586
FXUS63 KUNR 180021
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
621 PM MDT WED SEP 17 2025
KEY MESSAGES
-WIDESPREAD SHOWERS AND A FEW THUNDERSTORMS WILL CONTINUE THROUGH
TONIGHT BEFORE GRADUALLY ENDING THURSDAY INTO THURSDAY NIGHT
-TOTAL RAINFALL AMOUNTS OF ONE QUARTER INCH TO TWO INCHES ARE
EXPECTED, WITH THE HIGHEST AMOUNTS ACROSS WESTERN AND CENTRAL SD
-DRY AND WARMER WEATHER THIS WEEKEND AND MOST OF NEXT WEEK
DISCUSSION
(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 152 PM MDT WED SEP 17 2025
RADAR IMAGERY THIS AFTERNOON SHOWS WIDESPREAD RAIN AND A FEW
EMBEDDED THUNDERSTORMS ACROSS WESTERN SOUTH DAKOTA, WITH MORE
SCATTERED SHOWERS INTO NORTHEAST WYOMING. THIS ACTIVITY IS
ASSOCIATED WITH AN UPPER LEVEL LOW CENTERED NEAR KVTN, AND A
DEEPENING 1016MB SURFACE LOW NEAR DRAPER. THE WIDESPREAD RAIN
WILL CONTINUE TO WRAP AROUND THE LOW INTO THIS EVENING BEFORE
GRADUALLY SHIFTING EASTWARD OVERNIGHT INTO THURSDAY AS THE
SURFACE LOW MOVES OFF TO THE EAST PER 12Z GUIDANCE. RAIN CHANCES
NEAR 100 PERCENT TODAY ACROSS WESTERN SD WILL SUBSEQUENTLY
DIMINISH DOWN TO JUST SLIGHT/LOW CHANCES BY THURSDAY AFTERNOON
BEFORE ENDING ACROSS THE CWA BY THURSDAY NIGHT INTO EARLY FRIDAY.
LATEST QPF TOTALS FOR THIS EVENT INDICATE AROUND ONE HALF INCH OR
LESS OF RAINFALL ACROSS NORTHEAST WYOMING, WITH ONE HALF INCH
ALONG THE WY/SD BORDER TO NEAR 2 INCHES ALONG THE EASTERN CWA
BORDER. NO FLOODING IMPACTS ARE ANTICIPATED DUE TO THE LONG
DURATION OF THIS BENEFICIAL LIGHT TO MODERATE RAIN EVENT. OF NOTE,
NORTH TO NORTHEAST WINDS ARE ANTICIPATED TO INCREASE CONSIDERABLY
LATE TODAY INTO TONIGHT OVER THE WESTERN AND CENTRAL SD PLAINS AS
THE SURFACE LOW DEEPENS TO AROUND 1011MB PER CAMS, CREATING A
5-6MB PRESSURE GRADIENT BETWEEN KRAP AND KICR. THIS SHOULD ALLOW
FOR OCCASIONAL NORTH TO NORTHEAST WIND GUSTS REACHING THE 30-40
MPH RANGE IN OUR EASTERN HALF TONIGHT BEFORE SUBSIDING THURSDAY
MORNING.
THE UPPER LOW WILL LINGER ACROSS SD THROUGH FRIDAY BEFORE FINALLY
GETTING KICKED OFF TO THE EAST AS A STRONGER H5 SHORTWAVE SHIFTS
SOUTHEAST OUT OF SOUTHERN CANADA BY SATURDAY. DRY NORTHWEST FLOW
WILL BRING A DRY AND WARMER WEEKEND FOR THE REGION WITH HIGHS
WARMING BACK INTO THE 70S AND 80S FOR SATURDAY AND SUNDAY. THE
FORECAST FOR NEXT WEEK IS NOW MORE UNCERTAIN AS THE 12Z GFS/ECMWF
SHOW YET ANOTHER UPPER LOW TAKING SHAPE ACROSS THE NORTHERN
ROCKIES AND MOVING INTO THE NORTHERN PLAINS EARLY NEXT WEEK,
WHICH COULD POTENTIALLY BRING MORE RAIN AND THUNDERSTORMS TO THE
FORECAST AREA MONDAY AND TUESDAY. DUE TO THE UNCERTAINTY IN THE
OVERALL PATTERN AND THE PREVIOUSLY DRY FORECASTS, PRECIP CHANCES
WILL REMAIN LOW TO NEGLIGIBLE FOR EARLY NEXT WEEK, BUT MAY NEED
TO BE BUMPED UP IN THE COMING DAYS. REGARDLESS, THE LONG RANGE
PATTERN CONTINUES TO LOOK QUITE ACTIVE FOR THE NORTHERN PLAINS AS
A LARGE UPPER TROUGH TAKES HOLD OVER THE WESTERN CONUS.
AVIATION
(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 616 PM MDT WED SEP 17 2025
MVFR/IFR CONDITIONS WITH RAIN WILL CONTINUE THROUGH TONIGHT INTO
THURSDAY, ESPECIALLY ACROSS WESTERN SD. CONDITIONS WILL GRADUALLY
IMPROVING TO VFR FROM WEST TO EAST OVER THE NEXT 24 HOURS...FIRST
ACROSS NE WY TONIGHT, THEN WESTERN SD THROUGH THE DAY TOMORROW.
UNR WATCHES/WARNINGS/ADVISORIES
SD...NONE.
WY...NONE.
DISCUSSION/KEY MESSAGES...SHAMBURGER
AVIATION...13
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