OF THE CAROLINA COAST
Mesoscale Discussion 2067 NWS Storm Prediction Center Norman OK 0436 PM CDT Wed Aug 30 2023 Areas affected...portions of the Carolina coast Concerning...Tornado Watch 662... Valid 302136Z - 302230Z The severe weather threat for Tornado Watch 662 continues. SUMMARY...The risk for mini supercells and an attendant risk for a couple of tornadoes will likely continue to move northeast up the Carolina coast through the evening. A tornado watch will be considered to include portions of the Outer Banks to the northeast of the Tornado Watch #662 when the environment becomes more favorable for tornadoes. DISCUSSION...Late afternoon radar imagery from KLTX (Wilmington, NC) shows a cluster of quasi-discrete supercells near the northeast SC coast/Grand Strand vicinity and adjacent continental shelf waters south of Cape Fear. A significant increase in low-level shear has been observed at KLTX during the past 2 hours with 0-1 km SRH (using observed storm motion) in excess of 400 m2/s2. With a nearly saturated profile and mid 70s surface dewpoints, only weak buoyancy is analyzed. However, the strengthening low-level shear profiles and enlarging hodographs will continue to be favorable for low-level mesocyclones over the next few hours as the outer bands of Idalia continue northeastward up the coast. The area of favorable shear/buoyancy will probably overspread portions of the Outer Banks later this evening. ..Smith/Grams.. 08/30/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...MHX...RAH...ILM...CHS... LAT...LON 33427996 33767980 35397647 35447595 35287554 34847542 32957915 33147971 33427996 Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0357 PM CDT Wed Aug 30 2023 Valid 011200Z - 071200Z Wetting rain is expected across a large portion of the Northwest and northern California on Day 2/3. As a result, dry fuels will primarily be limited to eastern Montana into North Dakota, and portions of central/east Texas into Louisiana and far western Mississippi. Windy conditions are expected across much of the Great Basin and into the central Rockies Day 3-5, but given current fuel states and an increase in low-level moisture with each day, fire weather concerns should remain minimal during this period. The greatest concern may start to materialize across the central/northern Plains into the Upper Midwest. Fuels are not quite dry at this time, but are trending that direction. Several days of dry and breezy conditions at the end of this week and into the weekend will dry fuels further and eventually they may be dry enough to support large fire spread. Therefore, fuel status will be monitored closely in this region and critical probabilities may eventually be needed. ..Bentley.. 08/30/2023 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

WW 0662 Status Updates
STATUS REPORT ON WW 662 THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA. ..KERR..08/30/23 ATTN...WFO...ILM...CHS... STATUS REPORT FOR WT 662 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS NCC019-047-129-141-302140- NC . NORTH CAROLINA COUNTIES INCLUDED ARE BRUNSWICK COLUMBUS NEW HANOVER PENDER SCC005-013-015-019-029-035-043-049-051-053-089-302140- SC . SOUTH CAROLINA COUNTIES INCLUDED ARE ALLENDALE BEAUFORT BERKELEY CHARLESTON COLLETON DORCHESTER GEORGETOWN HAMPTON HORRY JASPER WILLIAMSBURG AMZ250-252-254-256-330-350-352-302140- CW . ADJACENT COASTAL WATERS INCLUDED ARE Read more

WW 662 TORNADO NC SC CW 301450Z - 310200Z
URGENT - IMMEDIATE BROADCAST REQUESTED Tornado Watch Number 662 NWS Storm Prediction Center Norman OK 1050 AM EDT Wed Aug 30 2023 The NWS Storm Prediction Center has issued a * Tornado Watch for portions of Southern coastal North Carolina Coastal South Carolina Coastal Waters * Effective this Wednesday morning and evening from 1050 AM until 1000 PM EDT. * Primary threats include... A few tornadoes likely Isolated damaging wind gusts to 70 mph possible SUMMARY...Hurricane Idalia will move northeastward today near the southeast Atlantic coast. The potential for tornadoes will increase through this afternoon across coastal South Carolina, and the tornado threat will also increase into southern coastal North Carolina later this afternoon into early tonight. The tornado watch area is approximately along and 30 statute miles either side of a line from 65 miles west southwest of Charleston SC to 15 miles east of Wilmington NC. