Severe Storms

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0346 PM CDT Tue Aug 15 2023 Valid 171200Z - 231200Z A weak upper low is expected to remain off the California coast perhaps into early next week. Model guidance continues to differ in terms of the evolution of the upper-level pattern late this week into the weekend. At some point, an upper trough in the Northwest is expected to phase with the weak upper low. High pressure at the surface will remain in the Plains through midweek. Thereafter, a cold front is forecast to push southward into parts of the southern Plains late this week. ...Northwest... Dry and windy conditions appear probable on Thursday and Friday from the east side of the Cascades into the Columbia Basin. Temperatures will be higher on Thursday than on Friday. This could lead to a small increase in RH on Friday. However, guidance still suggests both days will reach critically low values. Winds on Thursday will primarily be driven by the thermal pressure trough in the Basin. Mid-level winds will increase on Friday as the mid-level jet overspreads most of Washington. Critical fire weather potential will exist on both days, but the greater potential should exist on Friday given the greater expected coverage of 20-25 mph winds. Thunderstorms are expected to occur each day through the weekend in parts of Oregon. PWAT values will continue to increase and lead to wetting rainfall potential. There is some possibility that storms may be slightly drier on Friday in north-central/northeast Oregon with drier air working in from the south and strong mid-level winds moving in from the north. Coverage of dry thunderstorms should remain low, though lightning away from storm cores could still pose problems. ...Montana... With an upper-level trough approaching the Northwest, a surface low is expected to deepen in Alberta. There is some model disagreement as to the evolution of the surface low late this week, but enhanced downslope winds are expected on both Thursday and Friday in the lee of the northern Rockies. With temperatures expected to be higher on Thursday, greater confidence in critical fire weather exists. Cooler temperatures and the potential for a cold front to limit the duration of fire weather concerns leads to less confidence on Friday. ...Texas... Hot surface temperatures should return to the region by Thursday. The development of thermal pressure troughs may lead to some locally elevated conditions in the presence of extremely dry fuels. There may be some broader increase in surface winds on Friday as a large-scale surface trough develops into the southern Plains. Trends will need to be monitored, but wind speeds continue to look too weak for critical probabilities. In addition, isolated thunderstorms could develop in the surface trough with the extreme heat, but predictability is quite low. ..Wendt.. 08/15/2023 ...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 0236 PM CDT Tue Aug 15 2023 Valid 152000Z - 161200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM NORTH CAROLINA TO NEW JERSEY... ...SUMMARY... Damaging to severe thunderstorm gusts should be most common this through this evening from central North Carolina to southern New Jersey. ...20z Update... Only minor adjustments have been made to severe probabilities based on current location of the surface front and ongoing convection. Otherwise, the previous forecast remains on track. Reference ongoing severe thunderstorm watches 649 and 650, and forthcoming MCDs for short term severe storm info. ..Leitman.. 08/15/2023 .PREV DISCUSSION... /ISSUED 1059 AM CDT Tue Aug 15 2023/ ...NC to Mid-Atlantic Region... Morning water vapor imagery shows a large upper low over northwest OH, with a band of 50-60 knot southwesterly mid/upper level winds extending from TN/KY into the Mid-Atlantic region and southern New England. The associated surface cold front runs along/just west of the spine of the Appalachians from PA into east TN. Mostly clear skies ahead of the front will combine with dewpoints in the low-mid 70s to yield a very unstable air mass by mid-afternoon, with forecast soundings showing MLCAPE values of 2000-3000 J/kg. This should result in intensifying clusters of storms from western NC into central VA/southeast PA tracking eastward through the afternoon and early evening. Strong westerly flow aloft, steep low-level lapse rates, and high moisture content will likely result in bowing structures and a few supercells capable of severe wind gusts. