Severe Storms

WW 477 SEVERE TSTM MI OH LE LH 201655Z - 210000Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 477 NWS Storm Prediction Center Norman OK 1255 PM EDT Wed Jul 20 2022 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Eastern Lower Michigan Northwest Ohio Lake Erie Lake Huron * Effective this Wednesday afternoon and evening from 1255 PM until 800 PM EDT. * Primary threats include... Scattered damaging wind gusts to 70 mph likely Isolated large hail events to 1.5 inches in diameter possible SUMMARY...Thunderstorms are developing along a cold front sweeping across the watch area. Strong winds aloft and hot/humid conditions will pose a risk of damaging wind gusts and hail in the stronger cells. The severe thunderstorm watch area is approximately along and 45 statute miles east and west of a line from 40 miles north northeast of Alpena MI to 50 miles south southwest of Findlay OH. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU7). 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 60 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 25035. ...Hart Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1110 AM CDT Wed Jul 20 2022 Valid 201700Z - 211200Z ...NO CRITICAL AREAS... No changes to the ongoing forecast. ..Wendt.. 07/20/2022 .PREV DISCUSSION... /ISSUED 0159 AM CDT Wed Jul 20 2022/ ...Synopsis... A prominent mid-level ridge will continue to dominate the flow regime across the Four Corners and western US as a shortwave trough and ribbon of stronger flow aloft shift east toward the Great Lakes. Beneath the ridge, weak winds and extreme heat near a stalled front will develop over the southern and central Plains supporting localized fire weather concerns. ...Northern Great Basin into the central Rockies... Weak downslope flow will linger in the dry post-frontal airmass across the northern Great Basin, into WY and the central High Plains today. With mid-level flow decreasing as the ridge builds, sustained surface winds are not expected to reach more than 15-20 mph locally. Despite the weak winds, surface RH below 20% may support a few hours of locally elevated fire weather conditions given drought-stressed fuels. The most likely corridors for elevated fire weather concerns will remain near the lee of the higher terrain where downslope flow is forecast to be the strongest. ...Southern Plains... Another day of extreme heat is forecast beneath the strong upper ridge over the western US. 100F+ surface temperatures will support deep mixing heights and surface RH below 25%. Surface winds are expected to remain light, with the exception of locally stronger gusts near the stalled cold front and beneath high-based storms later in the afternoon. While flow will be light, the extreme heat and dry airmass may support a few hours of locally elevated to near critical fire concerns given exceptionally dry fuels. Isolated high-based thunderstorms will also be possible along the stalled front mainly across central OK and north TX this afternoon. While storms are not forecast to be dry given PWAT values of 1.2-1.5 inches, the hot temperatures and deep mixing heights may support a few drier lightning strikes away from the main precipitation cores. With area fuels critically dry, a few lightning ignitions will be possible. ...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 1107 AM CDT Wed Jul 20 2022 Valid 201630Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM LOWER MICHIGAN SOUTHWARD INTO KENTUCKY... ...SUMMARY... Damaging thunderstorm gusts, isolated hail and a tornado or two are possible over eastern Lower Michigan into the Ohio Valley. ...Great Lakes and Upper OH Valley... Morning water vapor imagery shows an upper low over Upper MI. The associated surface cold front extends across Lake Superior into IL/MO. This front will sweep eastward today into parts of eastern Lower MI and OH this afternoon, where strong heating/destabilization is occurring. Dewpoints in the 70s and relatively steep mid-level lapse rates will yield max afternoon MLCAPE values of around 2000 J/kg. Warm temperatures around 700mb should limit the number of storms that form through much of the day, but those storms that develop/sustain will be in an environment of sufficient westerly flow aloft for a risk of damaging wind gusts and perhaps hail. Later this afternoon and early evening, the cold front will sag southward into KY where a very moist and unstable air mass will reside. Dewpoints are currently in the mid/upper 70s, and afternoon MLCAPE values may exceed 4000 J/kg. Winds aloft will strengthen through the afternoon as the upper trough passes to the north. Several 12z CAM solutions suggest thunderstorms may develop along the front over western/central KY and spread eastward toward WV after dark. Given this solution, have extended the SLGT risk westward and maintained the SLGT across the remainder of KY/WV. Damaging winds should be the main threat. ...AL/GA/Carolinas... Visible imagery and surface obs show a region of significant low-level moisture in place from eastern TN into parts of GA/SC/NC. Dewpoints in the 70s and the potential for strong afternoon heating should result in scattered thunderstorms. Winds aloft are relatively weak, so the main threat would be water-loaded downdrafts with locally damaging wind gusts. ..Hart/Leitman.. 07/20/2022 Read more

No watches are valid as of Tue Jul 19 17:55:02 UTC 2022.