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU2). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Tornado Watch means conditions are favorable for tornadoes and severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. && OTHER WATCH INFORMATION...CONTINUE...WW 661... AVIATION...Tornadoes and a few severe thunderstorms with hail surface and aloft to 0.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 550. Mean storm motion vector 18030. ...Thompson Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0236 PM CDT Wed Aug 30 2023 Valid 311200Z - 011200Z No changes. See previous discussion below. ..Bentley.. 08/30/2023 .PREV DISCUSSION... /ISSUED 0154 AM CDT Wed Aug 30 2023/ ...Synopsis... As a trough across Montana lifts northward into Canada on Thursday, a secondary trough will deepen across the Pacific Northwest. This pattern will keep increased west to southwesterly gradients across much of Pacific Northwest into the Great Basin and Northern Rockies, with enhanced mid-level flow continuing to overspread these regions. Surface winds across northern Montana will be around 20-25 mph with relative humidity reductions to around 20-25 percent. Across central Wyoming, sustained winds around 20 mph will overlap afternoon relative humidity reductions to around 10-15 percent. Both of these regions have seen drying of fuels in recent windy/dry periods. However, ERCs remain largely at or below seasonal normals. Meteorological conditions will continue to be supportive of large fire growth and further drying of fuels, which supports maintaining an Elevated risk across Montana and introduction of an Elevated risk across central/southern Wyoming with this outlook. ...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 0233 PM CDT Wed Aug 30 2023 Valid 302000Z - 311200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER THE COASTAL CAROLINAS IN ASSOCIATION WITH TROPICAL CYCLONE IDALIA... ...SUMMARY... A few tornadoes are expected through tonight mainly across the coastal Carolinas in association with Hurricane Idalia. ...Carolinas... The center of T.C. Idalia is forecast to move northeastward along the coastal counties of SC through tonight, and toward the Wilmington NC area by Thursday morning. Observations indicate upper 70s F dewpoints already in place across these areas, with broken bands of cells developing over the ocean and proceeding northwestward over land. Low-level shear will remain strong and favorable for tornadic supercells with 0-1 SRH values of 200-300 m2/s2 developing northeastward ahead of the storm center. For more information see mesoscale discussion 2066. Tornado watch 662 remains in effect. ..Jewell.. 08/30/2023 .PREV DISCUSSION... /ISSUED 1126 AM CDT Wed Aug 30 2023/ ...Southeast Atlantic coast through tonight... The weakening remnants of Hurricane Idalia are forecast to continue moving northeastward near the southeast Atlantic coast through tonight (see latest NHC advisories for additional information). Flow will continue to veer and weaken across central/north FL and the tornado threat will likewise diminish through the afternoon. Farther north, more backed low-level flow and larger, curved hodographs (effective SRH 300-400 m2/s2) are expected in advance of Idalia's core across some of southeast GA and coastal SC this afternoon. Inland rainfall will reinforce a coastal baroclinic zone which will help focus the tornado threat near and just inland from the coast where surface-based buoyancy will be largest, as outer rain band supercells move inland. A similar environment and attendant tornado threat will spread northeastward across coastal NC late this afternoon through tonight. ...New England this afternoon... A pronounced midlevel trough will move over New England this afternoon along with an associated surface cold front. There will be a narrow zone of destabilization along the front, where weak bands of convection will be possible with a very low chance of wind damage given the moderately strong midlevel flow. However, will not add an outlook area since the window of opportunity will be small and confidence in storm development is relatively low. ...Eastern MT/western ND this afternoon/evening... A midlevel shortwave trough will progress eastward from the northern Rockies to the northern High Plains, and this midlevel trough will be preceded by a surface trough/cold front. Some high-based convection could occur along the front in the limited-moisture environment, and this convection could produce gusty outflow winds. The chance for severe outflow winds appears relatively low, precluding the need for an outlook area. Read more