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0146 PM CDT Tue Aug 15 2023 Valid 161200Z - 171200Z Only minor changes were made to the dry thunder area in northern California to account for current guidance. The forecast otherwise remains on track. ..Wendt.. 08/15/2023 .PREV DISCUSSION... /ISSUED 0152 AM CDT Tue Aug 15 2023/ ...Synopsis... Mid-level high pressure is forecast to build over the western US while a weak upper low moves off the West Coast. Across the central US, a mid-level trough is forecast to move out of southern Canada with an accompanying surface cold front sweeping southeastward across the northern Rockies. Dry downslope winds are likely to support locally elevated fire-weather concerns over parts of northern MT. Dry thunderstorms are also possible over parts of the Northwest. ...Northwest... Another round of showers and high-based thunderstorms are expected across parts of northern CA and southern OR D2/Wed, as the upper low moves off the West Coast. Monsoon moisture will continue to increase with PWATs exceeding 1 inch. With the low farther offshore, easterly flow aloft will slacken, resulting in gradually diminishing storm speeds. Widely scattered, initially dry, storms are expected, but precipitation efficiency should rise through the day as storms slow down and moisture values increase. While QPF is forecast to increase with time, very dry and receptive fuels, along with initially dry storms, will favor some risk for lightning ignitions. ...Northern Rockies... As the Alberta trough continues to move south into the US, a cold front/wind shift will move through the northern Rockies early D2/Wed. Gusty northwest winds will remain strong through the day with downslope gusts of 15-20 mph possible. While RH values will likely be higher from the cooler air mass behind the front, diurnal minimums below 35% are expected. A few hours of locally elevated fire-weather conditions are possible given dry fuels and breezy conditions across much of northern MT. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No watches are valid as of Mon Aug 14 22:18:01 UTC 2023.

MD 1995 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR SOUTHERN INDIANA
Mesoscale Discussion 1995 NWS Storm Prediction Center Norman OK 0356 PM CDT Mon Aug 14 2023 Areas affected...Southern Indiana Concerning...Severe potential...Watch unlikely Valid 142056Z - 142300Z Probability of Watch Issuance...20 percent SUMMARY...Thunderstorms developing along a cold front may pose an isolated hail and wind risk this afternoon and evening. However, watch issuance is not expected. DISCUSSION...Thunderstorms developing along a cold front across the Midwest have been slow to mature over the past few hours, but imagery from KIND has shown improving organization of a few cells over the past 30-60 minutes. Temperatures warming into the low 80s ahead of the cold front have allowed MLCAPE values to increase to around 1000 J/kg, and recent forecast soundings and KIND VWP observations show elongated, nearly straight hodographs with effective bulk shear near 45 knots. The strongly sheared environment may compensate for the otherwise marginal buoyancy and support sufficient storm organization for a large hail/severe wind threat. Initially discrete cells have shown a tendency for slow upscale growth, and this trend should continue into the evening hours, which may modulate the severe threat to some degree. Storms moving into central IN they will likely encounter a noted buoyancy gradient along a warm front, which should limit the northward extent of the severe threat. Watch issuance is not currently anticipated given modest downstream buoyancy and lackluster storm organization thus far. ..Moore/Hart.. 08/14/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...ILN...LMK...IND...PAH...ILX... LAT...LON 38038831 39118739 39778695 40098660 40058573 39858490 39498478 38868518 38298585 38028649 37858709 37788762 37788802 38038831 Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0349 PM CDT Mon Aug 14 2023 Valid 161200Z - 221200Z The upper-level ridge will shift east through the period. Along the West Coast, a weak upper low will continue to the north and slightly west. Toward the weekend, model guidance suggests that this feature will phase with a trough that will move southward into the Northwest. ...Northwest... Both thunderstorm and wind/RH concerns will be present during the extended period. Thunderstorms are possible on Wednesday, but coverage will likely be rather isolated. Storm coverage will begin to increase Thursday