957  
FXUS66 KSGX 050511  
AFDSGX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAN DIEGO CA  
910 PM PST SUN DEC 4 2016  
   
SYNOPSIS
 
 
CLOUDS WILL BE ON THE INCREASE TONIGHT WITH PATCHY FOG NEAR THE  
COAST. CLOUDINESS WILL CONTINUE NEAR THE COAST ON MONDAY AND COOLER  
CONDITIONS AS WINDS TURN BACK ONSHORE AND THE MARINE LAYER BUILDS  
IN. THE MOIST LAYER MAY GET DEEP ENOUGH FOR A FEW LIGHT SHOWERS OR  
SOME DRIZZLE ON TUESDAY. WARMING BEGINS ON WEDNESDAY AND CONTINUES  
THROUGH THE END OF THE WEEK AS WINDS TURN BACK OFFSHORE UNDER FAIR  
SKIES.  
 

 
   
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
 
 
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO  
COUNTIES...  
 
VERY WEAK ONSHORE FLOW HAS DEVELOPED AND WE'RE STARTING TO SEE SOME  
VERY LOW CLOUDS FORM ALONG THE COAST. HAVE INCREASED THE COVERAGE OF  
CLOUDINESS OVERNIGHT AND MONDAY MORNING NEAR THE COAST, AS WELL AS A  
LITTLE MORE LIKELY TO SEE AREAS OF FOG OVERNIGHT NEAR THE COAST. NO  
OTHER CHANGES HAVE BEEN MADE TO THE FORECAST THIS EVENING.  
   
..REMAINDER OF PREVIOUS DISCUSSION
 
 
THE PREVAILING OFFSHORE PATTERN IS TURNING AS THE BROAD HIGH  
PRESSURE AREA OVER THE GREAT BASIN COLLAPSES AHEAD OF A SAGGING  
POLAR TROUGH OVER THE PACNW. A SHORTWAVE EMBEDDED IN THE TROUGH  
SHOULD GUIDE IT EAST ACROSS THE GREAT PLAINS THIS WEEK, BUT IT WILL  
BE DRIVING INCREASING ONSHORE FLOW ACROSS SOCAL THROUGH TUE BEFORE  
COLD SFC HIGH PRESSURE TURNS OUR FLOW BACK OFFSHORE LATER IN THE  
WEEK. DRY AND MILD THU THROUGH SUN.  
 
CLOUDS/PRECIP...HIGH RES MODEL GUIDANCE SUGGESTS A RETURN OF COASTAL  
LOW CLOUDS AND SOME FOG BY EARLY MONDAY MORNING AS A COASTAL EDDY  
DEVELOPS. AS THE MARINE LAYER BUILDS, LOOK FOR MORE EXTENSIVE LOW  
CLOUD COVER, AND THERE MAY EVEN BE A FEW LIGHT SHOWERS OR SOME  
PATCHY DRIZZLE WEST OF THE MTS ON TUE/TUE NIGHT. AT THIS TIME,  
PRECIP DOES NOT LOOK SIGNIFICANT.  
 
WIND...THE SURFACE HIGH PRESSURE CENTER BUILDING SOUTH OVER THE  
ROCKIES THIS WEEK IS FORECAST TO REACH 1044 MBS OR MORE BY 12Z THU  
OVER WYOMING AS ARCTIC AIR SURGES SOUTH, EAST OF THE ROCKIES. THE  
RIDGE POSITION (ALIGNING WITH THE COLD ARCTIC AIR EAST OF THE  
ROCKIES) WILL HELP KEEP THE SFC GRADIENT FARTHER SW MORE MODERATE.  
WITH LITTLE ADDITIONAL SUPPORT ALOFT, AND THE CURRENT FORECAST  
POSITION OF THE SFC HIGH, OFFSHORE WINDS DO NOT LOOK TO BE NEAR THE  
STRENGTH OF THE EVENT LATE LAST WEEK.  
 
TEMPERATURES...COLDEST DAYS TUE/WED THIS WEEK WITH MAX TEMPS FROM 2  
TO 8 DEGREES F BELOW AVERAGE. WARMEST DAYS THU/FRI WITH TEMPS JUST  
A FEW DEGREES F ABOVE AVERAGE.  
 
LOOKING AHEAD TO NEXT WEEKEND...NOT MUCH DISCREPANCY IN THE 500 MB  
PATTERN BETWEEN THE 12Z GFS/ECMWF RUNS WITH LARGELY A ZONAL FLOW  
ALOFT. GEFSENSEMBLE LOOKS PRETTY FLAT AS WELL. THIS WOULD MEAN FAIR  
AND MILD WEATHER. THE OUTLIER 12Z GEM RUN HAS A SHARP TROUGH  
SWINGING THROUGH THE SW FOR MORE WIND AND POSSIBLE LIGHT PRECIP. FOR  
NOW, MODERATE CONFIDENCE NEXT WEEKEND WILL BE FAIR AND DRY.  
 

 
   
AVIATION
 
 
050500Z...COAST/VALLEYS...A COASTAL EDDY WILL HELP REDEVELOP LOW  
STRATUS TONIGHT ALONG THE COAST. LOW CLOUD BASES WILL BE AROUND 300-  
600 FT MSL, WITH TOPS TO 900 FT MSL THIS EVENING, AND LIFT 200-400  
FT BY MONDAY MORNING. VISIBILITY WILL LOWER TO 2-4 SM BR WHERE  
STRATUS FORMS, AND LOCALLY LOWER WHERE STRATUS NEARS HIGHER TERRAIN.  
HIGH CLOUDS WILL DETER FAST STRATUS DEVELOPMENT EARLY TONIGHT.  
STRATUS WILL BECOME FEW/SCT BY LATE MONDAY MORNING, THEN REDEVELOP  
ALONG THE COAST MONDAY EVENING.  
 
MOUNTAINS/DESERTS...FEW/SCT HIGH CLOUDS AND UNRESTRICTED VIS WILL  
CONTINUE THROUGH MONDAY.  
 

 
   
MARINE
 
 
WIND GUSTS MAY EXCEED 20 KNOTS NEAR SAN CLEMENTE ISLAND LATE TUESDAY  
OR TUESDAY NIGHT AS AN UPPER-LEVEL DISTURBANCE MOVES ACROSS THE  
REGION. OTHERWISE, NO HAZARDOUS MARINE WEATHER IS EXPECTED THROUGH  
FRIDAY.  
 

 
   
FIRE WEATHER
 
 
ANOTHER ROUND OF GUSTY OFFSHORE WINDS AND VERY DRY CONDITIONS WILL  
DEVELOP WEDNESDAY MORNING AND CONTINUE THROUGH THURSDAY, WEAKENING  
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/FIRE WEATHER...JAD/JMB  
AVIATION/MARINE...JJT  
 
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