No Mesoscale Discussions are in effect as of Tue Jul 19 17:55:02 UTC 2022.

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Tue Jul 19 2022 Valid 201200Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM SOUTHEAST LOWER MI INTO THE OH VALLEY... ...SUMMARY... Scattered severe thunderstorms are possible over southeast lower Michigan into the Ohio Valley on Wednesday. The primary severe risk will be damaging gusts, though isolated hail and a tornado or two are also possible. ...Synopsis... A rather strong mid/upper-level trough is forecast to move from the Great Lakes into parts of eastern Ontario and Quebec on Wednesday. An associated surface low is forecast to deepen slightly as it moves from near Lake Superior east-northeastward to near the Ontario/Quebec border by the end of the period. A cold front attendant to the surface low will move through parts of the lower Great Lakes and Ohio Valley. Elsewhere, an upper ridge will persist over the southwest CONUS. ...Southeast Lower MI into the OH Valley... Strong diurnal heating of a moist environment is expected to result in scattered thunderstorm development Wednesday afternoon, along and ahead of the cold front. Initial development may occur over eastern lower MI by mid afternoon, in closer proximity to the mid/upper-level trough, with storms expected to develop southwestward across the OH Valley by late afternoon. Updraft intensity may initially be limited by a dry midlevel environment, but MLCAPE of 2000-3500 J/kg will eventually support robust storm development. Moderate midlevel flow will support effective shear of 30-40 kt (greater with northward extent), sufficient to sustain organized storm structures during the afternoon/evening. A couple of supercells will be possible, with a tendency toward organized cluster development with time. Modestly enhanced low-level shear will support the potential for a couple tornadoes, especially if any supercells can be sustained into the early evening. Otherwise, damaging-wind gusts are expected to be the primary hazard, with some potential for isolated hail given the magnitude of the instability (despite rather warm midlevel temperatures). Some severe threat may reach as far east as western PA and as far south as the mid-MS and lower OH Valley before storms weaken Wednesday night. ...North Dakota... Diurnal heating and sufficient residual low-level moisture will support weak-to-moderate destabilization within a post-frontal regime across parts of ND. Limited large-scale ascent results in uncertainty regarding storm coverage, but steep low-level lapse rates would support an isolated severe gust risk with any sustained convection. ...Southern OK/North TX... Very strong heating and increasing PW may result in isolated high-based thunderstorm development across southern OK and north TX late Wednesday afternoon into the evening, in the vicinity of a remnant surface boundary. Inverted-v profiles may support an isolated downburst threat with this convection. ...Southeast CO/Northeast NM... Convection is expected to develop across the higher terrain of northern NM/southeast CO Wednesday afternoon. Slightly enhanced midlevel flow along the northeastern periphery of the upper ridge may support some weakly organized cells/clusters capable of isolated severe gusts, and perhaps marginal hail at higher elevations. ..Dean.. 07/19/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1132 AM CDT Tue Jul 19 2022 Valid 191700Z - 201200Z No changes to the ongoing forecast. Please see the previous forecast for greater details. ..Wendt.. 07/19/2022 .PREV DISCUSSION... /ISSUED 0158 AM CDT Tue Jul 19 2022/ ...Synopsis... A prominent ridge over the southwestern US is forecast to remain quasistationary as a compact upper low traverses its northern flank. Strong mid-level flow associated with the low will move east, but linger over the central Rockies and western Great Basin through the first part of the day. At the surface, a weak cold front will move slowly south, supporting a few thunderstorms over the southern High Plains. Extreme heat is forecast beneath the ridge across the Southern Plains, aiding in the development of locally elevated fire weather concerns. ...Central High Plains... In the wake of a dry frontal passage early this morning, downslope northwesterly winds are forecast over much of eastern WY and western NE. Dry west/northwest winds of 15-20 mph will be possible through the first half of the day along with surface RH below 25%. With plentiful critical fuels in place, elevated to locally critical fire weather conditions will be possible through the afternoon and early evening. Winds should weaken later in the afternoon through sunset ending the fire weather threat this evening. ...Southern High Plains... Extreme heat is forecast beneath the stagnant mid-level anticyclone centered over the southwestern US. While surface winds will likely be light owing to the high pressure, surface temperatures in excess of 110F are forecast through the afternoon. The very warm airmass will favor significant mixing and low afternoon relative humidity values below 20%. With fuels near record dryness, the very hot, dry and unstable conditions will likely support locally elevated fire weather concerns across much of TX, OK and western KS. Isolated high-based thunderstorms may also be possible across the TX Panhandle late this evening. While dry thunder chances appear modest given high PWATs, a few lightning strikes within dry fuels appear possible. ...