into the weekend with a general trend for storms to occur farther north each day. The overall potential for lightning ignitions remains uncertain as PWAT values will also be on the increase over time. There may be, however, a period of time where a few drier storms are possible. Mid-level winds increase with northward extent. As thunderstorms move into the Blue Mountain vicinity on Thursday would be the area and time of greatest concern. Model trends will need to be monitored, but confidence remains too low for highlights. Dry and windy conditions will also increase in the coming days. The thermal pressure trough in the Columbia Basin will continue to develop most afternoons. Westerly mid-level winds will also increase as a trough moves toward the Northwest. These features will drive strong surface winds through the Cascades into the Columbia Basin. Some potential for critical fire weather will exist on Thursday and Friday. ...Montana... Critical fire weather is probable on Thursday as westerly winds aloft increase across the northern Rockies. A surface low will also deepen to the north of the region. These factors will promote strong downslope winds within and to the lee of the terrain in parts of western Montana. Ahead of the cold front passage on Friday, strong westerly winds may persist within the same areas. Confidence on critically low RH is less than on Thursday, however. ...Northern California... Thunderstorms will be possible in the region each day through the weekend. PWAT values will generally come up quickly, however. With time, guidance does show a signal for dry air being pulled northward. A few drier storms may occur during the weekend, but the degree of fire weather risk is unclear as storms will have occurred on previous days over the same areas. ...Texas... Cooler conditions are expected to persist through Wednesday. Thereafter, hot conditions will likely return for parts of western/central Texas. With a surface trough/low developing, some increase in surface winds can be expected. Winds still appear too light for critical fire weather, but trends will need to be monitored given the very dry fuels. Furthermore, thunderstorms could develop. Some risk of lightning ignitions would exist with this activity. ..Wendt.. 08/14/2023 ...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 0232 PM CDT Mon Aug 14 2023 Valid 142000Z - 151200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE TENNESSEE VALLEY INTO THE MID-ATLANTIC... ...SUMMARY... Strong/locally severe thunderstorms are expected through this evening across portions of the Midwest, Kentucky and Tennessee, and extending eastward to the Mid-Atlantic Region. ...20z Update... The Marginal (level 1 of 5) risk has been expanded northwest across parts of eastern IA along the occluded surface front. While instability remains modest across this area, low-level vorticity is maximized along the boundary and beneath the cold core upper trough/low. 3 km MLCAPE is around 100-125 J/kg, though 0-1 km SRH is expected to remain modest. A couple of funnel clouds and/or a brief tornado will be possible the remainder of the afternoon with this activity. Some gusty winds or small hail also could accompany stronger cores. Reference MCD 1994 for more short term details. The Slight risk (level 2 of 5) as been removed from portions of northern KY into southern OH and southwest PA. Earlier day convection and persistent cloud cover has precluded much destabilization this afternoon. While some airmass recovery will continue into the evening in low-level warm advection ahead of the synoptic cold front, overall conditions appear only marginally favorable for isolated strong storms. Otherwise, modest adjustments have been made to the Marginal (level 1 of 5) risk across western KY/TN and northeast OH/western PA based on latest observed data and model forecast guidance. ..Leitman.. 