Severe Storms

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 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

No watches are valid as of Tue Sep 20 17:52:02 UTC 2022.

No Mesoscale Discussions are in effect as of Tue Sep 20 17:52:02 UTC 2022.

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

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook RESENT 1 NWS Storm Prediction Center Norman OK 1223 PM CDT Tue Sep 20 2022 Valid 201630Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS NORTHWEST WISCONSIN TO WESTERN UPPER MICHIGAN... ...SUMMARY... A conditional threat for a few supercells exists this evening across northwest Wisconsin into western Upper Michigan. Should storms become sustained, large hail and locally damaging winds will be the primary hazards. ...Northwest WI to western Upper MI vicinity... Substantial uncertainty exists regarding whether deep convection can become sustained this evening within the cat 2-SLGT risk. Will maintain it for the conditional threat of large hail. In the wake of an early-day MCS, with its remnants centered on southern Lake MI, a pronounced EML evident in 12Z soundings will inhibit surface-based thunderstorm development within the open warm sector. Storm potential will be tied to a cold front moving southeast across northern MN. However, guidance differs greatly with the degree of low-level convergence along the cold front during the early evening. Mid-level height falls do not appear to overspread the front until late evening/tonight as the Prairie Provinces positive-tilt shortwave trough begins to amplify. In addition, a plume of stratus remains entrenched across most of northwest/west-central WI, which will result in pronounced differential boundary-layer heating with greater insolation to the west/north of this plume. Most guidance suggests that little if any sustained convective development will occur. However, recent HRRR runs remain insistent that sustained deep convection will occur across northwest WI into the western Upper MI given its warmer boundary layer than other guidance. Robust speed shear yielding a rather elongated hodograph above the LFC amid rather steep mid-level lapse rates and moderate buoyancy will favor a conditional threat for large hail. This threat corridor may remain rather confined given the recent satellite trends and likelihood of pronounced MLCIN with southeast extent ahead of the front. ...Southern Lower MI vicinity... Remnants of an early-day MCS persist across southern Lake MI. See MCD 1805 for short-term forecast discussion. While this should gradually subside through the afternoon given the paucity of downstream surface-based buoyancy, low-level WAA will remain focused within this region, likely yielding persistent elevated convection. Another round of nocturnal strengthening is possible tonight along the periphery of the Upper Midwest EML. While a cluster mode will dominate, an adequate combination of MUCAPE and cloud-bearing shear will exist for a threat of marginally severe hail. ..Grams/Lyons.. 09/20/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1147 AM CDT Tue Sep 20 2022 Valid 201700Z - 211200Z Morning observations across south central Kansas/northern Oklahoma show south to southwest winds around 10-15 mph with gusts around 20 mph ahead of a southward advancing cold front located across northern Kansas. Winds will persist through the afternoon amid decreasing relative humidity as mixing increases through the day, creating a period of elevated fire-weather conditions. Elsewhere the forecast is on track in the Pacific Northwest with elevated fire-weather conditions expected along and east of the Cascades. ..Thornton/Bentley.. 09/20/2022 .PREV DISCUSSION... /ISSUED 0158 AM CDT Tue Sep 20 2022/ ...Synopsis... An expansive large-scale ridge will remain centered over the southern Plains, while a closed mid/upper-level low drifts slowly eastward toward northern California. At the surface, low pressure will develop over the northern Great Basin, while high pressure expands southward across the northern Rockies and adjacent Plains behind a southward-advancing cold front. ...Intermountain West... Between the surface low over the northern Great Basin and building high pressure over the northern Rockies/adjacent Plains, a tight pressure gradient will favor 15-20 mph northerly surface winds along and east of the Cascades. These winds, coupled with 15-20 percent minimum RH should yield elevated fire-weather conditions given modestly receptive fuels over the area. The strongest sustained surface winds will likely develop over the southwestern portion of the Columbia Basin during the afternoon. ...Central and Southern Plains... Ahead of the southward-advancing cold front, breezy southerly surface winds near 15-20 mph (with higher gusts) will overlap 25 percent minimum RH, resulting in elevated fire-weather conditions. The best overlap of breezy surface winds and low RH is expected over south-central KS into northwest OK during the afternoon. ...Great Basin... Downstream of the closed mid/upper-level low, a belt of strong south-southwesterly flow aloft will overspread a deepening boundary layer over parts of NV into western UT. This will likely lead to strong/gusty surface winds amid critically low RH. However, fuels do not appear overly receptive to large-fire spread at this time. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No watches are valid as of Mon Sep 19 17:55:02 UTC 2022.

