Severe Storm Outlook Narrative (AC)
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Issued by NWS
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769 ACUS01 KWNS 242001 SWODY1 SPC AC 241959 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0259 PM CDT Fri May 24 2024 Valid 242000Z - 251200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF NORTHERN TEXAS INTO EASTERN OKLAHOMA...AND OVER A SMALL PART OF NORTHEAST MISSOURI... ...SUMMARY... Severe thunderstorms remain posssible this afternoon and evening from north Texas/eastern Oklahoma and the Mid-South into the Midwest including parts of Missouri and Illinois. ...MO...IA...IL...IN... Several areas of thunderstorms are ongoing, which have produced stabilizing outflows. However, a plume of very strong instability remains over MO, and southwest winds ahead of the cold front from eastern IA into western MO will maintain a feed of unstable air, with some recovery expected, even into the overnight. As such, have left probabilities largely untouched from previous outlook. See mesoscale discussion 932 for more details. ...Eastern OK into northeast TX and AR... A very unstable air mass has developed beneath modest midlevel westerlies. Storms will continue to increase in coverage along the weak cold front, with large hail likely. See mesoscale discussion 933 for more details. ..Jewell.. 05/24/2024 .PREV DISCUSSION... /ISSUED 1131 AM CDT Fri May 24 2024/ ...Midwest including parts of IL/MO/southern WI... A previously intense/well-organized bow echo has weakened into northeast Illinois/southeast Wisconsin through late morning, with the gust/outflow boundary extending from the Chicagoland southwestward into west-central Illinois near/south of the IA/MO/IL border vicinity. The surface cold pool has considerably impacted the post-MCS environment, with likely ramifications for the magnitude and likelihood of the severe risk into far northern Illinois/Wisconsin, although some measure of air mass recovery will occur and severe storms will be possible even without a pristine boundary layer. The region is on the north-northeast periphery of a substantial elevated mixed layer (EML) sampled by 12z observed soundings including Topeka KS and Lincoln IL. The outflow boundary where it intercepts the approaching cold front, in general vicinity of the IA/MO/IL border, will likely be a favored zone for renewed severe storm development later this afternoon. Some initial supercell development can be expected before subsequent upscale growth by evening, with all severe hazards plausible in this corridor. Farther north, across far eastern Iowa/northern Illinois into southern Wisconsin, later-day severe potential is a bit more uncertain owing to this morning`s MCS. However, at least isolated severe storms capable of severe hail/damaging winds may occur near the eastward-advancing cold front pending the degree of air mass recovery/destabilization. ...Southern Plains including North TX/Eastern OK to Mid-South... Scattered thunderstorms, including locally intense supercells, are expected to develop into mid/late afternoon mainly near the southwest/northeast-oriented front, with more isolated near-dryline development possible into central Texas. After initial supercells, updraft growth is likely given the strong surface heating, abundant moisture (70s F dewpoints common), steep deep-layer lapse rates and intense buoyancy (4000-5000 J/kg MLCAPE). Low-level flow and hodograph size will be modest. However, ambient mid/upper winds will be strong enough to support supercells (left- and right-moving), with effective-shear values near 50 kt. Large to very large hail should be common in the first few hours after initiation, and locally severe gusts are expected as well. In the wake of predawn MCS, airmass recovery is expected into southeastern and east-central Oklahoma in the zone of warm/moist advection ahead of the front. A relatively dense and enhanced concentration of hail potential from eastern Oklahoma into north-central Texas is expected, with hailstones greater than 2 inches in diameter likely, and some hail perhaps exceeding 3 inches. Otherwise, deep, precip-loaded downdrafts will provide most of the wind potential early, with some upscale clustering and cold-pool aggregation possible to maintain damaging-wind potential into late evening, before activity generally weakens. ...Southeast States... Isolated severe thunderstorms are possible mainly this afternoon through early evening from the southern Appalachians vicinity/north Georgia to the coastal Carolinas. Steepening low-level lapse rates and ample buoyancy will support strong updrafts/downdrafts, with a modestly enhanced belt of mid-level westerlies contributing to multicell sustenance. $$