08/14/2023 .PREV DISCUSSION... /ISSUED 1101 AM CDT Mon Aug 14 2023/ ...TN Valley into Mid-Atlantic... Morning water vapor loop shows an upper low moving from IA into northern IL, with a relatively strong mid/upper level jet max rotating into the lower OH and TN Valleys. Widespread remnant clouds from overnight storms cover much of the OH/TN Valleys into the central Appalachians, which is limiting heating/destabilization. Despite rather strong westerly flow aloft and ample low-level moisture, muted heating will keep any severe risk rather low/localized through mid-afternoon. Some intensification of this activity may occur as it spreads east of the mountains into parts of PA/VA/NC, where strong heating is occurring. But this scenario is also relatively low confidence. Later this afternoon and evening, slow clearing/heating will eventually likely result in a pocket of rather strong CAPE from parts of middle/east TN into southeast KY. This area is probably the highest confidence in at least widely scattered strong to severe storms as the cold front approaches. Forecast soundings show sufficient deep-layer shear for a few bowing structures capable of damaging wind gusts. Time-of-day would be a negative, but there is some risk of storms maintaining some intensity as they move into the mountains of WV/western VA/western NC tonight. ...PA/NJ after dark... Most 12z CAM solutions continue to indicate that low-level winds will intensify after dark over parts of eastern PA as a shortwave trough rotates into the area. Favorable low-level shear profiles suggest some risk of rotating cells and tornado or two, although weak lapse rates and time-of-day will be unfavorable for robust updrafts. ...Northern IL... An occluded surface front extends northwestward from central IN into northern IL. Persistent clouds are limited heating in this area, but a zone of low-level convergence/vorticity will be present through the afternoon. A few rotating storms cannot be ruled out by mid/late afternoon, with a non-zero risk of a tornado or hail. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0217 PM CDT Mon Aug 14 2023 Valid 151200Z - 161200Z Minor modifications were made to the dry thunder area in the Northwest based on updated guidance. An area of dry conditions also appears probable in parts of central/eastern Texas behind the cold front. Winds however, will remain rather light at 10-15 mph which should mitigate some fire spread potential within the very dry fuels. ..Wendt.. 08/14/2023 .PREV DISCUSSION... /ISSUED 0156 AM CDT Mon Aug 14 2023/ ...Synopsis... Across the western US, mid-level ridging is forecast to intensify as a weak upper low moves offshore across western CA. Predominantly weak mid-level flow should keep winds light over much of the western US. Monsoon moisture drawn northward with the upper low may support showers and thunderstorms into parts of northern CA and southern OR. ...Northwest... As the upper low continues to move offshore, easterly mid-level flow will overspread northern CA and southern OR late D1/Mon into early D2/Tues. Showers, and a few thunderstorms, are possible through the early morning hours, and again with additional storms possible in the afternoon and evening. Storm coverage remains very uncertain with hi-res model guidance varying widely in the possible solutions. With weak elevated buoyancy and broad synoptic ascent from the passing low, isolated storms do appear possible. The dry low levels would also favor drier storms with the potential for lightning ignitions. Given the dry and receptive fuels, and at least some risk for lightning, an IsoDryT area has been added despite some uncertainty on storm coverage. ...Northern Rockies... A slight increase in mid-level flow from an approaching Alberta low will help bolster downslope surface winds over parts of northern MT late D2/Tues. Downslope gusts of 15-20 mph are possible, along with relatively low RH below 35%. The temporal overlap of dry and windy conditions will be limited by the arrival of the strongest winds overnight. However, a few hours of locally elevated conditions are possible given dry fuels. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

WW 0643 Status Updates
STATUS FOR WATCH 0643 HAS NOT BEEN ISSUED YET Read more

WW 643 SEVERE TSTM KS 132205Z - 140400Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 643 NWS Storm Prediction Center Norman OK 505 PM CDT Sun Aug 13 2023 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Central into southeast Kansas * Effective this Sunday afternoon and evening from 505 PM until 1100 PM CDT. * Primary threats include... Scattered damaging wind gusts to 70 mph likely Scattered large hail events to 1.5 inches in diameter likely SUMMARY...Scattered supercell development is expected this afternoon and storms will spread east-southeastward through late evening with an attendant threat for large hail up to 1.5 inches in diameter. Some clustering of storms is also expected, which will favor the potential for severe outflow gusts of 60-70 mph. The severe thunderstorm watch area is approximately along and 65 statute miles north and south of a line from 55 miles northwest of Medicine Lodge KS to 20 miles north northeast of Chanute KS. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU3). 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. && OTHER WATCH INFORMATION...CONTINUE...WW 640...WW 641...WW 642... AVIATION...A few severe thunderstorms with hail surface and aloft to 1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 550. Mean storm motion vector 29025. ...Thompson Read more

