080  
FXUS66 KSGX 221641  
AFDSGX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAN DIEGO CA  
941 AM PDT THU MAY 22 2025  
   
SYNOPSIS  
 
HIGH PRESSURE ALOFT WILL WEAKEN WITH A LOW PRESSURE SYSTEM MOVING  
INLAND THROUGH CALIFORNIA ON FRIDAY NIGHT. HIGH TEMPERATURES WILL  
COOL FROM AROUND 10 DEGREES ABOVE AVERAGE TODAY TO WITHIN A FEW  
DEGREES OF AVERAGE ON SATURDAY. SUNDAY WILL BE AROUND 5 DEGREES  
WARMER, THEN GRADUAL COOLING TO AROUND AVERAGE FOR NEXT WEDNESDAY.  
THERE WILL PERIODS OF STRONGER AND GUSTY SOUTHWEST TO WEST WINDS  
FOR THE MOUNTAINS AND DESERTS DURING THE AFTERNOON AND EVENING  
FOR TODAY AND THURSDAY WITH THE STRONGER GUSTS TODAY TO 30 TO 40  
MPH AND ON THURSDAY TO 35 TO 45 MPH. THE MARINE LAYER WILL DEEPEN  
INTO SATURDAY WITH NIGHT AND MORNING COASTAL LOW CLOUDS SPREADING  
FARTHER INLAND INTO THE VALLEYS EACH MORNING THROUGH SATURDAY.  
COASTAL LOW CLOUDS WON'T EXTEND AS FAR INTO THE VALLEYS ON SUNDAY.  
FOR THE EARLY AND MIDDLE PART OF NEXT WEEK, THE MARINE LAYER WILL  
BE DEEPEN WITH NIGHT AND MORNING COASTAL LOW CLOUDS EXTENDING  
INLAND ACROSS MUCH OF THE INLAND VALLEYS WITH SLOWER OR MORE  
LIMITED AFTERNOON CLEARING NEAR THE COAST.  
 
 
   
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE  
 
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO  
COUNTIES...  
 
UPDATE: AREAS OF FOG WITHIN SOME OF THE INLAND AREAS IS CONTINUING  
TO DISSIPATE, AND WILL CONTINUE TO DO SO THROUGHOUT THE NEXT COUPLE  
OF HOURS FROM EAST TO WEST. THE MARINE LAYER WILL REMAINED MORE  
CONFINED TO THE COASTAL AREAS UNTIL AROUND NOON. BY AFTERNOON, MOST  
AREAS SHOULD BE CLEARED OUT, ALTHOUGH THERE COULD STILL BE SOME  
LOCATIONS RIGHT ALONG THE COAST THAT COULD HAVE SKIES INTERMITTENTLY  
BECOME BROKEN TO OVERCAST THROUGHOUT THE AFTERNOON.  
 
MODELS HAVE REMAINED ON TRACK FOR WEAK TROUGHING MOVING IN  
TO ALLOW FOR INCREASED ONSHORE FLOW AND COOLER TEMPERATURES, WHICH  
WILL BE MUCH CLOSER TO THE SEASONAL AVERAGE FOR THIS TIME OF YEAR.  
THERE WILL CONTINUE TO BE MORE OF A PUSH OF THE MARINE LAYER, AND  
SOME AREAS OF DRIZZLE, OR EVEN LIGHT RAIN AGAINST THE FOOTHILLS,  
WHICH MAY OCCUR BY LATE TONIGHT THROUGH TOMORROW MORNING. TOMORROW  
WILL LIKELY BE THE COOLEST DAY OF THE WEEK FOR MOST LOCATIONS, THEN  
THERE WILL BE A SLIGHT WARMUP FOR SUNDAY.  
 
(PREVIOUS DISCUSSION SUBMITTED AT 243 AM):  
   
SHORT TERM (TODAY THROUGH SATURDAY)  
 
HIGH PRESSURE ALOFT WILL BEGIN TO WEAKEN TODAY WITH A LOW PRESSURE  
SYSTEM MOVING INLAND THROUGH CALIFORNIA ON FRIDAY NIGHT. HIGH  
TEMPERATURES WILL COOL FROM AROUND 10 DEGREES ABOVE AVERAGE TODAY  
TO WITHIN A FEW DEGREES OF AVERAGE ON SATURDAY. WITH THE COOLING,  
HIGH TEMPERATURES ON SATURDAY WILL RANGE FROM THE MID TO UPPER 60S  
NEAR THE COAST TO THE MID 70S TO LOWER 80S FOR THE INLAND EMPIRE  
WITH THE LOWER DESERTS IN THE MID TO UPPER 90S.  
 
