662  
FXUS65 KREV 212212  
AFDREV  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE RENO NV  
312 PM PDT MON AUG 21 2017  
   
SYNOPSIS
 
 
THUNDERSTORMS THIS EVENING FOR THE SIERRA AND WESTERN NEVADA WILL  
BRING LOCALIZED HEAVY RAINFALL AND GUSTY OUTFLOW WINDS. THE  
POTENTIAL FOR FLASH FLOODING INCREASES TUESDAY WITH SCATTERED  
THUNDERSTORMS EXPECTED. DRIER WEATHER RETURNS LATE WEEK.  
TEMPERATURES WILL REMAIN NEAR OR SLIGHTLY ABOVE AVERAGE THROUGH  
THE WEEK.  
 

 
   
SHORT TERM
 
 
INCREASED SHOWER COVERAGE TO SCATTERED AND ADDED A LOW CHANCE FOR  
THUNDERSTORMS LATE TONIGHT AND TUESDAY MORNING IN EASTERN CALIFORNIA  
FROM ABOUT PORTOLA SOUTH, OTHERWISE NO MAJOR CHANGES TO THE FORECAST.  
 
LOOKING AT SATELLITE IMAGERY, EASTERLY FLOW ALOFT AROUND THE UPPER  
LOW CENTERED NEAR THE CENTRAL/SOUTHERN CA COAST IS QUITE EVIDENT  
BASED ON THE MOTION OF CLOUDS. FORCING/CONVERGENCE FOR CONVECTION  
IS STRONGEST JUST WEST OF THE CREST BASED ON THE THUNDERSTORMS  
THERE AND ONLY WEAK DEVELOPMENT EAST OF THE CREST SO FAR. AS WE  
GO LATER INTO THE AFTERNOON AND ESPECIALLY EARLY EVENING, A FEW  
SHOWERS AND THUNDERSTORMS COULD FORM ALONG AND JUST EAST OF THE  
CREST DUE TO LOCAL BOUNDARY INTERACTIONS AND CONVERGENCE FROM A  
POSSIBLE WEAK WESTERLY WIND PUSH IN THE NORTHERN SIERRA. FOR  
WESTERN NV, ANY ACTIVITY SHOULD REMAIN ISOLATED AND CONFINED TO  
SOUTH OF HIGHWAY 50. STORM STRENGTHS LOOK SIMILAR TO THE LAST FEW  
DAYS, WITH GUSTY WINDS 30-40 MPH AND BRIEF MODERATE-HEAVY RAINFALL.  
A COUPLE STRONGER STORMS ARE ALWAYS POSSIBLE AND COULD BRING HAIL  
TO 1/2" IN DIAMETER OR SLIGHTLY LARGER IN VERY ISOLATED  
LOCATIONS.  
 
LATE TONIGHT, SIMULATIONS ARE INDICATING THE POSSIBILITY FOR  
NOCTURNAL SHOWERS AND POSSIBLY EVEN A FEW THUNDERSTORMS SOUTH OF  
INTERSTATE 80 AS A DISTURBANCE (CURRENTLY NEAR THE LOWER COLORADO  
RIVER VALLEY) WORKS AROUND THE EAST SIDE OF THE AFOREMENTIONED  
UPPER LOW. ELEVATED INSTABILITIES VARY AMONG SIMULATIONS WITH MORE  
CHANCE FOR A FEW THUNDERSTORMS IN THE NAM THAN IN THE GFS. WITH  
CLOUDS ON THE INCREASE TONIGHT, LOW TEMPERATURES ARE EXPECTED TO  
BE MILDER BY 4 TO 8 DEGREES THAN THIS MORNING IN MANY LOCATIONS.  
 
