252  
FXUS66 KSGX 070409  
AFDSGX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAN DIEGO CA  
909 PM PDT MON OCT 6 2025  
   
SYNOPSIS  
 
HIGH PRESSURE TO THE SOUTHEAST WILL BRING GRADUALLY WARMER DAYS  
INTO WEDNESDAY. THE MARINE LAYER WILL DECREASE IN DEPTH WITH NIGHT  
AND MORNING LOW CLOUDS NOT SPREADING AS FAR INTO THE VALLEYS BY  
WEDNESDAY. THURSDAY INTO SATURDAY, MOISTURE FROM THE REMNANTS OF  
HURRICANE PRISCILLA IS EXPECTED TO SPREAD INTO THE SOUTHWESTERN  
CALIFORNIA WITH CHANCES FOR SHOWERS PEAKING ON FRIDAY. LOW  
PRESSURE FROM THE NORTHWEST WILL BRING COOLING FOR NEXT WEEKEND  
WITH HIGH TEMPERATURES AS MUCH AS 5 TO 10 DEGREES BELOW AVERAGE  
FOR INLAND AREAS NEXT SUNDAY.  
 
 
   
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE  
 
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO  
COUNTIES...  
 
EVENING UPDATE:  
 
AS OF 8:30 PM, PATCHY LOW CLOUDS HAVE STARTED TO DEVELOP ALONG  
COASTAL AREAS. BASED ON THE 00Z SOUNDING, THE MARINE LAYER IS  
ABOUT 2,500 FEET DEEP AND THE BOUNDARY LAYER INVERSION IS  
NOTICEABLY MORE PRONOUNCED THAN YESTERDAY'S INVERSION.  
 
CLOUD COVERAGE IS EXPECTED TO INCREASE THROUGHOUT THE NIGHT AND  
BRING OVERCAST CONDITIONS TO ALL OF LOWER SD AND ORANGE COUNTIES  
BY TUESDAY MORNING, WITH SOME PATCHY CLOUDS EVEN REACHING INTO THE  
INLAND EMPIRE. WITH THIS INVERSION AND LACK OF A SYNOPTIC MIXING  
MECHANISM, THERE IS MODERATE TO HIGH CONFIDENCE THAT SKIES REMAIN  
MOSTLY CLOUDY WITHIN 5 MILES OF THE SD COUNTY COAST ALL DAY.  
ELSEWHERE, TEMPERATURES REMAIN ON TRACK TO EXCEED TODAY'S HIGH  
TEMPERATURES BY A FEW DEGREES, WHICH ARE WITHIN A FEW DEGREES OF  
AVERAGE FOR EARLY OCTOBER.  
 
PREVIOUS DISCUSSION, AS OF 1:42 PM:  
   
SHORT TERM  
 
A GRADUAL WARMING TREND CONTINUES THROUGH WEDNESDAY AS THE RIDGE  
CONTINUES TO NUDGE IN, BRINGING HIGH TEMPERATURES TO JUST ABOUT  
AVERAGE BY MID-WEEK.  
 
THE MARINE INVERSION WILL STRENGTHEN AND LOWER SLIGHTLY  
IN THE NEXT FEW DAYS, WITH MORE COASTAL LOW CLOUDS IN THE LATE  
EVENING THROUGH MID- TO LATE-MORNING EACH DAY THROUGH WEDNESDAY  
NIGHT.  
 
 
   
LONG TERM  
 
REMNANT MOISTURE FROM NOW HURRICANE PRISCILLA WILL START TO MOVE  
INTO THE AREA LATE WEDNESDAY INTO THURSDAY MORNING, DRAWN IN BY  
SOUTHWEST FLOW FROM A LARGE LOW PRESSURE SYSTEM MOVING DOWN THE  
OR/NORTHERN CA COAST. ENSEMBLE MODEL PWAT RISES TO JUST ABOVE AN  
INCH BY THE END OF THE DAY THURSDAY, THEN PEAKS AROUND 1.5" BY  
FRIDAY. THE AVERAGE PWAT FOR THIS TIME OF YEAR IS JUST UNDER  
0.75", SO THIS IS WELL ABOVE AVERAGE. HOWEVER, REMAINING MODEL  
SPREAD AND LIKELY A LACK OF STRONG FORCING MAKES FOR A LOW  
CONFIDENCE FORECAST.  
 