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 1129 AM CDT Tue Jul 19 2022 Valid 191630Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE UPPER MIDWEST AND GREAT LAKES REGIONS... ...SUMMARY... Severe thunderstorm gusts and large hail are expected over portions of the Upper Midwest and upper Great Lakes regions. ...Synopsis... A compact upper wave is evident in mid-morning water vapor imagery translating eastward across North Dakota. This feature will continue east into the Great Lakes region through 12 UTC Wednesday, and will be the focus for severe weather potential for today. A weakening upper disturbance over the eastern U.S. will continue to lift northeast into the western Atlantic, but residual influences from this wave will support lower severe probabilities across the Northeast and Southeast states this afternoon. Across the Southwest, hot and dry conditions prevail under a Four Corners ridge, though widespread monsoonal moisture will continue to support scattered thunderstorm chances with the potential for damaging downbursts for a couple of regions. ...Upper Midwest/Great Lakes... Surface analysis reveals a deepening surface low across the northern Red River Valley of the North with a cold front advancing east across the eastern Dakotas. Ahead of this front, temperatures are warming into the low 80s with widespread dewpoints in the upper 60s and low 70s. While this air mass is undergoing some destabilization, strong capping sampled in the 12 UTC ABR and MPX soundings will likely limit the potential for open warm sector convection. Thunderstorm development is more likely along the diffuse warm frontal zone that is currently draped across northern MN into western WI and where capping diminishes with eastward extent (per the 12 UTC INL and APX soundings). Evidence of strong lift is already evident across northern MN in satellite imagery with thunderstorm initiation likely by late afternoon as lingering inhibition is minimized. Deep-layer flow largely orthogonal to the boundary combined with strong ascent should support semi-discrete storm modes posing primarily a severe hail/wind risk. Storms along the front will continue eastward towards northern lower MI and the U.P. of MI overnight. While convection may become elevated due to diurnal cooling, forecast soundings show adequate MUCAPE and effective shear to maintain a hail, and perhaps damaging wind, threat. ...Northeast... Morning soundings across the region show poor mid-level lapse rates with evidence of low/mid-level stability evident in visible satellite imagery. However, upstream soundings from southeast Canada reveal much colder temperatures aloft, which should advect east through the day as the upper-level low shifts east/northeast. These cooling temperatures, combined with diurnal insolation and a nearly uni-directional wind profile featuring 30-40 knot winds will support a conditionally favorable environment for organized severe storms. While this favorable environment is noted, storm coverage remains uncertain. Thunderstorm development is possible by mid/late afternoon as a weak surface trough, currently just northwest of the international border, moves across the region. However, latest guidance continues to show sparse storm coverage, likely owing to the weak forcing for ascent. Recent downward convective trends of ongoing storms north of ME also limits confidence in storm coverage. Consequently, the potential for a more widespread severe threat appears too limited for a categorical upgrade. ...Southeast... The southern extension of the East Coast upper trough will continue to drift east towards the Atlantic Coast through the day. This will continue to provide lift across far eastern AL, GA, and the Carolinas over an air mass that is currently destabilizing under partly cloudy skies (with temperatures climbing into the upper 80s with rich low-level moisture). The combination of adequate buoyancy, sufficient lift, and modest upper-level flow should support a few strong to severe storms with a predominantly damaging wind risk (though sporadic severe hail is possible with the stronger updrafts). ...Southern High Plains... A deep, dry boundary layer are noted across the southern High Plains on the edge of the monsoonal moisture plume. By late afternoon, adequate mid-level moisture should support sufficient buoyancy for isolated to scattered thunderstorms. With inverted-V signatures noted in forecast soundings and a modest convective signal in most CAM guidance, the potential for strong to severe downburst winds appears sufficient to introduce wind probabilities. ...Southeast Arizona... A weak surface low over southern AZ is noted in morning surface obs. This feature should maintain weak south to southwesterly flow across southeast AZ through the day under modest easterly flow aloft. This should support 20-30 knots of 0-6 km shear through the day, which will aid in storm organization as convection develops off the terrain of the Mongolon Rim and western Gila region this afternoon. Similar to the southern High Plains, inverted-V low-level profiles are noted in forecast soundings, which, when combined with the slightly sheared environment, should support a few stronger storms with severe wind potential. ..Moore/Hart.. 07/19/2022 Read more

