943  
FXUS66 KHNX 210836  
AFDHNX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE HANFORD CA  
136 AM PDT SUN JUL 21 2019  
 
   
SYNOPSIS
 
A WARMING TREND BEGINS TOMORROW WITH WIDESPREAD TRIPLE  
DIGIT HEAT EXPECTED ACROSS THE LOWER ELEVATIONS ALL OF NEXT WEEK.  
MONSOONAL MOISTURE WILL BEGIN TO MOVE INTO THE REGION ON MONDAY FOR  
A CHANCE OF AFTERNOON THUNDERSTORMS OVER THE MOUNTAINS BEGINNING  
TUESDAY.  
 

 
   
DISCUSSION
 
WATER VAPOR IMAGERY SHOWS AN AREA OF MID AND UPPER  
LEVEL MOISTURE AND AN ASSOCIATED VORTICITY CENTER MOVING NORTHWARD  
TOWARD THE CENTRAL CALIFORNIA COAST. THIS MOISTURE APPEARS TO BE  
RATHER SHALLOW AND WITH THIS INITIAL PUSH, I DON'T EXPECT ANY  
CONVECTION TO DEVELOP. MEANWHILE TO THE SOUTHEAST, DECAYING  
CONVECTIVE COMPLEX OVER SOUTHERN ARIZONA IS PUSHING WEST TOWARDS  
THE LOWER COLORADO RIVER AREA AND THIS IS ADDING SOME ADDITIONAL  
MOISTURE FEED INTO EXTREME SOUTHEAST CALIFORNIA. ALL OF THIS  
ACTIVITY IS JUST THE BEGINNING OF A FUNDAMENTAL CHANGE TO A  
MONSOONAL PATTERN OVER THE REGION OVER THE NEXT SEVERAL DAYS AS  
WELL AS A PERIOD OF HOT WEATHER.  
 
MODELS PUSH THE OFFSHORE MID LEVEL MOISTURE UP THE COAST AS THE  
WEAK SHORTWAVE HEADS INTO NORTHERN CALIFORNIA. AGAIN, CONVECTION  
LOOKS TO BE NOT VERY LIKELY FROM THIS FEATURE. OVERNIGHT TONIGHT  
AND MONDAY THE UPPER LEVEL FLOW PATTERN INTO SOUTHERN AND CENTRAL  
CALIFORNIA BECOMES SOUTHERLY AND THE SOUTHEAST (HENCE THE MONSOON  
TERMINOLOGY) AND ADDITIONAL MID LEVEL MOISTURE GET ADVECTED  
NORTHWARD. THE NAM12 MODEL IS FASTEST WITH THE ARRIVAL OF THE  
MOISTURE WHILE THE GFS IS ABOUT 12 HOURS SLOWER. IT APPEARS IN  
EITHER CASE, FOR THE SIERRA ON MONDAY THAT THUNDERSTORMS WILL NOT  
DEVELOP UNTIL TUESDAY AS THE MOISTURE WILL COMBINE WITH DAYTIME  
HEATING OVER THE HIGH COUNTRY TO BREAK THROUGH ANY INVERSIONS OR  
"CAPS" THAT MAY BE PRESENT AT OR ABOVE 14000 FEET MSL. MODELS  
PRETTY MUCH KEEP ADDITIONAL SURGES OF MOISTURE INTO THE AREA FROM  
THE SOUTH OR SOUTHEAST THROUGH MUCH OF THE WEEK, THUS DAILY BOUTS  
OF AFTERNOON AND EVENING THUNDERSTORMS WILL BE POSSIBLE OVER THE  
SIERRA AND KERN COUNTY MOUNTAINS GENERALLY NORTH AND EAST OF  
TEHACHAPI.  
 
AS FOR TEMPERATURES, THE HOTTEST STRETCH OF WEATHER WILL OCCUR  
THIS WEEK AS THE DESERT SOUTHWEST HIGH PRESSURE SYSTEM BUILDS INTO  
CENTRAL CALIFORNIA. TRIPLE DIGIT HIGHS WILL OCCUR AT ALL LOWER  
ELEVATION LOCATIONS BEGINNING ON MONDAY WITH THE HEAT BUILDING  
THROUGH THE WEEK. AT THIS TIME THE HOTTEST DAYS WILL OCCUR IN THE  
WEDNESDAY THROUGH FRIDAY TIME RANGE AS THE RIDGE REACHES ITS  
MAXIMUM STRENGTH. OF COURSE IN THIS SCENARIO, IF THUNDERSTORM  
COMPLEXES DEVELOP AND SPREAD LOTS OF MID LEVEL CLOUDS INTO THE  
FORECAST AREA THEN THE HEATWAVE WILL GET A BREAK. WE WILL HAVE TO  
SEE IF THIS HAPPENS LATER THIS WEEK. ALL IN ALL THE FIRST  
"MONSOON" EPISODE WILL OCCUR THIS WEEK SO HOT WEATHER WITH SIERRA  
THUNDER WILL BE THE THEME OF THE WEEK.  
 

 
 
   
AVIATION
 
VFR CONDITIONS CAN BE EXPECTED ACROSS THE CENTRAL  
CA INTERIOR DURING THE NEXT 24 HOURS.  
 

 
   
AIR QUALITY ISSUES
 
 
NONE.  
 

 
   
CERTAINTY
 
 
THE LEVEL OF CERTAINTY FOR DAYS 1 AND 2 IS HIGH.  
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.HTML FOR ADDITIONAL INFORMATION  
AN/OR TO PROVIDE FEEDBACK.  
 

 
   
HNX WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
PUBLIC...DUDLEY  
AVIATION....DUDLEY  
 
WEATHER.GOV/HANFORD  
 
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