SPC Sep 24, 2022 1630 UTC Day 1 Convective Outlook

2 years 10 months ago
SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1118 AM CDT Sat Sep 24 2022 Valid 241630Z - 251200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATER THIS AFTERNOON/EVENING FOR EXTREME SOUTHEASTERN MO...NORTHEASTERN AR...WESTERN TN AND NORTHWESTERN MS... ...SUMMARY... Isolated damaging wind gusts and large hail may occur this evening across extreme southeastern Missouri, northeastern Arkansas, and adjacent areas of western Tennessee and northwestern Mississippi. ...Northeast AR and vicinity later this afternoon/evening... Around the southwestern periphery of a midlevel trough over the Great Lakes, an embedded speed max will dig southeastward from the northern High Plains to the mid MS Valley by tonight. In advance of this speed max, low-level moisture will continue to spread northeastward from east TX to AR and southern MO, south of a weak front/wind shift that now extends from southern KS eastward into southern MO. With daytime heating/mixing in cloud breaks, MLCAPE will increase to near 1500 J/kg, in an environment with effective bulk shear of 35-45 kt with straight hodographs. This will conditionally favor splitting supercells by this evening from extreme southeast MO into northeast AR. The main concern in this area is the specific focus for storm development this afternoon/evening. A band of mid clouds will likely persist from OK into northern AR as part of a remnant monsoonal moisture plume from the southern Rockies, and these clouds will mute surface heating in a zone immediately south of the subtle front/wind shift. Thus, with relatively subtle forcing for ascent, at least isolated thunderstorm development is possible both north and south of this cloud band on the wind shift and south in the differential heating zone, depending on how persistent the thicker clouds will be through the afternoon. The degree of surface heating/mixing will drive low-level lapse rates, downdraft potential, and any resultant threat for wind damage. Given the potential for splitting supercells with long hodographs, isolated hail may also occur. Given the subtle nature of the ascent and the mesoscale influence/location of the cloud band, will maintain a broader MRGL area, but acknowledge the potential for two separate, smaller corridors of wind/hail threat from mid-late afternoon into this evening. ..Thompson/Weinman.. 09/24/2022 Read more

SPC Sep 23, 2022 1730 UTC Day 2 Convective Outlook

2 years 10 months ago
SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1209 PM CDT Fri Sep 23 2022 Valid 241200Z - 251200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR THE AREA CENTERED ON CENTRAL AND EASTERN ARKANSAS... ...SUMMARY... A few strong thunderstorms may develop Saturday afternoon and evening from parts of Arkansas into adjacent portions of the Missouri Bootheel, western Tennessee, and northwest Mississippi. Isolated damaging wind gusts appear to be the primary threat. ...Synopsis... A mid-level speed max over MT early Saturday morning will quickly move east-southeast to the mid MS Valley by early Sunday morning. In the low levels, surface high pressure initially over the Appalachians will move east of the Carolina coast, while weak return flow in response to weak low pressure develops over the MS Valley before moving into the Great Lakes late. The southern portion of stronger westerlies will overspread a weak to moderately unstable (750-1500 J/kg MLCAPE) warm sector centered over AR. The latest model guidance indicates isolated to perhaps widely scattered storms developing late Saturday afternoon into the early evening from central AR northeastward to the MO Bootheel region. A couple of the storms could yield strong locally damaging gusts before this activity weakens after sunset. Elsewhere, general thunderstorms are expected over parts of the Great Lakes/OH Valley, southern half of the FL Peninsula, and portions of the Desert Southwest. ..Smith.. 09/23/2022 Read more