MD 1985 CONCERNING SEVERE THUNDERSTORM WATCH 641... FOR PORTIONS OF NORTHERN AND CENTRAL AL...INTO SOUTHERN TN AND NORTHWEST GA
Mesoscale Discussion 1985 NWS Storm Prediction Center Norman OK 0449 PM CDT Sun Aug 13 2023 Areas affected...portions of northern and central AL...into southern TN and northwest GA Concerning...Severe Thunderstorm Watch 641... Valid 132149Z - 132245Z The severe weather threat for Severe Thunderstorm Watch 641 continues. SUMMARY...The risk for damaging gusts should continue across WW641 this afternoon. Storms may continue farther south and east where a new weather watch is possible, but uncertain. DISCUSSION...As of 2135 UTC, regional radar analysis showed a linear cluster of storms ongoing across portions of the TN Valley. Over the last couple of hours, several reports of damaging gusts have been received with gusty outflow winds from these storms. The environment ahead of these storms remains strongly unstable, with 3000+ J/kg of MLCAPE, but only weak vertical shear. So far storms have been semi-organized along a propagating cold pool. Weak shear balance and the favorable buoyancy should allow for strong updrafts and damaging gust potential to continue across north-central AL and portions of southern TN over the next couple of hours. Farther south, uncertainty on the severe risk is higher as additional storms have resulted in some overturning of the air mass west of Atlanta into central AL. Outflow temperatures have dropped into the upper 70s F, which may limit the potential for stronger updrafts as the cluster moves south/southeast later this evening. If storms are able to retain strength as they move into the cooler air, as suggested by several HRRR runs, damaging gusts would be possible into parts of central AL and western GA. Convective trends will be monitored but it is unclear if a new weather watch is needed farther south. ..Lyons/Thompson.. 08/13/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...MRX...FFC...OHX...BMX...HUN...MEG... LAT...LON 35428635 36058538 36028466 35718457 35338456 34988457 34598462 34098474 33598494 33408505 33258532 33198566 33258614 33328649 33458710 33658756 33798782 33958811 34158819 34448816 34708786 34958738 35208676 35428635 Read more

WW 0642 Status Updates
STATUS FOR WATCH 0642 HAS NOT BEEN ISSUED YET Read more

WW 642 SEVERE TSTM OK TX 132145Z - 140400Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 642 NWS Storm Prediction Center Norman OK 445 PM CDT Sun Aug 13 2023 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Western and northern Oklahoma and the eastern Oklahoma Panhandle The eastern Texas Panhandle * Effective this Sunday afternoon and evening from 445 PM until 1100 PM CDT. * Primary threats include... Scattered damaging wind gusts to 70 mph likely Scattered large hail events to 1.5 inches in diameter possible SUMMARY...Clusters of storms will continue to form in the Texas Panhandle and spread into western and northern Oklahoma through late evening. The storm environment favors occasional severe outflow winds of 60-70 mph and isolated large hail of 1-1.5 inches in diameter. The severe thunderstorm watch area is approximately along and 85 statute miles east and west of a line from 20 miles northeast of Alva OK to 70 miles west southwest of Clinton OK. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU2). 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. && OTHER WATCH INFORMATION...CONTINUE...WW 640...WW 641... AVIATION...A few severe thunderstorms with hail surface and aloft to 1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 550. Mean storm motion vector 26025. ...Thompson Read more

WW 0641 Status Updates
STATUS REPORT ON WW 641 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 25 NE UOX TO 25 N HSV TO 25 ESE BWG. ..WEINMAN..08/13/23 ATTN...WFO...HUN...MEG...OHX... STATUS REPORT FOR WS 641 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS ALC033-049-059-071-077-079-083-089-095-103-132240- AL . ALABAMA COUNTIES INCLUDED ARE COLBERT DEKALB FRANKLIN JACKSON LAUDERDALE LAWRENCE LIMESTONE MADISON MARSHALL MORGAN MSC117-141-132240- MS . MISSISSIPPI COUNTIES INCLUDED ARE PRENTISS TISHOMINGO TNC003-015-031-041-051-061-103-111-127-149-159-165-169-177-189- 132240- TN . TENNESSEE COUNTIES INCLUDED ARE Read more

