505
ACUS01 KWNS 281630
SWODY1
SPC AC 281628
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1128 AM CDT MON SEP 28 2026
VALID 281630Z - 291200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN PLAINS...
..SUMMARY
ISOLATED STRONG TO SEVERE THUNDERSTORMS MAY OCCUR THIS AFTERNOON AND
EVENING ACROSS PARTS OF WESTERN/NORTHERN SOUTH DAKOTA AND VICINITY.
..NORTHERN PLAINS
CLOUDS AND ELEVATED THUNDERSTORMS REMAIN PREVALENT LATE THIS MORNING
ACROSS PARTS OF THE DAKOTAS. A NARROW WINDOW FOR STRONG TO LOCALLY
SEVERE THUNDERSTORMS MAY EXIST THIS AFTERNOON/EVENING ACROSS PARTS
OF WESTERN/NORTHERN SD AND VICINITY AS CONVECTION DEVELOPS
ALONG/EAST OF A WEAK SURFACE TROUGH. WHILE LAPSE RATES ALOFT SHOULD
REMAIN MODEST, FILTERED DAYTIME HEATING WITH SURFACE TEMPERATURES
REACHING THE MID/UPPER 70S WILL PROBABLY BE SUFFICIENT FOR ROBUST
THUNDERSTORM DEVELOPMENT. A BELT OF MODESTLY ENHANCED SOUTHWESTERLY
MID-LEVEL FLOW WILL EXTEND ACROSS THE NORTHERN ROCKIES/PLAINS TODAY,
AND 30-40 KT OF DEEP-LAYER SHEAR SHOULD SUPPORT UPDRAFT
ORGANIZATION. CURRENT EXPECTATIONS ARE FOR THUNDERSTORMS TO
INITIALLY FORM NEAR THE BLACK HILLS BY 20-22Z, AND THEN SPREAD
EAST-NORTHEASTWARD ALONG/NEAR A SURFACE FRONT THROUGH THE EVENING.
THE STRONGER CELLS MAY BE CAPABLE OF PRODUCING ISOLATED HAIL AND
GUSTY WINDS, BEFORE CONVECTION TENDS TO BECOME ELEVATED WITH
EASTWARD EXTENT ACROSS NORTHERN SD/SOUTHERN ND BY LATE EVENING.
..LOWER COLORADO RIVER VALLEY
SHOWERS AND THUNDERSTORMS SHOULD DEVELOP THIS AFTERNOON AS AN
ANOMALOUSLY MOIST LOW-LEVEL AIRMASS SPREADS NORTHWARD AHEAD OF A
MID-LEVEL SHORTWAVE TROUGH FORECAST TO MOVE FROM CA/NV TO THE LOWER
CO RIVER VALLEY THROUGH THE PERIOD. CLOUDINESS AND WEAK MID-LEVEL
LAPSE RATES SHOULD LIMIT INSTABILITY THROUGH EARLY AFTERNOON, BEFORE
CLOUD COVER GRADUALLY DIMINISHES THROUGH EARLY EVENING. A STRONGER
THUNDERSTORM OR TWO MAY OCCUR PARTS OF INTERIOR SOUTHERN
CA/NORTHWEST AZ/SOUTHERN NV, BUT THE OVERALL RISK FOR SEVERE
HAIL/WIND APPEARS TOO LIMITED TO INCLUDE ANY PROBABILITIES FOR THIS
REGION AT THIS TIME.
..GLEASON/CHALMERS.. 09/28/2026
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