839  
FXUS63 KUNR 231109  
AFDUNR  
 
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY  
NATIONAL WEATHER SERVICE RAPID CITY SD  
509 AM MDT SAT OCT 23 2021  
   
DISCUSSION
 
(TODAY THROUGH FRIDAY)  
ISSUED AT 129 AM MDT SAT OCT 23 2021  
 
INCREASINGLY PROGRESSIVE AND ACTIVE FLOW CAN BE EXPECTED IN THE  
PERIOD AS THE POLAR JET BEGINS TO SAG FURTHER SOUTH, SUPPORTING  
IMPULSE LADEN FLOW OVER THE REGION. THE FIRST IN A SERIES OF FAST  
MOVING SYSTEMS IS NOW PROPAGATING ACROSS WESTERN MT. THIS SYSTEM  
CONTINUES TO SUPPORT LEE SIDE PRESSURE FALLS WITH GUSTY SE WINDS  
MATERIALIZING OVER PORTIONS OF THE REGION. INCREASING LL MOISTURE  
PER SE FLOW IS SUPPORTING LOW CLOUDS AND SOME FOG ACROSS PORTIONS  
OF NW SD AND THIS WILL CONTINUE TO BE THE CASE THROUGH MORNING.  
SUSTAINED MOIST SE FLOW MAY FORCE LOW CLOUDS AND TO LINGER THROUGH  
MUCH OF THE DAY OVER NW SD. HENCE, CONTINUED TO SIDE WITH LOWER  
HIGHS THERE, WITH MORE UNCERTAINLY PER TEMPS IN THE MIDDLE SECTION  
OF THE CWA GIVEN CONCERNS ON LOW CLOUDS WITH INCREASING MID  
CLOUD. UPPER IMPULSE WILL PROPAGATE INTO THE REGION TONIGHT AND  
SUPPORT SOME RAIN SHOWERS AS THERMAL PROFILES WILL REMAIN QUITE  
WARM. FLOW WILL THEN SHIFT NW BEHIND A COOL FRONT SUNDAY WITH  
LINGERING SHOWERS PUSHING OUT OF THE AREA. WARMING WILL THEN ENSUE  
HEAD OF THE NEXT SYSTEM, WITH HIGHS IN THE 60S AND 70S MONDAY AND  
TUES, ALBEIT BREEZY. THE NEXT CHANCE FOR MAINLY RAIN SHOWERS WILL  
BE TUE-TUE NIGHT AS A STRONGER LONG WAVE TROUGH SHIFTS THROUGH  
THE REGION. SEASONAL TEMPS WITH HIGHS IN THE 50S AND 60S LOOK  
LIKELY FOR THE REMAINDER OF THE WEEK WITH NEAR ZONAL FLOW IN  
PLACE. INDICATIONS REMAIN FOR A STRONGER COLD FRONT NEXT WEEKEND.  
HOWEVER, FORECAST CONFIDENCE IN THIS REMAINS QUITE LOW GIVEN  
COMPLICATED FAST FLOW AND POOR MODEL AGREEMENT AND RUN TO RUN  
CONSISTENCY.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)  
ISSUED AT 507 AM MDT SAT OCT 23 2021  
 
AREAS OF IFR CONDITIONS DUE TO LOW STRATUS AND PATCHY FOG WILL  
CONTINUE THROUGH 14-16Z THIS MORNING. IMPROVEMENT TO VFR  
CONDITIONS IS EXPECTED BY LATE MORNING SATURDAY, CONTINUING  
THROUGH THE EVENING. ADDITIONAL LOW STRATUS/FOG POSSIBLE SATURDAY  
NIGHT. EXPECT GUSTY SOUTHEAST WINDS ON THE SD PLAINS TODAY.  
 

 
   
UNR WATCHES/WARNINGS/ADVISORIES
 
 
SD...NONE.  
WY...NONE.  

 
 

 
 
DISCUSSION...JC  
AVIATION...EAGAN  
 
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