Severe Storms

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.

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1212 PM CDT Sat Sep 17 2022 Valid 181200Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS CENTERED OVER CENTRAL ILLINOIS AND INTO INDIANA... ...SUMMARY... Risk for severe storms is evident across an area centered over central Illinois and into Indiana Sunday afternoon and evening. ...Synopsis... Gradual amplification of the upper flow field over the U.S. is expected to continue Sunday, as a low just off the California coast deepens as it retrogrades slowly southwestward. In response to the deepening low, riding centered over Texas is progged to expand northward across the southern Plains and into the central U.S. and the Rockies. A weak cyclonic disturbance is forecast to crest the developing ridge, crossing the northern Plains and then Upper Mississippi Valley through the day, and then pivoting east-southeastward across the Upper Great Lakes and Mid Ohio Valley overnight. At the surface, a cold front is forecast to shift across the Upper Midwest and into the Great Lakes and Mid Mississippi Valley region through the day, and should focus an area of vigorous convection over the corn belt region during the afternoon and overnight. ...Mid Mississippi and Lower Ohio Valley region... As the upper disturbance crests the ridge, and the weak cold front advances east-southeastward toward the Midwest, diurnal heating of a moist boundary layer will support moderate destabilization, with mixed-layer CAPE values peaking in the 2000 to 3000 J/kg range through late afternoon. The degree of instability in tandem with ascent focused at low levels in the vicinity of the front will support vigorous storm initiation -- likely in the southeastern Iowa/northeastern Missouri/west-central Illinois area initially. With initial storm mode expected to be isolated, and aided by strengthening/weakly veering flow with height, a few rotating storms are expected to evolve -- accompanied by all-hazards severe potential. With time, storms should tend to congeal -- likely into multiple clusters, with redevelopment of storms that move across some of the same areas possible given increasingly west-northwesterly flow aloft atop a persistent feed of high low-level theta-e air from the southwest. As this upscale growth occurs, risk for damaging winds and hail will likely be maintained into the evening, as convection spreads eastward/southeastward with time. Storms will likely spread into the Mid Ohio Valley region late, though severe potential should wane overnight as the airmass stabilizes diurnally. ..Goss.. 09/17/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1135 AM CDT Sat Sep 17 2022 Valid 171700Z - 181200Z ...NO CRITICAL AREAS... Dry and breezy conditions are ongoing across portions of the Southwest, but fuels remain moist across this region. Therefore, fire weather conditions remain minimal. Elsewhere, light winds preclude widespread fire weather concerns. See previous discussion below. ..Bentley.. 09/17/2022 .PREV DISCUSSION... /ISSUED 1259 AM CDT Sat Sep 17 2022/ ...Synopsis... A predominantly weak, zonal flow pattern across the CONUS will begin to break down throughout the day as a mid-level trough enters portions of the Pacific Northwest and northern California coast. Consequently, broad 20-25 kt southwesterly flow will overspread much of the West. At the surface, a cold front will move through portions of the Pacific Northwest. In advance of this front, diurnally driven southwesterly winds will develop, perhaps reaching sustained values of 15-20 mph, while RH values fall into the upper teens. These conditions may support a localized threat for elevated fire-weather conditions, mainly across northwest Nevada and far southeast Oregon. Otherwise, fire-weather concerns are expected remain low elsewhere across the CONUS. ...