456  
FXUS63 KUNR 232327  
AFDUNR  
 
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY  
NATIONAL WEATHER SERVICE RAPID CITY SD  
527 PM MDT TUE JUL 23 2019  
   
DISCUSSION
 
(THIS EVENING THROUGH TUESDAY)  
ISSUED AT 139 PM MDT TUE JUL 23 2019  
 
THE LATEST GOES-16 SATELLITE IMAGES AND RAP ANALYSES INDICATED A  
PRONOUNCED UPPER RIDGE OVER THE ROCKIES WITH MOSTLY SUNNY SKIES  
ACROSS THE CWA. SOME CUMULUS WERE FORMING OVER THE BLKHLS IN THE  
1000 J/KG MLCAPE AIR MASS, BUT THE -100 J/KG MLCIN AND LACK OF  
SYNOPTIC FORCING WERE KEEPING THINGS IN CHECK. A FEW STORMS WERE  
TRYING TO FORM OVER THE BIG HORN MOUNTAINS, BUT THESE WERE NOT  
MAKING IT OUT OVER THE PLAINS. THUS, THINK NERN WY SHOULD STAY  
FREE OF STORMS TODAY GIVEN MARGINAL LAPSE RATES AND MOISTURE. A  
SOUTHERLY LOW-LEVEL JET LATER TONIGHT SHOULD FOCUS ANY STORMS TO  
THE NORTHWEST OF THE CWA.  
 
THE MODELS ARE IN OVERALL GOOD AGREEMENT THROUGH AT LEAST 84  
HOURS, WITH THE RIDGE MOVING EAST AND BREAKING DOWN ON WEDNESDAY,  
FOLLOWED BY FROPA WEDNESDAY NIGHT AND THURSDAY MORNING, WITH ONLY  
MINIMAL THUNDERSTORM CHANCES THURSDAY AND FRIDAY. A PLUME OF STEEP  
LAPSE RATES AND PWS OF 125-150 PERCENT OF AVERAGE WILL MOVE ACROSS  
THE AREA LATER WEDNESDAY, RESULTING IN 2000-3000 J/KG OF SBCAPE  
FOR MUCH OF THE CWA. DEEP-LAYER SHEAR WILL BE FAVORABLE FOR SOME  
SUPERCELLS, AND HIGH CLOUD BASES SHOULD FAVOR STORMS WITH GUSTY  
WINDS. COVERAGE MAY BE SOMEWHAT LIMITED, SO THE SPC MARGINAL RISK  
LOOKS GOOD AT THIS TIME.  
 
FROPA SHOULD OCCUR FROM 06-18Z ON THURSDAY, WHICH SHOULD PRODUCE  
SOME GUSTY NORTHWEST WINDS AT LEAST EARLY IN THE DAY ON THURSDAY.  
A FEW STORMS MAY REDEVELOP OVER THE BLKHLS, AND IF THE BOUNDARY  
HANGS UP OVER SCNTRL SD IT IS POSSIBLE THAT A FEW STORMS COULD  
FIRE THERE AS WELL. OTHERWISE, FLOW WILL BE QUASI-ZONAL THROUGH  
FRIDAY WITH LIMITED MOISTURE AND INSTABILITY, SO THUNDERSTORMS  
WILL BE AT A MINIMUM.  
 
WEST-NORTHWEST UPPER FLOW SHOULD PERSIST SATURDAY THROUGH NEXT  
TUESDAY, WITH A MORE NOTABLE WAVE AND ANOTHER FROPA LATER SATURDAY  
AND SATURDAY NIGHT. THIS SHOULD RESULT IN ADDITIONAL SCATTERED  
THUNDERSTORMS ACROSS THE CWA, FOLLOWED BY A RELATIVE LULL IN  
STORMS SUNDAY AND MONDAY. TEMPERATURES WILL CONTINUE TO BE NEAR  
AVERAGE, BUT THE HUMIDITY WILL BE HIGHER THAN AVERAGE.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)  
ISSUED AT 526 PM MDT TUE JUL 23 2019  
 
MOSTLY VFR CONDITIONS WILL PREVAIL THROUGH WEDNESDAY MORNING. TSRA  
OVER THE BLACK HILLS WITH LOCAL IFR CONDITIONS WILL END EARLY THIS  
EVENING. ADDITIONAL STORMS WILL DEVELOP WEDNESDAY AFTERNOON WITH  
LOCAL MVFR CONDITIONS.  
 

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

 
 

 
 
DISCUSSION...BUNKERS  
AVIATION...HELGESON  
 
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