035  
FXUS66 KSGX 290424  
AFDSGX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAN DIEGO CA  
915 PM PDT FRI APR 28 2017  
   
SYNOPSIS
 
 
OFFSHORE FLOW WILL STRENGTHEN TONIGHT AND BRING STRONG NORTHEAST  
WINDS THROUGH AND BELOW PASSES AND CANYONS THROUGH MIDDAY SATURDAY.  
HIGH PRESSURE ALOFT WILL BRING DRY, WARM WEATHER NEXT WEEK WITH  
TEMPERATURES AVERAGING A LITTLE ABOVE NORMAL. SOME COASTAL LOW  
CLOUDS WILL RETURN EARLY NEXT WEEK.  
 

 
   
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
 
 
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO  
COUNTIES...  
 
SURFACE PRESSURE GRADIENTS HAVE TRENDED MORE STRONGLY OFFSHORE THE  
PAST 8 HOURS. AT NOON THE SAN-TPH GRADIENT WAS -3.6 MB, AND AT 8 PM  
IT WAS -8.8 MB. NORTH WINDS HAVE ADVECTED THE DRY AIRMASS INTO THE  
HIGH DESERTS WHERE THE DEW POINT AT APPLE VALLEY WAS 6 DEGREES AT 8  
PM AND THE WINDS WERE NE 12G21 MPH.  
 
THE WRF AND CANSAC MODELS CONTINUE TO SHOW STRONG SANTA ANA WINDS  
SURFACING ACROSS THE MOUNTAINS AND FOOTHILLS BETWEEN 05-09Z WITH THE  
STRONGEST WINDS BETWEEN 09-18Z SATURDAY. THE OFFSHORE FLOW WILL BE  
STRONG ENOUGH TO REACH COASTAL ORANGE COUNTY WHERE DOWNSLOPE  
ADIABATIC WARMING WILL REACH THE BEACH. AS A RESULT, TEMPERATURES  
THERE WILL PROBABLY BE ABOVE GUIDANCE, AND TEMPS WERE RAISED SEVERAL  
DEGREES NEAR THE COAST. HUNTINGTON BEACH, NEWPORT BEACH AND LAGUNA  
BEACH ALL HAVE A GOOD CHANCE TO CRACK 80 DEGREES. NO CHANGES TO THE  
REMAINDER OF THE FORECAST.  
 
*FROM PREVIOUS DISCUSSION*  
 
WE WILL BE UNDER A STRONG NORTH-NORTHWEST FLOW PATTERN THROUGH  
SATURDAY, AND THIS WILL COMBINE WITH A SURFACE HIGH BUILDING OVER  
THE GREAT BASIN AND A STABLE LAYER IN THE 800-700 MB LAYER FOR THE  
MOUNTAIN WAVE TO BRING SANTA ANA WINDS TO SOME AREAS, ESPECIALLY  
BELOW THE CAJON PASS AND IN ORANGE COUNTY WHERE LOCAL GUSTS OVER 60  
MPH ARE LIKELY LATE TONIGHT AND SATURDAY MORNING. SOME MODERATELY  
STRONG WINDS WILL OCCUR IN SAN DIEGO COUNTY FROM THE MOUNTAIN CRESTS  
WEST THROUGH THE FOOTHILLS, WITH LOCAL GUSTS OVER 50 MPH THERE.  
WINDS WILL DECREASE RAPIDLY SATURDAY AFTERNOON AS THE SUPPORT ALOFT  
DECREASES AS THE TROUGHING IN THE WEST SHIFTS EAST AND THE NORTH  
FLOW ALOFT WEAKENS. IT WILL BE MUCH WARMER WEST OF THE MOUNTAINS,  
ESPECIALLY NEAR THE COAST AS SOME TEMPS COULD BE ABOVE 90 WITHIN 10-  
15 MILES OF THE COAST, WITH HIGHEST TEMPS IN ORANGE COUNTY. 850 MB  
TEMPS WILL BE SEVERAL DEGREES HIGHER SUNDAY, BUT ONSHORE FLOW WILL  
PREVAIL BY THEN, SO MOUNTAINS AND DESERTS WILL BE WARMER, BUT  
COASTAL AREAS WILL COOL.  
 
