902  
FXUS66 KSGX 040957  
AFDSGX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAN DIEGO CA  
257 AM PDT SAT OCT 4 2025  
   
SYNOPSIS
 
 
GUSTY WEST WINDS IN THE MOUNTAINS AND DESERTS WILL WEAKEN THROUGH  
THE MORNING. WEAK OFFSHORE WINDS AND WARMING WEST OF THE  
MOUNTAINS SATURDAY. ANOTHER BRIEF COOL DOWN FOR EARLY NEXT WEEK,  
WITH A GRADUAL WARMING TREND INTO THE MIDDLE/LATTER PART OF NEXT  
WEEK. THERE IS THE POTENTIAL FOR TROPICAL MOISTURE TO MOVE INTO  
THE AREA LATE IN THE WEEK WITH A SLIGHT CHANCE OF SHOWERS OVER THE  
MOUNTAINS.  
 

 
   
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
 
 
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO  
COUNTIES...  
 
MORNING WATER VAPOR IMAGERY SHOWS THE UPPER LEVEL TROUGH AXIS  
MOVING INTO THE COLORADO RIVER VALLEY. WEST WINDS ARE GUSTING TO  
AROUND 25-40 MPH ON THE DESERT MOUNTAIN SLOPES AND THROUGH THE  
PASSES, LOCALLY UP TO 50 MPH BELOW THE SAN GORGONIO PASS. WINDS  
WILL CONTINUE TO WEAKEN THROUGH THE MORNING AS THE TROUGH MOVES  
OFF TO THE EAST AND SURFACE PRESSURE GRADIENTS RELAX AND TURN  
WEAKLY OFFSHORE TO THE NORTH. THE 00Z KNKX SOUNDING HAD A VERY  
WEAK MARINE INVERSION, AND AS A RESULT LOW CLOUD COVERAGE REMAINS  
VERY PATCHY. ANY LOW CLOUDS WILL CLEAR BY MID MORNING. OTHERWISE  
WARMER TODAY FOR MOST AREAS, EXCEPT THE LOWER DESERTS WHERE HIGHS  
WILL BE A COUPLE DEGREES LOWER THAN FRIDAY.  
 
A WEAK COASTAL EDDY IS FORECAST TO DEVELOP TONIGHT, WHICH WOULD  
HELP WITH LOW CLOUD DEVELOPMENT OVER THE COASTAL AREAS. WEAK  
POSITIVELY-TILTED TROUGHING REMAINS ACROSS THE WESTERN US ON  
SUNDAY, THEN A CLOSED LOW DEVELOPS AND RETROGRADES OFF THE CENTRAL  
CA COAST ON MONDAY, THEN OPENS UP AND MOVES OFF TO THE NORTHEAST  
AS ANOTHER LOW DROPS OUT OF THE GULF OF ALASKA AND DIGS OFF THE  
WEST COAST. OVERALL NOT MUCH CHANGE FOR SUNDAY THROUGH TUESDAY  
WITH HIGHS AROUND 3-6 DEGREES BELOW NORMAL AND NIGHT AND MORNING  
LOW CLOUDS OVER THE COASTAL AREAS AND WESTERN VALLEYS.  
 
BY WEDNESDAY EVENING ENSEMBLES REALLY BEGIN TO DIVERGE ON THE  
PLACEMENT OF THE LOW AS IT DROPS DOWN OFF THE PAC NW COAST. MOST  
EC MEMBERS HAVE A TRACK CLOSER TO THE COAST, THE GEFS IS MORE  
OFFSHORE, AND THE GEPS IS A MIX OF THE TWO. NOT ONLY WILL THIS  
HAVE IMPLICATIONS FOR HIGH TEMPERATURE FORECASTS FOR THE LATTER  
HALF OF THE WEEK, IT WILL GREATLY INFLUENCE WHERE TROPICAL  
MOISTURE TRACKS AND HOW MUCH FORCING WILL COEXIST WITH IT. THE  
TRACK OF THE TROPICAL SYSTEM ITSELF ALSO VARIES GREATLY. NEEDLESS  
TO SAY, THERE IS A LOT OF UNCERTAINTY AS WE HEAD INTO THE LATTER  
HALF OF THE WEEK. FOR NOW HAVE SLIGHT (15-20%) CHANCES OF SHOWERS  
OVER THE MOUNTAINS AND PARTS OF THE DESERTS FRI-SAT AS MOISTURE IS  
FAIRLY HIGH BASED, BUT IF WE GET STRONG ENOUGH FORCING (TROUGHING  
NEARBY), SHOWERS WEST OF THE MOUNTAINS WOULD NOT BE OUT OF THE  
QUESTION, AS INDICATED BY A HANDFUL OF ENSEMBLE MEMBERS. CURRENTLY  
INSTABILITY APPEARS TOO WEAK TO INCLUDE ANY THUNDERSTORMS IN THE  
FORECAST.  
 

 
   
AVIATION
 
 
040930Z....COASTS/VALLEYS...PATCHY LOW CLOUDS BASED 2500-3500 FT  
WILL REMAIN SCATTERED AND INTERMITTENT THROUGH THIS MORNING. ANY  
CLOUDS THAT REMAIN AFTER SUNRISE SHOULD SCATTER OUT BETWEEN 15-17Z.  
LOW CLOUDS WILL STRUGGLE TO REDEVELOP SATURDAY NIGHT. LESS THAN 30%  
CHANCE FOR CIGS AT COASTAL TAF SITES BEFORE 12Z SUN. ANY CLOUDS THAT  
DEVELOP SHOULD HAVE SIMILAR BASES AND REMAIN CONFINED TO COASTS AND  
WESTERN VALLEYS.  
 
MOUNTAINS/DESERTS...ELEVATED WEST WINDS WILL CONTINUE TO SUBSIDE  
THIS MORNING. OTHERWISE, VFR CONDITIONS PREVAILING THROUGH SATURDAY  
NIGHT.  
 

 
   
MARINE
 
 
WINDS AND SEAS WILL CONTINUE TO GRADUALLY DIMINISH THROUGH THIS  
MORNING. OTHERWISE, NO HAZARDOUS MARINE CONDITIONS ARE EXPECTED  
THROUGH WEDNESDAY MORNING.  
 

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

 
   
SGX WATCHES/WARNINGS/ADVISORIES
 
 
CA...WIND ADVISORY UNTIL 5 AM PDT EARLY THIS MORNING FOR SAN DIEGO  
COUNTY DESERTS-SAN GORGONIO PASS NEAR BANNING.  
 
PZ...NONE.  
 

 
 

 
 
PUBLIC...SS  
AVIATION/MARINE...KW  
 
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