WW 0473 Status Updates
STATUS FOR WATCH 0473 HAS NOT BEEN ISSUED YET Read more

WW 473 SEVERE TSTM CT DC DE MD NJ NY PA VA WV CW 181745Z - 190200Z
0-190200- URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 473 NWS Storm Prediction Center Norman OK 145 PM EDT Mon Jul 18 2022 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Western Connecticut District Of Columbia Northern Delaware Maryland New Jersey Southeast New York Eastern Pennsylvania Northern Virginia Eastern Panhandle of West Virginia Coastal Waters * Effective this Monday afternoon and evening from 145 PM until 1000 PM EDT. * Primary threats include... Scattered damaging wind gusts to 70 mph likely A tornado or two possible SUMMARY...Thunderstorms will intensify this afternoon along a corridor from northern Virginia into southeast New York. The stronger cells will pose a risk of locally damaging wind gusts. The severe thunderstorm watch area is approximately along and 45 statute miles either side of a line from 25 miles south southeast of Elkins WV to 25 miles east of Poughkeepsie NY. 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. && 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 500. Mean storm motion vector 25025. ...Hart Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1223 PM CDT Mon Jul 18 2022 Valid 191200Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR NORTHEAST ND...NORTHERN MN...WESTERN UPPER MI...CENTRAL/NORTHERN WI... ...SUMMARY... Widely scattered severe thunderstorms are possible on Tuesday and Tuesday night over portions of the Upper Midwest into parts of Wisconsin and upper Michigan. Severe gusts and large hail appear to be the primary hazards. ...Synopsis... A strong mid/upper-level trough will move from the northern High Plains into the Great Lakes region on Tuesday into Tuesday night. In conjunction with this trough, a surface low will deepen and move from northern MN toward Lake Superior, as an attendant cold front sweeps through the northern and central Great Plains. Downstream, a an upper trough will gradually move eastward across the Northeast and New England, while a weaker upper trough will move from the southern Appalachians toward the Carolinas. Elsewhere, an upper ridge will persist from the Southwest into the southern Plains. ...Upper Midwest/Great Lakes... One or more storm clusters may be ongoing Tuesday morning from northeast ND into northern MN, which could pose a threat of isolated hail and/or damaging wind early in the forecast period. This convection will likely leave a remnant outflow boundary somewhere over northern MN by late morning into the afternoon. Moderate destabilization is expected during the afternoon along/south of any outflow boundary and along/east of the cold front. Rather strong midlevel flow associated with the approaching mid/upper-level trough will support effective shear of 30-40 kt, resulting in a conditionally favorable severe thunderstorm environment across the region by mid/late afternoon. Despite having a seasonably strong synoptic system moving into the region, 12Z guidance continues to be relatively muted in terms of robust storm development along the cold front through much of the day, likely due to the presence of an initially strong capping inversion across the warm sector, and a tendency for the strongest ascent to lag behind the front. Redevelopment of storms during the afternoon appears most likely near/north of the remnant outflow boundary across northern MN, with more isolated development possible southward along the cold front into parts of WI and upper MI by early evening. The strongest cells/clusters will be capable of producing hail and damaging wind gusts. ...Northern New England... A notable midlevel shortwave embedded within the larger-scale trough is forecast to move across northern New England during the day on Tuesday. Low-level flow will become veered as a surface low departs the region during the morning, but residual low-level moisture will support moderate destabilization (MLCAPE of 1000-1500 J/kg) in conjunction with peak heating. Midlevel drying and weak surface convergence may limit storm coverage across the region, but moderate midlevel flow and deep-layer shear will support the potential for isolated cells/clusters capable of locally damaging wind gusts and possibly some hail. ...Southeast CO into the southern High Plains... Convection is expected to develop across the higher terrain of central/southern CO and northern NM during the afternoon. As this convection spreads into the increasingly hot lower elevations, strong to locally severe outflow gusts will be possible. Isolated high-based storms with gusty winds also cannot be ruled out near a weak front across the OK/TX Panhandles, though this scenario remains too uncertain for wind probabilities at this time. ..Dean.. 07/18/2022 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1127 AM CDT Mon Jul 18 2022 Valid 181630Z - 191200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS NORTHEAST MONTANA INTO NORTHERN NORTH DAKOTA... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE MID-ATLANTIC TO NEW ENGLAND REGIONS... ...SUMMARY... The greatest severe-thunderstorm threat will be for destructive, severe gusts and hail today into this evening, from northeastern Montana to northern North Dakota. ...Synopsis... A Four Corners upper ridge will continue to dominate the upper-level flow regime for today with broad troughing over the greater Great Lakes region. A pair of more notable embedded perturbations, one over the Great Lakes with a second approaching the northern Rockies, will drive severe weather chances for this afternoon and into tonight across the northern Great Plains as well as over the Mid-Atlantic and New England regions. ...Northern Plains... The eastward progression of a compact upper-level perturbation across the northern Rockies is apparent in mid-morning water vapor imagery. Ahead of this feature, surface pressure falls are noted across eastern MT and the Dakotas in recent surface observations, and the subsequent mass response is bolstering low-level moisture content with dewpoints increasing into the upper 60s and low 70s. Consequently, a broad warm frontal zone is becoming more apparent across ND and southern Canada. Lift ahead of the wave coupled with ascent along an advancing cold front should support thunderstorm development by late afternoon across eastern MT. Initially discrete cells will mature in an environment with somewhat marginal instability, but elongated hodographs and deep, well-mixed boundary layers that will support organized convection with a severe wind threat, including the potential for significant gusts. Convection will likely intensify as it continues eastward into the Dakotas where boundary-layer moisture will be richer. The best organized severe threat will likely be found in the vicinity of the triple point across northeast MT into northwest ND where lift will locally be maximized. Upscale growth into one or more segments into the late evening/overnight hours is possible across northern ND along a diffuse warm frontal zone. To the east, a strengthening low-level jet will augment warm advection over the frontal zone and support thunderstorm development across northwest to northern MN this evening. Storms will likely propagate to the east/southeast along the frontal zone and within a strong northwesterly flow regime. While storm mode is uncertain, a hail/wind threat appears probable across northern MN into northern lower MI through the overnight hours. ...Mid-Atlantic and New England... Latest analysis shows a surface low gradually deepening across Lake Eerie. This feature will continue to deepen through the day amid increasing mid and upper-level flow. A trailing surface trough should act as the impetus of thunderstorm development from New England into the southern Appalachians as it migrates east through the day. Mid-morning satellite imagery reveals extensive cloud cover across much of the New England region. This cloud cover was also sampled in regional 12 UTC soundings, which featured high column saturation and poor low and mid-level lapse rates. Despite the meager thermodynamic profile, boundary-layer moisture across the region is unseasonably high (surface dewpoints near or above the 90th percentile for mid-July were noted in morning observations). Because of this, any daytime heating that can occur will likely yield adequate buoyancy to support thunderstorm development this afternoon. The degree of destabilization across the New England region is questionable given the extensive cloud cover; however, the increasing flow across the region will boost low-level SRH along a broad warm frontal zone over the region. This will support the potential for not only damaging winds, but a few weak tornadoes as well. To the south across the Mid-Atlantic, patchy cloud cover is allowing for temperatures to quickly warm into the low to mid 80s. Regional VWPs already show winds in the lowest few kilometers increasing to 30 knots, with further strengthening expected through the day. Thunderstorms developing along the front will support a more robust severe wind threat compared to locations further north where instability is more questionable. While low-level hodographs may not feature as much curvature as areas to the north, forecast soundings feature enough low-level veering to support at least a low-end tornado concern. ...Lower Appalachians to Mid-South... A trailing surface trough/cold front draped across the lower Appalachians and into the mid-MS River Valley will support thunderstorm development through the afternoon. While deep-layer flow is meager (recent effective shear estimates near 20-25 knots were noted on recent ACARs soundings), favorable buoyancy should compensate for this weakness and support a damaging wind threat through the afternoon. Latest guidance continues to suggest a cluster of storms across northern MS may consolidate into a more cohesive, southward-propagating convective line that could pose a more widespread damaging wind threat, though confidence this potential remains low given the weak environment flow. ..Moore/Hart.. 07/18/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1127 AM CDT Mon Jul 18 2022 Valid 181700Z - 191200Z ...CRITICAL FIRE WEATHER AREA FOR SOUTHEAST IDAHO... The forecast remains on track without changes. See the previous discussion for more details. ..Wendt.. 