NEXT WEEK, THE HIGH PRESSURE RIDGE WILL SLOWLY MOVE FROM WEST TO  
EAST OVER CALIFORNIA, WITH WEAK TO MODERATE ONSHORE FLOW AT THE  
SURFACE. LOW CLOUDS AND FOG WILL RETURN TO THE COAST PROBABLY MONDAY  
NIGHT, POSSIBLY AS EARLY AS MONDAY MORNING. TEMPERATURES WILL  
AVERAGE A LITTLE ABOVE NORMAL, ESPECIALLY IN THE INLAND EMPIRE,  
MOUNTAINS AND DESERTS WHERE THE WARM PROFILE WILL BE LESS AFFECTED  
BY THE COASTAL MARINE LAYER. SOME LOWER DESERT LOCATIONS COULD REACH  
100 WED/THU. SOME COOLING COULD OCCUR LATE IN THE WEEK AS THE UPPER  
HIGH MOVES EAST AND A WEAK PACIFIC TROUGH APPROACHES THE WEST COAST.  
 

 
   
AVIATION
 
 
290345Z...DECREASING CLOUDS AOA 20000 FT MSL AND UNRESTRICTED VIS  
THROUGH SATURDAY EVENING. STRONG NORTH TO NORTHEAST WINDS WILL  
DEVELOP S/SW OF THE MOUNTAINS, INCLUDING NORTH PORTIONS OF THE  
COACHELLA VALLEY, AND BELOW THE PASSES AND CANYONS 06-20Z. LOCAL SFC  
GUSTS 35-50 KT, STG-SVR UDDFS, AND LLWS ARE LIKELY THROUGH SATURDAY  
AFTERNOON. WINDS WILL GRADUALLY WEAKEN LATE SATURDAY AFTERNOON AND  
EVENING.  
 

 
   
MARINE
 
 
NORTHWEST WIND GUSTS OF 25-30 KT WILL CONTINUE THROUGH EARLY  
SATURDAY. A SHORT-PERIOD, CHOPPY SWELL FROM 290 DEGREES PEAKING THIS  
EVENING AT 9-11 FEET WILL DIMINISH TONIGHT AND SATURDAY. A SMALL  
CRAFT ADVISORY CONTINUES THROUGH EARLY SATURDAY MORNING. NORTHWEST  
WINDS WILL INCREASE AGAIN SATURDAY EVENING AND MAY BRIEFLY POSE A  
HAZARD TO SMALL CRAFT.  
 

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

 
   
SGX WATCHES/WARNINGS/ADVISORIES
 
 
CA...WIND ADVISORY FROM 10 PM THIS EVENING TO 2 PM PDT SATURDAY FOR  
RIVERSIDE COUNTY MOUNTAINS-SAN DIEGO COUNTY DESERTS-SAN  
DIEGO COUNTY MOUNTAINS-SAN DIEGO COUNTY VALLEYS-SAN  
GORGONIO PASS NEAR BANNING.  
 
HIGH WIND WARNING FROM 10 PM THIS EVENING TO 2 PM PDT SATURDAY  
FOR ORANGE COUNTY COASTAL AREAS-ORANGE COUNTY INLAND AREAS-  
SAN BERNARDINO COUNTY MOUNTAINS-SAN BERNARDINO AND  
RIVERSIDE COUNTY VALLEYS-THE INLAND EMPIRE-SANTA ANA  
MOUNTAINS AND FOOTHILLS.  
 
PZ...SMALL CRAFT ADVISORY UNTIL 5 AM PDT SATURDAY FOR COASTAL WATERS  
FROM SAN MATEO POINT TO THE MEXICAN BORDER AND OUT TO 30 NM-  
WATERS FROM SAN MATEO POINT TO THE MEXICAN BORDER EXTENDING  
30 TO 60 NM OUT INCLUDING SAN CLEMENTE ISLAND.  
 

 
 

 
 
PUBLIC...MOEDE  
AVIATION/MARINE/BEACHES...SS  
 
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