810
FXUS63 KUNR 221959
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
159 PM MDT TUE SEP 22 2026
KEY MESSAGES
- SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WILL MOVE ACROSS THE
CWA TONIGHT/WEDNESDAY
- DRYING OUT FOR THE REST OF THE WEEK, BUT SOUTHWEST FLOW ALOFT
WILL BRING THE POSSIBILITY OF SHOWERS OR THUNDERSTORMS
- BREEZY/WINDY SPOTS THROUGH WEDNESDAY
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 WEDNESDAY)
ISSUED AT 1119 AM MDT TUE SEP 22 2026
LOW CLOUDS WILL PERSIST FOR AREAS EAST/SOUTH OF THE BLACK HILLS
FOR MOST OF TUESDAY. MVFR CONDITIONS ARE EXPECTED IN THIS AREA
UNTIL THEY MOVE OUT LATER WEDNESDAY MORNING, LIKELY AFTER 12Z.
SOME LIGHT SHOWERS ARE POSSIBLE IN FAR NORTHEAST WY OVERNIGHT, BUT
CONFIDENCE REMAINS LOW ON TIMING/PLACEMENT.
UNR WATCHES/WARNINGS/ADVISORIES
SD...NONE.
WY...NONE.
DISCUSSION...HELGESON
AVIATION...SCHWEIGERT
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