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 1127 AM CDT Sat Sep 17 2022 Valid 171630Z - 181200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS NORTHERN MN AND THE MID-MO VALLEY... ...SUMMARY... A couple tornadoes, scattered severe hail, and isolated damaging winds are possible across a portion of northern Minnesota during the late afternoon to early evening. Scattered large hail, damaging winds, and a brief tornado are also possible this evening across a portion of the Mid-Missouri Valley. ...Central to northern MN... A low-amplitude shortwave trough approaching the Upper Red River Valley will move across northern MN into northwest ON by this evening. Partial cloud breaks are evident ahead of this wave mixed with patches of persistent but thinning low-level stratus. The 12Z NAM appears overdone with MLCAPE magnitude given its depiction of mean mixing ratios from 14-15 g/kg later today when upstream 12Z observed soundings sampled only 12-13 g/kg at most. With the EML plume and attendant steep mid-level lapse rates also displaced south of this region, MLCAPE will probably only peak towards 1500 J/kg. Surface-based thunderstorm development will likely be focused in a confined corridor near the evolving frontal wave, currently over northeast SD, as it tracks east-northeast into northern MN. 12Z guidance has generally trended toward a weaker depiction of low-level mass response relative to the 00Z ECMWF, suggesting low-level hodograph curvature may remain small except along the surface warm front. Favorable elongation of the mid to upper hodograph given speed shear with height amid southwest flow should support a few discrete supercells. Severe hail will probably be the primary hazard in coverage, but a couple tornadoes are possible if activity can remain rooted where SRH is enhanced along the west/east-oriented warm front. These threats will likely diminish into late evening as activity spreads towards northeast MN. ...IA to central KS... A weakening MCS persists across southern IA and northwest MO with large-scale outflow analyzed from the I-70 corridor in northeast KS arcing to the northwest in central NE. Air mass recovery will occur across the Mid-MO Valley into this evening, but will clearly be impacted by this morning's activity, which renders uncertainty in just how intense redevelopment this evening will truly be. A hot air mass will be prevalent from the southern High Plains into central KS. Isolated high-based thunderstorms will probably develop along the dryline to triple-point intersection with a threat for isolated severe gusts and hail. More prevalent convective redevelopment will occur atop the residual outflow/differential heating zone this evening as a southwesterly low-level jet intensifies. Forecast soundings differ, but given the presence of the upstream EML and limited time for intense boundary-layer heating it appears most probable that convection will be rooted from elevated parcels, especially with time after dusk. This renders low confidence in a greater tornado threat despite low-level hodographs becoming highly enlarged. With weak changes in magnitude in winds with height above 700 mb, a cluster convective mode should dominate. This should subdue the large hail threat and the weak low-level lapse rates deeper into IA should limit the overall severe wind threat with northeast extent as well. Still with upscale growth into a slow-moving MCS and embedded organized updrafts probable this evening, will maintain a cat 2 severe risk delineation. ..Grams/Lyons.. 09/17/2022 Read more

