367  
FXUS63 KUNR 062307  
AFDUNR  
 
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY  
NATIONAL WEATHER SERVICE RAPID CITY SD  
507 PM MDT TUE JUN 6 2023  
   
DISCUSSION
 
(THIS EVENING THROUGH TUESDAY)  
ISSUED AT 214 PM MDT TUE JUN 6 2023  
 
LITTLE CHANGE IN THE FORECAST OVER THE PAST 12-24 HOURS. CONDITIONS  
THROUGH TOMORROW WILL DEVIATE ONLY MODESTLY FROM PERSISTENCE.  
INCREASING COVERAGE OF THUNDERSTORMS AND A PERIOD OF NEAR TO  
SLIGHTLY BELOW AVERAGE TEMPERATURES CONTINUE TO LOOK LIKELY LATE  
THIS WEEK INTO EARLY IN THE WEEKEND. GIVEN WEAK FLOW/SHEAR AND  
INCREASING PWATS, LOCALLY HEAVY RAINFALL CANNOT BE RULED OUT DURING  
THIS TIME. MORE ACTIVE PATTERN POSSIBLE EARLY NEXT WEEK, BUT  
CONFIDENCE IS LOW IN TIMING OF ANY MIDLEVEL/UPPER-LEVEL FLOW  
TRANSITION GIVEN PSEUDO-BLOCKING PATTERN OVER MUCH OF THE CONUS.  
 
WATER VAPOR IMAGERY THIS AFTERNOON SHOWS UPPER RIDGING IN PLACE OVER  
THE NORTH CENTRAL CONUS, WITH AN UPPER HIGH CENTERED NEAR THE CN/US  
BORDER TO OUR EAST. COMPARED TO YESTERDAY, COVERAGE OF CU IS LIMITED  
AT THIS HOUR, WITH SHALLOW CU (PER VIS/IR/CLOUD PHASE DISTINCTION  
RGB) LIMITED TO THE NORTHERN BLACK HILLS AND FROM THE SANDHILLS  
NORTHWARD THROUGH CENTRAL SD. MORE ROBUST CU AND SOME THUNDERSTORMS  
ARE EVIDENT OVER THE BIGHORNS. LIKE YESTERDAY, SURFACE FEATURES OVER  
THE REGION REMAIN RELATIVELY ILL-DEFINED, THOUGH A SURFACE TROF WAS  
RECENTLY ANALYZED FROM EASTERN MT SOUTHWARD INTO THE LEE OF THE  
BIGHORNS. GENERALLY LOWER PRESSURES TO THE WEST AND HIGHER PRESSURES  
TO THE EAST CONTINUE TO SUPPORT LARGELY SOUTHERLY/SOUTHEASTERLY FLOW  
AWAY FROM THE BLACK HILLS, WITH TERRAIN-DRIVEN FLOW CLOSER TO THE  
HILLS. ABOVE AVERAGE TEMPERATURES CONTINUE, WITH EARLY AFTERNOON  
TEMPERATURES IN THE 70S TO 80S AREA-WIDE.  
 
CONVECTIVE COVERAGE MAY INCREASE OVER CAMPBELL COUNTY LATER THIS  
AFTERNOON IF OUTFLOW CAN EMERGE FROM ONGOING STORMS OVER THE  
BIGHORNS OR IF MOISTURE CONVERGENCE CAN INCREASE IN THE VICINITY OF  
THE AFOREMENTIONED WEAK TROF. FOR NOW, THIS DOES NOT LOOK PROBABLE.  
EITHER WAY, THE ENVIRONMENT CONTINUES TO LOOK UNSUPPORTIVE OF  
CONVECTIVE ORGANIZATION, WITH MLCAPE < 500 J/KG AND PALTRY DEEP-  
LAYER SHEAR. ANY SHOWER/STORM ACTIVITY SHOULD DIMINISH AFTER SUNSET.  
 
OVER THE NEXT FEW DAYS, MIDLEVEL RIDGING OVER THE CENTRAL CONUS WILL  
BECOME INCREASINGLY SQUEEZED BY A SLOWLY PROGRESSING TROF OVER THE  
SOUTHWESTERN CONUS AND A BROADENING LONGWAVE TROF OVER THE EASTERN  
CONUS. IN TIME, THE RIDGE IS PROJECTED TO BECOME RATHER ELONGATED AS  
IT SHIFTS SLIGHTLY WESTWARD, EXTENDING FROM THE SOUTHERN PLAINS  
NORTHWESTWARD THROUGH AB/SK. AS A SHORTWAVE APPROACHES IN THE  
BROADER CYCLONIC FLOW TO OUR EAST, PWATS WILL GRADUALLY INCREASE  
THROUGH FRIDAY, CLIMBING TO 150-175% OF NORMAL IN SPOTS. MEANWHILE,  
INCREASING DEFORMATION/FGEN AND MOISTURE CONVERGENCE ALONG THE  
EASTERN PERIPHERY OF THE RIDGE SHOULD LEAD TO A NW-SE ORIENTED ZONE  
OF FAVORABLE ASCENT ACROSS THE AREA. IN SHORT, EXPECTING AN INCREASE  
IN COVERAGE OF SHOWERS/STORMS IN THE FRIDAY TO SATURDAY TIME FRAME.  
WEAK FLOW ALOFT WILL PROMOTE SLOW-MOVING STORMS, POTENTIALLY LEADING  
TO LOCALLY HEAVY RAINFALL. HOWEVER, SOILS SHOULD BE CAPABLE OF  
ABSORBING ANY MOISTURE THAT FALLS. A BACKDOOR COLD FRONT ASSOCIATED  
WITH THE AFOREMENTIONED SHORTWAVE SHOULD BRING SLIGHTLY COOLER TEMPS  
FOR THE WEEKEND--LIKELY NEAR OR SLIGHTLY BELOW AVERAGE. BEYOND  
SUNDAY, FORECAST CONFIDENCE DECREASES OWING TO DIVERGING MODEL  
GUIDANCE.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)  
ISSUED AT 506 PM MDT TUE JUN 6 2023  
 
VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD. THE ONLY EXCEPTION  
WILL BE WITH ISOLATED THUNDERSTORMS EARLY THIS EVENING OVER  
NORTHEAST WY, PRIMARILY WEST OF THE KGCC TERMINAL.  
 

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

 
 

 
 
DISCUSSION...SHERBURN  
AVIATION...JC  
 
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