348
ACUS01 KWNS 262001
SWODY1
SPC AC 261959
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0259 PM CDT WED AUG 26 2026
VALID 262000Z - 271200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN GREAT LAKES/MIDWEST...CENTRAL HIGH PLAINS...AND
OZARKS/MID SOUTH INTO THE LOWER MISSISSIPPI VALLEY...
..SUMMARY
ISOLATED TO WIDELY SCATTERED SEVERE THUNDERSTORMS ARE FORECAST TODAY
ACROSS PARTS OF THE SOUTHERN GREAT LAKES INTO THE MIDWEST,
CENTRAL/SOUTHERN HIGH PLAINS, AND THE OZARKS INTO THE MID-SOUTH AND
LOWER MISSISSIPPI VALLEY. SEVERE/DAMAGING WINDS SHOULD BE THE MAIN
THREAT ACROSS THESE REGIONS, THOUGH LARGE HAIL IS ALSO POSSIBLE,
PARTICULARLY ACROSS THE CENTRAL HIGH PLAINS.
..20Z UPDATE
..CENTRAL GREAT PLAINS
VISIBLE SATELLITE IMAGERY DEPICTS AN AREA OF AGITATED CUMULUS
DEVELOPING IN CLOSE PROXIMITY TO A WEAK SURFACE BOUNDARY ACROSS
EASTERN COLORADO. RECENT HRRR/RRFS RUNS ARE SPLIT ON THE EVOLUTION
OF THIS CONVECTION, WITH THE HRRR SUGGESTING MINIMAL THUNDERSTORM
DEVELOPMENT AND THE RRFS DEPICTING THE DEVELOPMENT OF A
SOUTHEASTWARD-PROPAGATING CLUSTER. THIS SCENARIO REMAINS UNCERTAIN;
HOWEVER, THE 5% WIND PROBABILITIES HAVE BEEN EXPANDED SOUTHEASTWARD
TO ACCOUNT FOR THE POTENTIAL FOR A CLUSTER OF THUNDERSTORMS TO
EVOLVE FROM THIS REGION. SEE MCD 2139 FOR ADDITIONAL SHORT-TERM
INFORMATION.
..MID-SOUTH AND LOWER GREAT LAKES
SEVERE PROBABILITIES WERE TRIMMED SLIGHTLY ACROSS PORTIONS OF
NORTHEASTERN IL, NORTHWESTERN IN, AND SOUTHWESTERN MI IN THE WAKE OF
ONGOING CONVECTION AND THE PASSAGE OF A SURFACE COLD FRONT. SEVERE
PROBABILITIES WERE ALSO TRIMMED ACROSS PORTIONS OF THE MID SOUTH
WHERE INCREASED LOW-LEVEL STATIC STABILITY OWING TO OUTFLOW FROM
PRIOR CONVECTION CASTS UNCERTAINTY ON ADDITIONAL CONVECTIVE
DEVELOPMENT THIS AFTERNOON/EVENING.
ELSEWHERE, THE FORECAST REMAINS LARGELY ON TRACK WITH ONLY MINOR
CHANGES MADE TO THE EXISTING OUTLOOK. SEE THE TEXT BELOW FOR
ADDITIONAL INFORMATION.
..CHALMERS/THORNTON.. 08/26/2026
PREV DISCUSSION
/ISSUED 1127 AM CDT WED AUG 26 2026/
..MID-SOUTH/TN VALLEY
AN MCS CONTINUES TO PUSH GRADUALLY SOUTHWARD/SOUTHEASTWARD ACROSS
WESTERN AND MIDDLE TN. THE DOWNSTREAM AIRMASS IS HEATING AND
DESTABILIZING, BUT VERTICAL SHEAR REMAINS WEAK AND THE OVERALL
SYSTEM HAS NOT STRENGTHENED NOTABLY IN THE PAST HOUR.
