885  
FXUS66 KSGX 051542  
AFDSGX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAN DIEGO CA  
842 AM PDT SUN OCT 5 2025  
   
SYNOPSIS
 
 
BELOW NORMAL TEMPERATURES THROUGH MONDAY, WITH A GRADUAL WARMING  
TREND INTO THE LATTER PART OF THE WEEK. AREAS OF NIGHT AND MORNING  
LOW CLOUDS AND FOG WILL CONTINUE ALONG THE COASTS AND PARTS OF  
THE VALLEYS THROUGH MIDWEEK. MID AND HIGH LEVEL TROPICAL MOISTURE  
MOVING INTO THE REGION WILL BRING A SLIGHT CHANCE OF SHOWERS LATE  
THURSDAY THROUGH SATURDAY.  
 

 
   
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
 
 
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO  
COUNTIES...  
 
THE EXPECTED COASTAL EDDY CIRCULATION FINALLY DEVELOPED EARLY THIS  
MORNING, PUSHING PATCHY LOW CLOUDS INLAND INTO WESTERN SAN DIEGO  
COUNTY VALLEYS AND LOCALIZED PARTS OF ORANGE COUNTY. THESE WILL  
HANG OUT IN AREAS THROUGH 10-11 AM BEFORE CLEARING TO OFFSHORE.  
 
ZOOMING OUT, A LARGE SCALE POSITIVELY TILTED TROUGH IS OVER MUCH  
OF THE NORTH-CENTRAL AND WESTERN U.S. A SHORTWAVE CAN BE SEEN  
DEVELOPING ON THE WEST SIDE OF THE TROUGH OFF THE NORTHERN  
CALIFORNIA COAST CURRENTLY. THIS WILL DEVELOP INTO A LITTLE CLOSED  
LOW LATE TODAY INTO MONDAY MORNING AS IT MOVES DOWN TO THE SOUTH-  
CENTRAL CALIFORNIA COAST, AS THE WEAK RIDGE OVER THE SOUTHERN U.S.  
MOVES TO COVER SOUTHERN CALIFORNIA. THIS WILL RESULT IN A GRADUAL  
WARM UP FOR AREAS INLAND FROM THE IMMEDIATE COAST THROUGH TUESDAY,  
STARTING WITH INLAND HIGH TEMPERATURES TODAY THAT WILL BE 2-5  
DEGREES WARMER THAN YESTERDAY'S. TEMPERATURES WILL STILL BE A  
COUPLE OF DEGREES BELOW THE DAILY AVERAGE TODAY, DESPITE THIS  
MILD WARM UP. A FEW DEGREES OF WARMING EACH DAY THROUGH TUESDAY  
WILL BRING TEMPERATURES CLOSER TO NORMAL.  
 
OUR WEAK INVERSION WILL STRENGTHEN TONIGHT, LEADING TO MORE  
WIDESPREAD LOW CLOUD COVERAGE OVERNIGHT. CLOUDS THAT DEVELOP THIS  
EVENING WILL STILL INITIALLY BE QUITE PATCHY, AND COULD REMAIN  
PATCHY TO A CERTAIN EXTENT OVERNIGHT, BUT WILL BE MUCH MORE  
UNIFORM THAN PREVIOUS DAYS AND MAKE IT FURTHER INLAND, EVEN  
POSSIBLY INTO PARTS OF THE WESTERN AND SOUTHERN INLAND EMPIRE.  
SIMILAR STORY FOR THE NEXT FEW NIGHTS.  
 
THE LOW LIFTS NORTH AND OPENS UP LATE TUESDAY INTO EARLY  
WEDNESDAY, WITH LITTLE CHANGE TO THE LOCAL AREA. A VERY LARGE LOW  
PRESSURE SYSTEM WILL DROP SOUTH FROM THE GULF OF ALASKA MID- TO  
LATE-WEEK, THOUGH MODELS HAVE COME TO MORE OF A CONSENSUS THAT  
THIS WILL REMAIN PRETTY WELL TO OUR NORTH/NORTHWEST.  
 
PREVIOUS DISCUSSION...310 AM PDT SUN OCT 5 2025...  
 