SPC Day 1 Fire Weather Outlook

2 years 10 months ago
SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1124 AM CDT Fri Sep 23 2022 Valid 231700Z - 241200Z ...NO CRITICAL AREAS... The current forecast is on track. See discussion below for more details. ..Thornton/Weinman.. 09/23/2022 .PREV DISCUSSION... /ISSUED 1231 AM CDT Fri Sep 23 2022/ ...Synopsis... An upper-level trough will continue eastward through the northern Plains into parts of the upper Midwest today. Farther west, ridging aloft will begin to amplify along the western coast. At the surface, a cold front will move out onto the northern and central Plains. High pressure will increase within the intermountain West. Localized elevated conditions are possible from central Montana into northeastern Colorado as downslope winds increase to around 20 mph. Some areas may experience RH as low as 15-20%. Given recent precipitation, significant fire potential will be low. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Sep 23, 2022 1630 UTC Day 1 Convective Outlook

2 years 10 months ago
SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1113 AM CDT Fri Sep 23 2022 Valid 231630Z - 241200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected through tonight. ...Synopsis... Within the primary branch of the westerlies, a midlevel shortwave trough will move east-southeastward from the northern Plains to the Upper Midwest by tonight. Low-level moisture return remains quite limited across the Plains in advance of an associated lee trough, as a result of a prior frontal intrusion to the Gulf coast. Very weak buoyancy within a midlevel moisture plume across KS/NE, in combination with relatively steep midlevel lapse rates from NE into the eastern Dakotas, could be sufficient for isolated/elevated thunderstorms in the zone of ascent preceding the midlevel trough. Otherwise, scattered thunderstorms are expected along the primary baroclinic zone across central FL, and within the lingering monsoonal moisture plume with daytime heating over the higher terrain in AZ/NM this afternoon. ..Thompson/Kerr.. 09/23/2022 Read more

SPC Sep 22, 2022 1730 UTC Day 2 Convective Outlook

2 years 10 months ago
SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1223 PM CDT Thu Sep 22 2022 Valid 231200Z - 241200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... No severe threat is expected over the continental United States on Friday. ...Synopsis... A mid-level anticyclone will remain over the southern Great Plains while a mid-level trough will progress east across the northern Great Plains into the Upper Midwest. A narrow moist sector resulting in weak instability may result in a few thunderstorms across the eastern Dakotas and parts of the Upper Midwest. Elsewhere, general thunderstorms are also forecast across the FL Peninsula and the Desert Southwest. Weak buoyancy/shear will preclude organized severe thunderstorms. ..Smith.. 09/22/2022 Read more

SPC Day 1 Fire Weather Outlook

2 years 10 months ago
SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1126 AM CDT Thu Sep 22 2022 Valid 221700Z - 231200Z Morning observations show winds across the Columbia Basin sustained at 10-15 mph, gusting to around 20 mph, with temperatures warming into the mid 50s to 60s. Through the afternoon, increasing westerly winds and downslope warming and drying could lead to elevated fire-weather conditions. See discussion below for more details. ..Thornton/Bentley.. 09/22/2022 .PREV DISCUSSION... /ISSUED 0102 AM CDT Thu Sep 22 2022/ ...Synopsis... A closed mid/upper-level low will cross the northern Rockies, while an expansive large-scale ridge remains centered over TX. At the surface, low pressure will deepen over the northern High Plains, with a lee trough extending southward along the central High Plains. ...Columbia Basin... On the backside of the mid/upper-level low, enhanced northwesterly flow aloft will overspread the Cascades, favoring dry/breezy conditions across the Columbia Basin. Here, 15-20 mph sustained westerly surface winds coupled with 20-25 percent RH (aided by downslope warming/drying) will yield elevated to locally critical fire-weather conditions during the afternoon. ...Northern/Central Rockies and Adjacent Plains... Breezy southerly surface winds will develop across the northern and central Plains in response to the lee troughing, while strong westerly surface winds are expected over WY. For the Plains, a minimal overlap of strong surface winds and low RH should generally mitigate the fire-weather threat, though locally elevated conditions could still occur where fuels are dry. Over WY, a corridor of strong westerly surface winds could overlap dry boundary-layer conditions, though recent/ongoing precipitation casts uncertainty on fuel receptiveness. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Sep 22, 2022 1630 UTC Day 1 Convective Outlook

