850
FXUS63 KUNR 221729
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1129 AM MDT FRI AUG 22 2025
KEY MESSAGES
- CHANCES OF SHOWERS AND THUNDERSTORMS THROUGH TONIGHT.
- MILD AND MOSTLY DRY CONDITIONS THIS WEEKEND THROUGH MUCH OF NEXT
WEEK.
DISCUSSION
(TODAY THROUGH THURSDAY)
ISSUED AT 221 AM MDT FRI AUG 22 2025
LATEST WATER VAPOR IMAGERY SHOWS AN UPPER LOW CENTERED OVER THE
SASKATCHEWAN/MANITOBA BORDER WITH THE UPPER TROF EXTENDING
THROUGH EASTERN MONTANA AND A VORT MAX MOVING THROUGH NORTHWESTERN
SOUTH DAKOTA. ADDITIONALLY, A LARGE AREA OF HIGH PRESSURE IS
CENTERED OVER THE SOUTHERN ROCKIES, CREATING ZONAL FLOW ACROSS THE
FORECAST AREA. UPPER LEVEL ANALYSIS SHOWS DIVERGENCE AT 300 MB
WITH A SLIGHT 500 MB HEIGHT PERTURBATION OVER NORTHWESTERN SOUTH
DAKOTA. AT THE SURFACE, THE FRONTAL BOUNDARY EXTENDS FROM EASTERN
SOUTH DAKOTA, THROUGH SOUTH CENTRAL SOUTH DAKOTA INTO WESTERN
NEBRASKA/SOUTHEASTERN WYOMING AND THEN UP THROUGH CENTRAL WYOMING
INTO WESTERN MONTANA. LATEST RADAR IMAGERY IS SHOWING SCATTERED
SHOWERS AND THUNDERSTORMS ONGOING ACROSS NORTHWESTERN SOUTH
DAKOTA CORRELATING TO THE VORT MAX AND THE UPPER LEVEL DIVERGENCE
AND IN CENTRAL SOUTH DAKOTA NEAR THE FRONT.
FOR TODAY, THE UPPER TROF WILL CONTINUE TO PUSH EAST AND THE FRONT
WILL CONTINUE TO SINK SOUTHWARD. THOUGH THE UPPER JET WILL SINK
SOUTHWARD, THE CORE OF THE STREAK WILL SHIFT EASTWARD AWAY FROM THE
REGION, WHICH WILL BRING INCREASED FORCING FOR ASCENT BUT DECREASING
DEEP-LAYER BULK SHEAR MAGNITUDES. ALTOGETHER, THIS SHOULD LEAD TO
CONTINUED SHOWER/STORM ACTIVITY--ESPECIALLY CLOSER TO THE BAROCLINIC
ZONE--BUT IT WILL ALSO REDUCE THE POTENTIAL FOR STRONG/SEVERE STORMS.
SHOWERS AND STORMS WILL END TONIGHT, AS THE UPPER TROF SHIFTS EAST
OF THE AREA. HIGH PRESSURE OVER THE SOUTHERN ROCKIES WILL CONTINUE
TO BUILD, PUTTING THE AREA INTO A NORTHWEST FLOW PATTERN. ENSEMBLE
MODEL CONSENSUS INDICATES NORTHWEST FLOW WILL CONTINUE FOR MUCH OF
THE UPCOMING WEEK. AS IS THE NORM FOR NORTHWEST FLOW, WE COULD SEE
SOME ENERGY PUSH THROUGH AT TIMES, CREATING A CHANCE FOR AN ISOLATED
SHOWER OR STORM. HOWEVER, MOISTURE WILL BE LIMITED AS THE AIR DRIES
OUT COMING OVER THE ROCKIES. 850 TEMPS LOOK TO REMAIN BELOW NORMAL
THROUGH TUESDAY, BEFORE RISING SLIGHTLY TO NEAR NORMAL FOR WEDNESDAY
THROUGH FRIDAY NEXT WEEK. AS SUCH, A MILD AND MOSTLY DRY PERIOD IS
LIKELY FROM SATURDAY THROUGH MUCH OF NEXT WEEK.
AVIATION
(FOR THE 18Z TAFS THROUGH 18Z SATURDAY)
ISSUED AT 1124 AM MDT FRI AUG 22 2025
SCATTERED SHOWERS AND A FEW THUNDERSTORMS ARE POSSIBLE OVER
SOUTHWEST SOUTH DAKOTA THIS AFTERNOON INTO THIS EVENING, WITH A
DIMINISHING TREND OVERNIGHT. INCLUDED/KEPT A PROB30 GROUP AT RAP;
HOWEVER, CONFIDENCE WAS LOWER AT GCC, SO KEPT IT OUT OF THE TAF
THEIR. CEILINGS ARE EXPECTED TO BE AROUND 6-8KFT. IMPROVING
CONDITIONS CAN BE EXPECTED AT EACH TAF SITE FOR SATURDAY. WINDS
ARE EXPECTED TO BE AROUND 15KT OR LESS WITH THE GREATEST GUSTS
THIS AFTERNOON INTO EARLY THIS EVENING.
UNR WATCHES/WARNINGS/ADVISORIES
SD...NONE.
WY...NONE.
DISCUSSION/KEY MESSAGES...SMITH
AVIATION...COOLEY
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