608  
FXUS63 KUNR 090446  
AFDUNR  
 
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY  
NATIONAL WEATHER SERVICE RAPID CITY SD  
1046 PM MDT TUE JUL 8 2025  
   
KEY MESSAGES  
 
- ISOLATED TO SCATTERED THUNDERSTORMS CONTINUE OVER THE NEXT FEW  
DAYS, SOME OF WHICH COULD BE STRONG TO SEVERE, ESPECIALLY  
WEDNESDAY AFTERNOON AND EVENING ACROSS NORTHWESTERN SOUTH DAKOTA.  
 
- HOTTER TEMPERATURES PERSIST THROUGH TOMORROW, WITH MILDER  
CONDITIONS EXPECTED BY FRIDAY AS A SERIES OF DISTURBANCES  
CROSSES THE REGION.  
 
 
   
DISCUSSION  
(THIS EVENING THROUGH TUESDAY)  
ISSUED AT 118 PM MDT TUE JUL 8 2025  
 
WATER VAPOR IMAGERY THIS AFTERNOON PRIMARILY REVEALS A BUILDING  
RIDGE OVER THE WESTERN HALF OF THE CONUS. HOWEVER, A PAIR OF  
EMBEDDED SHORTWAVE DISTURBANCES/VORTICITY MAXIMA CAN BE IDENTIFIED  
NEAR THE GREAT BASIN AND OFF THE NORTHWESTERN CA COAST. THESE WILL  
BECOME IMPACTFUL FOR WEATHER CLOSE TO HOME OVER THE NEXT 24 TO 48  
HOURS. ANOTHER, MORE SUBTLE DISTURBANCE OVER THE NORTH CENTRAL CONUS-  
-ALONG WITH DIURNAL TERRAIN-DRIVEN CONVERGENCE--MAY BE CONTRIBUTING  
TO CONVECTIVE INITIATION OVER THE BLACK HILLS AT THIS HOUR. LATEST  
SPC MESOANALYSIS REVEALS MLCAPE OF 1500-2500 J/KG PAIRED WITH  
EFFECTIVE BULK SHEAR MAGNITUDES OF 20-25 KT, WITH THE CAVEAT THAT  
THE MESOANALYSIS IS LIKELY NOT REPRESENTING LOCAL EFFECTS ON SHEAR  
OWING TO THE BLACK HILLS. WOULD NOT BE SURPRISED TO SEE FURTHER  
INTENSIFICATION OF THESE STORMS WITH AN OUTSIDE CHANCE AT MARGINALLY  
SEVERE HAIL IF A PERSISTENT ROTATING UPDRAFT CAN EMERGE.  
 
TOMORROW, MIDLEVEL RIDGING CONTINUES TO SHIFT EASTWARD, WITH THE  
RIDGE AXIS EXTENDING FROM THE FOUR CORNERS NORTHEASTWARD THRU THE  
NORTHERN ROCKIES AND INTO SOUTH CENTRAL CN. ATOP THE RIDGE, THE  
SHORTWAVE CURRENTLY OVER THE GREAT BASIN REGION WILL RAPIDLY  
APPROACH THE AREA EARLY TOMORROW, CROSSING THE REGION FROM THE  
AFTERNOON INTO THE EVENING AFTER BEING CONVECTIVELY ENHANCED TODAY  
INTO TONIGHT. THE WARMING/EXPANDING LOW-LEVEL THERMAL RIDGE WILL  
LEAD TO DECREASING BOUNDARY LAYER MOISTURE/INSTABILITY ACROSS OUR  
WEST/SOUTHWEST BY EARLY AFTERNOON, BUT FARTHER NORTH AND EAST,  
SBCAPE OF 1500-2500 J/KG PAIRED WITH DEEP-LAYER BULK SHEAR  
MAGNITUDES OF 25 TO 35 KT WILL BE SUFFICIENT TO SUPPORT ROBUST  
MULTICELLULAR OR SUPERCELLULAR UPDRAFTS. WEAK LOW-LEVEL SHEAR BUT  
RELATIVELY STRONG MIDLEVEL SHEAR COUPLED WITH AMPLE DCAPE, CAPE  
WITHIN THE HAIL GROWTH ZONE, AND MIDLEVEL LAPSE RATES (8+ C/KM)  
SHOULD SUPPORT THE POTENTIAL FOR BOTH LARGE/SIGNIFICANT HAIL AND  
DAMAGING WINDS, WITH THE PREDOMINANT HAZARD BEING DEPENDENT UPON  
MODE.  
 
IN THE WAKE OF THE WAVE TOMORROW AFTERNOON/EVENING, SHORTWAVE  
RIDGING MAY BRIEFLY OVERSPREAD THE REGION, LEADING TO A BRIEF  
REPRIEVE OF CONVECTION. THEREAFTER, A MORE ROBUST  
SHORTWAVE/VORTICITY MAXIMUM APPROACHES THE REGION, WHICH WILL BRING  
ANOTHER ROUND OF THUNDERSTORMS TO THE AREA. THE TIMING OF THE WAVE  
CONTINUES TO LOOK A BIT EARLY FOR PEAK HEATING, AT LEAST ACROSS OUR  
WEST. FARTHER EAST, THE ENVIRONMENT MAY HAVE SUFFICIENT TIME TO  
DESTABILIZE, WITH LREF MEAN SBCAPE REACHING 1000-2000 J/KG FROM WEST  
TO EAST BY 18Z. REGARDLESS OF BUOYANCY, DEEP-LAYER SHEAR VECTOR  
MAGNITUDES ON THE LARGE SCALE REMAIN PALTRY (LREF MEAN 0-6 KM  
BULK SHEAR MAGNITUDES OF 15-25 KT AREAWIDE). AS SUCH, CONVECTION  
MAY BE LARGELY DISORGANIZED, WITH MARGINAL HAIL AND STRONG WIND  
GUSTS THE PRIMARY CONCERNS. HOWEVER, ANY AREAS OF LOCALLY ENHANCED  
SHEAR, PARTICULARLY IN THE VICINITY OF ANY LINGERING BOUNDARIES  
FROM CONVECTION WEDNESDAY AFTERNOON THROUGH THE OVERNIGHT, COULD  
PROMOTE MORE ROBUST, ORGANIZED CONVECTION WITH INCREASED SEVERE  
POTENTIAL.  
 
A MORE AMPLIFIED, BROADER TROF CROSSES THE REGION THURSDAY NIGHT  
INTO FRIDAY, BRINGING MILDER TEMPERATURES AND BREEZY NORTHWEST  
WINDS. LINGERING LOW-LEVEL TO MIDLEVEL MOISTURE MAY SUPPORT  
ADDITIONAL SHOWER ACTIVITY, BUT DECREASING MUCAPE (<500 J/KG) SHOULD  
LIMIT MUCH IN THE WAY OF THUNDERSTORM ACTIVITY. DEEP RIDGING RETURNS  
ON SATURDAY, BRINGING WARMER AND DRIER CONDITIONS TO START THE  
WEEKEND.  
 
 
   
AVIATION  
(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)  
ISSUED AT 1045 PM MDT TUE JUL 8 2025  
 
VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. THE EXCEPTION  
WOULD BE MVFR CONDITIONS WITH ANY STORMS THAT DEVELOP WEDNESDAY  
AFTERNOON.  
 
 
   
UNR WATCHES/WARNINGS/ADVISORIES  
 
SD...NONE.  
WY...NONE.  
 
 
 
 
DISCUSSION/KEY MESSAGES...SHERBURN  
AVIATION...13  
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