2 years 10 months ago
SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1056 AM CDT Thu Sep 22 2022 Valid 221630Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS COASTAL SOUTHERN NEW ENGLAND TO EASTERN NORTH CAROLINA...AND SOUTHEAST MONTANA TO NORTHEAST WYOMING... ...SUMMARY... Isolated damaging winds remain possible this afternoon from coastal southern New England into eastern North Carolina. Isolated marginally severe hail/wind may also occur across a portion of southeast Montana and northeast Wyoming later this afternoon. ...Southern New England to NC... Potential still exists for convection to briefly strengthen from NJ to southern New England. A confined corridor of robust insolation from NJ southward yielded surface temperatures warming into the upper 70s to mid 80s just ahead of mixed convective/stratiform frontal rain bands. The time-window for convection to intensify before the front shifts off the coast is limited to the next hour or two, but strong deep-layer flow will support a conditional damaging wind threat along the immediate coastal areas. From the Delmarva into eastern NC, a longer duration period of robust boundary-layer heating will yield very warm surface temperatures and a relatively deeper mixed boundary-layer. Observed 12Z soundings sampled very poor 600-400 mb lapse rates south of the intense mid-level jet centered across the Mid-Atlantic to New England, where 500-mb temps were -4 to -6 C. This suggests convection developing along the trailing extent of the cold front impinging from the northwest will struggle to deepen and produce lightning. By late afternoon, there may just enough slight cooling aloft coupled with peak boundary-layer heating to support a few stronger gusts in convection that spreads towards the coast through early evening. ...Southeast MT and northeast WY... A shortwave trough centered on northwest MT will gradually shift east across the state through the period. While a leading lobe of ascent is moving through eastern MT late this morning, the next lobe will shift east-northeast from the Yellowstone/Upper Snake Valley area. A pocket of 500-1000 J/kg of MLCAPE should develop between these two waves in the lee of the Big Horns where steepening mid-level lapse rates overspread modest boundary-layer heating. Although forecast soundings indicate pronounced weaknesses in the hodograph through 600 mb where surface-based storms are expected, strong speed shear above that will yield potential for a few cells with transient mid-level rotation. Marginally severe hail and isolated strong to localized severe wind gusts will be possible for a few hours centered on late afternoon. ..Grams/Lyons.. 09/22/2022 Read more

SPC Sep 21, 2022 1730 UTC Day 2 Convective Outlook

2 years 10 months ago
SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1228 PM CDT Wed Sep 21 2022 Valid 221200Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE MID-ATLANTIC STATES INTO NORTH CAROLINA... ...SUMMARY... An isolated threat for damaging thunderstorm gusts will be possible on Thursday across parts of the Mid Atlantic southwestward into North Carolina. ...Mid-Atlantic states into NC... A large-scale mid-level trough initially over the Great Lakes will move east-southeast during the period and reach the coast of the Mid-Atlantic states/Northeast by early Friday morning. In the low levels, a cold front over the Appalachians Thursday morning will push southeast during the day and reach the southern portion of the Delmarva southwestward into the Carolina Piedmont by peak heating. Weak to moderate buoyancy (750-1500 J/kg MLCAPE) is forecast ahead of the front from the Delmarva southwest to the Research Triangle. Although 0-2 km lapse rates will steepen (8 deg C/km) through the early to mid afternoon, mid-level lapse rates will remain limited. Around 30-kt effective shear will probably support a few organized multicells/line segments where the primary hazard will be locally damaging gusts. This activity will likely weaken by early evening as instability wanes. ...Southeast New England... Scattered to numerous showers and a few thunderstorms are expected Thursday morning from the lower Hudson Valley northeastward into southern ME. Considerable cloud cover will likely encompass much of this region ahead of the front. However, relatively moist low levels could lead to weak destabilization during the morning. Forecast soundings show a strong wind profile but uncertainty remains whether a few surface-based storms will develop in the RI and southeast MA vicinity before the front moves offshore. Will defer the inclusion of low-severe probabilities for the time being. Elsewhere, general thunderstorms are forecast across a large part of the Four Corners northward into the north-central Rockies and adjacent plains. ..Smith.. 09/21/2022 Read more