WW 0661 Status Updates
STATUS REPORT ON WW 661 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 60 ENE SSI TO 25 NNE SSI TO 25 W SAV. PARTS OF REMAINING VALID PORTION OF WW ARE BEING LOCALLY EXTENDED IN TIME FOR AN HOUR OR SO. ..KERR..08/30/23 ATTN...WFO...JAX...MLB...TBW...TAE...CHS...FFC... STATUS REPORT FOR WT 661 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS GAC029-031-051-103-109-179-183-191-251-267-301900- GA . GEORGIA COUNTIES INCLUDED ARE BRYAN BULLOCH CHATHAM EFFINGHAM EVANS LIBERTY LONG MCINTOSH SCREVEN TATTNALL AMZ354-301900- CW . ADJACENT COASTAL WATERS INCLUDED ARE COASTAL WATERS FROM SAVANNAH GA TO ALTAMAHA SOUND GA OUT 20 NM ...INCLUDING GRAYS REEF NATIONAL MARINE SANCTUARY THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY. PLEASE REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL Read more

WW 0659 Status Updates
STATUS REPORT ON WW 659 THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA. ..THORNTON..08/29/23 ATTN...WFO...MSO...TFX... STATUS REPORT FOR WS 659 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS IDC035-049-059-292340- ID . IDAHO COUNTIES INCLUDED ARE CLEARWATER IDAHO LEMHI MTC001-023-039-057-063-077-081-093-292340- MT . MONTANA COUNTIES INCLUDED ARE BEAVERHEAD DEER LODGE GRANITE MADISON MISSOULA POWELL RAVALLI SILVER BOW THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY. PLEASE REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL INFORMATION ON COUNTIES...INDEPENDENT CITIES AND MARINE ZONES CLEARED FROM SEVERE THUNDERSTORM AND TORNADO WATCHES. Read more

WW 659 SEVERE TSTM ID MT 292055Z - 300300Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 659 NWS Storm Prediction Center Norman OK 255 PM MDT Tue Aug 29 2023 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Northeast Idaho Southwest Montana * Effective this Tuesday afternoon and evening from 255 PM until 900 PM MDT. * Primary threats include... Scattered damaging wind gusts to 70 mph possible Isolated large hail events to 1 inch in diameter possible SUMMARY...Scattered thunderstorms will form and spread northeastward across northeast Idaho and southwest Montana through late evening. Storm clusters and short line segments will be capable of producing damaging outflow gusts of 60-70 mph and isolated large hail up to 1 inch in diameter. The severe thunderstorm watch area is approximately along and 75 statute miles east and west of a line from 55 miles west northwest of Drummond MT to 45 miles southeast of Salmon ID. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU9). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. Severe thunderstorms can and occasionally do produce tornadoes. && AVIATION...A few severe thunderstorms with hail surface and aloft to 1 inch. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 24025. ...Thompson Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0428 PM CDT Tue Aug 29 2023 Valid 311200Z - 061200Z Some dry and breezy post-frontal conditions are expected across northern and eastern Montana on Thursday in a region which is expected to get minimal precipitation tonight and Wednesday. Therefore, fuels should remain dry and favorable for large fire spread on Thursday. Windy conditions are expected to continue from the Great Basin into the central Rockies for much of the extended period as moderate southwesterly mid-level flow persists across the region. However, fuels in this region are mostly moist. In addition, by this weekend, some monsoon moisture will lift northeast and relative humidity will increase with increasing wetting rain/wet thunderstorm chances. In addition, dry and breezy conditions are likely across the Plains and into the Upper Midwest Thursday through the weekend. Fuels are not dry at this time, but after several days of dry and breezy conditions, fuels may become more receptive by this weekend. Fuel states will continue to be monitored as this weekend approaches. ..Bentley.. 