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FXUS63 KUNR 231728
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1128 AM MDT WED SEP 23 2026
KEY MESSAGES
- SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WILL MOVE ACROSS THE
REGION AT TIMES TONIGHT AND WEDNESDAY, ALTHOUGH MANY AREAS WILL
ALSO SEE LONG DRY PERIODS.
- DRYING OUT FOR THE REST OF THE WEEK, BUT SOUTHWEST FLOW ALOFT
WILL BRING SOME POSSIBILITY OF SHOWERS OR THUNDERSTORMS.
- BREEZY/WINDY SPOTS THROUGH WEDNESDAY.
UPDATE
ISSUED AT 1046 PM MDT TUE SEP 22 2026
FOCUS OF THIS EVENING'S FORECAST UPDATE WAS TO REWORK POPS AND QPF
(AND RESULTANT WX GRIDS) TONIGHT AND WEDNESDAY TO CAPTURE RADAR
TRENDS AND THE NEW SUITE OF HIGH-RES GUIDANCE. NOTHING
PARTICULARLY HEAVY OR WIDESPREAD IS EXPECTED, BUT ENOUGH CHANCE OF
ISOLATED TO SCATTERED SHOWERS AT TIMES TO WARRANT EXPANDED
COVERAGE AND REDISTRIBUTION OF LIGHT POPS. AS THE LOW REFERENCED
BELOW LIFTS NORTHEAST TOMORROW AFTERNOON AND A SURFACE FRONT
INTRUDES INTO THE NORTHERN CWA, SOME CAMS ARE SUPPORTING ROBUST
CONVECTION FOR A FEW HOURS ACROSS THE NORTHWESTERN SOUTH DAKOTA
PLAINS, WITH MODEL SOUNDINGS ADVERTISING MODERATE INSTABILITY AND
STRONG DEEP-LAYER SHEAR OVER 40KTS. THE HREF WIND GUST MAX DOES
PRODUCE LOCALIZED SEVERE WIND GUSTS WITH THESE CELLS, SO THAT WILL
BE SOMETHING TO WATCH TOMORROW.
DISCUSSION
(THIS EVENING THROUGH TUESDAY)
ISSUED AT 156 PM MDT TUE SEP 22 2026
19Z SURFACE ANALYSIS HAD HIGH OVER THE GREAT LAKES WITH A WARM
FRONT FROM CENTRAL MT INTO EASTERN CO. MODESTLY TIGHT PRESSURE
GRADIENT INBETWEEN PROMOTING SOUTHEASTERLY WIND GUSTS INTO THE 30S
ON THE WESTERN SD PLAINS THIS AFTERNOON. FEW SHRA/TS CRAWLING
ACROSS SOUTH-CENTRAL SD UNDER WEAK THETA-E ADVECTION REGIME. WATER
VAPOUR LOOP HAD UPPER RIDGE FROM TX INTO EASTERN WY WITH UPPER
LOW NEAR KSLC. EFFECT OF THIS SYSTEM MAIN FORECAST CONCERN.
TONIGHT/WEDNESDAY, UPPER LOW LIFTS NORTHEAST AS IT OPENS UP OVER
WY/MT. STRONGER LOW LEVEL JET DEVELOPS AHEAD OF IT TONIGHT
CREATING WEAK BUOYANCY (<1KJ/KG MUCAPE) IN MODEST LOW LEVEL
THETA-E ADVECTION REGIME. RESULT WILL BE SOME SHRA/TS LIFTING
NORTHEAST ACROSS THE AREA INTO WEDNESDAY. UPSLOPE COMPONENT TO LOW
LEVEL FLOW MAY SUPPORT SOME FOG IN/NEAR BLACK HILLS/ADJACENT
PLAINS OVERNIGHT. TEMPERATURES WILL BE NEAR GUIDANCE AS LOW CLOUDS
SLOWLY SCOUR OUT EAST OF THE BLACK HILLS WEDNESDAY AFTERNOON PER
MOVEMENT OF WARM FRONT.
THURSDAY INTO EARLY NEXT WEEK, SOUTHWEST FLOW ALOFT WILL PERSIST
WITH PERIODIC FRONTAL PASSAGES/SHORTWAVES/DOWNSLOPE FLOW. WARMING
TREND EXPECTED WITH ENSEMBLES IN RELATIVELY GOOD AGREEMENT FOR
TEMPERATURES (5-10F SPREADS). EACH WIGGLE WILL BRING POPS, BUT
THERE WILL BE PLENTY OF DRY HOURS AHEAD OF MOST FOLKS.
AVIATION
(FOR THE 18Z TAFS THROUGH 18Z THURSDAY)
ISSUED AT 1112 AM MDT WED SEP 23 2026
LOW CLOUDS HAVE MOVED OUT OF THE AREA LEADING TO VFR CONDITIONS.
THESE WILL PERSIST THROUGH THE FORECAST PERIOD.
UNR WATCHES/WARNINGS/ADVISORIES
SD...NONE.
WY...NONE.
UPDATE...KSMITH
DISCUSSION...HELGESON
AVIATION...SCHWEIGERT
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