682
ACUS03 KWNS 111928
SWODY3
SPC AC 111927
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0227 PM CDT MON AUG 11 2025
VALID 131200Z - 141200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE WEDNESDAY
INTO WEDNESDAY NIGHT ACROSS MUCH OF CENTRAL AND EASTERN SOUTH DAKOTA
AND ADJACENT PORTIONS OF THE GREAT PLAINS...
..SUMMARY
THE EVOLUTION OF AN ORGANIZED CLUSTER OF THUNDERSTORMS ACCOMPANIED
BY STRONG TO SEVERE WIND GUSTS APPEARS POSSIBLE ACROSS PARTS OF
CENTRAL THROUGH EASTERN SOUTH DAKOTA BY WEDNESDAY EVENING.
..DISCUSSION
MODELS INDICATE THAT THE STRONGER WESTERLIES WILL REMAIN CONFINED TO
THE NORTHERN MID-LATITUDES, MOSTLY TO THE NORTH OF THE CANADIAN/U.S.
BORDER THROUGH THIS PERIOD. ONE SIGNIFICANT EMBEDDED SHORT WAVE
TROUGH SHIFTING ACROSS ONTARIO THROUGH QUEBEC MAY BECOME SHEARED
WHILE BECOMING ABSORBED WITHIN AN INCREASINGLY CONFLUENT REGIME,
PRECEDED IN LOWER LATITUDES BY NORTHEASTWARD ACCELERATING MID-LEVEL
TROUGHING OFFSHORE OF THE CANADIAN MARITIMES. UPSTREAM, ANOTHER
SIGNIFICANT SHORT WAVE PERTURBATION, INITIALLY DIGGING NEAR THE
CANADIAN ROCKIES, IS FORECAST TO TURN EASTWARD ACROSS THE CANADIAN
PRAIRIES AND PROVIDE SUPPORT FOR SIGNIFICANT LOWER/MID-TROPOSPHERIC
CYCLOGENESIS ACROSS SOUTHERN ALBERTA THROUGH CENTRAL/NORTHERN
SASKATCHEWAN BY LATE WEDNESDAY NIGHT. IN LOWER LATITUDES AHEAD OF
THIS FEATURE, THERE APPEARS A CONSENSUS AMONG LATEST MODEL OUTPUT
THAT A MUCH MORE SUBTLE PERTURBATION WILL DIG EAST-SOUTHEAST OF THE
NORTHERN U.S. ROCKIES LATE WEDNESDAY THROUGH WEDNESDAY NIGHT, WITHIN
WEAKER FLOW ON THE NORTHERN PERIPHERY OF MODEST MID-LEVEL RIDGING.
..NORTHERN GREAT PLAINS
THE NAM, WITH SUPPORT FROM OTHER MODEL OUTPUT, INCLUDING THE LATEST
ECMWF, DEPICTS THE EVOLUTION OF A NOTABLE CONVECTIVE PERTURBATION
WEDNESDAY EVENING INTO WEDNESDAY NIGHT ACROSS THE CENTRAL/EASTERN
SOUTH DAKOTA VICINITY. THIS APPEARS FOCUSED WHERE
LOWER/MID-TROPOSPHERIC WARM ADVECTION MAY BECOME ENHANCED, NEAR THE
LEADING EDGE OF A PLUME OF WARM, ELEVATED MIXED LAYER AIR ADVECTING
EASTWARD ACROSS THE MIDDLE MISSOURI VALLEY, SUPPORTED BY A
STRENGTHENING NOCTURNAL LOW-LEVEL JET. LOW-LEVEL MOISTURE RETURN TO
THE VICINITY OF DEEPENING LEE SURFACE TROUGHING MAY BE SEASONABLY
MODEST, BUT IT STILL APPEARS THAT SIZABLE CAPE MAY DEVELOP ACROSS
PARTS OF CENTRAL SOUTH DAKOTA BY LATE AFTERNOON, NEAR THE NOSE OF A
CORRIDOR OF SEASONABLY STRONG BOUNDARY-LAYER HEATING AND DEEP
MIXING, SOUTH THROUGH EAST OF THE BLACK HILLS.
IT REMAINS UNCLEAR WHETHER STRONGER CONVECTIVE DEVELOPMENT WILL
INITIATE FROM LATE AFTERNOON HIGH-BASED THUNDERSTORM DEVELOPMENT
NEAR/NORTH OF THE BLACK HILLS, OR PERHAPS AN INITIAL SUPERCELL
FORMING NEAR A FOCUSED AREA OF LOW-LEVEL CONVERGENCE ACROSS CENTRAL
SOUTH DAKOTA. HOWEVER, LARGE-SCALE FORCING FOR ASCENT PROBABLY WILL
LEAD TO UPSCALE GROWING CONVECTION BY WEDNESDAY EVENING, IN AN
ENVIRONMENT CONDUCIVE TO A FEW STRONG DOWNBURSTS, AND A
CONSOLIDATING, STRENGTHENING SURFACE COLD POOL WITH POTENTIAL TO
PRODUCE A SWATH OF STRONG TO SEVERE GUSTS. IT IS POSSIBLE THAT
SEVERE PROBABILITIES MAY STILL NEED TO BE INCREASED FURTHER IN LATER
OUTLOOKS FOR THIS PERIOD.
..KERR.. 08/11/2025
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page