112  
FXUS63 KUNR 220510  
AFDUNR  
 
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY  
NATIONAL WEATHER SERVICE RAPID CITY SD  
1110 PM MDT THU SEP 21 2017  
   
DISCUSSION
 
(THIS EVENING THROUGH THURSDAY)  
ISSUED AT 137 PM MDT THU SEP 21 2017  
 
A LARGE TROUGH ACROSS THE WESTERN CONUS WILL INFLUENCE OUR  
WEATHER THROUGH THE UPCOMING WEEKEND. AT 19Z A COLD FRONT HAD  
PUSHED THROUGH OVER 1/2 OF THE CWA AND WAS FROM ROUGHLY KD07 TO  
KIEN. THIS WILL MOVE RATHER SLOWLY TONIGHT AND FRIDAY, REACHING  
KICR AROUND 18Z FRIDAY, AND PUSHING SOUTHEAST OF THE CWA FRIDAY  
EVENING. ALOFT, SOUTHWEST FLOW WILL PREVAIL WITH PERIODIC SHORT-  
WAVE TROUGHS EJECTING OUT OF THE WESTERN CONUS TROUGH ABOUT EVERY  
24 HOURS. IT LOOKS LIKE ONE IMPULSE WILL BRING A ROUND OF SHOWERS  
AND EMBEDDED THUNDERSTORMS LATE FRIDAY AND FRIDAY NIGHT, WITH THE  
BEST CHANCE OF THUNDERSTORMS OVER SOUTH-CENTRAL SOUTH DAKOTA.  
ENSEMBLE DATA THEN SUGGEST A STRONGER WAVE SATURDAY NIGHT INTO  
SUNDAY WITH FAIRLY WIDESPREAD PRECIPITATION.  
 
TEMPERATURES WILL BE NOTABLY LOWER THIS WEEKEND, WITH 850-MB  
TEMPERATURES DROPPING FROM AROUND 14-18C TODAY TO 2-6C BY SUNDAY  
MORNING. THIS WILL RESULT IN A CHANCE OF SNOW FOR THE HIGHEST  
ELEVATIONS OF THE BLACK HILLS AND NORTHEASTERN WY FOR THE OVERNIGHT  
PERIODS, ESPECIALLY LATE SATURDAY, SUNDAY, AND MONDAY NIGHTS.  
 
IT LOOKS LIKE THE FINAL NOTEWORTHY SHORT-WAVE WILL EJECT SUNDAY  
NIGHT INTO MONDAY WITH THE UPPER LOW MOVING NORTHEAST OF THE CWA  
LATER ON TUESDAY. THIS WILL BE FOLLOWED BY SLOWLY BUILDING HEIGHTS  
AND GRADUALLY WARMER WEATHER TOWARD THE END OF NEXT WEEK.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)  
ISSUED AT 1106 PM MDT THU SEP 21 2017  
 
VFR CONDITIONS CAN BE EXPECTED TONIGHT. AREAS WILL EXPERIENCE  
BREEZY NORTHWESTERLY WINDS AS THE COLD FRONT SLOWLY MOVES EAST  
OUT OF THE AREA. TOWARDS THE END OF THE FORECAST PERIOD, THERE  
WILL BE LOCALIZED IFR CONDITIONS AS SHOWERS BEGIN LATE FRIDAY AND  
FRIDAY NIGHT.  
 

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

 
 

 
 
DISCUSSION...BUNKERS  
AVIATION...FOSCATO  
 
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