No Mesoscale Discussions are in effect as of Fri Sep 16 17:49:02 UTC 2022.

No watches are valid as of Fri Sep 16 17:49:02 UTC 2022.

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1234 PM CDT Fri Sep 16 2022 Valid 171200Z - 181200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE MINNESOTA/IOWA AREA... ...SUMMARY... Isolated severe thunderstorms -- and local/all-hazards severe potential -- are expected Saturday from parts of the Upper Mississippi Valley area/Upper Midwest into/across portions of the Mid Missouri Valley. ...Synopsis... An initially low-amplitude upper flow pattern over the U.S. will gradually amplify, especially over the West. This amplification will result from a broad low from British Columbia to just off the Pacific Northwest Coast early in the day, that is expected to strengthen/consolidate as it shifts southward to just off the northern California coast late. As this occurs, ridging will begin to expand across the south-central U.S., while a belt of fast southwesterly flow in between the two features persists from the Intermountain West to the Upper Great Lakes. At the surface, the primary feature of interest will be a weak low -- forecast to evolve over the eastern South Dakota/southwestern Minnesota border area during the afternoon. A weak cool front should extend south-southwestward across eastern Nebraska and into Kansas, while the warm front extends east-northeastward across northern Minnesota. The main severe potential Saturday should reside in the vicinity of the warm sector of this system. ...Minnesota to southwestern Wisconsin/Iowa, and southwestward across northeastern Kansas... Though hindered in some areas by ongoing/remnant clouds/convection early in the period, daytime heating and low-level moist advection within the southerly flow regime will result in moderate afternoon airmass destabilization from the Upper Midwest into Kansas. As a short-wave trough crosses the Dakotas early and eventually approaches Minnesota, ascent -- focused near a weak low progged to evolve near the South Dakota/Minnesota border -- will likely result in isolated storm development by late afternoon. Farther south, focus for convective initiation appears more nebulous, without a clear low-level focusing mechanism. Still, low-level warm advection across this region should result in isolated to scattered convective development -- initially during the afternoon, with a second round of storms possible as a southerly low-level jet intensifies overnight. With 35 to 40 kt west-southwesterly mid-level flow spreading across the area with time, atop low-level southerlies, a few of the stronger storms will likely acquire rotation -- posing risk for hail and/or locally damaging wind gusts. A tornado or two may also occur -- with a favored area possibly over central/northern Minnesota near the anticipated low/warm frontal position. Storms will likely continue -- especially across the Iowa vicinity -- overnight, aided by persistent low-level warm advection, though any lingering severe potential should wane gradually through late evening. ..Goss.. 09/16/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1144 AM CDT Fri Sep 16 2022 Valid 161700Z - 171200Z ...NO CRITICAL AREAS... Some dry and breezy conditions are expected across portions of New Mexico, but fuels are very moist across the region. Therefore, fire weather concerns remain low. ..Bentley.. 09/16/2022 .PREV DISCUSSION... /ISSUED 0158 AM CDT Fri Sep 16 2022/ ...Synopsis... An upper-level shortwave trough currently over Nevada is forecast to move east-northeastward toward the central/northern Plains today. Meanwhile, another upper-level shortwave trough will move onto the Pacific Northwest coast as an upper low deepens offshore. At the surface, a lee trough will deepen over the High Plains throughout the day. Overall, the overlap of strong winds and low RH with dry fuels appears minimal across the CONUS, limiting the fire-weather concerns today. ...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 1053 AM CDT Fri Sep 16 2022 Valid 161630Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS WESTERN TO CENTRAL NEBRASKA... ...SUMMARY... Isolated to perhaps scattered severe thunderstorms are anticipated across a portion of the central Great Plains, centered on 3 to 10 PM CDT. ...Central Great Plains... A low-amplitude shortwave trough over the central Rockies will move east-northeast into the Dakotas by tomorrow morning. Large-scale ascent associated with this wave will impinge on a destabilizing downstream air mass to aid in scattered thunderstorms over the higher terrain spreading across the High Plains later this afternoon. This initial activity will be high-based, forming over weak but sufficient moisture and deep/well-mixed sub-cloud layers. Wind profiles west of the lee trough will be nearly unidirectional, limiting effective shear, despite gradually increasing mid/upper-level speeds. Scattered strong to isolated severe gusts and small to marginally severe hail will be the main hazards this afternoon amid moderate mid-level lapse rates. Thunderstorms forming on or crossing the lee trough may eventually gain greater severe potential in the early evening, as activity impinges on a more favorably moist boundary layer, currently evident in GOES PW imagery across the eastern half of NE. While the expectation is for the character of convection to be outflow-dominant/cold-pool-driven by this point, sufficient veering and strengthening of the wind profile with height will yield an elongated hodograph that would support potential for a few embedded supercells. The more probable evolution is for this to maintain persistence of a mostly isolated and marginal severe wind/hail threat after dusk into the late evening, before convective intensities subside overnight. ...Southern High Plains... Isolated thunderstorms should develop along a portion of the dryline centered on the Panhandles where surface temperatures breach 90 F. Modest mid-level lapse rates and weak buoyancy will be limiting factors to storm intensity. But 20-25 kt effective shear and steep low-level lapse rates could support locally strong gusts in the more robust storms during the late afternoon to early evening. ..Grams/Moore.. 09/16/2022 Read more

No watches are valid as of Thu Sep 15 17:43:02 UTC 2022.

No Mesoscale Discussions are in effect as of Thu Sep 15 17:43:02 UTC 2022.