SPC MD 1812

2 years 10 months ago
MD 1812 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR NORTH-CENTRAL/NORTHEAST OH...NORTHWEST PA...FAR SOUTHWEST NY
Mesoscale Discussion 1812 NWS Storm Prediction Center Norman OK 1231 PM CDT Wed Sep 21 2022 Areas affected...North-Central/Northeast OH...Northwest PA...Far Southwest NY Concerning...Severe potential...Watch possible Valid 211731Z - 211930Z Probability of Watch Issuance...40 percent SUMMARY...Strong to severe thunderstorms capable of isolated hail and/or damaging gusts may occur from north-central/northeast OH into southwest NY this afternoon. Uncertainty regarding severe thunderstorm coverage currently merits low watch probabilities. DISCUSSION...A large area of showers and embedded thunderstorms continues to move eastward/southeastward across southwestern Ontario and Lake Erie. Current motion of the leading edge of this area is estimated at 35-40 kt, which brings it to the eastern shore of Lake Erie around 18Z. Cloud cover associated with this precipitation has already spread into areas in the lee of Lake Erie, which is tempering diurnal heating. Current observations show temperatures in the mid 70s across southwest NY, increasing into the low 80s in north-central OH. Dewpoints increase from the mid 60s across southwest NY to the upper 60s across north-central OH. These surface conditions are precluding the erosion of the convective inhibition in place, particularly across western PA and southwest NY. Thunderstorm development is still expected as this area of ascent reaches the lee of Lake Erie, but, given the low-level stability still in place, most of these storm will likely be elevated. The best chance of surface-based storms is back across north-central/northeast OH. Elevated character to most of the storms should limit the overall coverage, with isolated hail as the most likely risk. A few strong gusts could also occur, particularly if any bowing line segments are able to develop/mature. ..Mosier/Grams.. 09/21/2022 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BUF...CTP...PBZ...CLE... LAT...LON 41398287 41478180 42197992 42647897 42027832 41197951 40888078 40728290 41398287 Read more

SPC MD 1811

2 years 10 months ago
MD 1811 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PORTIONS OF WESTERN AND CENTRAL UTAH AND EASTERN NEVADA
Mesoscale Discussion 1811 NWS Storm Prediction Center Norman OK 1226 PM CDT Wed Sep 21 2022 Areas affected...portions of western and central Utah and eastern Nevada Concerning...Severe potential...Watch possible Valid 211726Z - 211930Z Probability of Watch Issuance...60 percent SUMMARY...Ahead of a deep upper low, scattered thunderstorm development/ organization is expected early this afternoon. Damaging wind gusts, and hail will be possible with strong to severe storms later this afternoon. Conditions are being monitored for a possible watch. DISCUSSION...Evident on regional water vapor imagery, a deep upper low and 70-80 kt cyclonically curved jet streak over the western Great Basin were supporting broad diffluence and lift across much of the intermountain West. With the commencement of diurnal heating, increasingly agitated cumulus was noted on area visible imagery across the higher terrain of eastern NV and western UT. Further destabilization is expected as temperatures warm and as surface dewpoints in the 40s and 50s F are transported northward from the Southwest. While not overly steep, 7 C/km mid-level lapse rates were observed east of the cold core center, aiding in the development of weak buoyancy (MUCAPE of 500-1000 J/kg). As ascent increases through the late morning and early afternoon, scattered thunderstorms should develop and detach from the higher terrain before spreading north/northeastward. Favorable deep-layer shear (0-6 km 50-60 kt) will likely support a mix of cluster and more discrete storms with some mid-level storm rotation possible. Low-level inverted-v structures and strong mid-level flow will favor a risk for damaging wind gusts, some of which could be significant with stronger downdrafts able to develop. Some severe hail may also be possible given elongated upper-level hodographs and cool mid-level temperatures, though the weaker buoyancy casts some uncertainty on updraft strength. Latest hi-res guidance and observations suggest storm development may occur as early as 18z across portions of southwestern UT, closest to the strongest ascent and orographic lift. Storms should quickly spread north/northeast into western and central UT with a severe risk through this afternoon and into the evening. With scattered storm coverage and greater potential for organization expected, conditions are being monitored for a possible weather watch. ..Lyons/Grams.. 09/21/2022 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...SLC...VEF...LKN... LAT...LON 37241374 37231399 37501415 38381429 39441450 39911459 40421484 40981517 41341539 41701526 41921489 41981418 41981283 41861234 41571193 41181179 40741168 39281221 37811286 37461319 37241374 Read more