07/18/2022 .PREV DISCUSSION... /ISSUED 0204 AM CDT Mon Jul 18 2022/ ...Synopsis... On the northwestern periphery of the strong mid-level anticyclone, a compact and deep upper low will move quickly eastward across the Northwest and northern Rockies today. Flattening the ridge as it passes, strong mid-level westerlies will overspread the northern Great Basin and Rockies, supporting critical fire weather concerns. A strong cold front may also trigger isolated thunderstorms, some dry, across portions of Montana and Wyoming. ...Eastern Idaho and northern Great Basin... With the passage of the strong upper low to the north, a belt of 40-60 kt mid-level flow should bolster low-level surface winds from northern Nevada eastward into portions of central and eastern Idaho. Dry downslope winds and warm temperatures should easily support widespread RH below 15% through the afternoon. The strongest winds, and most likely corridor for sustained critical conditions, should remains across eastern Idaho. However, given the strong flow aloft, locally critical conditions will be possible for a few hours in the lee of the Sierra as well. ...Central High Plains... East of the main upper low, very warm temperatures and increasing westerly flow should favor the development of a lee trough across eastern Wyoming and the central High Plains. West/southwest winds near the higher terrain should reach 15-20 mph with locally higher gusts possible. Widespread RH below 20%, gusty winds, and very dry fuels should support elevated fire weather conditions through the afternoon and early evening. ...Thunderstorms... Plentiful heating ahead of strong height falls associated with the deep upper low should result in isolated thunderstorms across the northern and central Rockies this afternoon. With these high-based and relatively fast moving storms, wetting rain potential appears low. A few dry strikes are possible, along with gusty and erratic winds with stronger downdrafts. However, the coverage of dry lightning should remain below the threshold for IsoDryT conditions given recent rainfall. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

MD 1508 CONCERNING SEVERE POTENTIAL...WATCH LIKELY FOR PARTS OF FAR NORTHERN VA...MD...EASTERN PA...NORTHERN DE...NJ...SOUTHERN NY...WESTERN MA AND CT
Mesoscale Discussion 1508 NWS Storm Prediction Center Norman OK 1118 AM CDT Mon Jul 18 2022 Areas affected...parts of far northern VA...MD...eastern PA...northern DE...NJ...southern NY...western MA and CT Concerning...Severe potential...Watch likely Valid 181618Z - 181815Z Probability of Watch Issuance...95 percent SUMMARY...Damaging gusts and a couple of tornadoes are possible this afternoon across parts of the Mid-Atlantic into southwest New England. The severe threat is expected to increase over the next couple of hours, and a watch will likely be needed for portions of the region. DISCUSSION...Areas of clearing from northern VA into eastern PA/NJ have allowed temperatures to warm into the 80s at midday. This has allowed weak to moderate destabilization to occur amid 70s surface dewpoints. Further north into the Hudson Valley and southwestern New England, thicker cloud cover and showers are keeping temperatures in the low/mid 70s and limiting stronger destabilization. However, some clearing across these areas through the afternoon should allow for modest heating and at least weak destabilization later today. Latest visible satellite indicates a cluster of vertically developing CU near the PA/NJ border as of 16z. Latest radar trends are increasing with this activity as well. This convection is developing along an axis of greater instability extending from the northern Chesapeake Bay toward northern NJ. Thunderstorms are expected to gradually increase across this area over the next couple of hours. Moderate vertical shear will support organized clusters and semi-discrete supercell structures capable of damaging gusts. Stronger low-level shear and more favorably curved hodographs will reside from northeast PA/northern NJ toward the lower Hudson Valley. Latest VWP data from KBMG and KENX show enlarged low-level hodographs with 0-1 km SRH values greater than 300 m2/s2. However, weaker instability in conjunction with poor lapse rates may limit intensity/longevity of any stronger cells across this area. Nevertheless, any sustained convection will pose a risk for a couple of tornadoes. Given current trends, a watch will likely be needed in the next 1-2 hours. ..Leitman/Hart.. 07/18/2022 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BOX...OKX...ALY...PHI...BGM...CTP...LWX... LAT...LON 38907664 38807723 38987772 39257778 39817763 40777703 41607631 42407532 42507523 42737443 42727351 42587303 42277270 41717255 41317265 40877347 39247597 38907664 Read more

No watches are valid as of Sun Jul 17 17:55:01 UTC 2022.

No Mesoscale Discussions are in effect as of Sun Jul 17 17:55:01 UTC 2022.