MD 1801 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF THE MID-ATLANTIC INTO SOUTHERN NEW ENGLAND
Mesoscale Discussion 1801 NWS Storm Prediction Center Norman OK 1252 PM CDT Mon Sep 19 2022 Areas affected...Portions of the Mid-Atlantic into southern New England Concerning...Severe potential...Watch unlikely Valid 191752Z - 192015Z Probability of Watch Issuance...20 percent SUMMARY...Isolated strong to damaging winds may occur as thunderstorms move eastward this afternoon. Watch issuance appears unlikely at this time. DISCUSSION...Loosely organized clusters will continue to spread eastward across parts of central/eastern NY and southern New England this afternoon. This activity is being aided by a shortwave trough moving over these regions. Recent VWPs from KBGM/KENX show gradually strengthening and veering winds with height through mid levels. This is supporting around 25-30 kt of deep-layer shear and modest thunderstorm organization. Even with mostly cloudy skies, some filtered diurnal heating has occurred with occasional cloud breaks. Weak destabilization, with MLCAPE generally 500-1000 J/kg, has occurred ahead of the ongoing convection. Poor mid-level lapse rates observed on the 12Z ALB sounding should temper instability from increasing much more through the rest of the afternoon. At this point, isolated strong to damaging winds should be the main threat given the mainly linear mode expected. There will be some potential for a greater concentration of near-severe (45-55 mph) winds across eastern NY and vicinity where the best heating has occurred so far, and where high-resolution guidance suggests convection will gradually increase in coverage and intensity. Still, the overall severe wind threat will probably remain limited by the weak instability, and watch issuance appears unlikely at this time. ..Gleason/Grams.. 09/19/2022 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BOX...BTV...ALY...BGM... LAT...LON 42807593 43227531 44007475 44087387 43867315 43417281 42667261 42097280 41747337 41657422 41767556 42047606 42807593 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1227 PM CDT Mon Sep 19 2022 Valid 201200Z - 211200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR WISCONSIN INTO CENTRAL LOWER MICHIGAN... ...SUMMARY... Isolated large hail and damaging gusts are possible for parts of the western Great Lakes on Tuesday. ...WI east into Lower MI... A large mid-level anticyclone will remain centered over the south-central U.S. while a closed mid-level low moves little to the west of north-central CA. A mid-level speed max and associated mid-level trough will move east-southeastward from the southern Prairie Provinces into the Upper Midwest by early Wednesday. A surface low will develop east across northern Ontario while an attendant cold front sweeps southeast across the Upper Midwest. A couple of showers/thunderstorms are possible over WI/Lake MI during the morning in association with 850-mb WAA. This activity will likely dissipate during the day before a renewed chance for isolated to widely scattered thunderstorms occurs during the afternoon/evening. Model guidance varies considerably on the location of the later-day storm development due in part to a capping inversion. It seems plausible at least a few storms will eventually develop near the front. Long hodographs coupled with a moist/strongly unstable boundary layer will conditionally support a supercell mode. Large hail and damaging gusts will be the primary threats before this activity likely weakens after sunset. ..Smith.. 09/19/2022 Read more