SPC Day 1 Fire Weather Outlook

2 years 10 months ago
SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1059 AM CDT Wed Sep 21 2022 Valid 211700Z - 221200Z Elevated fire weather conditions are expected across portions of the Columbia Basin this afternoon. See details in previous discussion below. ..Thornton/Bentley.. 09/21/2022 .PREV DISCUSSION... /ISSUED 0520 AM CDT Wed Sep 21 2022/ ...Synopsis... A closed mid/upper-level low will track northeastward from northern CA into the Intermountain West, while an expansive large-scale ridge remains centered over the southern Plains. At the same time, a weak surface low will evolve northward across the northern Great Basin, while surface ridging expands southward across the northern and central Plains behind a southward-advancing cold front. ...Columbia Basin... Between the surface ridging over the northern/central Plains and surface low over the northern Great Basin, an enhanced pressure gradient and breezy northeasterly surface winds will develop east of the Cascades in WA -- particularly over the Columbia Basin. Here, 15-20 mph sustained surface winds (with gusts upwards of 30 mph) will overlap 15-20 percent minimum RH, resulting in elevated fire-weather conditions given modestly receptive fuels over the area. ...Northern Great Basin and Northern Rockies... Preceding the mid/upper-level low, strengthening large-scale ascent amid a plume of enhanced midlevel moisture will support scattered thunderstorms across the northern Great Basin into the northern Rockies. Initially, a deeply mixed boundary layer beneath the midlevel moisture will yield inverted-V thermodynamic profiles supportive of dry thunderstorms -- aided by fast southwesterly storm motions. However, strengthening large-scale ascent should favor quick upscale growth and increasing precipitation across the area. Therefore, isolated lightning-induced ignitions will be possible in the early stages of storm development, though the threat appears too brief for Dry Thunderstorm highlights. Strong to severe outflow winds could also accompany the stronger storms, especially over southern ID. For details on the severe weather threat, see the Day 1 Convective Outlook. ...Northern and Central Plains... Breezy northerly surface winds are expected across the northern and central Plains behind the southward-advancing cold front. With that said, cool temperatures within the post-frontal airmass will temper RH reductions where the strongest surface winds are expected -- generally mitigating the fire-weather threat. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Sep 21, 2022 1630 UTC Day 1 Convective Outlook

