408
FXUS63 KUNR 011125
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
525 AM MDT SUN JUN 1 2025
KEY MESSAGES
- WARM TODAY WITH RETREATING SMOKE
- LEAD SHORTWAVE/PRE-FRONTAL TROUGH BRING A CHANCE OF
THUNDERSTORMS TONIGHT
- UPPER TROUGH PUSHES COLD FRONT THROUGH CWA MONDAY BRINGING
THUNDERSTORMS, SOME OF WHICH WILL BE ACTIVE OVER SOUTH-CENTRAL
SD, AND THEN GUSTY WINDS BEHIND IT, ALONG WITH THE POTENTIAL FOR
MORE SMOKE
- UNSETTLED WEATHER CONTINUES THROUGH NEXT WEEK WITH DAILY
CHANCES FOR SHOWERS AND THUNDERSTORMS
DISCUSSION
(TODAY THROUGH SATURDAY)
ISSUED AT 225 AM MDT SUN JUN 1 2025
08Z SURFACE ANALYSIS HAD WEAK HIGH OVER THE SOUTHERN PLAINS WITH
A COLD FRONT FROM EASTERN AB TO ID AND PRE-FRONTAL TROUGH INTO
CENTRAL WY. EARLY SATURDAY EVENING SATELLITE/CURRENT SURFACE
OBSERVATIONS/HRRR SMOKE GUIDANCE INDICATE SMOKE OVER THE FAR
EASTERN REACHES OF THE CWA. WATER VAPOUR LOOP HAD UPPER RIDGE OVER
THE NORTHERN PLAINS IN RESPONSE TO UPPER TROUGH SLIDING THROUGH
SOUTHWEST CANADA/NORTHWEST CONUS. EFFECT OF THESE FEATURES THE
MAIN FORECAST CONCERN.
TODAY, UPPER THERMAL/RIDGE PEAK OVER THE CWA AS PRE-FRONTAL
TROUGH SLIDES INTO NORTHEASTERN WY. SMOKE SHIFTS EAST, BOTH
ALOFT/NEAR SURFACE. TEMPERATURES WILL BE NEAR GUIDANCE, WHICH IS
10-20F ABOVE NORMAL.
TONIGHT/MONDAY, UPPER TROUGH MOVES ACROSS THE US/CANADIAN BORDER
PUSHING PRE-FRONTAL TROUGH INTO THE CWA TONIGHT AND THEN MAIN COLD
FRONT MONDAY. LEAD SHORTWAVE TONIGHT WILL SUPPORT WEAK 700MB
THETA-E ADVECTION/MUCAPE <500J/KG. WEAK ELEVATED CONVECTION
ASSOCIATED WITH THESE FEATURES, WHICH IS SUPPORTED BY CAMS.
LINGERING ECHOES MONDAY MORNING AS COLD FRONT MOVES INTO SOUTH-
CENTRAL SD BY 18Z. COLD FRONT WILL BECOME THE FOCUS FOR SURFACE-
BASED CONVECTION MONDAY AFTERNOON AS 1-2KJ/KG SBCAPE POOLS AND
BETTER 0-6KM BULK SHEAR TRIES TO CATCH-UP WITH FRONT. MOST CAMS
SHOW CONVECTIVE INITIATION ALONG COLD FRONT AROUND 21Z. THUS,
THERE IS A MARGINAL RISK (1 OUT OF 5) OF SEVERE THUNDERSTORMS OVER
SOUTH-CENTRAL SD LATE MONDAY AFTERNOON/EARLY EVENING. ADDITIONAL
SHOWERS/TS EXPECTED AS QG/FRONTOGENETIC FORCING TAP INTO LIMITED
POST-FRONTAL MOISTURE. LATEST ENSEMBLE GUIDANCE CONTINUES TO TAMP
DOWN QPF AMOUNTS OVER MOST OF THE CWA (HREF/LREF 50% CHANCE
0.10", <20% CHANCE >0.50"), EXCEPT FOR SOUTH-CENTRAL SD WHERE
BENEFICIAL QPF CHANCES BETTER (LREF/NBM 50% >0.50"). EXPECT GUSTY
NORTHERLY WINDS BEHIND THE COLD FRONT MONDAY JUST EAST OF THE
BLACK HILLS PER 25-40KT 850-750MB WINDS AND 2-5MB/3HR PRESSURE
RISES. BOUNDARY LAYER FLOW MAY WHISK SMOKE BACK INTO WESTERN SD.
HREF/LREF GUIDANCE SHOWS 30-50% CHANCE OF 45MPH WIND GUSTS, THUS
NO WIND HEADLINES NEEDED FORTHWITH, BUT LATER SHIFTS WILL
CONTINUE TO REASSESS. GIVEN FRONTAL PASSAGE MONDAY, CONFIDENCE IN
TEMPERATURES NOT SPECTACULAR WITH 60S BEHIND THE FRONT AND 80S
AHEAD OF IT.
THE REST OF NEXT WEEK LOOKS UNSETTLED AS PROGRESSIVE NEAR-ZONAL FLOW
KICKS SEVERAL SURFACE BOUNDARIES THROUGH THE NORTHERN PLAINS. AFTER
SLIGHTLY BELOW NORMAL TEMPERATURES TUESDAY, A SLOW WARMING TREND TO
SLIGHTLY ABOVE NORMAL BY THE END OF THE WEEK IS FORESEEN.
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 523 AM MDT SUN JUN 1 2025
MAINLY VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD. SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS WILL OCCUR OVER NORTHEASTERN WY/FAR
WESTERN SD TONIGHT WITH LOCAL MVFR CONDITIONS POSSIBLE, BUT THE
PROBABILITY IS NOT HIGH ENOUGH TO INCLUDE IN THE TERMINAL
FORECASTS AT THIS TIME.
UNR WATCHES/WARNINGS/ADVISORIES
SD...NONE.
WY...NONE.
DISCUSSION/KEY MESSAGES...HELGESON
AVIATION...HELGESON
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