Severe Storm Outlook Narrative (AC)
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Issued by NWS
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984 ACUS01 KWNS 041631 SWODY1 SPC AC 041629 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1129 AM CDT Tue Jun 04 2024 Valid 041630Z - 051200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF CENTRAL AND EASTERN OKLAHOMA... ...SUMMARY... Scattered severe thunderstorms are probable across central and eastern Oklahoma this evening. A tornado and large to very large hail will be possible this evening, before severe outflow winds of 60-85 mph potentially accompany the more intense downdrafts this evening into tonight. ...Southern Plains to lower MS Valley through tonight... Radar/satellite imagery late this morning shows a south-southeastward moving MCS along the TX/LA border. Heating of the airmass ahead of the MCS will continue to lead to strong destabilization. A rejuvenation of storm intensity along the western flank of the MCS is possible where a reservoir of very rich low-level moisture and steep 700-500 mb lapse rates will aid in strong/severe storm potential. Damaging gusts and perhaps large hail will be the primary hazards with the stronger storms. Outflow from the morning storms will reinforce a composite outflow boundary across north TX northward into OK. It appears that the outflow air mass will modify through the day across OK. Surface dewpoints are forecast to increase into the mid 70s across central-southern OK where isolated thunderstorm development is forecast by late this afternoon/early evening along the edge of richer moisture. Forecast soundings show MLCAPE could exceed 5000 J/kg with only small convective inhibition. However, forcing for ascent will be rather nebulous and storm initiation/initial coverage is uncertain. Nonetheless, a short window of opportunity may exist for a tornado risk if a quasi-discrete mode can occur early in the convective life cycle. Very large buoyancy and nearly dry adiabatic lapse rates across OK will support large/tall storms capable of producing isolated very large hail initially, and an increase in the threat for damaging winds (60-85 mph) as storms grow upscale into another MCS tonight. Have opted to upgrade to a 30-percent significant wind area for greater confidence in a severe MCS across central/eastern OK. Farther north, thunderstorms for forecast to develop across KS this afternoon into early tonight, as a weak surface cold front and associated midlevel trough will move southeastward and impinge on the very moist/unstable warm sector. Hail/wind will be the primary risks with those stronger storms. ...Mid MO to upper MS Valleys this afternoon/evening... A midlevel shortwave trough and associated cold front will move eastward from NE/Dakotas to eastern KS/IA and WI by the end of the period. The richest low-level moisture will remain farther south, but surface heating in pre-frontal cloud breaks and boundary-layer dewpoints in the 60s will contribute to MLCAPE of 1000-2000 J/kg. Some low-level hodographs enlargement in northern MN may aid in some brief updraft rotation potential before an extensive band of storms becomes outflow dominant. Vertical shear will be relatively weak in the warm sector which will primarily support multicell clusters and line segments capable of producing occasional wind damage and marginally severe hail. ...MO/IL today... A midlevel low over west central MO this morning will move northeastward toward central/northern IL by this evening. Lingering clouds will tend to slow surface heating, though cloud breaks could allow modest destabilization and support a few strong thunderstorm clusters capable of producing isolated strong/damaging outflow gusts and marginally severe hail. ..Smith/Barnes.. 06/04/2024 $$