08/29/2023 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0428 PM CDT Tue Aug 29 2023 Valid 311200Z - 061200Z Some dry and breezy post-frontal conditions are expected across northern and eastern Montana on Thursday in a region which is expected to get minimal precipitation tonight and Wednesday. Therefore, fuels should remain dry and favorable for large fire spread on Thursday. Windy conditions are expected to continue from the Great Basin into the central Rockies for much of the extended period as moderate southwesterly mid-level flow persists across the region. However, fuels in this region are mostly moist. In addition, by this weekend, some monsoon moisture will lift northeast and relative humidity will increase with increasing wetting rain/wet thunderstorm chances. In addition, dry and breezy conditions are likely across the Plains and into the Upper Midwest Thursday through the weekend. Fuels are not dry at this time, but after several days of dry and breezy conditions, fuels may become more receptive by this weekend. Fuel states will continue to be monitored as this weekend approaches. ..Bentley.. 08/29/2023 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

MD 2059 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PORTIONS OF EASTERN WA/OR...CENTRAL ID AND WESTERN MT
Mesoscale Discussion 2059 NWS Storm Prediction Center Norman OK 0331 PM CDT Tue Aug 29 2023 Areas affected...portions of eastern WA/OR...central ID and western MT Concerning...Severe potential...Watch possible Valid 292031Z - 292230Z Probability of Watch Issuance...40 percent SUMMARY...Scattered high-based convection should develop through the afternoon with a risk for damaging outflow winds and hail into the early evening hours. Scattered storm coverage and the potential for gusts to 70 mph suggests a WW is possible. DISCUSSION...Across portions of the Pacific Northwest, regional WV imagery showed a negatively tilted mid-level trough and jet streak ejecting eastward into portions of the northern Rockies. Ahead of the trough, broad synoptic ascent was evident in a deepening convective arc stretching from eastern WA/OR into portions of central ID. Despite limited surface moisture, (surface dewpoints in the 30s and 40s F), strong diurnal surface heating and cooling aloft are supporting 500-1000 J/kg of MLCAPE. As forcing for ascent continues through the afternoon, the sufficient buoyancy should allow for continued updraft development off of local terrain circulations. Scattered high-based storms should mature through the afternoon and continue into the early evening. As the trough and jet streak shift eastward, stronger mid-level flow will overspread the developing storms. Area RAP soundings show deep-layer shear of 30-40 kt which would favor some storm organization. A few longer-lived updrafts or clusters, including weak supercell structures, may evolve given the favorable shear and CAPE. With low-level inverted-v profiles present, strong negatively buoyant downdrafts capable of damaging gusts to 60-70 mph are possible. Small hail is also possible with the more sustained storms. As storms continue to develop, severe potential will likely increase over central and northeastern ID, into western MT this evening. Uncertainty on the severity of the threat is still relatively high given the modest buoyancy, but conditions will be monitored for a possible weather watch. ..Lyons/Thompson.. 08/29/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...TFX...PIH...MSO...BOI...OTX...PDT... LAT...LON 44161184 43621273 43531359 44311599 45731761 47051768 48021582 47801386 46711288 45641214 44551173 44161184 Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0251 PM CDT Tue Aug 29 2023 Valid 292000Z - 301200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF FLORIDA IN ASSOCIATION WITH HURRICANE IDALIA...AND CENTERED OVER THE BITTERROOTS... ...SUMMARY... A few tornadoes will be possible late this afternoon through tonight, mainly from the west central Florida Peninsula into the Big Bend area, within the northeast quadrant of strengthening Hurricane Idalia. Occasional damaging wind gusts will be possible across the northern Rockies. ...20Z Update... Little change was made to the existing severe probabilities at 20Z, except for a minor eastward shift for a low wind threat into central MT where minimal instability will develop due to steepening lapse rates. For the Southeast, the threat for a few tornadoes will increase tonight, primarily after 03Z as stronger shear associated with Hurricane Idalia overspreads parts of the western FL Peninsula, and eventually into parts of the Big Bend. ..Jewell.. 