299  
FXUS66 KSGX 152013  
AFDSGX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAN DIEGO CA  
112 PM PDT SUN JUL 15 2018  
   
SYNOPSIS
 
 
HIGH PRESSURE ALOFT WILL PERSIST OVER THE SOUTHWEST THROUGH MUCH OF  
THE WEEK WITH SEASONALLY WARM WEATHER. THE MARINE LAYER WILL KEEP  
COASTAL AREAS COOLER WITH AREAS OF NIGHT AND MORNING LOW CLOUDS AND  
FOG. MONSOONAL MOISTURE IN WEAK EASTERLY FLOW AND DAYTIME HEATING  
WILL CONTINUE ISOLATED SHOWERS AND THUNDERSTORMS OVER THE MOUNTAINS  
EACH AFTERNOON AND EVENING, INCREASING THROUGH MIDWEEK UNDER A  
WESTBOUND TROPICAL WAVE.  
 

 
   
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
 
 
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO  
COUNTIES...  
 
THE MARINE STRATUS DISSIPATED BETTER ALONG THE IMMEDIATE COAST  
TODAY. AROUND MIDDAY...STRATUS WAS STILL VISIBLE WELL OFFSHORE, AND  
BEGINNING TO DRIFT BACK TOWARD THE COAST. MEANWHILE OVER THE  
DESERTS...WIDESPREAD MID/HIGH CLOUDS HAD THICKENED. CUMULUS WERE  
ALSO OVER SOME MOUNTAIN AREAS, BUT NO THUNDERSTORM ACTIVITY HAD BEEN  
DETECTED THROUGH 1 PM PDT. THE SFC PRESSURE GRADIENTS TO THE DESERTS  
WERE A BIT WEAKER THAN YESTERDAY, BUT SEVERAL MTN/DESERT SITES HAD  
PEAK WESTERLY WIND GUSTS NEAR 25 MPH.  
 
A HIGH PRESSURE RIDGE WITH AN EAST-WEST AXIS WILL GRADUALLY LIFT  
NORTH THROUGH TUESDAY, RESULTING IN INCREASING EASTERLY FLOW ALOFT  
OVER SOCAL. MONSOONAL MOISTURE WILL EDGE UP FROM AROUND 1.5 INCH TO  
NEAR 2 INCHES, ACCOMPANIED BY MORE MID/HIGH CLOUDS. MOISTURE PEAKS  
WITH THE PASSAGE OF AN EASTERLY WAVE THROUGH NW MEXICO LATE NIGHT  
TUE/EARLY WED, THEN DECREASES AS WINDS VEER MORE SOUTHERLY INTO NEXT  
WEEKEND.  
 
THE GLOBAL MODELS HAVE COME INTO FAIR AGREEMENT IN THE MEDIUM TERM  
WITH THE HANDLING OF THE UPPER HIGH OVER THE SW INTO NEXT WEEKEND.  
THE DIFFUSE CENTER FINDS ITS WAY TO NEAR THE FOUR CORNERS AREA AND  
SMOTHERS MUCH OF THE GREAT BASIN WITH 500H EXCEEDING 598DM ON  
SUNDAY. AT THE SAME TIME AN UPPER LOW DEVELOPS OFF THE COAST AND  
TRACKS NW. THE FLOW BETWEEN THESE TWO SYSTEMS DRIVE SOUTHERLY WINDS  
ALOFT OVER SOCAL AND SOME DRYING. TEMPERATURES WILL TREND UPWARD  
OVER THE WEEKEND DUE TO THE DRIER AIR AND INCREASING HEIGHTS BUT  
ONSHORE FLOW SHOULD HOLD, KEEPING A MARINE LAYER WEST OF THE MTS.  
 
LOOKING BEYOND THE WEEKEND, SOME ADDITIONAL HEATING IS POSSIBLE WITH  
THE HIGH CENTER FORECAST TO MOVE OVER SOCAL. IF THE CURRENT  
PROJECTIONS VERIFY, WE COULD BE BACK INTO AN EXCESSIVE HEAT  
SITUATION NEXT WEEK FOR PORTIONS OF THE FORECAST AREA.  
 
SHOWER/TSTM POTENTIAL...SLIGHT CHANCE CONTINUES IN THE FORECAST  
BASED ON THE FLOW PATTERN AND CLIMATOLOGY, WITH SOME INCREASE IN THE  
CHANCE MIDWEEK DUE TO THE BUMP UP IN MOISTURE AND PASSING EASTERLY  
WAVE. STILL...INSTABILITY AND FORCING FOR ANY HEAVY ACTIVITY LOOK  
MARGINAL AT THIS TIME.  
 

 
   
AVIATION
 
 
152030Z...COAST/VALLEYS...LOW CLOUDS WILL GATHER AND SPREAD ASHORE  
THIS EVENING AFTER 05Z AND UP TO ABOUT 15 MILES INLAND OVERNIGHT  
WITH CLOUD BASES AROUND 1200 FEET MSL AND TOPS TO 1800 FEET. SCATTER  
OUT MONDAY IS EXPECTED BY 15-17Z.  
 
MOUNTAINS/DESERTS...SCT-BKN CLOUDS AT/ABOVE 15000 FEET MSL WILL  
CONTINUE OVER THE DESERT WITH CUMULUS CLOUDS BASED AT 8000 FEET MSL  
MAINLY OVER MOUNTAINS THROUGH THE AFTERNOON. ISOLATED SHRA POSSIBLE  
IN THE MOUNTAINS THROUGH 01Z. SCATTERED RESIDUAL DEBRIS CLOUDS AOA  
15000 FEET MSL TONIGHT INTO MONDAY.  
 

 
   
MARINE
 
 
NO HAZARDOUS MARINE WEATHER IS FORECAST THROUGH FRIDAY.  
 

 
   
SKYWARN
 
 
SKYWARN ACTIVATION IS NOT REQUESTED. HOWEVER WEATHER SPOTTERS ARE  
ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS.  
 

 
   
SGX WATCHES/WARNINGS/ADVISORIES
 
 
CA...NONE.  
PZ...NONE.  
 

 
 

 
 
PUBLIC...10  
AVIATION/MARINE...MM  
 
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