279
FXUS63 KUNR 222331
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
531 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 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 531 PM MDT TUE SEP 22 2026
MVFR CIGS (OCCASIONAL IFR) WILL PERSIST ACROSS MUCH OF THE
WESTERN SOUTH DAKOTA PLAINS THROUGH TONIGHT AND TUESDAY MORNING,
ESPECIALLY AS ISOLATED TO SCATTERED SHOWERS CROSS THE AREA. THESE
SHOWERS WILL FIRST CROSS NE WY/SW SD LATE TONIGHT BEFORE LIFTING
NEWRD. VFR CONDITIONS ARE EXPECTED TUESDAY AFTERNOON.
UNR WATCHES/WARNINGS/ADVISORIES
SD...NONE.
WY...NONE.
DISCUSSION...HELGESON
AVIATION...13
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