THE MARINE LAYER IS SLOWLY DEEPENING EARLY THIS MORNING.  
SATELLITE IMAGERY SHOWS MORE WIDESPREAD LOW CLOUDS SPREADING  
INLAND PAST INTERSTATE 5 IN ORANGE COUNTY AND INTO THE FAR  
WESTERN VALLEYS IN SAN DIEGO COUNTY. DEEPENING OF THE MARINE LAYER  
TO AROUND 1500 FEET IS EXPECTED FOR THIS MORNING, 2000 FEET FOR  
FRIDAY MORNING, AND 2500 FEET FOR SATURDAY MORNING. COASTAL LOW  
CLOUDS WILL SPREAD FARTHER INTO THE WESTERN VALLEYS FOR EARLY  
FRIDAY MORNING, AND INTO PORTIONS OF THE INLAND VALLEYS FOR EARLY  
SATURDAY MORNING.  
 
ONSHORE FLOW WILL STRENGTHEN FOR TODAY AND THURSDAY. THERE WILL  
PERIODS OF STRONGER AND GUSTY SOUTHWEST TO WEST WINDS FOR THE  
MOUNTAINS AND DESERTS DURING THE AFTERNOON AND EVENING FOR TODAY  
AND THURSDAY WITH THE STRONGER GUSTS TODAY TO 30 TO 40 MPH AND ON  
THURSDAY TO 35 TO 45 MPH.  
 
 
   
LONG TERM (SUNDAY THROUGH WEDNESDAY)  
 
HIGH PRESSURE ALOFT FOR SUNDAY WILL RESULT IN AROUND 5 DEGREES OF  
WARMING. THEN GRADUALLY COOLER FOR MONDAY THROUGH WEDNESDAY WITH  
HIGH TEMPERATURES FOR NEXT WEDNESDAY NEAR AVERAGE. THE MARINE  
LAYER WILL DECREASE IN DEPTH TO AROUND 2000 FEET ON SUNDAY WITH  
COASTAL LOW CLOUDS NOT EXTENDING AS FAR INTO THE VALLEYS FOR EARLY  
SUNDAY.  
 
FOR THE EARLY AND MIDDLE PART OF NEXT WEEK, A WEAK UPPER LEVEL  
LOW PRESSURE SYSTEM MAY DEVELOP IN THE VICINITY OF SOUTHERN  
CALIFORNIA. THE MARINE LAYER WILL DEEPEN WITH NIGHT AND MORNING  
COASTAL LOW CLOUDS EXTENDING INLAND ACROSS MUCH OF THE INLAND  
VALLEYS WITH SLOWER OR MORE LIMITED AFTERNOON CLEARING NEAR THE  
COAST.  
 
 
   
AVIATION  
 
221600Z...COAST...LOW CLOUDS (BASED 400-1000FT MSL) AND FOG THAT  
MOVED IN ABOUT 10 MILES INLAND THIS MORNING ARE NOW EFFICIENTLY  
ERODING FROM EAST TO WEST AND SHOULD FULLY CLEAR BY 17Z THIS  
MORNING. VISIBILITY HAS BEEN GRADUALLY IMPROVING, BUT VIS DOWN 2-5SM  
REMAINS POSSIBLE FOR COASTAL MESAS AND INLAND VALLEYS UNTIL THE  
CLOUDS CLEAR. MARINE LAYER CLOUDS REDEVELOP AGAIN TONIGHT, PUSHING  
ASHORE AS EARLY AS 02-03Z WITH SLIGHTLY HIGHER BASES - LIKELY ABOVE  
700FT MSL WITH BETTER VISIBILITY ALONG THE COASTS AND WESTERN  
VALLEYS, BUT VIS RESTRICTIONS FOCUSED MORE WITHIN INLAND HIGHER  
TERRAIN. CLEARING FRIDAY MORNING EXPECTED AT A SIMILAR TIME AS THIS  
MORNING, AROUND 17-18Z.  
 
ELSEWHERE...CLEAR WITH UNRESTRICTED VIS THROUGH FRIDAY MORNING. WEST-  
NORTHWEST WIND GUSTS LOCALLY 25-35 KTS THIS AFTERNOON WITHIN  
MOUNTAIN PASSES AND ALONG DESERT MOUNTAIN SLOPES STRENGTHEN TO 35-45  
KTS FRIDAY AFTERNOON.  
 
 
   
MARINE  
 
WINDS GUSTING NEAR 20 KTS NEAR SAN CLEMENTE ISLAND ON FRIDAY  
AFTERNOON, OTHERWISE, NO HAZARDOUS MARINE CONDITIONS ARE EXPECTED  
THROUGH TUESDAY.  
 
 
   
SKYWARN  
 
SKYWARN ACTIVATION IS NOT REQUESTED. HOWEVER WEATHER SPOTTERS ARE  
ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS.  
 
 
   
SGX WATCHES/WARNINGS/ADVISORIES  
 
CA...NONE.  
PZ...NONE.  
 
 
 
 
 
UPDATE...STEWEY  
PUBLIC...17  
AVIATION/MARINE...MUNYAN  
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