2 years 10 months ago
SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1054 AM CDT Wed Sep 21 2022 Valid 211630Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LOWER GREAT LAKES...UPPER OHIO VALLEY...AND THE NORTHEAST GREAT BASIN... ...SUMMARY... Scattered thunderstorms capable of severe hail, damaging winds, and a couple of tornadoes are expected into this evening across the Upper Ohio River Valley and the Lower Great Lakes. Isolated to scattered severe wind gusts are also possible across portions of the northeast Great Basin this afternoon. ...Lower Great Lakes/Upper OH Valley... Clusters of elevated strong storms are ongoing across southeast Lower MI into southwest ON within a corridor of 850-700 mb warm theta-e advection and leading mid-level height falls attendant to a positive-tilt shortwave trough centered on northern ON. Consensus of 12Z CAM guidance, including recent HRRR runs, have failed to simulate this activity. The HRW-NSSL and NAM-Nest have some semblance of these storms and appear reasonable with indicating movement to the southeast downstream of the Lake Erie area through the afternoon. Steep mid-level lapse rates sampled by the 12Z DTX sounding are already in place downstream with an EML expected to spread at least into western portions of PA/NY. These elevated clusters should build into the destabilizing boundary layer, especially across northern OH given warmer and more moist conditions advecting from the west. It's plausible that clusters may still hold onto a slightly elevated character with eastern extent in NY/PA owing to the lack of surface-based instability at this time and relatively early convective evolution for the main severe scenario. This setup suggests the primary severe threats will be large hail and damaging winds. The tornado threat is more uncertain and will likely be confined to a corridor within the surface-based instability gradient where low-level hodographs can remain enlarged and semi-discrete supercell structures can develop within the southeast-moving clusters. This still appears most probable in the eastern OH/western PA vicinity later this afternoon. ...Eastern/northern Great Basin and the Interior West... A deep mid/upper trough centered on the northern CA vicinity will pivot northeast into the Interior Northwest through tonight. Broad large-scale ascent ahead of this trough in conjunction with the northern extent of a Gulf of CA moisture plume should aid in an arc of thunderstorm development this afternoon from western UT across southern ID. While buoyancy will be scant with northern extent, elongated mid to upper-level hodographs will favor potential for a few supercells with mid-level rotation, focused on northwest UT to south-central ID. Strong to isolated severe wind gusts along with isolated/marginally severe hail are the expected hazards. Regenerative convection will likely persist this evening into tonight but the overall severe threat will diminish with onset of nocturnal surface cooling. ..Grams/Lyons.. 09/21/2022 Read more

SPC Sep 20, 2022 1730 UTC Day 2 Convective Outlook

2 years 10 months ago
SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1231 PM CDT Tue Sep 20 2022 Valid 211200Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR THE LOWER GREAT LAKES AND FROM NORTHERN UTAH INTO SOUTHERN IDAHO... ...SUMMARY... Scattered thunderstorms will be capable of a severe risk from Utah into Idaho and in a separate area over the Lower Great Lakes mainly Wednesday afternoon into the evening. ...Great Basin into the Northern Rockies... A mid-level low initially over northern CA will migrate northeastward during the period and reach the ID/OR border by early Thursday morning. A belt of strong 50+ kt southwesterly 500-mb flow will move through the base of the larger-scale trough and into UT during the day. A plume of adequate low-level moisture will extend from the Desert Southwest northward through the Eastern Great Basin and into ID during the day. Strong heating in the wake of some early day clouds over UT will favor the development of steep low- to mid-level lapse rates from southwest UT northward into ID in closer proximity to the mid-level low. Strengthening flow fields will promote some storm organization despite weak buoyancy (200-700 J/kg SBCAPE). Model CAM guidance indicates cells to cell-in-cluster convection. The heavier precip cores will be most conducive for severe gusts as they move across the outlook area during the afternoon and evening. ...Lower Great Lakes into the OH Valley... A weak mid-level ridge over the Lower Great Lakes in between two troughs early Wednesday morning will move east off the New England coast, as a large-scale mid-level trough over the Upper Midwest moves into the Great Lakes. A surface cold front will push southeastward across the Great Lakes during the period. Ahead of the front, a reservoir of relatively rich moisture (characterized by 65-70 deg F surface dewpoints) coupled with heating and advection of steep 700-500 mb lapse rates (around 7-7.5 deg C/km) will result in a moderately to strongly unstable airmass (1500-2500 J/kg MLCAPE). Supercell potential appears highest over the Upper OH Valley and Lower Great Lakes. However, little speed shear in the westerly component to the 800-300mb flow will probably favor a relatively quick transition to a HP supercell structure and clustering. As a result, large hail and damaging gusts appear to be the primary hazards, although a localized risk for a supercell tornado is possible. This activity will likely diminish during the evening. ..Smith.. 09/20/2022 Read more
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