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook CORR 1 NWS Storm Prediction Center Norman OK 1241 PM CDT Sun Jul 17 2022 Valid 181200Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE MONDAY AFTERNOON AND EVENING ACROSS PARTS OF NORTHEASTERN MONTANA INTO NORTHWESTERN NORTH DAKOTA... CORRECTED FOR A COUPLE TYPOS ...SUMMARY... Strong to locally severe thunderstorm development is possible near the Canadian/U.S. border, from the Great Plains into the upper Great Lakes region, as well as across parts of the northern Mid Atlantic region, Monday afternoon into Monday night. ...Synopsis... Models indicate that lower/mid-tropospheric ridging will generally persist from the subtropical western Atlantic through much of the southern and central tier of the U.S. through this period. This will continue to include one prominent embedded mid-level high centered over the southern Rockies vicinity, and another elongated along 30N latitude across the western Atlantic, with weak mean troughing in between, roughly along an axis from the lower Mississippi Valley into the western slopes of the Appalachians. It does appear that flow may become a bit more progressive across the northern tier of the U.S., with a vigorous short wave trough and embedded low within one belt of westerlies forecast to accelerate across the northern Rockies into the northern Great Plains by late Monday night. Downstream, a more modest impulse likely will accelerate from the lower Great Lakes/upper Ohio Valley vicinity through northern New England. Both of these perturbations (preceding significant short wave impulses within a branch to the north, including one digging near or just south of southern Hudson Bay and another accelerating inland of the British Columbia coast) may be accompanied by surface cyclogenesis, with the lead cyclone probably becoming the more prominent while migrating from the lee of the lower Great Lakes into the St. Lawrence Valley. ...Northern Mid Atlantic... Pre-frontal surface troughing, extending from near the migratory low southward through the Mid Atlantic, likely will become the focus for the more prominent boundary-layer destabilization during the day Monday. The boundary-layer probably will become characterized by seasonably high moisture content, but lower/mid tropospheric lapse rates are expected to be generally weak, and most guidance suggests that CAPE may not reach 1000 J/kg. However, a belt of 30-40+ kt southwesterly flow in the 850-500 mb layer will potentially contribute to an environment conducive to organized convection given sufficient destabilization. It is possible that this could include a couple of supercells with a risk for tornadoes, particularly across the Poconos and Catskills into Hudson Valley vicinity by late Monday afternoon. ...Northern Rockies into upper Great Lakes region... In association with the short wave developments, models indicate that a lower/mid tropospheric front within an evolving deformation zone will become focused near the international border area, from the Great Plains into the upper Great Lakes region. Along and to the southwest of this front, a plume of warm and capping elevated mixed-layer air is forecast to advect east of the Rockies. At mid-levels (around 700 mb) the northeastern periphery of this air mass may generally extend from north of the international border across the Great Plains into the western Lake Superior/Upper Michigan vicinity by early Monday evening. Beneath this regime, in the presence of moderate west/northwesterly mid-level flow, there may be sufficient moisture to contribute to mixed-layer CAPE on the order of 2000+ J/kg, and the environment appears likely to become at least conditionally supportive of severe storms, potentially including isolated supercells and organizing storm clusters. However, forcing to overcome the mid-level inhibition remains unclear across much of the region. Most guidance does appear to suggest that a concentrated area of strong forcing for ascent, just to the east-northeast of the approaching mid-level low, may overcome inhibition and promote sustained thunderstorm development across parts of northeastern Montana by early Monday evening. This may be accompanied by the risk for severe wind and hail, which probably will spread into portions of northwestern and north central North Dakota through Monday night. ..Kerr.. 07/17/2022 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sun Jul 17 2022 Valid 171630Z - 181200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE OZARK PLATEAU THROUGH THE OHIO RIVER VALLEY... ...SUMMARY... Damaging thunderstorm gusts and isolated large hail are possible today from the Ozarks to the central Appalachians, as well as across eastern North Dakota and northwest Minnesota. ...Synopsis... A pair of weak upper-level disturbances/MCVs remain evident in mid-level reflectivity mosaics across central IL and the upper OH River Valley. Embedded within a broad trough across the great Great Lakes region, these features are expected to continue to propagate to the east/northeast through the day. Widespread stratiform rain with embedded convection in the vicinity of these two features is diabatically reinforcing a stalled cold front draped through the OH River Valley into the southern Plains. This front is expected to gradually migrate southward through the day and will likely be the impetus for thunderstorm development and/or intensification later this afternoon. Across the west, ample monsoonal moisture across the Great Four Corners region and into the northern Rockies will support scattered thunderstorm development with the potential for severe downburst winds. ...Upper OH River Valley... The ongoing showers and thunderstorms across the mid to upper OH River Valley are limiting the potential for daytime heating across the region. Temperatures are currently struggling to climb above the mid 70s with few breaks in cloud cover expected through at least mid afternoon. With lift and