MAIN STORY THIS WEEK REMAINS THE POTENTIAL FOR TROPICAL MOISTURE  
FROM WHAT IS NOW TROPICAL STORM PRISCILLA BEING DRAWN INTO THE  
REGION LATE THURSDAY THROUGH SATURDAY. ENSEMBLE MEAN PRECIPITABLE  
WATER FROM BOTH THE EC AND GEFS ARE AROUND 1.5", WHICH ISN'T BAD  
FOR EARLY OCTOBER. HOWEVER, IT LOOKS LIKE MOST OF THIS MOISTURE  
WILL BE ABOVE THE 700 MB LEVEL.  
 
THE REAL QUESTION IS HOW MUCH FORCING WE'LL HAVE TO WORK WITH.  
INSTABILITY REMAINS WEAK WITH MUCAPE LESS THAN 100 J/KG, SO  
THUNDERSTORM PROBABILITIES ARE LESS THAN 10%. WHILE THERE IS LESS  
SPREAD AMONGST THE ENSEMBLES WITH RESPECT TO THE POSITION OF THE  
LARGE UPPER LOW OFF THE COAST DURING THIS PERIOD, ENOUGH SPREAD  
REMAINS THAT UNCERTAINTY IN FORCING AND THEREFORE RAINFALL AMOUNTS  
REMAIN. WITH THE LOW FURTHER WEST, PLACING US MORE UNDER THE  
INFLUENCE OF THE RIDGE TO THE EAST, ACCUMULATING PRECIPITATION  
WILL BE HARDER TO COME BY. A FURTHER WEST TRACK OF THE LOW WOULD  
PROVIDE A LITTLE MORE LIFT AND PRECIPITATION.  
 
GIVEN THE LACK OF STRONG DYNAMICS EITHER WAY, THIS GENERALLY  
LOOKS LIKE A CASE WHERE RAINFALL RATES WILL REMAIN ON THE LOW END  
ABSENT ANY THUNDERSTORMS DEVELOPING, REALLY LIMITING THE FLOODING  
THREAT. NBM 10TH/90TH PERCENTILE 48 HR RAINFALL ACCUMULATIONS  
RANGE FROM ZERO TO AROUND AN INCH FOR LATE THU-LATE SAT, THOUGH  
THE 90TH PERCENTILE IS DEFINITELY SKEWED BY A COUPLE OF VERY WET  
ENSEMBLE MEMBERS. NBM MEAN IS CLOSER TO 0.2-0.3". ENSEMBLE PW  
FALLS OFF A CLIFF ON SUNDAY AS THE UPPER TROUGH PASSES, PUSHING  
TROPICAL MOISTURE OUT OF THE AREA. HIGHS WILL REMAIN NEAR NORMAL  
THROUGH FRIDAY, THEN A COOLING TREND FOLLOWS FOR SATURDAY AND  
SUNDAY AS THE TROUGH MOVES THROUGH.  
 

 
   
AVIATION
 
 
051530Z....COASTS/VALLEYS...PATCHY LOW CLOUDS 1200-1800 FT MSL AT  
THE COAST, MOST WIDESPREAD IN SAN DIEGO COUNTY. LOW CLOUDS SHOULD  
CLEAR INLAND AREAS BY 19Z, BUT MAY LINGER AT THE IMMEDIATE COASTLINE  
THIS AFTERNOON. CLOUDS WITH BASES 1200-1800 FT MSL WILL START TO  
MOVE INLAND AFTER 00Z MON, SPREADING INTO THE VALLEYS AND PORTIONS  
OF THE INLAND EMPIRE. THERE IS A 40% CHANCE OF LOW CLOUDS REACHING  
KONT BY 12Z MON.  
 
MOUNTAINS/DESERTS...VFR CONDITIONS WILL PREVAIL INTO MON MORNING.  
 

 
   
MARINE
 
 
NO HAZARDOUS MARINE CONDITIONS ARE EXPECTED THROUGH THURSDAY  
MORNING.  
 

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

 
 

 
 
PUBLIC...CSP/SS  
AVIATION/MARINE...CO  
 
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