486  
FXUS66 KHNX 201102  
AFDHNX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD CA  
402 AM PDT SUN AUG 20 2017  
 
   
SYNOPSIS
 
AN AREA OF LOW PRESSURE WILL REMAIN ANCHORED OFF THE  
SOUTHERN CALIFORNIA COAST THROUGH TUESDAY AND BRING A CHANCE OF  
MAINLY AFTERNOON SHOWERS AND THUNDERSTORMS TO THE SIERRA. THE  
THREAT OF THUNDERSTORMS WILL EXTEND INTO THE KERN COUNTY MOUNTAINS  
AND DESERT AND THE SIERRA FOOTHILLS BY EARLY NEXT WEEK WITH THE  
ARRIVAL OF MONSOONAL MOISTURE.  
 

 
   
DISCUSSION
 
SOME MID LEVEL CLOUDS REMAIN OVER THE DISTRICT FROM  
AFTERNOON CONVECTIVE ACTIVITY. OTHERWISE CLEAR SKIES PREVAILING  
THIS MORNING. TEMPERATURES RUNNING COOLER ACROSS THE CENTRAL  
VALLEY DUE TO A DEEPER MARINE LAYER ALONG COAST. OTHERWISE LITTLE  
CHANGE ELSEWHERE. THUNDERSTORMS OCCURRED OVER THE SIERRA NEVADA  
AND KERN MOUNTAINS AND EXPECT A REPEAT OF THUNDERSTORM ACTIVITY  
FOR SUNDAY AFTERNOON AND EVENING. CONDITIONS REMAIN CONDITIONAL  
UNSTABLE WITH LITTLE CHANGE IN AIRMASS AND PRECIPITABLE WATER  
VALUES UP TO 120 PERCENT ABOVE NORMAL OVER CENTRAL CA. WATER  
VAPOR IMAGERY SHOW AN UPPER TROUGH OFF THE CA COAST DEVELOPING  
SOUTHWARD. THIS FEATURE WILL PROVIDE FAVORABLE CONDITIONS FOR  
CONTINUED CONVECTIVE FORCING WITH THE AFTERNOON WIND CONVERGENCE  
OVER THE MOUNTAINS.  
 
MODELS IN AGREEMENT THAT THE TROUGH WILL REMAIN OFF THE  
CA COAST THROUGH TUESDAY. ANOTHER UPPER DISTURBANCE WILL MOVE  
SOUTH INTO THE TROUGH RETROGRADING THE TROUGH FURTHER OFFSHORE.  
THIS WILL MAINTAIN AN EAST TO SOUTHEAST MID LEVEL FLOW TAPPING  
INTO SOME DEEPER MONSOONAL MOISTURE OVER ARIZONA AND NORTHERN  
MEXICO. MODELS SHOW THE MOISTURE WILL BEGIN TO INFILTRATE THE KERN  
COUNTY MOUNTAINS AND DESERT BY LATE SUNDAY NIGHT AND ADVECT  
NORTHWARD UP THE SIERRA DURING THE DAY MONDAY. THIS AREA WILL  
BECOME THE PRIMARY FOCUS FOR MORE WIDESPREAD SHOWERS AND  
THUNDERSTORMS EARLY NEXT WEEK. THE GFS MODELS INDICATE A MODERATE  
E TO SE FLOW MONDAY NIGHT AND TUESDAY AS THE LOW CLOSES OFF POINT  
CONCEPTION. THIS COULD BRING THE CONVECTIVE STORMS INTO THE INTO  
THE FOOTHILLS OR THE EAST SIDE AND SOUTH END OF THE SAN JOAQUIN  
VALLEY.  
 
THE MODELS FORECAST THE TROUGH TO WEAKEN AS IT MOVES ONSHORE OVER  
S CA WEDNESDAY. A WESTERLY FLOW ALOFT SHOULD BRING DRIER AND  
STABLE CONDITIONS THURSDAY. A WARM AND DRY TREND EXPECTED  
THEREAFTER AS AN UPPER LEVEL RIDGE BUILDS NORTHWESTWARD FROM  
TEXAS.  
 

 
   
AVIATION
 
 
ISOLATED TO SCATTERED THUNDERSTORMS OVER MOUNTAINS AFTER 20Z THIS  
AFTERNOON AND EXTENDING INTO DESERT AREAS AFTER 06Z TONIGHT.  
OTHERWISE VFR CONDITIONS EXPECTED ACROSS THE CENTRAL CA INTERIOR  
DURING THE NEXT 24 HOURS.  
 

 
   
AIR QUALITY ISSUES
 
 
PLEASE SEE SFOAQAHNX FOR AN AIR QUALITY ALERT  
 
ON SUNDAY AUGUST 20 2017... UNHEALTHY FOR SENSITIVE GROUPS IN  
FRESNO... KERN... KINGS AND TULARE COUNTIES AND SEQUOIA NATIONAL  
PARK AND FOREST.  
FURTHER INFORMATION IS AVAILABLE AT VALLEYAIR.ORG  
 

 
   
CERTAINTY
 
 
THE LEVEL OF CERTAINTY FOR DAYS 1 AND 2 IS MEDIUM.  
THE LEVEL OF CERTAINTY FOR DAYS 3 THROUGH 7 IS MEDIUM.  
 
CERTAINTY LEVELS INCLUDE LOW...MEDIUM...AND HIGH. PLEASE VISIT  
WWW.WEATHER.GOV/HNX/CERTAINTY.PHP FOR ADDITIONAL INFORMATION  
AN/OR TO PROVIDE FEEDBACK.  
 

 
   
HNX WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
PUBLIC...MV  
AVN/FW...JEB  
PREV DISCUSSION...DURFEE  
SYNOPSIS...MV  
 
WEATHER.GOV/HANFORD  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab CA Page Main Text Page