DESTABILIZATION ACROSS THE REGION IS STRONGEST FROM THE MID-SOUTH
INTO THE LOWER MS VALLEY, WHERE DEWPOINTS ARE LARGELY IN THE MID
70S. LESS LOW-LEVEL MOISTURE IS NOTED FROM MIDDLE TN INTO NORTHERN
AL, BUT AIRMASS DESTABILIZATION IS STILL ANTICIPATED AMID MODEST
HEATING. THE GENERAL EXPECTATION IS FOR THE MCS TO CONTINUE, BUT
WITH NEW AND/OR STRONGER UPDRAFTS LIKELY TRENDING TOWARDS THE
WESTERN FLANK WHERE THE BUOYANCY IS GREATEST. EVEN THEN, THE LACK OF
STRONGER VERTICAL SHEAR SUGGESTS AN OUTFLOW-DOMINANT MODE WITH
MINIMAL ORGANIZATION. AS SUCH, SPORADIC DAMAGING GUSTS ARE POSSIBLE,
PARTICULARLY VIA UPDRAFT AUGMENTATION VIA STORM INTERACTIONS, BUT
THE CURRENT MAGNITUDE AND ORIENTATION OF THE WIND PROBABILITY SEEMS
SUFFICIENT.
..ARKLATEX ACROSS MUCH OF AR INTO THE MID-SOUTH/LOWER MS VALLEY
A SOMEWHAT SEPARATE AREA OF THUNDERSTORM DEVELOPMENT IS ANTICIPATED
THIS AFTERNOON WEST OF WHAT WAS DISCUSSED IN THE PREVIOUS PARAGRAPH,
ALTHOUGH SOME INTERACTION BETWEEN THESE TWO REGIMES MAY OCCUR OVER
THE MID-SOUTH VICINITY. RECENT SURFACE OBSERVATIONS DEPICT A SURFACE
LOW ALONG THE CENTRAL TX/OK BORDER (IN THE GYI/DUA VICINITY). THIS
LOW IS FORECAST TO PROGRESS GRADUALLY EASTWARD INTO A MOIST AND
DIURNALLY DESTABILIZED AIRMASS FROM THE ARKLATEX ACROSS MUCH OF AR
AND NORTHERN LA. A WEAK MCV, NOTED IN VISIBLE SATELLITE IMAGERY,
LAGS BEHIND THIS SURFACE LOW, AND COULD AUGMENT ASCENT AS IT TOO
MOVES EASTWARD. LOW-LEVEL CONVERGENCE ON A STALLED FRONTAL BOUNDARY
THAT EXTENDS ACROSS CENTRAL AR AS WELL AS ALONG A FRONT APPROACHING
NORTHERN AR THIS EVENING COULD ACT AS ADDITIONAL MECHANISMS FOR
THUNDERSTORM INITIATION. ALL OF THESE FACTORS WILL LIKELY RESULT IN
SCATTERED TO NUMEROUS THUNDERSTORMS ACROSS THE REGION.
MODEST DEEP-LAYER SHEAR SHOULD SUPPORT SOME UPDRAFT ORGANIZATION,
WITH MULTICELL CLUSTERS LIKELY THE DOMINANT MODE. HIGH TOTAL
PRECIPITABLE WATER VALUES AND LARGE BUOYANCY WILL SUPPORT ROBUST
DOWNBURSTS CAPABLE OF DAMAGING WIND GUSTS. STRONG BUOYANCY COULD
SUPPORT OCCASIONAL HAIL AS WELL. CLUSTERING MAY EVENTUALLY RESULT IN
SEVERAL BOWING SEGMENTS THIS EVENING. AS SUCH, THERE IS POTENTIAL
FOR AT LEAST ISOLATED DAMAGING WINDS TO PERSIST ACROSS PARTS OF
SOUTHERN LA/MS.
..SOUTHERN GREAT LAKES INTO THE MIDWEST
SATELLITE IMAGERY CONTINUES TO SHOW A WELL-DEFINED SHORTWAVE TROUGH
MOVING ACROSS THE UPPER GREAT LAKES. PRIMARY SURFACE LOW ASSOCIATED
WITH THIS SYSTEM IS OCCLUDED OVER NORTHWEST ONTARIO, BUT A SECONDARY
TRIPLE POINT LOW IS MOVING ACROSS UPPER MI. THIS SYSTEM IS FORECAST
TO MOVE EASTWARD TODAY, WITH THE ATTENDANT COLD FRONT PROGRESSING
SOUTHEASTWARD. MODEST LOW-LEVEL MOISTURE ADVECTION AND HEATING AHEAD
OF THIS FRONT WILL RESULT IN A CORRIDOR OF MODERATE TO STRONG
BUOYANCY FROM CENTRAL IL NORTHEASTWARD INTO SOUTHERN LOWER MI.
