236  
FXUS65 KREV 201014  
AFDREV  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE RENO NV  
314 AM PDT SUN AUG 20 2017  
   
SYNOPSIS
 
 
SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE MAINLY ACROSS THE SIERRA  
THROUGH MONDAY WITH INCREASING COVERAGE EXPECTED FOR TUESDAYS.  
ISOLATED FLASH FLOODING AND GUSTY OUTFLOW WINDS ARE EXPECTED THROUGH  
MONDAY, BUT AN ENHANCED POTENTIAL FOR FLASH FLOODING IS EXPECTED BY  
TUESDAY AFTERNOON. TEMPERATURES WILL REMAIN A BIT ABOVE SEASON  
AVERAGES THROUGH THE WEEK WITH LIGHT AFTERNOON BREEZES EACH  
AFTERNOON.  
 

 
   
SHORT TERM
 
 
A SLOW MOVING CUT-OFF LOW OFF OF THE SOUTHERN CALIFORNIA COAST WILL  
PROVIDE A PERSISTENT PATTERN OF AFTERNOON SIERRA SHOWERS AND  
THUNDERSTORMS THROUGH MONDAY WITH INCREASED POTENTIAL AND COVERAGE  
EXPECTED ON TUESDAY. STORM FORMATION WILL BE FAVORED ALONG THE  
SIERRA, PARTICULARLY ACROSS NORTHERN MONO COUNTY THROUGH THE SOUTHERN  
TAHOE BASIN. EASTERLY STEERING FLOW SHOULD KEEP CELLS CONFINED TO  
THE SIERRA AND WEST SLOPES PARTICULARLY ON MONDAY WHEN THE FLOW  
INCREASES TO 20-25 KNOTS ROUGHLY SOUTH OF HWY 50.  
 
THESE STORMS WILL BE CAPABLE OF PRODUCING LOCALIZED HEAVY RAINFALL  
WITH A POTENTIAL FOR LOCALIZED FLASH FLOODING IN FAVORED AREAS SUCH  
AS STEEP TERRAIN AND RECENT WILDFIRE BURN AREAS. THUNDERSTORMS WILL  
ALSO BE CAPABLE OF PRODUCING SMALL PEA SIZE HAIL AND FREQUENT CLOUD  
TO GROUND LIGHTNING. THE INVERTED-V SOUNDINGS AND DRY BOUNDARY LAYER  
WILL HAVE POTENTIAL FOR STRONG GUSTY OUTFLOW WINDS UP TO 50 MPH.  
 
TUESDAY LOOKS TO BE THE MOST FAVORABLE DAY FOR STORMS DUE TO FLOW  
BECOMING LIGHTER AND SHIFTING SOUTHERLY. THIS WILL HELP TRANSPORT  
DEEP LAYER MOISTURE THROUGH THE AREA AND ALSO POSITION DIVERGENT  
FLOW ALOFT ACROSS NORTHERN NEVADA. THIS DEEPER MOISTURE, SLOWER  
STORM MOTIONS, AND FORCING COULD HELP DEVELOP LINES OF TRAINING  
STORMS WHICH WILL PROVIDE AN ELEVATED RISK FOR FLASH FLOODING ACROSS  
THE REGION. THOSE WITH OUTDOOR PLANS SHOULD CLOSELY MONITOR THE  
FORECAST AND CONSIDER ALTERNATE PLANS.  
 
ALSO, CLOSELY WATCHING THE POTENTIAL FOR SMOKE, HAZE, AND CLOUDS FOR  
THE ECLIPSE VIEWING ON MONDAY MORNING. MOST OF THE SMOKE AND HAZE IS  
ORIGINATING FROM FIRES THROUGH CALIFORNIA AND OREGON, SO THE GOOD  
NEWS HERE IS THAT AS THE LOW NEARS THE COAST, WE EXPECT EASTERLY  
FLOW TO STRENGTHEN THROUGH MONDAY WHICH WOULD AID IN KEEPING THE  
SMOKE AWAY FROM OUR REGION. CLOUD COVER ON THE OTHER HAND MAY BE A  
BIT MORE PROBLEMATIC, PARTICULARLY FOR AREAS SUCH AS SOUTHERN MONO  
AND MINERAL COUNTIES. MOISTURE WILL BEGIN TO SURGE NORTHWARD ON  
MONDAY, BUT THE BULK OF THE MID AND HIGH LEVEL CLOUDS IS LOOKING TO  
REMAIN ROUGHLY SOUTH OF HIGHWAY 50 THROUGH THE MORNING AND THEN  
INCREASE NORTHWARD THROUGH THE AFTERNOON. OVERALL PARTLY CLOUDY  
CONDITIONS WILL REMAIN IN THE FORECAST, WITH BETTER CHANCES FOR LESS  
CLOUDS NORTH OF HIGHWAY 50 THROUGH TO THE OREGON BORDER WHERE  
WILDFIRE SMOKE MAY BE MORE OF THE ISSUE THERE. FUENTES  
 
