151
FXUS63 KUNR 131137
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
537 AM MDT SUN SEP 13 2026
KEY MESSAGES
- AT OR BELOW NORMAL TEMPERATURES FOR THE REMAINDER OF THE
WEEKEND.
- RAINFALL CHANCES OVERNIGHT LOOKING A LITTLE LESS LIKELY, WITH
BETTER CHANCES COMING SUNDAY NIGHT
- SEASONAL TEMPERATURES THROUGH THE WEEK, WITH RAINFALL CHANCES
RETURNING BY MIDWEEK.
UPDATE
ISSUED AT 918 PM MDT SAT SEP 12 2026
EVENING UPDATES WERE MAINLY FOCUSED ON THE WINDS AND CHANCES OF
PRECIP. FOR TONIGHT, KEPT THE RAIN CHANCES TO SOUTH CENTRAL SD
AND MAINLY AFTER 10PM WITH LOW END RAIN CHANCES LASTING THROUGH
THE OVERNIGHT HOURS. ANOTHER ROUND OF PRECIP FROM THE SOUTHWEST IS
LOOKING LIKELY LATE SUNDAY INTO EARLY MONDAY. A PROJECTED SURFACE
LOW LOOKS TO DEVELOP NEAR NORTH CENTRAL WY SUNDAY AFTERNOON
BEFORE TRACKING NORTHEAST SUNDAY NIGHT. THIS WOULD GIVE NE WY AND
W SD A DECENT CHANCE AT PASSING RAIN AND THUNDERSHOWERS.
WITH RESPECT TO THE WINDS, ALLOWED WIND GUSTS TO BE DECREASED
FROM INHERITED FORECAST. THE FORECASTED WIND GUSTS FOR SUNDAY WERE
DECREASED AFTER REVIEWING LATEST HI-RES GUIDANCE, ENSEMBLES, AND
WIND GUST PROBABILITIES. THAT BEING SAID, WIND GUSTS AROUND 35 TO
45 MPH ARE LIKELY IN THE NW WY AND SD PLAINS WITH ISOLATED GUSTS
TO NEAR 50 POSSIBLE. SO IT WILL STILL BE A WINDY DAY BUT, AT LEAST
FOR NOW, HEADLINES DON'T LOOK TO BE NEEDED. MONDAY IS A DIFFERENT
STORY WITH FORECASTED WIND GUSTS UPWARDS OF 40 TO 50 MPH FOR NW
SD ARE LOOKING A LITTLE MORE LIKELY. STAY TUNED.
DISCUSSION
(THIS EVENING THROUGH SATURDAY)
ISSUED AT 1237 PM MDT SAT SEP 12 2026
LATEST WATER VAPOR IMAGERY SHOWS BROAD UPPER HIGH PRESSURE LOCATED
ACROSS THE SOUTHERN TIER OF THE COUNTRY WITH A DIGGING 500HPA LOW
OFF OF THE PACIFIC NW COAST. QUICK MOVING ZONAL FLOW IS FOUND
ACROSS THE UPPER MIDWEST. AT THE SURFACE HIGH PRESSURE IS LOCATED
ACROSS MUCH OF THE WESTERN DAKOTAS WITH A WEAK SURFACE TROUGH
SLIDING SOUTHEAST ACROSS EASTERN SD. AT 18Z SKIES WERE MAINLY
CLEAR TO PARTLY CLOUDY EXCEPT FOR ALONG THE ND/SD BORDER WHERE
MORE CLOUDS WERE FOUND. TEMPERATURES WERE IN THE MID 50S TO MID
60S.
MODELS ARE STILL ADVERTISING 700HPA THETA-E RIDGE AND ASSOCIATED
FORCING TO SLIDE ACROSS SOUTHERN TIER COUNTIES OVERNIGHT. DID TRIM
BACK INHERITED POPS BUT AM STILL A BIT CONCERNED THAT WE MIGHT BE
OVERDOING THE FORECAST. ENSEMBLES ARE ONLY SHOWING 10-20 PERCENT
PROBABILITIES OF SEEING GREATER THAN 0.01 INCH OF RAIN ACROSS OUR
SOUTHERN COUNTIES, AND LESS THAN THAT OF SEEING 0.05 INCH OF
RAINFALL.
SUNDAY WILL LOOKS TO BE DRY TO BEGIN WITH AND BECOMING BREEZY WITH
EASTERLY UPSLOPE FLOW. THIS WILL RESULT IN A FEW MORE CLOUDS WHICH
WILL AID IN KEEPING TEMPERATURES DOWN A BIT MORE. SUNDAY NIGHT
INTO MONDAY MORNING MAIN UPPER TROUGH FINALLY KICKS OUT ACROSS
REGION WITH ASSOCIATED 700HPA THETA-E RIDGE AND FORCING. BETTER
MOISTURE TRACKS ALONG WITH THIS FEATURE AND THIS IS WHEN OUR BEST
CHANCE OF SEEING RAINFALL OCCURS. AS THE MOISTURE SHIELD TRACKS
WEST TO EAST IT WILL BECOME MORE WIDESPREAD. EXPECTING MORE TO
FALL IS RAIN, ALTHOUGH CAN'T RULE OUT SOME SCATTERED
THUNDERSHOWERS HERE OR THERE THROUGH THE PERIOD.
THE REMAINDER OF THE WEEK LOOKS TO BE SEASONABLE TEMPERATURE WISE,
WITH RAINFALL CHANCES RETURNING BACK TO THE FORECAST AREA AROUND
MID-WEEK.
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 535 AM MDT SUN SEP 13 2026
VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. BREEZY
SOUTHEAST WINDS WILL DEVELOP OVER THE AREA BY THIS AFTERNOON WITH
GUSTS OF 25-35KT OVER THE PLAINS. TSRA MAY MOVE INTO THE AREA THIS
EVENING, EXPECT LCL MVFR CONDITIONS NEAR ANY CELLS.
UNR WATCHES/WARNINGS/ADVISORIES
SD...NONE.
WY...NONE.
UPDATE...GS
DISCUSSION...HINTZ
AVIATION...WONG
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