091
FXUS63 KUNR 232345
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
545 PM MDT SUN AUG 23 2026
KEY MESSAGES
- MARGINAL TO SLIGHT (LEVEL 1-2 OUT OF 5) RISK OF SEVERE
THUNDERSTORMS THIS EVENING.
- ISOLATED STRONG/SEVERE THUNDERSTORMS POSSIBLE MONDAY
AFTERNOON/EVENING.
- UPPER RIDGE WILL DOMINATE THE WEATHER WITH SUBTLE DISTURBANCES
THROUGH NEXT WEEK WITH TEMPERATURES ABOUT 4-8F ABOVE NORMAL
DISCUSSION
(THIS AFTERNOON THROUGH SATURDAY)
ISSUED AT 1043 AM MDT SUN AUG 23 2026
16Z SURFACE ANALYSIS HAD FRONTAL BOUNDARY FROM EASTERN MT TO
EASTERN CO AND A TROUGH FROM EASTERN CO INTO NORTHEASTERN NE.
WATER VAPOUR LOOP HAD UPPER RIDGE OVER THE SOUTHWEST CONUS WITH A
SHORTWAVE OVER NORTH-CENTRAL WY. OVERNIGHT MCS ABOUT TO FULLY EXIT
THE CWA WITH LEFTOVER LOW STRATUS BURNING OFF PER 0.5KM 1-MINUTE
VISIBLE IMAGERY. MAIN CONCERN THIS FORECAST WILL BE EFFECT OF
NORTH-CENTRAL WY SHORTWAVE.
THIS AFTERNOON/TONIGHT, SHORTWAVE MOVES INTO THE DAKOTAS WITH
SLIGHT INCREASE IN MID-LEVEL FLOW RESULTING IN 30-45KT EFFECTIVE
BULK SHEAR LATER THIS AFTERNOON. TD/S IN THE 60S WILL BE SUSTAINED
PER BREEZY SOUTHEAST WINDS AHEAD OF FRONTAL BOUNDARY. BAND OF
2-3KJ/KG MLCAPE FORECAST THIS AFTERNOON OVER FAR WESTERN SD WITH
MINIMUM CAP. CONVECTIVE INITIATION (CI) WILL LIKELY BE OVER THE
BLACK HILLS AROUND 20Z WITH SUPERCELLS MOVING SOUTH/SOUTHEAST AT
10-20KTS PER BUNKERS STORM MOTION PROGNOSTICATIONS. ANOTHER AREA
OF STRONG/SEVERE CI MAY DEVELOP OVER NORTHWESTERN SD ALONG THE
FRONTAL BOUNDARY/TROUGH INTERACTION LATE THIS AFTERNOON. CAMS
HANDLE THIS SCENARIO IN DIFFERENT FASHION WITH SOME EMPHASIZING
MLCIN EAST OF THE BLACK HILLS WITH SOME MEMBERS NOT SO MUCH.
OTHER STRONG/ISOLATED SEVERE CONVECTION MAY OCCUR OVER THE REST
OF THE CWA. SUFFICIENT BUOYANCY/BULK SHEAR FOR MARGINAL/SLIGHT
(1-2 OUT OF 5) OF SEVERE THUNDERSTORMS. LARGE HAIL/DAMAGING WIND
THE MAIN THREATS WITH CIG1 MAGNITUDES OVER WESTERN SD.
TEMPERATURES WILL BE A BIT BELOW GUIDANCE THIS AFTERNOON PER LOW
LEVEL MOISTURE/DISSIPATING STRATUS.
MONDAY, DIURNALLY DRIVEN CONVECTION POSSIBLE IN THE
AFTERNOON/EVENING, BUT THE UPPER SUPPORT LESS CERTAIN COMPARED TO
TODAY. TEMPERATURES WILL BE NEAR GUIDANCE.
THE REST OF THE FORECAST WILL BE DOMINATED BY THE UPPER RIDGE
OVER THE SOUTHWEST CONUS. RIDGE AMPLIFICATION INTO THE NORTHERN
PLAINS FOR THE SECOND HALF OF THE WEEK SUGGESTS SOMEWHAT QUIETER
AND DRIER WEATHER.
AVIATION
(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)
ISSUED AT 545 PM MDT SUN AUG 23 2026
ISOLATED THUNDERSTORMS THIS EVENING WILL CONTINUE TO PRODUCE HAIL,
GUSTY WINDS, AND BRIEF VSBY DROPS TO MVFR FOR A FEW MORE HOURS,
ESPECIALLY ACROSS THE NORTHWESTERN SOUTH DAKOTA PLAINS, WITH VFR
CONDITIONS OTHERWISE DOMINATING. PROB30S HAVE ENDED AT THE TAF
TERMINALS. ADDITIONAL ISOLATED THUNDERSTORMS ARE POSSIBLE MONDAY
AFTERNOON AND EVENING, WITH CAMS CURRENTLY OFFERING THE BEST
CONSENSUS OVER THE BLACK HILLS (INITIATION AROUND 19Z/1PM)
SPREADING ESE ACROSS THE I-90 CORRIDOR AND SOUTHERN SOUTH DAKOTA
PLAINS THROUGH EVENING. A NEW PROB30 HAS BEEN ADDED FOR KRAP.
UNR WATCHES/WARNINGS/ADVISORIES
SD...NONE.
WY...NONE.
DISCUSSION...HELGESON
AVIATION...KSMITH
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