THUNDERSTORM DEVELOPMENT IS ANTICIPATED WITHIN THIS CORRIDOR THIS
AFTERNOON.
LOW/MID-LEVEL WINDS WILL TEND TO REMAIN FAIRLY MODEST AND VEERED,
BUT 25-35 KT OF DEEP-LAYER SHEAR SHOULD FOSTER SOME UPDRAFT
ORGANIZATION. A MIX OF MULTICELL CLUSTERS AND MARGINAL SUPERCELLS
SHOULD POSE A THREAT FOR BOTH HAIL AND DAMAGING WINDS, WITH THE WIND
THREAT POTENTIALLY BECOMING THE PRIMARY RISK WITH EASTWARD EXTENT
INTO THE MIDWEST AS THUNDERSTORMS GROW UPSCALE. VEERED LOW-LEVEL
FLOW SHOULD KEEP THE TORNADO POTENTIAL LOW. THE OVERALL SEVERE
THREAT WILL LIKELY DIMINISH QUICKLY THIS EVENING AS CONVECTION
OUTPACES THE LOW-LEVEL MOISTURE/INSTABILITY, AND NOCTURNAL COOLING
STABILIZES THE BOUNDARY LAYER.
..CENTRAL HIGH PLAINS
LOW LEVELS ACROSS THE CENTRAL HIGH PLAINS ARE CURRENTLY
CHARACTERIZED BY DEWPOINTS IN THE UPPER 50S AND LOW 60S. MODEST
LOW-LEVEL UPSLOPE FLOW WILL HELP MAINTAIN THIS LOW-LEVEL MOISTURE
THROUGH THE AFTERNOON. THIS MOISTURE COMBINED WITH DIURNAL HEATING
AND STEEP MID-LEVEL LAPSE RATES WILL RESULT IN AIRMASS
DESTABILIZATION AND MODERATE BUOYANCY BY THE LATE AFTERNOON.
ADDITIONALLY, SOUTHERN PERIPHERY OF THE ENHANCED NORTHWESTERLY FLOW
EXTENDING FROM THE NORTHERN PLAINS INTO THE MID MS VALLEY WILL BE
OVER THE CENTRAL HIGH PLAINS, RESULTING IN 25 TO 35 KT OF EFFECTIVE
BULK SHEAR. LATE AFTERNOON THUNDERSTORM DEVELOPMENT IS ANTICIPATED
WITHIN THIS ENVIRONMENT, WITH SOME ISOLATED SUPERCELLS POSSIBLE.
HAIL WILL BE THE PRIMARY RISK INITIALLY, PARTICULARLY ACROSS THE CO
FOOTHILLS. A TREND TOWARDS CLUSTERING AND MORE DAMAGING WIND
POTENTIAL IS EXPECTED AS THIS ACTIVITY SPREADS EAST-SOUTHEASTWARD
THROUGH THE EVENING.
..SOUTHERN HIGH PLAINS
MID-LEVEL FLOW AND RELATED DEEP-LAYER SHEAR SHOULD BE SOMEWHAT
WEAKER THAN AREAS FARTHER NORTH. STILL, CONVECTION THAT DEVELOPS
ACROSS CENTRAL INTO EASTERN NM MAY BECOME LOOSELY ORGANIZED WHILE
POSING AN ISOLATED THREAT FOR SEVERE GUSTS GIVEN THE PRESENCE OF A
VERY WELL-MIXED BOUNDARY LAYER. THIS THREAT MAY CONTINUE INTO PARTS
OF THE OK/TX PANHANDLES AND WEST TX THROUGH THE EVENING BEFORE
EVENTUALLY WEAKENING.
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