488
FXUS63 KUNR 130346
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
946 PM MDT FRI JUN 12 2026
KEY MESSAGES
- UNSETTLED AND COOL WEATHER THIS WEEKEND
- FROST POSSIBLE NORTHEASTERN WY PLAINS SUNDAY MORNING
- WARMING TREND NEXT WEEK
UPDATE
ISSUED AT 932 PM MDT FRI JUN 12 2026
UPPER IMPULSE AND ASSOCIATED JET STREAK STARTING TO FORCE SOME
PRECIP OVER FAR NW SD THIS EVENING. SYSTEM IS ON TRACK TO SUPPORT
RAIN ACROSS NE WY AND FAR WESTERN SD SAT, WITH BELOW NORMAL TEMPS
AS HIGHS TOP OUT IN THE 50S AND LOW 60S THERE. WARMER AND DRY FOR
THE REMAINDER OF THE FA SAT, WITH MAINLY 70S EXPECTED TOWARD
CENTRAL SD. BREEZY ACROSS MUCH OF THE SD PLAINS SAT, ESP NW SD.
COOL AND DRY CONDS EXPECTED SAT NIGHT WIGHT WINDS BECOMING LIGHT.
THIS WILL ALLOW TEMPS TO FALL INTO 40S MOST AREAS WITH 30S
EXPECTED IN NE WY. THE HIGHER ELEVATIONS OF THE BH WILL SEE EVEN
COOLER TEMPS WITH SOME UPPER 20S EXPECTED IN VALLEYS AND LOW
SPOTS. EXPECT FROST WHERE TEMPS FALL INTO THE 30S OR BELOW ACROSS
THE BH AND NORTHEAST WY. WARMING UP NEXT WEEK GRADUALLY WITH
SPOTTY CHANCES FOR RAIN TOWARD THE END OF THE WEEK.
DISCUSSION
(THIS EVENING THROUGH FRIDAY)
ISSUED AT 142 PM MDT FRI JUN 12 2026
19Z SURFACE ANALYSIS HAD WEAK TROUGH OVER THE CWA WITH A FRONTAL
BOUNDARY ACROSS NORTHERN MT/ND. WATER VAPOUR LOOP HAD MEAN TROUGH
OVER CENTRAL CANADA WITH NEXT SHORTWAVE TROUGH OF INTEREST OVER
SOUTHERN AB/NORTHWEST MT, CURRENTLY CONJURING SOME SHRA/TS. FEW CU
OVER THE CWA. MAIN CONCERN THIS FORECAST IS UPSTREAM SHORTWAVE
TROUGH.
TONIGHT/SATURDAY, SHORTWAVE TROUGH SLIPS EAST/SOUTHEAST ALONG
FRONTAL BOUNDARY. NICE BAND OF 800-600MB FRONTOGENESIS SETS UP
BEHIND FRONT TAPPING INTO LIMITED MOISTURE. SHOULD SEE A BAND OF
SHOWERS OVER SOUTHEAST MT/NORTHEASTERN WY LATER TONIGHT (PROBABLY
POKING INTO FAR WESTERN SD), PEAKING SATURDAY MORNING. SYNOPTIC
SUPPORT QUICKLY ENDS MIDDAY SATURDAY, ALLOWING QPF BAND TO
DISSIPATE. GUSTY NORTHWEST WINDS EXPECTED ON THE SD PLAINS
SATURDAY GIVEN BOUNDARY LAYER FLOW/MIXING. TEMPERATURES
TONIGHT/SATURDAY NEAR GUIDANCE.
CLEARING SKIES AND SLACKENING WIND SATURDAY NIGHT MAY LEAD TO
FROST OVER NORTHEASTERN WY PLAINS SUNDAY MORNING. WILL LET LATER
SHIFTS TAKE A LOOK AT POTENTIAL HEADLINES.
LOOKING AHEAD TO NEXT WEEK, MOST GUIDANCE SUGGESTS SLOW EXPANSION
OF UPPER/THERMAL RIDGE INTO THE NORTHERN PLAINS, BUT WE'LL STILL
BE UNDER NORTHWEST FLOW ALOFT WITH POTENTIAL FOR MOISTURE-STARVED
WEAK DISTURBANCES/FRONTS AND EVEN PERHAPS A SMATTERING OF POPS.
OVERALL GENERAL TREND WILL BE WARMER/DRIER, HOWEVER.
AVIATION
(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 941 PM MDT FRI JUN 12 2026
RAIN SHOWERS WILL PUSH INTO NORTHEAST WYOMING LATE TONIGHT,
DEVELOPING AFTER 13/09-11Z ALONG WITH MVFR/IFR CEILINGS. THESE
SHOWERS AND LOWERED FLIGHT CONDITIONS WILL BE FOUND ACROSS
NORTHEAST WYOMING (INCLUDING KGCC) AND INTO THE BLACK HILLS,
INCLUDING KSPF AND KCUT; TRANSIENT LIFR CONDITIONS POSSIBLE FROM
13/11-20Z ACROSS THESE AREAS. CONFIDENCE IS LOW THAT SHOWERS AND
LOWERED FLIGHT CONDITIONS WILL IMPACT KRAP; HAVE ADDED A PROB30
GROUP BEGINNING AT 13/17Z FOR KRAP. EXPECT VFR CONDITIONS TO
PERSIST OUTSIDE OF THESE AREAS ACROSS THE WESTERN SD PLAINS INTO
CENTRAL SD. CONDITIONS OVERALL WILL IMPROVE TOWARD THE END OF THE
TAF PERIOD.
UNR WATCHES/WARNINGS/ADVISORIES
SD...NONE.
WY...NONE.
UPDATE...JC
DISCUSSION...HELGESON
AVIATION...SCHULTZ
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