944  
FXUS63 KUNR 221116  
AFDUNR  
 
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY  
NATIONAL WEATHER SERVICE RAPID CITY SD  
516 AM MDT FRI JUN 22 2018  
   
DISCUSSION
 
(TODAY THROUGH THURSDAY)  
ISSUED AT 157 AM MDT FRI JUN 22 2018  
 
AN UPPER WAVE OVER THE NORTHERN ROCKIES IS HELPING TO  
PRODUCE SOME THUNDERSTORMS ACROSS SOUTHEASTERN MT/SOUTHWESTERN  
ND/NORTHWESTERN SD/NORTHEASTERN WY. SURFACE HIGH RESTS OVER CENTRAL  
NE, AND WITH THE SURFACE TROUGH APPROACHING FROM THE WEST, WINDS ARE  
SOUTHERLY AROUND 10 KTS. TEMPERATURES AT 2 AM ARE IN THE 50S AND  
LOWER 60S.  
 
SHOWERS AND THUNDERSTORMS WILL CONTINUE ACROSS NORTHWESTERN SD THIS  
MORNING. ACTIVITY WILL EXPAND ACROSS MUCH OF THE CWA THIS AFTERNOON,  
AS THE UPPER WAVE AN ITS ASSOCIATED COLD FRONT SLIDE INTO THE  
NORTHERN PLAINS. MLCAPE OF 1000-2000 J/KG COULD ALLOW FOR A COUPLE  
STRONG TO SEVERE STORMS; HOWEVER, 0-6 KM SHEAR IS WEAK. GREATER  
CHANCES FOR SEVERE STORMS WILL BE TO THE SOUTH, WHERE INSTABILITY  
AND SHEAR ARE BETTER. HIGHS TODAY WILL BE IN THE 70S TO LOWER 80S,  
COOLER ACROSS THE NORTHWESTERN HALF OF THE CWA.  
 
PRECIPITATION WILL LINGER ACROSS NORTHWESTERN SD TO SOUTH CENTRAL SD  
AND EASTWARD SATURDAY, BEFORE THE FIRST WAVE FINALLY EXITS THE  
REGION. WEAK RIDGING WILL ALLOW FOR A BRIEF PERIOD OF DRY WEATHER  
FOR THE WESTERN CWA BEFORE THE NEXT SYSTEM MOVES IN. POSITIVELY  
TILTED UPPER WAVE WILL DIG INTO THE CENTRAL ROCKIES LATE SATURDAY,  
AND SLOWLY CROSS THE NORTHERN PLAINS THIS WEEKEND INTO EARLY NEXT  
WEEK. BOTH THE GFS AND NAM SHOW THE UPPER LOW SLIDING JUST TO THE  
SOUTH OF THE CWA, WHILE THE ECMWF HAS IT FARTHER NORTH.  
SHOWERS/STORMS ARE EXPECTED TO BEGIN PUSHING INTO THE AREA  
SATURDAY EVENING, WITH WIDESPREAD PRECIPITATION ON SUNDAY, AND  
RAIN LINGERING INTO MONDAY. MODELS ARE SHOWING 1-2 INCHES OF QPF  
POSSIBLE, MAINLY ACROSS THE SOUTHERN PARTS OF THE CWA. WITH PWATS  
150% OF NORMAL AND SLOW STORM MOTION OVER A COUPLE OF DAYS OF  
PRECIPITATION ON ALREADY SATURATED SOILS, A FLOOD WATCH MAY NEED  
TO BE CONSIDERED FOR SUNDAY/MONDAY. WILL HOLD OFF FOR NOW, IN CASE  
THE TRACK OF THE LOW SHIFTS. TEMPERATURES THROUGH THE WEEKEND  
WILL BE MAINLY IN THE 70S.  
 
SLIGHT RIDGING/ZONAL FLOW IS EXPECTED FOR THE MIDDLE OF NEXT WEEK,  
RESULTING IN WARMER AND DRIER WEATHER.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)  
ISSUED AT 515 AM MDT FRI JUN 22 2018  
 
SCATTERED THUNDERSTORMS WILL MOVE ACROSS NORTHWEST SOUTH DAKOTA  
THIS MORNING, AND ACROSS MUCH OF THE AREA THIS AFTERNOON AND  
EVENING. IFR CONDITIONS WITH THE STRONGER THUNDERSTORMS.  
 

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

 
 

 
 
DISCUSSION...POJORLIE  
AVIATION...7  
 
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