108  
FXUS63 KUNR 032322  
AFDUNR  
 
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY  
NATIONAL WEATHER SERVICE RAPID CITY SD  
522 PM MDT FRI JUL 3 2020  
   
DISCUSSION
 
(THIS EVENING THROUGH FRIDAY)  
ISSUED AT 1234 PM MDT FRI JUL 3 2020  
 
PAC NW UPPER TROUGH WILL REMAIN ANCHORED IN THE PERIOD,  
SUPPORTING ACTIVE SW FLOW OVER THE REGION AT TIMES, AS DEEP  
MOISTURE WAVERS OVER THE REGION. WEAK SUBSIDENCE ONGOING ACROSS  
THE REGION TODAY BEHIND A DEPARTING IMPULSE. MOISTURE HAS BEEN  
DEPLETED SOME FROM YESTERDAYS IMPULSE, BUT STILL ENOUGH AROUND  
TO SUPPORT 1000-2000 J/KG OF ML CAPE, HIGHEST IN NW SD WHERE THE  
STRONGEST CAPPING IS IN PLACE. ANOTHER SHORTWAVE TROUGH WILL  
ROTATE TOWARD THE REGION FROM THE FOUR CORNERS, SUPPORTING ISOLD  
SHOWERS AND THUNDERSTORMS BY LATE AFTERNOON EVENING, MAINLY ACROSS  
THE SW THIRD WHERE DIURNAL HEATING WILL SUPPORT THE WEAKEST CIN.  
OTHER ISOLATED TS WILL BE POSSIBLE OVER THE NORTHERN AND CENTRAL  
BLACK HILLS, MAINLY THE HIGHER ELEVATIONS THIS AFTERNOON.  
AFOREMENTIONED SUFFICIENT CAPE WILL BE IN PLACE FOR A FEW STRONGER  
CELLS, HOWEVER DEEP LAYER SHEAR WILL BE LACKING. THIS WILL SETUP  
A PULSE ENVIRONMENT WITH COLLAPSING CORES CAPABLE OF PRODUCING  
GUSTY WINDS AND SMALL HAIL, POTENTIALLY OVER 50 KNOTS IN SOME  
AREAS GIVEN CLASSIC INVERTED V PROFILES. MAIN FORCING COMPONENT  
AND OVERLAP OF INSTABILITY AND SHEAR WILL REMAIN WELL NW OF THE FA  
IN MT AND ND WHERE THE BEST SEVERE THREAT WILL BE. HOWEVER, THE  
SOUTHERN PERIPHERY OF AN EXPECTED TS COMPLEX MAY CLIP THE FAR NW  
ZONES BEING DRIVEN BY A LLJ OVERNIGHT IF CAPPING CAN BE OVERCOME.  
SOUTHERN FA ACTIVITY WILL PUSH NE AND WANE THIS EVENING, WITH ONLY  
THE FAR NORTH EXPECTING ANY ACTIVITY AFTER MIDNIGHT. IMPULSE  
DRIVEN LLJ WILL SUPPORT A BREEZY NIGHT INVOF OF THE BLACK HILLS  
TONIGHT WITH FAVORED DOWNSLOPE AREAS SEEING 20 TO 30 MPH WINDS  
POTENTIALLY AT TIMES, ESP THE NORTHERN FOOTHILLS. MORE OF THE SAME  
TOMORROW AND SUNDAY AS ACTIVE SW FLOW SUPPORTS ANOTHER SET OF  
IMPULSES WHICH WILL TIME WITH DIURNAL INSTABILITY AND A SFC TROUGH  
INVOF OF THE REGION, COUPLED WITH TYPICAL BLACK HILLS DRIVEN  
EARLY AFTERNOON CONVECTION IN A CONDITIONALLY UNSTABLE  
ENVIRONMENT. DEEP LAYER BULK SHEAR WILL BE A LITTLE BETTER EACH  
DAY, POTENTIALLY SUPPORTING AN INCREASED SEVERE THREAT WITH TIME  
GIVEN SUFFICIENT CAPE. OTHERWISE, CONVECTION WILL BE POSSIBLE  
NEARLY EVERY DAY IN THE REMAINDER OF THE PERIOD AS A SFC TROUGH  
WAVERS OVER THE REGION IN UNSETTLED SW FLOW WITH SEASONALLY WARM  
TEMPS.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)  
ISSUED AT 520 PM MDT FRI JUL 3 2020  
 
MAINLY VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD. THE  
EXCEPTION WILL BE THUNDERSTORMS THAT DEVELOP THIS AFTERNOON AND  
EVENING, RESULTING IN LOCAL MVFR CONDITIONS AND GUSTY/ERRATIC  
WINDS. MORE THUNDERSTORMS WILL BE POSSIBLE SATURDAY AFTERNOON AND  
EVENING ACROSS NORTHEAST WY AND WESTERN SD.  
 

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

 
 

 
 
DISCUSSION...JC  
AVIATION...13  
 
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