Severe Storm Outlook Narrative (AC)
Issued by NWS
Issued by NWS
547 ACUS03 KWNS 040730 SWODY3 SPC AC 040729 Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0229 AM CDT Sat May 04 2024 Valid 061200Z - 071200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE SOUTHERN/CENTRAL PLAINS... ...SUMMARY... Numerous severe thunderstorms will likely develop and move eastward Monday afternoon and evening across parts of the southern/central Plains. Strong tornadoes, very large to giant hail, and damaging winds all appear possible. ...Synopsis... A negatively tilted upper trough with embedded 50-70 kt mid-level speed maximum will eject northeastward across the northern/central Plains on Monday. At the surface, the primary low should consolidate over the northern High Plains of eastern MT/western ND and vicinity, with a secondary surface low possibly developing over the central High Plains by Monday evening. A rather moist low-level airmass, with surface dewpoints generally in the mid 60s to low 70s, will spread northward across the southern/central Plains ahead of an eastward-mixing dryline. A warm front should eventually extend eastward across parts of NE/IA, and this boundary will probably be the northern limit of appreciable severe-thunderstorm potential. ...Southern/Central Plains... A severe-weather outbreak still appears possible across parts of the southern/central Plains on Monday, focused from south-central/ southeast NE into central/eastern KS and much of OK. Robust diurnal heating of the moist low-level airmass, coupled with steep mid-level lapse rates overspreading much of the warm sector, will likely foster moderate to strong instability (MLCAPE generally ranging from 2000-3500 J/kg) by Monday afternoon. Enhanced mid-level winds and a favorably veering/strengthening wind profile with height through mid/upper levels will support around 40-55 kt of effective bulk shear, stronger with northward extent in KS/NE. Current expectations are for scattered supercells to erupt along the length of the dryline in south-central NE and western/central KS by mid to late Monday afternoon, coincident with stronger large-scale ascent overspreading this region. Given the rather favorable thermodynamic and kinematic parameter space, very large to giant hail (2-4 inch diameter) will likely be a threat with these initial supercells. The threat for tornadoes should quickly increase through the late afternoon and early evening in tandem with a strengthening southerly low-level jet. Ample 0-1 km and effective SRH shown in various NAM/GFS forecast soundings suggest a threat for strong tornadoes with any supercell that can remain discrete. With time Monday evening and into early Tuesday morning, upscale growth into multiple linear structures is probable, with an increased threat for severe/damaging winds, along with embedded tornadoes given the forecast strength of the low-level shear. The southward extent of the substantial severe risk into OK and north TX remains somewhat uncertain, as better forcing for ascent will tend to remain across the central Plains. Still, modest mid-level height falls should encourage isolated to perhaps widely scatted supercells developing along the length of the dryline into the southern Plains. Very large hail and strong tornadoes will be the main threats with any supercell that can develop and persist across this region Monday afternoon/evening. Model trends will also be monitored for a more favorable corridor of strong tornadoes and giant hail, which may necessitate greater severe probabilities for Monday in a later outlook. ..Gleason.. 05/04/2024 $$