258
FXUS63 KUNR 270909
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
309 AM MDT WED AUG 27 2025
KEY MESSAGES
- SEASONABLY WARM THIS WEEK.
- SHOWERS AND STORMS ARE POSSIBLE ACROSS NORTHEASTERN WY INTO THE
BLACK HILLS AND SOUTHWESTERN SD THIS AFTERNOON INTO THURSDAY.
- INCREASING CHANCES FOR SHOWERS AND STORMS ACROSS THE AREA FOR
THE END OF WEEK INTO THE WEEKEND (50-70% FRIDAY AND SATURDAY).
DISCUSSION
(TODAY THROUGH TUESDAY)
ISSUED AT 307 AM MDT WED AUG 27 2025
MAIN FORECAST CONCERN FOR TODAY WILL BE SHOWERS AND THUNDERSTORMS
OVER NORTHEASTERN WY INTO THE BLACK HILLS AND SOUTHWESTERN SD. A
RATHER MESSY AND UNSETTLED UPPER LEVEL PATTERN DEVELOPS TODAY AS
THE UPPER LEVEL RIDGE BEGINS TO FLATTEN OUT THANKS TO A SHORTWAVE
TROF PUSHING INTO THE PNW. NARROW CORRIDOR OF 1000- 1500 J/KG SB
CAPE PROGGED TO DEVELOP ACROSS NORTHEASTERN WY INTO THE BLACK
HILLS AND SOUTHWESTERN SD. THIS WILL PROVIDE A FOCUS FOR STORM
DEVELOPMENT THIS AFTERNOON AND EVENING AS THE SHORTWAVE
APPROACHES. SHOWERS AND STORMS WILL CONTINUE OVER SOUTHWESTERN SD
INTO THE BLACK HILLS AND NORTHEASTERN WY INTO THURSDAY AS THE
SHORTWAVE SLOWLY DRIFTS THROUGH THE REGION. CHANCES FOR STORMS
INCREASE OVER THE WHOLE OF THE CWA FRIDAY AND SATURDAY AS A SERIES
OF DISTURBANCES CROSS THE REGION. WHILE INSTABILITY WILL BE
ENOUGH TO SUPPORT THUNDERSTORMS, THE WEAK FLOW ALOFT MEANS THAT
DEEP LAYER SHEAR WILL BE MARGINAL AT BEST AND UNSUPPORTIVE OF ANY
ORGANIZED CONVECTION.
PWAT VALUES INCREASE TO 1-1.5" BY FRIDAY AND SATURDAY, WHICH
COULD LEAD TO LOCALLY HEAVY RAINFALL IN THE STRONGER UPDRAFTS. IN
TERMS OF PRECIP ACCUMULATIONS, MUCH OF THE AREA WILL SEE 0.1+" QPF
BY SUNDAY MORNING WITH THE 00Z LREF GRAND ENSEMBLE RUN PAINTING
70-90+% PROBS ACROSS THE CWA.
AVIATION
(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1054 PM MDT TUE AUG 26 2025
VFR CONDITIONS ARE EXPECTED THROUGH THE FORECAST PERIOD. SCATTERED
THUNDERSTORMS WILL BE POSSIBLE ACROSS THE AREA WEDNESDAY AFTERNOON
AND EVENING.
UNR WATCHES/WARNINGS/ADVISORIES
SD...NONE.
WY...NONE.
DISCUSSION/KEY MESSAGES...WONG
AVIATION...13
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