090
FXUS63 KUNR 201112
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
412 AM MST SAT DEC 20 2025
KEY MESSAGES
- COOLER TODAY, BUT STILL ABOVE AVERAGE.
- GRADUALLY WARMING TEMPERATURES THROUGH THE UPCOMING WEEK.
- MOSTLY DRY CONDITIONS, BUT LIGHT SHOWERS ARE POSSIBLE IF
MOISTURE CAN BE FOUND DUE TO EXPECTED INSTABILITY.
DISCUSSION
(TODAY THROUGH FRIDAY)
ISSUED AT 204 AM MST SAT DEC 20 2025
LATEST UPPER LEVEL ANALYSIS SHOWS QUASI-ZONAL FLOW OVER THE FORECAST
AREA WITH A LOW OVER MANITOBA AND A WEAK TROUGH EXTENDING THROUGH
THE WESTERN HIGH PLAINS. AT THE SURFACE, A COLD FRONT EXTENDS FROM A
SURFACE LOW IN SOUTHWEST ONTARIO, DOWN THROUGH THE NORTHERN PLAINS
AND INTO SOUTHEAST WYOMING. TEMPERATURES AT 08Z RANGE FROM THE LOW
20S ACROSS NORTHWESTERN SOUTH DAKOTA AND PORTIONS OF NORTHEASTERN
WYOMING, INTO THE UPPER 30S ACROSS SOUTH CENTRAL SOUTH DAKOTA.
TODAY WILL BE COLDER, BUT STILL ABOVE SEASONAL AVERAGES, WITH HIGHS
RANGING FROM THE MID 30S ACROSS THE BLACK HILLS AND NORTHEASTERN
WYOMING INTO THE MID 40S IN THE EASTERN FOOTHILLS AND SOUTHWESTERN
SOUTH DAKOTA. WEST NORTHWEST WINDS OF 15 TO 20 MPH WILL BE COMMON
OVER THE SOUTH DAKOTA PLAINS, DUE TO SURFACE HIGH PRESSURE BUILDING
INTO THE AREA. HI-RES MODELS INDICATE A 30-50% CHANCE OF WIND GUSTS
GREATER THAN 30 MPH ACROSS NORTHWESTERN SOUTH DAKOTA THIS MORNING.
FOR TONIGHT, MOSTLY CLEAR SKIES AND HIGH PRESSURE OFF TO THE EAST
WILL ALLOW TEMPERATURES TO FALL INTO THE TEENS AND UPPER 20S. FINER
RESOLUTION MODELS ARE PICKING UP ON A SHORTWAVE MOVING THROUGH THE
FLOW ALONG A 700MB THETA-E RIDGE AFTER 10Z, PRODUCING SOME LIGHT
SNOW OVER FAR SOUTHWESTERN SOUTH DAKOTA AND NORTHEASTERN WYOMING.
MOISTURE APPEARS TO BE LIMITED UNTIL ABOUT 12Z SUNDAY MORNING, SO
HAVE KEPT CHANCES OF LIGHT SNOW OUT OF THE FORECAST FOR NOW FOR THE
OVERNIGHT PERIOD.
FOR SUNDAY, HAVE ADDED LOW POPS TO THE FORECAST BASED ON THE HI-RES
MODELS INDICATING LIGHT PRECIP COINCIDING WITH THE WAVE AND
INSTABILITY. MOISTURE AVAILABILITY IS THE BIGGEST QUESTION, BUT
OVERALL FIGURED LOW POPS WERE WARRANTED BASED ON THE DYNAMICS.
MESSY ZONAL/SOUTHWEST FLOW WILL PROMOTE ABOVE NORMAL TEMPERATURES
THROUGH MUCH OF CHRISTMAS WEEK. A FEW WEAK DISTURBANCES MAY SPARK
SOME LIGHT PRECIPITATION CHANCES THROUGHOUT THE WEEK; HOWEVER,
EXPECT MOSTLY DRY AND WARM CONDITIONS TO PREVAIL.
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 412 AM MST SAT DEC 20 2025
VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD.
UNR WATCHES/WARNINGS/ADVISORIES
SD...NONE.
WY...NONE.
DISCUSSION/KEY MESSAGES...SMITH
AVIATION...SMITH
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