352  
FXUS63 KUNR 251113  
AFDUNR  
 
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY  
NATIONAL WEATHER SERVICE RAPID CITY SD  
513 AM MDT TUE JUL 25 2017  
   
DISCUSSION
 
(TODAY THROUGH MONDAY)  
ISSUED AT 312 AM MDT TUE JUL 25 2017  
 
09Z VAPOR SHOWS AN UPPER LOW OVER EASTERN SASKATCHEWAN/WESTERN  
MANITOBA, A SMALL WAVE MOVING THROUGH NORTHWESTERN SOUTH DAKOTA,  
AND SOUTHWEST FLOW ACROSS THE FORECAST AREA. AT THE SURFACE, A  
BOUNDARY IS DRAPED ACROSS NORTHWEST SOUTH DAKOTA WITH ANOTHER  
BOUNDARY ALONG THE SOUTH DAKOTA/NEBRASKA BORDER. LATEST RADAR  
IMAGERY HAS CONVECTION ACROSS SOUTHERN MONTANA, SOUTHWESTERN NORTH  
DAKOTA, AND NORTHWESTERN SOUTH DAKOTA.  
 
SHOWERS AND STORMS ACROSS NORTHWESTERN SOUTH DAKOTA WILL DISSIPATE  
THIS MORNING. HOWEVER, ADDITIONAL STORMS ARE EXPECTED AFTER 18Z  
TODAY. THE MULTIPLE SURFACE BOUNDARIES COMBINED WITH A WELL DEFINED  
SHORTWAVE, WILL LEAD TO WIDESPREAD SHOWERS AND STORMS TONIGHT. BY  
00Z PW VALUES WILL RISE TO 150-200% OF NORMAL AS MOISTURE POOLS  
ALONG THE SOUTHWESTERN BOUNDARY CREATING 2000 J/KG MLCAPE AND LITTLE  
MLCIN. COULD SEE SOME TRAINING STORMS AND/OR LOCALLY HEAVY RAIN,  
ESPECIALLY WITH LIGHT STEERING WINDS. 0-6KM BULK SHEAR WILL BE  
SUFFICIENT FOR ISOLATED SEVERE STORMS THIS AFTERNOON AND EVENING  
WITH A DECENT CHANCE OF A MCS OVERNIGHT FOR SOUTH CENTRAL SOUTH  
DAKOTA.  
 
ON WEDNESDAY AND THURSDAY, THE UPPER RIDGE WILL BEGIN TO REBUILD  
OVER THE WESTERN CONUS. TEMPERATURES WILL BE SLIGHTLY COOLER WITH  
THE CHANCE FOR SHOWERS AND STORMS, MAINLY OVER NORTHEASTERN WYOMING  
AND FAR WESTERN SOUTH DAKOTA.  
 
FRIDAY THROUGH SUNDAY, THE UPPER RIDGE WILL BUILD OVER THE HIGH  
PLAINS WITH WARMER TEMPERATURES AND SMALL CHANCES FOR THUNDERSTORMS.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)  
ISSUED AT 512 AM MDT TUE JUL 25 2017  
 
A FEW THUNDERSTORMS WILL GRADUALLY MOVE OUT OF NORTHWESTERN SD  
THIS MORNING. MORE WIDESPREAD THUNDERSTORMS ARE EXPECTED TO  
DEVELOP ACROSS MUCH OF THE AREA THIS AFTERNOON AND OVERNIGHT. MVFR  
CONDITIONS WILL BE POSSIBLE IN STORMS, OTHERWISE VFR CONDITIONS  
ARE EXPECTED.  
 

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

 
 

 
 
DISCUSSION...MLS  
AVIATION...POJORLIE  
 
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