351
FXUS63 KUNR 312321
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
421 PM MST WED DEC 31 2025
KEY MESSAGES
- GENERALLY QUIET WEATHER IN STORE TO START THE NEW YEAR.
- COOLER TEMPS FRIDAY.
DISCUSSION
(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 141 PM MST WED DEC 31 2025
LATEST ANALYSIS SHOWS BROAD UPPER TROUGH ACROSS THE EASTERN CONUS
WITH UPPER RIDGING LOCATED ACROSS THE WESTERN CONUS, LEAVING THE
FORECAST AREA IN QUICK MOVING NORTHWEST FLOW ALOFT. DEEPENING
500HPA LOW LOCATED OFF THE SOUTHERN CA COAST WITH ABUNDANT
MOISTURE STREAMING ONSHORE. AT THE SURFACE, WEAK LOW PRESSURE IS
LOCATED IN CENTRAL SD WITH COLD FRONT/BAROCLINIC ZONE STRETCHING
FROM CENTRAL MT THROUGH NORTHWEST SD AND INTO CENTRAL MT. LOW
CLOUD SHIELD ON THE NORTH SIDE OF THIS BOUNDARY IS SLOWLY SAGGING
SOUTHEAST. THERE IS ALSO A WIDE TEMPERATURE DIFFERENCE ACROSS THIS
BOUNDARY, WITH TEMPS AT 18Z RANGING FROM THE UPPER SINGLE DIGITS
IN NORTHEAST SD TO THE MID 50S ACROSS SOUTHWEST SD.
THERE ARE A COUPLE OF TRICKY ASPECTS TO THE FORECAST. THE FIRST
IS THE COLD FRONT/BAROCLINIC BOUNDARY THAT WILL WOBBLE
SOUTHWEST/NORTHEAST THROUGH THE FORECAST PERIOD. THIS WILL HAVE A
DRAMATIC EFFECT ON SENSIBLE TEMPERATURES FOR THOSE IN THE VICINITY
OF THE BOUNDARY. THE SECOND MINOR THING TO DEAL WITH IS THE MINOR
RIPPLE IN THE 500HPA AND 700HPA FLOW THAT MODELS ARE SHOWING TO
PASS THROUGH THE AREA DURING THE DAY ON FRIDAY. AS THIS SYSTEM
DOES, IT WILL PULL THE BOUNDARY FURTHER SOUTH, ALLOWING 850HPA
COOLER TEMPS TO MOVE FURTHER WEST/SOUTH INTO OUR FORECAST AREA,
DROPPING HIGH TEMPERATURES WHEN COMPARED TO WHAT THEY WILL BE ON
THURSDAY. HOWEVER, HIGH TEMPERATURES WILL STILL BE ABOVE CLIMATIC
NORMS FOR THE BEGINNING OF JANUARY. ADDITIONALLY, WHILE MODELS
ALSO SHOW 700HPA THETA-E RIDGING PUSHING INTO THE FORECAST AREA
ASSOCIATED WITH THE 700HPA WAVE, ENSEMBLES SHOW PROBABILITIES OF
RECEIVING ANY MEASURABLE PCPN AT LESS THAN 10%. WOULDN'T BE
COMPLETELY SURPRISED TO SEE A FLURRY OR SPRINKLE FALL OUT OF THE
CLOUDS DURING THE MORNING HOURS FRIDAY, BUT NOT CONFIDENT ENOUGH TO
MAKE A MENTION IN THE FORECAST.
FOR THE WEEKEND, UPPER RIDGING RETURNS OVER THE ROCKIES WITH
INCREASING 500HPA HEIGHTS AND 850HPA TEMPS TRENDING UPWARD. LOOK
FOR THE DRY AND ABOVE SEASONAL NORMAL TEMPS TO CONTINUE THROUGH
THE WEEKEND INTO THE FIRST OF NEXT WEEK.
AVIATION
(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 415 PM MST WED DEC 31 2025
MVFR/IFR CIGS ACROSS CENTRAL SD WILL SLOWLY SLIDE WESTWARD INTO
THE WESTERN SD PLAINS, THEN STALL LATE TONIGHT. EXACTLY WHERE THE
CEILING STOPS PROGRESSING ISN'T CERTAIN, BUT RIGHT NOW IT IS NOT
EXPECTED TO MAKE IT TO KRAP. FOG MAY DEVELOP ACROSS THESE
AREAS...EVEN RIGHT UP TO THE NORTHEASTERN FOOTHILLS OF THE BLACK
HILLS. WESTERLY FLOW WILL DEVELOP EARLY THU MORNING, WHICH SHOULD
PUSH BACK EASTWARD THE FOG/LOW CIGS BY MID MORNING. ELSEWHERE, VFR
CONDITIONS EXPECTED THROUGH THE TAF PERIOD.
UNR WATCHES/WARNINGS/ADVISORIES
SD...NONE.
WY...NONE.
DISCUSSION/KEY MESSAGES...HINTZ
AVIATION...13
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