039
ACUS01 KWNS 210538
SWODY1
SPC AC 210537
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1237 AM CDT TUE APR 21 2026
VALID 211200Z - 221200Z
..NO SEVERE THUNDERSTORM AREAS FORECAST
..SUMMARY
THUNDERSTORMS ARE EXPECTED TODAY OVER MUCH OF TEXAS, FROM ILLINOIS
INTO OHIO, AND OVER PORTIONS OF CENTRAL CALIFORNIA. SEVERE WEATHER
IS NOT CURRENTLY FORECAST.
..SYNOPSIS
AN UPPER RIDGE WILL MOVE INTO THE PLAINS AS AN UPPER TROUGH MOVES
INLAND OVER THE WEST, WITH A STRONG CYCLONIC SPEED MAX MOVING ACROSS
CA AND INTO THE GREAT BASIN. MEANWHILE, NORTHWEST FLOW ALOFT WILL
EXTEND FROM THE GREAT LAKES INTO THE MID ATLANTIC. FARTHER SOUTH, A
WEAKENING DISTURBANCE WILL MOVE OUT OF TX AND TOWARD THE LOWER MS
VALLEY.
AT THE SURFACE, HIGH PRESSURE WILL REMAIN OVER MUCH OF THE EASTERN
STATES AND ACROSS THE GULF COAST. SOUTHERLY WINDS ACROSS THE PLAINS
AND AROUND THIS HIGH MAY SUPPORT MID TO UPPER 50S F DEWPOINTS AS FAR
NORTH AS IA AND IL BY 00Z, WHILE HIGHER DEWPOINTS REMAIN RELEGATED
TO SOUTHERN TX. HERE, SCATTERED SHOWERS AND THUNDERSTORMS WILL
LIKELY BE ONGOING EARLY ON TUESDAY WHERE WEAK ELEVATED INSTABILITY
WILL REMAIN.
..IL/IN/OH
A SURFACE TROUGH IS FORECAST TO DEVELOP FROM LOWER MI INTO SOUTHERN
WI AND NORTHERN IL BY LATE AFTERNOON, BENEATH THE NORTHWEST FLOW
REGIME AND WITH COOL MIDLEVEL TEMPERATURES. SOUTHWEST SURFACE WINDS
AND DAYTIME HEATING SHOULD LEAD TO 40S AND 50S F DEWPOINTS, WITH A
RELATIVELY DRY BOUNDARY LAYER OVERALL. MODELS SUGGEST AT LEAST
ISOLATED LATE DAY AND EVENING THUNDERSTORMS WILL DEVELOP AHEAD OF
THIS TROUGH, THOUGH INSTABILITY LEVELS ARE UNCERTAIN. DESPITE
MARGINAL DEWPOINTS/MOISTURE, THE COOL TEMPERATURES ALOFT MAY SUPPORT
A FEW CELLS CAPABLE OF SMALL HAIL FROM IL INTO IN BY LATE AFTERNOON.
WIND GUST POTENTIAL IS MORE UNCERTAIN AND DEPENDENT ON STORM
COVERAGE/OUTFLOW PRODUCTION, WITH THE DRY BOUNDARY LAYER
CONDITIONALLY HELPING STRONG GUST POTENTIAL INTO THE EVENING AND
PERHAPS OVERNIGHT.
..CENTRAL CA
COLD TEMPERATURES ALOFT NORTH OF THE MIDLEVEL JET WILL SUPPORT WEAK
INSTABILITY OVER PARTS OF THE CENTRAL VALLEYS. GIVEN EARLY
PRECIPITATION AND CLOUDS, AS WELL AS MARGINAL LOW-LEVEL SHEAR,
SEVERE STORMS APPEAR UNLIKELY. HOWEVER, A FEW STRONG STORMS MAY
OCCUR LATE IN THE AFTERNOON IF SUFFICIENT HEATING OCCURS BEHIND THE
EARLY DAY RAIN. SMALL HAIL APPEARS MOST PROBABLE WITH THE STRONGEST
CELLS.
..JEWELL.. 04/21/2026
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