MD 1800 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR EASTERN NORTH DAKOTA AND FAR NORTHWESTERN MINNESOTA
Mesoscale Discussion 1800 NWS Storm Prediction Center Norman OK 1201 PM CDT Mon Sep 19 2022 Areas affected...eastern north Dakota and far northwestern Minnesota Concerning...Severe potential...Watch unlikely Valid 191701Z - 191830Z Probability of Watch Issuance...5 percent SUMMARY...Elevated storms capable of isolated hail may continue for another couple of hours. Gradual weakening is expected early this afternoon and a watch is unlikely. DISCUSSION...As of 1700 UTC, regional radar analysis showed a cluster of elevated thunderstorms ongoing across portions of eastern ND. Likely driven by subtle warm air advection ahead of a southern Canadian shortwave trough, lift should begin to decrease as storms shift farther east with time. Supported by weak buoyancy aloft (MUCAPE of 500-750 J/kg) a few elevated supercell structures may persist for a couple more hours given 45-50 kt of effective shear. Strong upper-level storm relative winds, sufficient buoyancy/lapse rates, and the supercell mode suggests isolated severe hail may accompany the stronger storms as they approach the I-29 corridor. However, buoyancy becomes increasingly limited with eastern extant as storms outrun the stronger warm advection and elevated destabilization. This is matched by the latest hi-res guidance which shows a gradual weakening of storms near the ND/MN border. Thus, with the limited buoyancy and severe coverage, a weather watch is not expected. ..Lyons/Grams.. 09/19/2022 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...FGF...BIS... LAT...LON 47889902 48179802 48309709 48259684 48179658 47989631 47669615 47579611 47329608 47189618 47089674 47109779 47299883 47439909 47549928 47889902 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Mon Sep 19 2022 Valid 191630Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS NORTHEAST STATES...UPPER MIDWEST...AND SACRAMENTO VALLEY... ...SUMMARY... Isolated severe thunderstorms are possible over parts of the Northeast, the Upper Midwest, and the Sacramento Valley. ...Northeast... 12Z observed soundings sampled weak, moist-adiabatic lapse rates and modest low to mid-level westerlies, downstream of a broad swath of weak convection across western NY/PA. This suggests that boundary-layer heating will be the primary mechanism required for intensification of this ongoing activity, which appears most pronounced from the Lower Hudson to DE Valleys. Still, MLCAPE will likely remain weak from 500-1000 J/kg. While there will be some increase in 850-500 mb winds, the bulk of stronger flow aloft will largely remain relegated west of the Appalachians this afternoon in the southwest flank of the shortwave trough shifting east across southeast ON and the Upper Saint Lawrence Valley. Lower-level flow should largely peak from 30-35 kt with the convection that spreads east, suggesting that strong but predominately sub-severe gusts should dominate as convective intensities peak in the late afternoon. These will still be capable of producing isolated to perhaps even scattered tree damage, but the threat for severe gusts appears too marginal to warrant an upgrade. Late morning CAM guidance suggests that the Upper Hudson Valley vicinity will have the greatest relative potential for multicell clustering, but observational data suggests boundary-layer heating will likely be stronger to the south. Colder mid-level temperatures attendant to the shortwave trough will overspread the region downstream of the Lower Great Lakes during the early evening, as a mid-level jetlet spreads into western NY. Despite the increasingly unfavorable time of day with respect to the diurnal heating cycle, this setup could support a second round of convective development that may produce a 2-3 hour period of marginally severe hail and locally damaging gusts until convection wanes tonight. ...Eastern ND vicinity... Low-level WAA-driven convection persists and will likely spread northeast towards the international border while further decaying this afternoon. In the wake of this activity, a pronounced EML and attendant MLCIN appears likely to mitigate surface-based development along a weakly convergent surface trough in central ND this afternoon. Another round of low-level WAA-driven elevated thunderstorms might occur in the early morning tomorrow, similarly centered on central to eastern ND. While guidance differs greatly on this scenario, favorable speed shear through the cloud-bearing layer will support a conditional threat for isolated severe hail. ...Western WI vicinity... A corridor of elevated convection driven by low-level WAA along the eastern periphery of the north-central states EML appears probable overnight. Ample elevated buoyancy and some cloud-bearing shear could support isolated severe hail in the early life-cycle of the convective development. Convection will likely evolve into a broad cluster and temper individual updraft intensity towards 12Z. ... Sacramento Valley... A few low-topped storms should develop during the late afternoon within the left-exit region of a broad mid-level southwesterly jet centered across central CA into NV. Favorable elongation of the mid to upper-level hodograph could support small to marginally severe hail in the strongest updrafts amid weak mid-level lapse rates and MLCAPE of 500 J/kg or less. ..Grams/Lyons.. 09/19/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1133 AM CDT Mon Sep 19 2022 Valid 191700Z - 201200Z Expanded the Elevated delineation northward to include northern Wyoming and far southern Montana where winds of 15 to 25 mph and relative humidity of 10-20 percent are expected. Elsewhere, the forecast is on track and no changes are necessary. See previous discussion below. ..Bentley/Thornton.. 09/19/2022 .PREV DISCUSSION... /ISSUED 0139 AM CDT Mon Sep 19 2022/ ...Synopsis... An upper-level anticyclone will persist across the central and southern U.S. while an upper low meanders along the West Coast today. Strong mid-level flow will pivot around the periphery of the upper-level anticyclone and overspread a dry boundary layer across the Great Basin into the central Rockies and northern High Plains. As such, dry or windy conditions should develop by mid to late afternoon across much of the Intermountain West into portions of the Plains states. However, Wyoming seems to be the best location where longer term dry and windy conditions will overlap with receptive fine fuels (i.e. grasses), warranting Elevated highlights. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No watches are valid as of Sun Sep 18 17:55:02 UTC 2022.

No Mesoscale Discussions are in effect as of Sun Sep 18 17:55:02 UTC 2022.

