074
ACUS01 KWNS 270505
SWODY1
SPC AC 270503
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1203 AM CDT FRI JUN 27 2025
VALID 271200Z - 281200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THE AFTERNOON
INTO EARLY TONIGHT ACROSS THE NORTHERN PLAINS...AND THIS
AFTERNOON/EVENING ACROSS SOUTHEAST LOWER MICHIGAN...
..SUMMARY
AT LEAST WIDELY SCATTERED THUNDERSTORMS ARE EXPECTED LATE THIS
AFTERNOON/EVENING ACROSS THE DAKOTAS AND NEBRASKA, WHERE VERY LARGE
HAIL AND SEVERE OUTFLOW WINDS WILL BE POSSIBLE. THERE WILL ALSO BE
A WINDOW OF OPPORTUNITY FOR TORNADOES THIS EVENING ACROSS THE
CENTRAL DAKOTAS. OCCASIONAL WIND DAMAGE WILL BE POSSIBLE THIS
AFTERNOON/EVENING ACROSS SOUTHEAST LOWER MICHIGAN.
..NORTHERN PLAINS LATE THIS AFTERNOON INTO EARLY TONIGHT
A LOW-AMPLITUDE MIDLEVEL TROUGH WITH EMBEDDED SPEED MAXIMA WILL MOVE
EASTWARD FROM THE NORTHERN ROCKIES TO THE NORTHERN HIGH PLAINS
THROUGH TONIGHT. AT THE SURFACE, LEE CYCLOGENESIS IS EXPECTED THIS
AFTERNOON IN THE VICINITY OF NORTHEAST WY, WHILE LOW-LEVEL MOISTURE
SPREADS NORTHWARD ACROSS THE DAKOTAS THROUGH THIS EVENING. THE
MOISTENING WILL OCCUR BENEATH AN ELEVATED MIXED LAYER WITH MIDLEVEL
LAPSE RATES OF 8.5-9.5 C/KM, AND DAYTIME HEATING WILL RESULT IN
MLCAPE EXCEEDING 4000 J/KG. THE ELEVATED MIXED LAYER WILL ALSO ACT
AS A CAP AND SURFACE TEMPERATURES WILL NEED TO REACH THE MID 90S IN
SD AND THE MID-UPPER 80S IN ND TO LARGELY ELIMINATE CONVECTIVE
INHIBITION. AS SUCH, STORM TIMING/COVERAGE IS A BIT UNCERTAIN WITH
MODEST FORCING FOR ASCENT.
WHERE STORMS FORM, THE STEEP LAPSE RATES/EXTREME BUOYANCY AND
EFFECTIVE BULK SHEAR IN EXCESS OF 40 KT WILL CONDITIONALLY FAVOR
SUPERCELLS WITH VERY LARGE HAIL (POTENTIALLY GREATER THAN 3 INCHES
IN DIAMETER). THERE COULD ALSO BE A WINDOW OF OPPORTUNITY FOR
TORNADOES AS LOW-LEVEL SHEAR INCREASES IN THE EVENING, WHERE STORMS
REMAIN DISCRETE PRIOR TO CONVECTIVE INHIBITION INCREASING TONIGHT.
OTHERWISE, ANY STORM CLUSTERS WILL HAVE THE POTENTIAL TO PRODUCE
SEVERE OUTFLOW WINDS OF 60-80 MPH, ESPECIALLY IN THE DEEPER MIXED
ENVIRONMENT FARTHER SOUTH IN SD.
..SOUTHEAST LOWER MI THIS AFTERNOON/EVENING
A MIDLEVEL SHORTWAVE TROUGH AND ASSOCIATED WEAK WAVE CYCLONE NOW
OVER THE UPPER MS VALLEY WILL CONTINUE EASTWARD OVER THE UPPER GREAT
LAKES THROUGH THIS EVENING, WHILE A TRAILING COLD FRONT CROSSES
LOWER MI. DAYTIME HEATING AND BOUNDARY-LAYER DEWPOINTS IN THE LOW
70S IN THE WARM SECTOR WILL CONTRIBUTE TO MLCAPE ABOVE 2000 J/KG
DURING THE AFTERNOON ACROSS LOWER MI AS CONVECTIVE INHIBITION
WEAKENS. LOW-LEVEL ASCENT ALONG THE FRONT WILL SUPPORT A BROKEN
BAND OF STORMS BY MID AFTERNOON, AND THE STORMS WILL SPREAD EASTWARD
BEFORE WEAKENING BY LATE EVENING. THOUGH MIDLEVEL LAPSE RATES AND
DEEP-LAYER VERTICAL SHEAR WILL NOT BE STRONG, ~35 KT MIDLEVEL FLOW
AND STEEP LOW-LEVEL LAPSE RATES SUGGEST THE POTENTIAL FOR OCCASIONAL
WIND DAMAGE WITH MULTICELL CLUSTERS AND/OR SHORT LINE SEGMENTS.
..APPALACHIANS INTO THE SOUTHEAST THIS AFTERNOON/EVENING
ANOTHER AFTERNOON/EVENING OF WIDELY SCATTERED THUNDERSTORMS AND
ISOLATED DOWNBURST POTENTIAL IS EXPECTED ACROSS A BROAD AREA FROM
THE APPALACHIANS INTO THE SOUTHEAST/FL. LOCAL SEA BREEZE
CIRCULATIONS, TERRAIN CIRCULATIONS AND RESIDUAL OUTFLOW/DIFFERENTIAL
HEATING ZONES WILL HELP FOCUS THUNDERSTORM DEVELOPMENT.
THERMODYNAMIC PROFILES WILL BE SUFFICIENT FOR ISOLATED WIND DAMAGE
WITH DOWNBURSTS.
..THOMPSON/LYONS.. 06/27/2025
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