082  
FXUS63 KUNR 220433  
AFDUNR  
 
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY  
NATIONAL WEATHER SERVICE RAPID CITY SD  
1033 PM MDT WED MAY 21 2025  
   
KEY MESSAGES  
 
- FROST ADVISORY ISSUED FOR PORTIONS OF NORTHWEST SOUTH DAKOTA FOR  
THURSDAY MORNING. WITH LOWS DROPPING INTO THE LOWER 30S SOME  
PLACES, AREAS OF FROST IS LIKELY.  
 
- A BRIEF WARMUP FOR THURSDAY MOST AREAS, CONTINUING INTO FRIDAY  
FOR PORTIONS OF NORTHEAST WY AND SOUTHWEST SD. STILL A FEW  
THUNDERSTORMS POSSIBLE THURSDAY NIGHT AND FRIDAY NIGHT.  
 
- MORE WIDESPREAD SHOWERS AND THUNDERSTORMS MOVE BACK INTO THE  
AREA FOR THE WEEKEND, WITH HIGH TEMPERATURES RETURNING TO MUCH  
BELOW AVERAGE FOR THIS TIME OF YEAR. HIGHS WILL STRUGGLE TO GET  
OUT OF THE 50S SATURDAY AND SUNDAY.  
 
 
   
DISCUSSION  
(THIS EVENING THROUGH WEDNESDAY)  
ISSUED AT 247 PM MDT WED MAY 21 2025  
 
SHORT TERM (THROUGH THURSDAY NIGHT)...STRATUS HOLDING FIRM FROM  
NORTHERN PERKINS IN ZIEBACH COUNTIES THIS AFTERNOON KEEPING TEMPS IN  
THE 40S STILL THERE. MEANWHILE MORE CONVECTIVE CLOUDS ASSOCIATED  
WITH MID LEVEL FORCING CO-LOCATED WITH AN AREA OF INSTABILITY ALOFT  
HAVE GENERATED SHOWERS AND ISOLATED THUNDERSTORMS ACROSS MAINLY THE  
SOUTHERN HILLS AND PORTIONS OF NORTHEAST WY. CONVECTIVE ALLOWING  
MODELS STRUGGLED WITH THIS SCENARIO INITIALLY BUT HAVE FINALLY  
CAUGHT ON, AND THESE SHOWERS AND STORMS SHOULD DISSIPATE AFTER  
SUNSET WITH SKIES CLEARING THEREAFTER. WITH GOOD RADIATIONAL COOLING  
AFTER MIDNIGHT, DO EXPECT WINDS TO LIGHTEN AND TEMPERATURES TO DROP  
INTO THE 30S MOST PLACES. NEAR THE ND BORDER WHERE ALTHOUGH CLOUDS  
WILL BE LAST TO CLEAR, TEMPS WILL DROP INTO THE LOW 30S. PATCHY TO  
AREAS OF FROST WILL BE LIKELY AND A FROST ADVISORY HAS BEEN ISSUED  
FOR THOSE COUNTIES IN NORTHWEST SD. TRANSITORY UPPER RIDGING WILL  
MOVE INTO THE NORTHERN PLAINS THURSDAY WITH LARGER SCALE  
SUBSIDENCE PREVALENT ACROSS MOST OF THE AREA. THIS WILL LEAD TO  
GOOD INSOLATION ACROSS THE AREA AND AFTERNOON TEMPS RETURNING TO  
NEAR AVERAGE FOR THIS TIME OF YEAR, IN THE UPPER 60S TO LOW 70S.  
THE FASTER UPPER FLOW OVER THE NORTHERN ROCKIES WILL CREATE LOW  
PRESSURE IN THE LEE OF THE MOUNTAINS AND THE RESPONSE WILL BE FOR  
WINDS TO TURN TO SOUTHERLY. THE NEXT UPPER LEVEL PV ANOMALY AND  
ASSOCIATED LARGE SCALE ASCENT WILL MOVE INTO THE HIGH PLAINS LATE  
IN THE DAY THURSDAY AND WILL ENHANCE THE OROGRAPHIC LIFT ENOUGH TO  
GENERATE A FEW THUNDERSTORMS OVER THE BLACK HILLS AND THE  
ADJACENT PLAINS THURSDAY NIGHT.  
 
FRIDAY THROUGH THE WEEKEND...THIS INITIAL UPPER PV ANOMALY WILL  
MOVE QUICKLY OUT OF THE REGION WHICH WILL ALLOW FOR GOOD SUNSHINE  
ACROSS THE WESTERN AND SOUTHERN PORTION OF THE FORECAST AREA. IN  
RESPONSE, HIGH TEMPERATURES WILL JUMP INTO THE 70S THERE FRIDAY,  
WHILE TEMPS WILL HOLD IN THE 50S WHERE CLOUD COVER REMAINS FURTHER  
NORTH. SOUTHERLY WINDS WILL CONTINUE TO BRING IN ADDITIONAL  
MOISTURE AND AS THE MUCH LARGER SYSTEM MOVES INTO THE GREAT BASIN  
BY SATURDAY, THUNDERSTORM CHANCES WILL INCREASE ONCE AGAIN AND  
WILL BE MORE WIDESPREAD THROUGH THE WEEKEND. TEMPS WILL REMAIN  
WELL BELOW AVERAGE ACROSS THE AREA SATURDAY THROUGH MONDAY, AND  
WILL ONLY BE IN THE 50S MOST AREAS THIS WEEKEND UNDER PLENTY OF  
CLOUDS AND INTERMITTENT SHOWERS AND THUNDERSTORMS.  
 
 
   
AVIATION  
(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)  
ISSUED AT 1031 PM MDT WED MAY 21 2025  
 
VFR CONDITIONS ARE EXPECTED THROUGH THE TAF FORECAST PERIOD.  
 
 
   
UNR WATCHES/WARNINGS/ADVISORIES  
 
SD...FROST ADVISORY UNTIL 7 AM MDT THURSDAY FOR SDZ001-002-013-014-  
078.  
WY...NONE.  
 
 
 
 
DISCUSSION/KEY MESSAGES...STOPPKOTTE  
AVIATION...15  
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