modest, but sufficient, deep-layer flow already in place ahead of the MCVs, the greater severe threat will likely reside along and south of the OH River Valley where some destabilization is already noted. Latest CAMs support this idea and show clusters developing by late afternoon through the region. Severe probabilities have been adjusted southward to reflect this trend. ...Ozark Plateau into the lower OH River Valley... Morning showers and thunderstorms across southern MO and into adjacent parts of AR, IL, and KY will likely limit diurnal heating through at least early afternoon. Some guidance suggests sufficient clearing can take place to allow thunderstorm development across central to southern MO by mid-afternoon, and latest visible satellite imagery and surface temperature trends across western MO support this idea, but the degree of destabilization that can occur remains uncertain. Confidence in storm development is higher to the south across AR and into the mid-MS River Valley where destabilization is already ongoing with temperatures climbing into the low/mid 80s. While mid to upper-level flow will be modest, adequate deep-layer shear should be in place to support semi-discrete storms to clusters from western AR into western KY/TN to support an isolated hail/severe wind threat. A brief tornado or two appears possible across the mid-MS River Valley region where low-level helicity along and just ahead of the front will be maximized, but confidence in storm mode and coverage remains too limited for higher probabilities. ...Red River Valley of the North... Latest surface observations across northeast ND into northwest MN show surface pressure falling over the past several hours, which is resulting in a slight bolstering of generally southerly low-level flow through the region. In turn, dewpoints have increased into the 70s through the region, which is boosting MLCAPE estimates to over 2000 J/kg. Despite the improving buoyancy, 12 UTC soundings from BIS and ABR reveal some mixed-layer inhibition, which remains a concern for convective potential later this afternoon. Forecast soundings suggest this inhibition may become negligible by this afternoon, and several CAMs show discrete supercell potential as storms develop along a weak surface trough. However, some spread in guidance remains with other solutions showing little to no activity south of the international border. The Marginal risk has been expanded south to encompass much of the Red River Valley, but this is to more accurately address spatial extent of the severe threat rather than indicate an increase in the probability for thunderstorms. ...Montana... Morning soundings from MT and ID sampled 50-60 knot winds aloft ahead of a shortwave trough located across the Pacific Northwest. These soundings also sampled mid-level monsoonal moisture and fairly dry boundary layers. With daytime heating already underway, thermodynamic profiles across southern MT should be favorable for thunderstorms with strong to severe downbursts by late this afternoon. Combined ascent ahead of the shortwave trough and via orographic ascent should support isolated to scattered thunderstorms across the region. ...Nevada/Utah... Similar to southern MT, 12 UTC soundings from LKN, VEF, and SLC all sampled dry boundary layers with adequate mid-level monsoonal moisture to support thunderstorms by this afternoon. Forecast soundings show 2 to 3 km deep sub-cloud layers with steep low-level lapse rates that will be supportive of strong to severe downburst winds. Latest CAM guidance shows a strong convective signal across northeast NV into northwest UT this afternoon, which gives sufficient confidence to introduce severe wind probabilities given the expected thermodynamic environment. ..Moore/Hart.. 07/17/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1114 AM CDT Sun Jul 17 2022 Valid 171700Z - 181200Z The ongoing forecast reasoning remains valid. Locally critical fire weather remains possible in far northwest Nevada into southeastern Oregon. See the previous discussion for further information. ..Wendt.. 07/17/2022 .PREV DISCUSSION... /ISSUED 0147 AM CDT Sun Jul 17 2022/ ...Synopsis... To the northwest of a prominent anticyclone over the Southwest, a deepening Pacific trough will move ashore, overspreading strong flow aloft across the Northwest and Great Basin. At the surface, a cold front will move inland triggering isolated thunderstorms along the Cascades and northern Rockies. The strong surface flow, and dry/warm conditions across the southern Cascades/Great Basin will support several hours of elevated to near-critical fire weather conditions. ...Northern Great Basin... With flow aloft strengthening on the periphery of the upper ridge, dry downslope winds will develop off the Sierra and into the northern Great Basin this afternoon and evening. Deep mixing within the dry airmass across the region will support sustained winds of 15-20 mph and locally higher gusts. With widespread surface RH expected below 15%, the environment will easily support widespread elevated to near-critical fire weather conditions into early evening. Confidence in sustained critical conditions is lower, owing to borderline winds. However, the most likely corridor for some critical concerns appears to be across far northern NV into southeastern OR closer to the mid-level jet axis. A few hours of stronger sustained winds may develop here, but confidence remains too low for a Critical area at this time. Farther east, modest mid-level moisture on the periphery of the ridge will support a few thunderstorms across portions of central/eastern ID. Model soundings show high-based and fast-moving storms which may produce occasional lightning over dry fuels. While some risk of dry thunder likely exists given minimal wetting rain potential, storm coverage appears too low to warrant IsoDryT probabilities. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No watches are valid as of Sat Jul 16 17:56:02 UTC 2022.