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1213 PM CDT Thu Sep 15 2022 Valid 161200Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS CENTERED OVER PORTIONS OF WESTERN AND CENTRAL NEBRASKA... ...SUMMARY... Severe thunderstorms are possible across portions of the central High Plains and central Plains on Friday. ...Synopsis... Broad/low-amplitude cyclonic flow will persist across the western and north-central U.S. Friday, while cyclonic flow also persists across the Northeast. In between, weak ridging will prevail from the Great Lakes to the Gulf of Mexico. Weak short-wave disturbances/cyclonic vorticity maxima will progress east-northeastward across the Rockies and central U.S. with time, embedded within the weakly cyclonic west-southwesterlies. At the surface, high pressure will prevail over most of the eastern half of the country. Lee troughing is expected across the High Plains vicinity, with weak cyclogenesis expected across the eastern Wyoming vicinity as one of the aforementioned vorticity maxima shifts across this region during the afternoon and evening hours. ...Eastern Wyoming/northeastern Colorado east-southeastward to eastern Nebraska... As a weak lee low/trough strengthens a bit with time, the combination of increasing ascent, and afternoon heating/destabilization, should support storm development over the central High Plains. Initial convection should evolve over portions of eastern Wyoming and northeastern Colorado, in an isolated/cellular manner. Given low-level southeasterlies beneath moderate mid-level west-southwesterlies, shear will likely prove sufficient for multicell/local supercell organization, and attendant risk for hail and/or damaging wind gusts with the stronger updrafts. As storms shift eastward with time toward lower elevations through late afternoon/early evening, greater instability anticipated with eastward extent may support upscale/linear growth. Models continue to suggest evolution of an at least loosely organized convective band, that would shift across parts of southern South Dakota and Nebraska with time. While surface wind-gust potential will likely become more hindered with time as the boundary layer cools/stabilizes through the evening, it appears at this time that potential warrants upgrade to a small SLGT risk/15% wind probability, centered from the Nebraska Panhandle into central portions of the state for the late afternoon/early-evening time period. ..Goss.. 09/15/2022 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1113 AM CDT Thu Sep 15 2022 Valid 151630Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE CENTRAL AND SOUTHERN PLAINS.... ...SUMMARY... Isolated severe-thunderstorm gusts are possible this afternoon/early evening across portions of the central Plains and southern High Plains. ...Central and Southern Plains... A broad but weak upper trough will persist across the Rockies and western states today, with a shortwave trough apparent on WV approaching eastern CO/western KS. This will result in relatively cool temperatures aloft and moderately steep mid-level lapse rates over much of the central and southern Plains today, along with a corridor of around 1000 J/kg of afternoon MLCAPE. A consensus of 12z CAM solutions show multiple clusters of thunderstorms from west TX northward into parts of KS/NE/SD this afternoon. Forecast soundings show rather weak mid-level winds, which should limit the degree of convective organization. However, steep low-level lapse rates and merging outflows will lead to localized gusty winds in the strongest clusters. ..Hart/Lyons.. 09/15/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1039 AM CDT Thu Sep 15 2022 Valid 151700Z - 161200Z ...NO CRITICAL AREAS... The previous forecast (see below) remains on track. ..Squitieri.. 09/15/2022 .PREV DISCUSSION... /ISSUED 1222 AM CDT Thu Sep 15 2022/ ...Synopsis... Large-scale troughing and enhanced west-southwesterly midlevel flow will persist across the western CONUS, while a few embedded shortwave impulses overspread the north-central Rockies. At the surface, lee troughing accompanied by a tight pressure gradient will persist over the Plains. This pattern will once again favor breezy/gusty southerly surface winds across most of the Plains, though sufficient boundary-layer moisture should limit any substantial RH reductions. Given the marginal RH and ongoing precipitation over modestly receptive fuels, Elevated highlights have been withheld despite the breezy/gusty surface winds. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No watches are valid as of Wed Sep 14 17:59:02 UTC 2022.

No Mesoscale Discussions are in effect as of Wed Sep 14 17:59:02 UTC 2022.