640  
FXUS63 KUNR 230920  
AFDUNR  
 
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY  
NATIONAL WEATHER SERVICE RAPID CITY SD  
320 AM MDT TUE MAY 23 2017  
   
DISCUSSION
 
(TODAY THROUGH MONDAY)  
ISSUED AT 256 AM MDT TUE MAY 23 2017  
 
THE LOW PRESSURE SYSTEM THAT WAS LOCATED OVER SWRN ONTARIO  
YESTERDAY, HAS DROPPED SOUTHWARD ACROSS MINNESOTA OVERNIGHT AND IS  
EXPECTED TO BE LOCATED IN CENTRAL IOWA BY THIS EVENING. THERE WILL  
BE ENOUGH MOISTURE AND INSTABILITY TODAY TO INCLUDE A SLIGHT  
CHANCE OF SHOWERS ALONG THE FAR EASTERN PART OF THE FORECAST AREA,  
TOWARD CENTRAL SOUTH DAKOTA. MODELS ARE ALSO INDICATING A LITTLE  
INSTABILITY OVER THE BLACK HILLS AND SOUTHWESTERN SOUTH DAKOTA  
UNTIL EARLY AFTERNOON. HAVE ALSO INCLUDED A SLIGHT CHANCE OF  
SHOWERS IN THOSE AREAS UNTIL EARLY AFTN, ALTHOUGH MOISTURE IS  
LIMITED AND WILL BECOME DRIER THIS AFTERNOON AS THE UPPER RIDGE  
BUILDS IN FROM THE NORTHWEST. TEMPERATURES WILL BE SIMILAR TO  
YESTERDAY WITH HIGHS IN THE MID-50S TO MID-60S. GUSTY NORTHERLY  
WINDS ARE EXPECTED OVER WESTERN SOUTH DAKOTA.  
 
SOUTHERLY RETURN FLOW WILL DEVELOP ON WEDNESDAY WITH MUCH WARMER  
TEMPERATURES. EARLY THURSDAY, A COLD FRONT WILL PUSH THROUGH THE  
FORECAST AREA SWITCHING WINDS AROUND TO THE NORTHWEST AND COOLING  
TEMPERATURES A LITTLE. FRIDAY THROUGH SUNDAY WILL BE A LITTLE  
COOLER THAN NORMAL AS THE NEXT UPPER TROUGH MOVES SLOWLY THROUGH  
THE NORTHERN CONUS FROM AN UPPER LOW OVER SOUTHERN CANADA. THIS  
UPPER TROUGH WILL CREATE UNSETTLED CONDITIONS WITH CHANCES FOR  
PRECIPITATION OVER VARIOUS PARTS OF THE FORECAST AREA THROUGH THE  
WEEKEND.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)  
ISSUED AT 931 PM MDT MON MAY 22 2017  
 
VFR CONDITIONS EXPECTED THROUGH TUESDAY.  
 

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

 
 

 
 
DISCUSSION...10  
AVIATION...JOHNSON  
 
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