WHAT WE DO HAVE A WIDESPREAD 15-20% CHANCE FOR MEASURABLE (>=  
0.01"), GENERALLY SHOWERY PRECIPITATION ACROSS THE REGION AS EARLY  
AS THURSDAY MORNING, INCREASING TO 25-35% THURSDAY INTO FRIDAY.  
RAINFALL TOTALS ARE STILL IN QUESTION WITH MODEL UNCERTAINTY  
REMAINING (DESPITE BETTER AGREEMENT TODAY). 24 HOUR TOTAL  
PROBABILITIES OF RAINFALL >= 0.25 ARE ABOUT 20% OVER SOUTHERN AND  
EASTERN PORTIONS OF THE AREA AND 30% OVER THE MOUNTAINS AND PARTS  
OF THE DESERTS BY LATE FRIDAY.  
 
PROBABILITY FOR >=1.00" IS ABOUT 10%, LOCALLY 15%, OVER THE SD,  
RIVERSIDE, AND EASTERN SBD MOUNTAINS AND PARTS OF THE DESERTS. THE  
MAJORITY OF ENSEMBLE MEMBERS SHOW GENERALLY LIGHT PRECIPITATION  
FOR WEST OF THE MOUNTAINS WITH A FEW STAND OUT MEMBERS, BUT THERE  
IS THE POTENTIAL FOR FAIRLY GOOD UPSLOPE FLOW UNDER THE SOUTHWEST  
WINDS ALOFT, ESPECIALLY FOR PARTS OF THE SBD MOUNTAINS. ANOTHER  
POINT OF UNCERTAINTY IS THE THUNDERSTORM POTENTIAL. DYNAMICS  
DON'T LOOK GREAT, WITH MINIMAL MUCAPE EVEN AT ITS PEAK ON  
SATURDAY, BUT ENOUGH FOR A 10-15% CHANCE FOR THUNDERSTORMS MOST  
OVER THE MOUNTAINS AND SD DESERT.  
 
THE NORTHWEST TROUGH MOVES MORE FULLY INTO THE REGION LATE  
SATURDAY/SUNDAY, EFFECTIVELY CUTTING OFF THE MOISTURE SOURCE AND  
ALSO COOLING TEMPERATURES BACK TO 5-10 DEGREES BELOW AVERAGE OVER  
THE WEEKEND INTO EARLY NEXT WEEK.  
 
 
   
AVIATION  
 
070340Z....COASTS/VALLEYS...STRATUS WITH BASES 1400-1800 FT MSL AND  
TOPS TO 2500 FT MSL FILLING IN ACROSS THE COASTAL AREAS AND WESTERN  
VALLEYS THROUGH 07Z, THEN SPREADING INTO THE INLAND EMPIRE THROUGH  
11Z. THERE IS A 60% CHANCE OF CIGS AT KONT AND A 30% CHANCE AT KSBD  
AFTER 10Z. AREAS OF VIS 3-5 SM IN BR/HZ WHERE LOW CLOUDS MOVE INTO  
THE VALLEYS. CLOUDS/VIS RESTRICTIONS CLEARING INLAND 14-17Z AND NEAR  
THE COAST 17-20Z. CLEARING AT KSAN AND KCRQ MAY BE LIMITED AGAIN,  
WITH A 30% CHANCE OF CIGS THROUGH THE AFTERNOON. LOW CLOUDS  
REDEVELOPING AND SPREADING BACK INLAND AFTER 08/02Z WITH SIMILAR  
BASES AND TOPS.  
 
MOUNTAINS/DESERTS...CLEAR WITH UNRESTRICTED VISIBILITY THROUGH  
TUESDAY EVENING.  
 
 
   
MARINE  
 
NO HAZARDOUS MARINE CONDITIONS ARE EXPECTED THROUGH SATURDAY.  
 
 
   
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...WESTERINK  
AVIATION/MARINE...SS  
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