278
ACUS01 KWNS 212000
SWODY1
SPC AC 211958
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0258 PM CDT TUE OCT 21 2025
VALID 212000Z - 221200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
THE SOUTHERN GREAT LAKES...
..SUMMARY
ISOLATED STRONG TO LOCALLY SEVERE GUSTS ARE POSSIBLE THIS AFTERNOON
OVER PARTS OF THE SOUTHERN GREAT LAKES.
..20Z UPDATE
MINIMAL CHANGES WERE MADE WITH THIS UPDATE. THE MRGL RISK AREA WAS
TRIMMED BEHIND AN EASTWARD-MOVING BAND OF LOW-TOPPED CONVECTION IN
SOUTHEAST LOWER MI, WHERE TEMPERATURES HAVE DROPPED INTO THE LOWER
50S. AS THESE STORMS CONTINUE EASTWARD ACROSS THE REMAINDER OF FAR
SOUTHEAST LOWER MI AND NORTHERN OH THIS AFTERNOON, STRONG TO LOCALLY
SEVERE GUSTS (45-60 MPH) WILL REMAIN POSSIBLE -- AIDED BY STEEPENED
PRE-CONVECTIVE BOUNDARY-LAYER LAPSE RATES AND 35-40-KT FLOW BELOW 2
KM AGL (PER VWP DATA).
FARTHER SOUTH, THE TSTM AREA WAS TRIMMED BEHIND THE
SOUTHEASTWARD-MOVING COLD FRONT IN THE SOUTHEAST, AND IN THE
SOUTHERN APPALACHIANS WHERE CONVECTION HAS GENERALLY OUTPACED THE
REMAINING BUOYANCY.
..WEINMAN.. 10/21/2025
PREV DISCUSSION
/ISSUED 1125 AM CDT TUE OCT 21 2025/
..SYNOPSIS
MORNING WATER-VAPOR LOOP AND UPPER-AIR DATA INDICATE A MIDLEVEL LOW
TRACKING EAST-SOUTHEASTWARD OVER THE UPPER MIDWEST -- ACCOMPANIED BY
COLD 500-MB TEMPERATURES (AROUND -28C). THIS FEATURE WILL CONTINUE
EASTWARD ACROSS THE GREAT LAKES THROUGH THE PERIOD, WHILE A COLD
FRONT MOVES FROM THE UPPER OH VALLEY TO THE ATLANTIC COAST. WITHIN
THE BASE OF THE MIDLEVEL LOW, AN EMBEDDED VORTICITIY MAXIMUM WILL
MOVE ACROSS THE LOWER GREAT LAKES THROUGH THE AFTERNOON, WHILE A
RELATED SURFACE FRONT/WIND SHIFT OVERSPREADS IN, OH, AND LOWER MI.
..SOUTHERN GREAT LAKES
IN THE WAKE OF A WEAKENING BAND OF SHOWERS ALONG THE DEPARTING FRONT
OVER THE UPPER OH VALLEY, MOSTLY CLEAR SKIES WILL PROMOTE
BOUNDARY-LAYER HEATING/STEEPENING LOW-LEVEL LAPSE RATES (SHALLOW
INVERTED-V PROFILES) BENEATH THE MIDLEVEL COLD POCKET -- YIELDING
MARGINAL DESTABILIZATION ACROSS PARTS OF NORTHERN OH AND SOUTHEAST
LOWER MI. AS WIDELY SCATTERED CONVECTION ALONG THE SECONDARY SURFACE
FRONT/WIND SHIFT SPREADS/DEVELOPS INTO THIS ENVIRONMENT, A MODEST
UPTICK IN UPDRAFT INTENSITY IS POSSIBLE THIS AFTERNOON. GIVEN STRONG
DEEP-LAYER FLOW FLANKING THE MIDLEVEL LOW, ISOLATED STRONG-LOCALLY
SEVERE CONVECTIVELY ENHANCED WIND GUSTS (45-60 MPH) WILL BE POSSIBLE
DURING THE LATE AFTERNOON INTO EARLY EVENING TIME FRAME. SMALL HAIL
WILL ALSO BE POSSIBLE WITH ANY SHALLOW CELLULAR CONVECTION.
..CENTRAL GULF COAST VICINITY
A WARM, MOIST, AND UNCAPPED AIR MASS AHEAD OF THE TAIL-END OF THE
COLD FRONT WILL SUPPORT ISOLATED THUNDERSTORMS ACROSS PARTS OF EAST
TX INTO SOUTHERN LA THIS AFTERNOON. WHILE MODERATE SURFACE-BASED
BUOYANCY AND AROUND 25 KT OF EFFECTIVE SHEAR COULD PROMOTE A COUPLE
STRONG STORMS ALONG THE FRONT, WARM TEMPERATURES ALOFT AND MINIMAL
LARGE-SCALE FORCING FOR ASCENT SHOULD GENERALLY LIMIT UPWARD
ACCELERATIONS IN UPDRAFTS.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page