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1220 PM CDT Sun Sep 18 2022 Valid 191200Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHEAST...AND A SMALL PORTION OF THE NORTHERN PLAINS... ...SUMMARY... Thunderstorms capable of producing gusty winds/possible tree damage will be possible on Monday over parts of the Northeast. An isolated storm or two -- accompanied by potential for strong winds and hail -- will be possible near the Canadian border region of northeastern North Dakota and northwestern Minnesota. ...Synopsis... An amplified flow field aloft will persist across the U.S. on Monday, as a deep upper low lingers off the West Coast, and a corresponding, stout ridge prevails over the central portion of the country. Meanwhile, mean troughing will persist over the Northeast, as a short-wave feature progresses into the broader cyclonic flow field across this area. At the surface, a weak cold front is forecast to cross the Great Lakes/Ohio Valley through the day, and then move into the Northeast with time. Meanwhile, a second, weak front is forecast to advance slowly southward across the north-central and northwestern states through the period. ...The Northeast... Widespread/ongoing convection is forecast across the Ohio Valley and Lower Great Lakes region and into southern Ontario at the start of the period, ahead of a short-wave mid-level trough crossing the Upper Great Lakes early. The downstream effect of this convection -- and associated cloud cover -- will be a potential hindrance of heating/destabilization into the Northeast. Thus, with weak lapse rates and only modest CAPE anticipated across most of the region, risk for severe storms appears limited/localized. Still, where pockets of heating/destabilization can occur, moderate flow aloft is sufficient to support gusty winds at the surface -- particularly if a short convective line segment or two could evolve. As such, will maintain 5% wind risk across the area for any intensification of ongoing storms -- or perhaps new storm development nearer the cold front, in the wake of the initial convective activity. ...Canadian Border region of the northern Plains... As a mid-level short-wave trough shifts east-northeastward across southern portions of the Canadian Prairie Provinces, a cold front will gradually sag southeastward across the northern Plains. Despite rather steep lapse rates aloft, a capping inversion is expected to hinder convective initiation in most areas south of the border. Locally though, ascent focused near the front may allow an updraft or two to breach the cap and become sustained -- aided by ample shear for updraft organization. As such, will maintain 5%/MRGL risk for hail/wind for the late afternoon/early evening time frame, to cover this potential. ..Goss.. 09/18/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1159 AM CDT Sun Sep 18 2022 Valid 181700Z - 191200Z ...NO CRITICAL AREAS... No changes. See previous discussion below. ..Bentley.. 09/18/2022 .PREV DISCUSSION... /ISSUED 0104 AM CDT Sun Sep 18 2022/ ...Synopsis... An upper-level anticyclone will persist across the south-central U.S. as a mid-level cyclone continues to meander along the West Coast today. Widespread showers and thunderstorms should accompany the West Coast cyclone, mainly over northern and central California, which may help dampen fuels that are currently very dry. Farther east, from the Great Basin to the Intermountain West and parts of the central Plains, modestly dry and occasionally windy surface conditions are expected. Periodic Elevated conditions are possible, but fuels appear too marginally receptive to fire spread to support significant wildfire-growth concerns. ...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 1130 AM CDT Sun Sep 18 2022 Valid 181630Z - 191200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS SOUTHEAST IOWA...NORTHEAST MISSOURI...AND WEST-CENTRAL ILLINOIS... ...SUMMARY... A few intense supercells, capable of very large to giant hail, along with tornadoes, one or two of which may be strong, may evolve into an MCS producing scattered severe wind gusts. This appears most likely across portions of south-central to southeast Iowa, northeast Missouri, and west-central Illinois, beginning after 5 PM CDT and continuing through tonight. ...IA/MO/IL... A low-amplitude shortwave impulse over the western Dakotas will move east across the Upper MS Valley to the south of a deeper shortwave trough shifting from MB to far northwest ON. This evolution will yield an amplifying mid-level jetlet (with 500-mb winds in excess of 50 kts) across southern MN and IA into WI by this evening. A strengthening baroclinic zone across IA, aided by robust differential boundary-layer with low 90s into northwest MO and low 70s behind the cold front in northern IA, will support initial thunderstorm development in the 22-00Z time frame centered on south-central IA as MLCIN wanes. The initial environment will be characterized by weak 0-1 km SRH, but large 0-3 km SRH with further increase in wind speeds through the mid to upper portion of large buoyancy amid rather steep mid-level lapse rates. This setup appears favorable for potentially a few long-lived discrete supercells with the primary hazard being very large to giant hail given the expected hodograph structure. The degree of tornado threat is more uncertain. Low-level southwesterlies will strengthen this evening, but primarily across northern MO and displaced largely south of expected convective development. The greatest tornado threat may evolve with the southern-most supercell which would have uninterrupted inflow and greater 0-1 km SRH near the IA/MO/IL border during the early evening. As such, have shifted the inherited 10 sig tor area south, but this threat appears more conditional than previously forecast. Consensus of latest CAM guidance still suggests potential upscale growth into a small MCS as supercells congeal near/east of the MS River, with the relatively greatest severe wind threat across southeast IA and far northeast MO into west-central IL. How far downstream this threat lasts is more uncertain, as there's a reasonable signal for low-level warm theta-e advection to support potential regenerative supercells on the upshear (northwestward) side of broader-scale convective outflow within the feed of steeper mid-level lapse rates. This may yield a persistent threat for large hail into the early morning before convection weakens further into the overnight. ..Grams/Lyons.. 09/18/2022 Read more

No watches are valid as of Sat Sep 17 18:01:02 UTC 2022.

No Mesoscale Discussions are in effect as of Sat Sep 17 18:01:02 UTC 2022.