08/29/2023 .PREV DISCUSSION... /ISSUED 1128 AM CDT Tue Aug 29 2023/ ...FL Gulf coast through tonight... Hurricane Idalia is strengthening as of midday over the southeast Gulf of Mexico and is forecast to make landfall Wednesday morning near the FL Big Bend as a major hurricane (please see latest NHC advisories for additional information). Storm motion will be largely parallel to the FL west coast into early tonight, so eastward expansion of the stronger wind field and more favorable low-level hodograph structures will be a gradual process (per the trends in the VWPs from Key West and Tampa). Surface observations show 77-80 F dewpoints across almost all of central/south FL, which will help maintain surface-based buoyancy into this evening and overnight. Thus, the primary increase in supercell/tornado threat is expected late this afternoon into tonight from near Tampa northward along the coast with the more cellular convection within the outer eastern/northeastern bands. ...Northern Rockies this afternoon/evening... A midlevel shortwave trough now over far northern CA and OR will progress east-northeastward toward the northern Rockies by this evening. Though low-level moisture is rather limited, strong surface heating/deep mixing will result in inverted-V profiles with weak buoyancy in advance of the midlevel trough and an associated cold front. Thunderstorm development is expected this afternoon through early tonight in the zone of ascent preceding the midlevel trough (and along the front). The highest confidence in storm development coincident with the steep low-level lapse rates and some enhancement to midlevel flow will be later this afternoon over the Bitterroots, where a few damaging outflow gusts of 60-70 mph will be possible. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0251 PM CDT Tue Aug 29 2023 Valid 292000Z - 301200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF FLORIDA IN ASSOCIATION WITH HURRICANE IDALIA...AND CENTERED OVER THE BITTERROOTS... ...SUMMARY... A few tornadoes will be possible late this afternoon through tonight, mainly from the west central Florida Peninsula into the Big Bend area, within the northeast quadrant of strengthening Hurricane Idalia. Occasional damaging wind gusts will be possible across the northern Rockies. ...20Z Update... Little change was made to the existing severe probabilities at 20Z, except for a minor eastward shift for a low wind threat into central MT where minimal instability will develop due to steepening lapse rates. For the Southeast, the threat for a few tornadoes will increase tonight, primarily after 03Z as stronger shear associated with Hurricane Idalia overspreads parts of the western FL Peninsula, and eventually into parts of the Big Bend. ..Jewell.. 08/29/2023 .PREV DISCUSSION... /ISSUED 1128 AM CDT Tue Aug 29 2023/ ...FL Gulf coast through tonight... Hurricane Idalia is strengthening as of midday over the southeast Gulf of Mexico and is forecast to make landfall Wednesday morning near the FL Big Bend as a major hurricane (please see latest NHC advisories for additional information). Storm motion will be largely parallel to the FL west coast into early tonight, so eastward expansion of the stronger wind field and more favorable low-level hodograph structures will be a gradual process (per the trends in the VWPs from Key West and Tampa). Surface observations show 77-80 F dewpoints across almost all of central/south FL, which will help maintain surface-based buoyancy into this evening and overnight. Thus, the primary increase in supercell/tornado threat is expected late this afternoon into tonight from near Tampa northward along the coast with the more cellular convection within the outer eastern/northeastern bands. ...Northern Rockies this afternoon/evening... A midlevel shortwave trough now over far northern CA and OR will progress east-northeastward toward the northern Rockies by this evening. Though low-level moisture is rather limited, strong surface heating/deep mixing will result in inverted-V profiles with weak buoyancy in advance of the midlevel trough and an associated cold front. Thunderstorm development is expected this afternoon through early tonight in the zone of ascent preceding the midlevel trough (and along the front). The highest confidence in storm development coincident with the steep low-level lapse rates and some enhancement to midlevel flow will be later this afternoon over the Bitterroots, where a few damaging outflow gusts of 60-70 mph will be possible. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0200 PM CDT Tue Aug 29 2023 Valid 301200Z - 311200Z Added an Elevated area for the Snake River Valley where winds of 20 to 25 mph and relative humidity of 15 to 20 percent are expected tomorrow. Fine fuels have started to dry in the region and will be increasingly susceptible to large fire, especially after dry and breezy conditions today. Also added an Elevated area across much of southern and eastern Wyoming. Winds of 20 to 30 mph with some gusts to 35 mph are expected across Wyoming tomorrow. Fuels in this area are not excessively dry, but given the high-end critical meteorological conditions, felt an Elevated delineation is warranted. Elsewhere no changes were needed. See previous discussion below. ..Bentley.. 08/29/2023 .PREV DISCUSSION... /ISSUED 0146 AM CDT Tue Aug 29 2023/ ...Synopsis... Two regions of Elevated fire weather conditions will be possible on Wednesday. Across portions of northern Montana, post frontal northerly flow will overlap drying fuels and relative humidity reductions to around 15-25 percent. Though fuels within this region are drying, they remain too moist to support inclusion of a Critical region at this time. Across the southern US, a tropical system impacting the Gulf of Mexico will bring an increase in northerly gradients across portions of Texas, Louisiana, Arkansas, and Mississippi. Areas across eastern Texas, northern Louisiana, and western Mississippi have seen prolonged heat and drought conditions, which has resulted in explosive fire behavior under more marginal meteorological conditions due to extremely critically dry fuels. Some questions remains how recent rainfall and any potential additional rainfall in the coming 24 hours will change the status of fuels. Given potential for sustained winds around 10-15 mph and relative humidity as low as 20 percent, an Elevated delineation was maintained with this outlook with a slight extension further south in Texas/Louisiana. This area will need to be monitored for Critical highlights in future outlook updates. ...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 0200 PM CDT Tue Aug 29 2023 Valid 301200Z - 311200Z Added an Elevated area for the Snake River Valley where winds of 20 to 25 mph and relative humidity of 15 to 20 percent are expected tomorrow. Fine fuels have started to dry in the region and will be increasingly susceptible to large fire, especially after dry and breezy conditions today. Also added an Elevated area across much of southern and eastern Wyoming. Winds of 20 to 30 mph with some gusts to 35 mph are expected across Wyoming tomorrow. Fuels in this area are not excessively dry, but given the high-end critical meteorological conditions, felt an Elevated delineation is warranted. Elsewhere no changes were needed. See previous discussion below. ..Bentley.. 08/29/2023 .PREV DISCUSSION... /ISSUED 0146 AM CDT Tue Aug 29 2023/ ...Synopsis... Two regions of Elevated fire weather conditions will be possible on Wednesday. Across portions of northern Montana, post frontal northerly flow will overlap drying fuels and relative humidity reductions to around 15-25 percent. Though fuels within this region are drying, they remain too moist to support inclusion of a Critical region at this time. Across the southern US, a tropical system impacting the Gulf of Mexico will bring an increase in northerly gradients across portions of Texas, Louisiana, Arkansas, and Mississippi. Areas across eastern Texas, northern Louisiana, and western Mississippi have seen prolonged heat and drought conditions, which has resulted in explosive fire behavior under more marginal meteorological conditions due to extremely critically dry fuels. Some questions remains how recent rainfall and any potential additional rainfall in the coming 24 hours will change the status of fuels. Given potential for sustained winds around 10-15 mph and relative humidity as low as 20 percent, an Elevated delineation was maintained with this outlook with a slight extension further south in Texas/Louisiana. This area will need to be monitored for Critical highlights in future outlook updates. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No watches are valid as of Mon Aug 28 21:42:02 UTC 2023.