WW 641 SEVERE TSTM AL MS TN 131835Z - 140100Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 641 NWS Storm Prediction Center Norman OK 135 PM CDT Sun Aug 13 2023 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Northern Alabama Northeast Mississippi Middle Tennessee * Effective this Sunday afternoon and evening from 135 PM until 800 PM CDT. * Primary threats include... Scattered damaging wind gusts to 60 mph possible SUMMARY...Storms are expected to continue to intensify across the region with a linear cluster evolving, with damaging winds as the primary severe hazard. The severe thunderstorm watch area is approximately along and 80 statute miles north and south of a line from 60 miles northwest of Muscle Shoals AL to 60 miles southeast of Nashville TN. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU1). 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. && OTHER WATCH INFORMATION...CONTINUE...WW 640... AVIATION...A few severe thunderstorms with hail surface and aloft to 1 inch. Extreme turbulence and surface wind gusts to 50 knots. A few cumulonimbi with maximum tops to 550. Mean storm motion vector 28025. ...Guyer Read more

WW 0640 Status Updates
STATUS REPORT ON WW 640 THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA. ..WEINMAN..08/13/23 ATTN...WFO...GYX...CAR... STATUS REPORT FOR WS 640 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS MEC001-003-005-007-009-011-013-015-017-019-021-023-025-027-031- 132240- ME . MAINE COUNTIES INCLUDED ARE ANDROSCOGGIN AROOSTOOK CUMBERLAND FRANKLIN HANCOCK KENNEBEC KNOX LINCOLN OXFORD PENOBSCOT PISCATAQUIS SAGADAHOC SOMERSET WALDO YORK NHC001-003-015-017-132240- NH . NEW HAMPSHIRE COUNTIES INCLUDED ARE BELKNAP CARROLL ROCKINGHAM STRAFFORD 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 640 SEVERE TSTM ME NH 131750Z - 140100Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 640 NWS Storm Prediction Center Norman OK 150 PM EDT Sun Aug 13 2023 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Maine Eastern New Hampshire * Effective this Sunday afternoon and evening from 150 PM until 900 PM EDT. * Primary threats include... Scattered damaging wind gusts to 65 mph possible Scattered large hail events to 1.5 inches in diameter possible SUMMARY...Scattered thunderstorms are forecast to intensify this afternoon with the stronger storms being capable of large hail and damaging gusts. This activity will gradually move from west to east across the watch area through the afternoon into the early evening. The severe thunderstorm watch area is approximately along and 70 statute miles east and west of a line from 30 miles northwest of Caribou ME to 10 miles southeast of Portsmouth NH. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU0). 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 1.5 inches. Extreme turbulence and surface wind gusts to 55 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 26025. ...Smith Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0352 PM CDT Sun Aug 13 2023 Valid 151200Z - 211200Z The extended period forecast remains challenging with upper low/Rex block pattern in the eastern Pacific. Model guidance continues to vary with the progression/evolution of this feature in the near term. This variance increases with time. At the surface, a cold front will move through the Southern Plains early in the week. Other cold fronts will make progress into the Plains mid/late week. ...Northwest... Thunderstorm chances will increases into southern Oregon starting on Tuesday. Another push of mid-level moisture will begin on Thursday and renew thunderstorm potential. Activity will move northward each day into the weekend and early next week. There is some uncertainty as to when thunderstorm activity will begin to decrease. The GFS is more bullish on moving a shortwave trough across the Canadian border and pushing moisture out of the region at least temporarily. PWAT values will be a bit on the marginal side for dry thunderstorms in addition to storm motions being relatively slow between the upper low and the stronger mid-level winds to the north. As storms move northward, though, some drier storms would be possible along the leading edge of the moisture. Given all the complicating factors, confidence in placing dry thunderstorm highlights is low. Potential for locally dry and windy conditions is evident within