   
LONG TERM...WEDNESDAY AND BEYOND
 
 
THE LOW OFF THE SOUTHERN CALIFORNIA COAST BEGINS TO WEAKEN AND SHIFT  
INLAND ON WEDNESDAY IN RESPONSE TO A STRONGER AREA OF LOW PRESSURE  
MOVING THROUGH THE PACIFIC NORTHWEST. THIS WILL PROVIDE STEEPENING  
UPPER LEVEL LAPSE RATES, WITH A SECONDARY VORT MAX ROTATING THROUGH  
THE FLOW AIDING IN THUNDERSTORM DEVELOPMENT ON WEDNESDAY. DEEP  
MOISTURE REMAINS ACROSS THE REGION ON WEDNESDAY WITH PWATS IN THE  
0.8-1.0" RANGE. STEERING FLOW IS LIGHT, BUT WILL STRENGTHEN SLIGHTLY  
GOING INTO THE EVENING HOURS, TURNING FROM THE SOUTHEAST TO SOUTH  
SOUTHWEST. DESPITE THE INCREASE, FLOW IS LIGHT ENOUGH TO KEEP THE  
CONCERN FOR FLASH FLOODING ESPECIALLY OVER STEEP TERRAIN OR RECENT  
BURN SCARS. SOUNDINGS WOULD ALSO SUGGEST THE POTENTIAL FOR STRONG  
AND GUSTY OUTFLOW WINDS. THE ONE CAVEAT IS THAT IF WE END UP WITH  
EXTENSIVE CLOUD COVER WEDNESDAY MORNING FROM THE CONVECTIVE DEBRIS  
TUESDAY AND TUESDAY NIGHT, WHICH IS POSSIBLE GIVEN THE SITUATION, WE  
MAY NOT REALIZE THE FULL INSTABILITY POTENTIAL.  
 
BEHIND THE LOW, DRIER WESTERLY FLOW RETURNS TO THE REGION WITH  
INCREASED AFTERNOON BREEZES. THERE MAY BE ENOUGH LINGERING MOISTURE  
AND INSTABILITY ACROSS NORTH CENTRAL NEVADA EASTWARD FOR A STRAY  
THUNDERSTORMS TO FORM THURSDAY. BY FRIDAY AND INTO THE WEEKEND,  
STORM CHANCES LOOK MINIMAL IF NOT NON-EXISTENT AS MOST ENSEMBLE  
MEMBERS ARE INDICATING A LARGE RIDGE BUILDING ACROSS THE WEST. THIS  
IS LIKELY TO BRING HIGH TEMPERATURES 5-8 DEGREES ABOVE NORMAL BY THE  
WEEKEND. -DAWN  
 

 
   
AVIATION
 
 
SCATTERED SHOWERS AND THUNDERSTORMS ARE MOST LIKELY OVER THE SIERRA  
AFTER 21Z WITH ISOLATED STORMS ACROSS WESTERN NEVADA, MAINLY NEAR  
AND SOUTH OF I-80 AFTER 22Z. THE EASTERLY FLOW WILL HELP STORMS THAT  
DO DEVELOP SLOWLY DRIFT WESTWARD, HOWEVER OUTFLOW BOUNDARIES CAN  
CAUSE STORMS TO DEVIATE FROM THE OVERALL FLOW. STORMS WILL DISSIPATE  
BETWEEN 03-05Z.  
 
BRIEF PERIODS OF HEAVY RAIN, GUSTY AND ERRATIC OUTFLOW WINDS CAN BE  
EXPECTED WITH LESSER CHANCES FOR A HAIL THREAT. LOCALIZED TERRAIN  
OBSCURATION IS A CONCERN ALONG WITH SHORT PERIODS OF MVFR-IFR  
CONDITIONS UNDER THE RAIN CORE OF THE STORMS.  
 
CHANCES AND MOST LIKELY TIMING FOR A THUNDERSTORM TO IMPACT OR BE IN  
THE VICINITY OF A TERMINAL SITE:  
 
KRNO AND KCXP: 15 PERCENT, 22Z-04Z  
KTRK AND KTVL: 25 PERCENT, 21Z-04Z  
KMMH AND KBAN: 35 PERCENT, 21Z-04Z  
KNFL AND KLOL: 15 PERCENT, 23Z-04Z  
 
THUNDERSTORM CHANCES AND COVERAGE WILL INCREASE THE FIRST HALF OF  
THE WEEK.  
 
OTHERWISE, EXPECT VFR CONDITIONS WITH AFTERNOON WESTERLY BREEZES OF  
8-12 KTS. EARLY MORNING PATCHY FOG REMAINS POSSIBLE AROUND KTRK IF  
THE AIRFIELD RECEIVES RAINFALL. FOG STARTED TO FORM EARLY THIS  
MORNING AT KTRK, BUT INCREASING CLOUDS HELPED TO LIMIT DEVELOPMENT.  
-DAWN  
 

 
   
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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