449
ACUS01 KWNS 211625
SWODY1
SPC AC 211624
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1124 AM CDT FRI MAR 21 2025
VALID 211630Z - 221200Z
..NO SEVERE THUNDERSTORM AREAS FORECAST
..SUMMARY
SEVERE THUNDERSTORMS ARE NOT FORECAST TODAY.
..IOWA VICINITY
AN UPPER SHORTWAVE TROUGH WILL MOVE ACROSS THE MIDWEST TODAY AND
TONIGHT, WITH INCREASING DEEP-LAYER WEST/NORTHWEST FLOW ASSOCIATED
WITH THIS FEATURE OVERSPREADING THE REGION. BOUNDARY LAYER MOISTURE
WILL REMAIN SCANT AHEAD OF AN EAST/SOUTHEAST MOVING COLD FRONT
SWEEPING ACROSS THE LOWER MO/MID-MS VALLEY THIS AFTERNOON AND
EVENING. NEVERTHELESS, VERY COLD TEMPERATURES ALOFT (NEAR -25 C AT
500 MB, AS SAMPLED BY 12Z REGIONAL BALLOON OBSERVATIONS), WILL
SUPPORT STEEP MIDLEVEL LAPSE RATES. ADDITIONALLY, SURFACE HEATING
INTO THE MID 50S TO LOW 60S WILL SUPPORT STEEPENING LOW-LEVEL LAPSE
RATES. THESE STEEP LAPSE RATES AMID COLD TEMPERATURES ALOFT SHOULD
BE SUFFICIENT FOR SBCAPE VALUES UP TO 300 J/KG. AS SUCH, ISOLATED
HIGH-BASED, LOW-TOPPED THUNDERSTORMS ARE EXPECTED THIS AFTERNOON AND
EVENING FROM THE MID-MO VALLEY INTO THE MID-MS VALLEY. GIVEN THE DRY
BOUNDARY LAYER AND NEAR 30-40 KT FLOW BETWEEN 850-700 MB, CONVECTION
MAY LOCALLY ENHANCE ALREADY GUSTY SURFACE WINDS, AND A FEW STRONGER
GUSTS NEAR 40-45 KT MAY OCCUR, ESPECIALLY ACROSS SOUTHEAST IOWA INTO
NORTHWEST IL. A COUPLE INSTANCES OF SMALL HAIL/GRAUPEL ALSO COULD
ACCOMPANY THIS ACTIVITY.
..PACIFIC NORTHWEST/NORTHERN ROCKIES
AN UPPER SHORTWAVE TROUGH WILL MOVE ACROSS THE REGION TONIGHT.
COOLING ALOFT WILL SUPPORT STEEPENING LAPSE RATES AND SUFFICIENT
DESTABILIZATION TO SUPPORT ISOLATED LIGHTNING FLASHES.
..LEITMAN/HALBERT.. 03/21/2025
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