the Cascade gaps/Columbia Gorge as temperatures increase into the Columbia Basin. The signal for more broadly critical fire weather is currently on Thursday when mid-level winds will be stronger and a surface low will deepen to the northeast. This could continue on Friday afternoon as well, but model differences in the upper/low-level patterns decrease confidence. ...Northern California... Thunderstorm activity is possible each afternoon from Tuesday into potentially the weekend. Storm motions will initially be slow and PWAT values will be somewhat high. Lighting outside of storm cores would remain a concern. The upper low is forecast to remain off the central California coast into the weekend and even intensify. As this occurs, drier air may get pulled northward. Thunderstorm potential will gradually decrease south to north with time. A few drier storms may occur later in the week, but with storm potential every afternoon in the same areas, fuels may be affected by that time. ...Montana... With an upper-level trough moving through the northern Plains on Tuesday/Wednesday, some dry and windy conditions are possible for parts of Montana. Some downslope enhancement is possible in the lee of the Rockies on Tuesday. Spatial extent of the fire weather threat appears very limited given the modest surface gradient and upper-level winds. Greater potential for critical fire weather is evident on Thursday as mid-level winds will be somewhat stronger across the terrain and a deeper surface low is expected to the north. Some potential could also exist into Friday, but the evolution of the upper-level/surface pattern is a bit too uncertain for highlights. ...Texas... Cooler, but relatively dry, northerly winds will be present behind the cold front perhaps into Tuesday/Wednesday of next week. There is low-end potential for a pocket of dry and windy conditions to develop in parts of East Texas on the western flank of an upper trough on Tuesday. Heat will return by late week. With a surface trough remaining in the region into the weekend, some concerns for elevated fire weather may develop in portions of western/central Texas. Furthermore, isolated thunderstorms are possible during the afternoons with the intense heat and may pose some concern for lightning ignitions given the dry fuels. ..Wendt.. 08/13/2023 ...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 Sun Aug 13 2023 Valid 132000Z - 141200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE OZARKS... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE SOUTH-CENTRAL PLAINS TO THE TENNESSEE VALLEY...AND PORTIONS OF NEW ENGLAND... ...SUMMARY... Severe thunderstorm wind gusts, large hail and a tornado threat are expected late this afternoon into tonight, especially across the south-central Plains and Ozarks. Other severe thunderstorms will persist into early evening across New England. ...20z Update... The overall forecast philosophy is unchanged from the 1630z outlook (see previous discussion below). The only minor change in severe probabilities is across parts of southeast MN into extreme southwest WI and eastern IA where the Marginal (level 1 of 5) risk has been expanded. This expansion is related to severe potential late tonight into early Monday morning associated with convection beneath the cold core of the upper shortwave trough and in the vicinity of the surface low. Damaging wind potential will continue this afternoon across the TN Valley as an ongoing MCS spreads east/southeast. Ref Severe Thunderstorm Watch 641 and forthcoming MCDs for short term severe trends. Additional isolated severe storms will continue the next several hours across parts of Maine and vicinity where Severe Thunderstorm Watch 640 is in effect until early 01z. Severe potential is expected to increase from late afternoon into this evening across the south-central Plains toward southern MO. See MCD 1982 for short term severe potential across parts of KS. Early day convection has modified and stabilized the low-levels across MO (per mesoanalysis and 18z SGF RAOB) and will likely delay convection until this evening as the airmass recovers and a low-level jet increases. Convection will then spread east/southeast from KS/OK along residual outflow/differential heating corridor posing an all-hazards risk. ..Leitman.. 