257  
FXUS63 KUNR 142325  
AFDUNR  
 
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY  
NATIONAL WEATHER SERVICE RAPID CITY SD  
525 PM MDT TUE AUG 14 2018  
   
DISCUSSION
 
(THIS EVENING THROUGH TUESDAY)  
ISSUED AT 322 PM MDT TUE AUG 14 2018  
 
CURRENT SURFACE ANALYSIS SHOWS COLD FRONT SOUTH AND EAST OF THE  
FORECAST AREA. UPPER LEVEL ANALYSIS SHOWS AN AREA OF LOW PRESSURE  
OVER EASTERN PORTIONS OF THE CENTRAL PLAINS, WITH A SHORTWAVE  
TROUGH OVER THE EASTERN HALF OF MT. HIGH PRESSURE REMAINS ACROSS  
THE FOUR CORNERS REGION. SKIES ARE VARIABLY CLOUDY WITH AN AREA OF  
SHOWERS AND THUNDERSTORMS OVER PARTS OF SOUTHWEST INTO SOUTH  
CENTRAL SD, GRADUALLY DISSIPATING. REGIONAL RADARS SHOW STORMS  
DEVELOPING WEST OF THE FORECAST AREA, ESPECIALLY OVER THE HIGHER  
TERRAIN. TEMPS ARE IN THE MID 60S TO UPPER 70S, WITH WINDS  
SOUTHEASTERLY OR BECOMING SOUTHEASTERLY ACROSS MUCH OF THE AREA.  
 
UNSETTLED WEATHER WILL CONTINUE OVER THE NEXT COUPLE OF DAYS AS THE  
UPPER LEVEL SYSTEM SLOWLY MOVES ACROSS THE NORTHERN PLAINS. STORMS  
TO THE WEST WILL MOVE INTO NORTHEAST WY LATE THIS AFTERNOON/EARLY  
EVENING AND INTO WESTERN SD THIS EVENING/OVERNIGHT. THE BEST  
INSTABILITY LATE THIS AFTERNOON AND EVENING WILL BE ACROSS EASTERN  
WY TO FAR SOUTHWEST SD, 1000 TO 1500 J/KG MUCAPE. SHEAR WILL BE  
QUITE FAVORABLE FOR STRONGER STORMS/SUPERCELLS ACROSS NORTHEAST WY.  
THERE IS A SLIGHT RISK FOR SEVERE STORMS ACROSS NORTHEAST WY WITH  
LARGE HAIL AND STRONG WIND GUSTS THE MAIN THREATS. SHEAR PROFILE IN  
THE LOWER LEVELS WOULD SUGGEST THAT A TORNADIC STORM CANNOT BE RULED  
OUT OVER NORTHEAST WY AS WELL LATE TODAY. WITH PRECIPITABLE WATER  
VALUES 125 TO 150 PERCENT OF AVERAGE, THERE WILL BE LOCALLY HEAVY  
RAINFALL WITH STRONGER STORMS TODAY AND TONIGHT.  
 
THE TROUGH WILL CLOSE OFF OVER THE NORTHERN PLAINS WEDNESDAY AND  
WEDNESDAY NIGHT, WITH SCATTERED TO NUMEROUS SHOWERS AND  
THUNDERSTORMS EXPECTED IN MANY AREAS. THE EXCEPTIONS WILL LIKELY BE  
ACROSS WESTERN PARTS OF NORTHEAST WY AND FAR NORTHWEST SD. FORECAST  
INSTABILITY WILL BE SUFFICIENT FOR STRONGER STORMS FROM THE BLACK  
HILLS EASTWARD IN THE AFTERNOON/EARLY EVENING. HIGHS WILL  
GENERALLY BE IN THE 70S TO AROUND 80. ACTIVITY WILL SLOWLY END  
FROM WEST TO EAST LATE WEDNESDAY AND WEDNESDAY NIGHT. WILL KEEP  
SOME LOW CHANCES ACROSS SOUTH CENTRAL SD INTO THURSDAY. OTHERWISE,  
WARMER AND MAINLY DRY WEATHER IS EXPECTED THURSDAY INTO FRIDAY AS  
A SHORTWAVE RIDGE MOVES ACROSS THE REGION.  
 
ANOTHER FAIRLY STRONG UPPER LEVEL SYSTEM FOR THIS TIME OF YEAR WILL  
MOVE ACROSS THE AREA OVER THE WEEKEND, BRINGING GOOD CHANCES FOR  
SHOWERS AND STORMS SATURDAY AND SUNDAY. THERE IS POTENTIAL FOR SOME  
SEVERE STORMS AND HEAVIER RAINFALL ACROSS AT LEAST PORTIONS OF THE  
AREA. THAT SYSTEM WILL EXIT EARLY IN THE WEEK, WITH SOME DRIER  
WEATHER RETURNING FOR THE FIRST HALF OF THE WEEK.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)  
ISSUED AT 523 PM MDT TUE AUG 14 2018  
 
STRONG THUNDERSTORMS OVER NORTHEASTERN WYOMING WILL CONTINUE  
EASTWARD INTO WESTERN SOUTH DAKOTA THIS EVENING AND OVERNIGHT  
WITH LOCAL IFR CONDITIONS. OUTSIDE OF ANY STORMS, VFR CONDITIONS  
ARE EXPECTED THROUGH THE PERIOD.  
 

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

 
 

 
 
DISCUSSION...26  
AVIATION...10  
 
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