TUESDAY IS STILL LOOKING LIKE THE BEST DAY FOR THUNDERSTORM  
COVERAGE AS THE REGION GETS INTO A FAVORABLE AREA OF DIVERGENCE  
ALOFT AHEAD OF THE UPPER LOW. DAYTIME HEATING SHOULD FIRE OFF  
SCATTERED THUNDERSTORMS IN THE EASTERN SIERRA AND FOR WESTERN  
NEVADA BY EARLY TO MID AFTERNOON. PWATS REMAIN ELEVATED IN THE  
0.7" TO 0.95" RANGE AND STORM MOTIONS SHOULD REMAIN MOSTLY AROUND  
10 MPH OR LESS SO LOCALIZED HEAVY RAINFALL REMAINS LIKELY. FLASH  
FLOODING IS NOT OUT OF THE QUESTION IF HEAVY, PERSISTENT RAIN  
FALLS ON BURN SCARS OR AREAS WHERE VEGETATION HAS BEEN STRIPPED.  
 
WEDNESDAY WILL FEATURE ONE MORE DAY OF ISOLATED TO SCATTERED  
SHOWERS AND THUNDERSTORMS WITH LOCALIZED HEAVY RAINFALL (SLOW  
STORM MOTIONS) BEFORE DRIER, MORE STABLE SOUTHWEST FLOW ALOFT  
INVADES FOR LATE WEDNESDAY NIGHT AND THURSDAY.  
   
LONG TERM...FRIDAY THROUGH MONDAY
 
 
DRY WEATHER IS EXPECTED FRIDAY THROUGH AT LEAST SATURDAY BEFORE  
FLOW ALOFT RETURNS TO SOUTHERLY AS HIGH PRESSURE BUILDS OVER THE  
GREAT BASIN. HIGH TEMPERATURES SHOULD RISE TO AT LEAST 4 TO 8  
DEGREES ABOVE AVERAGE WITH SOLID 90S FOR THE LOWER VALLEYS FOR THE  
WEEKEND. THE SOUTHERLY FLOW AND ABOVE AVERAGE TEMPERATURES SHOULD  
ALLOW INSTABILITY TO BEGIN BUILDING OVER THE HIGHER SIERRA  
TERRAIN, WITH SOME CUMULUS BUILDUPS POSSIBLE BY LATER IN THE  
WEEKEND. WITH LOW POTENTIAL COVERAGE, THUNDERSTORMS WERE LEFT OUT  
OF THE FORECAST FOR EARLY NEXT WEEK. -SNYDER  
 

 
   
AVIATION
 
 
CHANCES AND MOST LIKELY TIMING FOR A THUNDERSTORM TO IMPACT OR BE IN  
THE VICINITY OF A TERMINAL SITE THROUGH 03-04Z THIS EVENING:  
 
KRNO AND KCXP: 5%  
KTVL: 30-35%  
KTRK: 15%  
KMMH: 5%  
KNFL AND KLOL: 2%  
 
THUNDERSTORMS THIS EVENING COULD BRING OUTFLOW WINDS TO 30 KTS,  
BRIEF HEAVY RAINFALL WITH HIGHER TERRAIN OBSCURATION, AND A FEW  
LIGHTNING STRIKES.  
 
THE GREATEST THUNDERSTORM COVERAGE IS ANTICIPATED TO BE ON TUESDAY  
AFTERNOON AND EVENING WITH ADDITIONAL STORMS POSSIBLE ON WEDNESDAY.  
STORM CHANCES WILL WANE THURSDAY INTO THE WEEKEND WITH TYPICAL  
WESTERLY AFTERNOON BREEZES. CONDITIONS WILL BE VFR OUTSIDE OF  
THUNDERSTORMS. EARLY MORNING PATCHY FOG REMAINS POSSIBLE AROUND  
KTRK IF THE AIRFIELD RECEIVES RAINFALL. DAWN/SNYDER  
 

 
   
REV WATCHES/WARNINGS/ADVISORIES
 
 
NV...NONE.  
CA...NONE.  

 
 

 
 
FOR MORE INFORMATION FROM THE NATIONAL WEATHER SERVICE VISIT...  
HTTP://WEATHER.GOV/RENO  
 
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