08/13/2023 .PREV DISCUSSION... /ISSUED 1154 AM CDT Sun Aug 13 2023/ ...South-Central Plains/Ozarks/Mid-South... The Lower Missouri Valley/Ozarks continue to be considerably influenced by persistent convection/MCVs at midday, with only modestly broken cloud cover across much of the warm sector ahead of the primary front. But a gradual trend of thinning/less prevalent cloud cover is noted from the west across the south-central Plains, which should allow for moderate to locally strong destabilization into/around peak heating. Deep convection is expected to develop in multiple zones by late afternoon/sunset, including across the middle Missouri Valley/eastern South Dakota vicinity near the surface low, and otherwise near the south/southeastward-moving front across southeast Nebraska and portions of Kansas, as well as across the Oklahoma/Texas Panhandles and western/northern Oklahoma. Some of this convection, as it evolves across eastern Kansas toward the Ozarks, will interface with residual differential heating and a weak residual boundary or two. Seasonally strong winds aloft will influence supercell-favorable hodographs, with large hail initially the primary hazard. Several clusters of storms should evolve by early evening, potentially including northern Oklahoma/southeast Kansas into the Ozarks, where a somewhat higher-probability for wind damage, along with some tornado potential, is expected to exist this evening, and possibly linger into the overnight. ...Tennessee Valley/southern Appalachians... On the northern fringe of the upper ridge and stronger capping aloft, a remnant cluster/MCV across far southeast Missouri/northeast Arkansas at midday will likely influence additional downstream convective development and intensification this afternoon within a moderate to strongly unstable environment. Westerlies remain a bit stronger than typical mid-August scenarios, and this should influence the persistence and organization of the storms, with some semi-organized multicellular clusters possible. Wind damage will be the primary hazard regionally. For additional details, see Mesoscale Discussion 1981. ...New England... A Slight Risk has been introduced for expectations of a somewhat greater severe-weather potential today. Isolated/widely scattered thunderstorms are expected to further develop through early afternoon along and ahead of the surface cold front. A moderately unstable environment and with deep-layer shear around 30-35 kt will support some organized multicells capable of severe hail and locally damaging wind gusts. For additional details, see Mesoscale Discussion 1980. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0214 PM CDT Sun Aug 13 2023 Valid 141200Z - 151200Z The forecast generally remains on track. Breezy conditions are expected behind the cold front in Texas. However, RH will generally remain above critical thresholds. Some locally elevated conditions are certainly possible. Dry thunderstorm activity remains possible overnight in northern California. Coverage still appears to be very low at this time. ..Wendt.. 08/13/2023 .PREV DISCUSSION... /ISSUED 0152 AM CDT Sun Aug 13 2023/ ...Synopsis... High pressure over the Northwest is forecast to intensify as it moves inland over portions of WA and OR. Gusty north winds and hot surface conditions are expected to support local fire-weather concerns. A weak mid-level low and monsoon moisture will also lift north across CA, supporting the potential for dry thunderstorms late D2/Monday into early D3/Tuesday. ...Northwest... As the upper ridge continues to intensify and move inland, northerly flow is forecast to increase across portions of southwest WA and central OR. Bolstered by a thermally induced surface trough, surface gusts of 15-25 mph gusts are expected within the higher terrain. Poor overnight humidity recoveries from the dry northerly flow and hot afternoon temperatures will support surface RH values below 35%. A few hours of elevated fire-weather conditions appear likely given critically dry fuels. ...Northern CA... Monsoon moisture associated with the weak upper low is forecast to move into portions of northern CA late D2/Monday into early D3/Tuesday. Model soundings show PWAT values of 0.7 to 0.8 inches atop dry low levels. Weak buoyancy aloft may support isolated thunderstorms into the overnight hours, with the potential for lightning ignitions given the dry low-level air mass. However, significant uncertainty remains on storm coverage and the exact placement with relatively modest forcing for ascent. IsoDryT highlight will be withheld for now, but may be needed should greater confidence in dry storm coverage develop in subsequent forecasts. ...Please see www.spc.noaa.gov/fire for graphic product... Read more