039  
FXUS66 KLOX 211133  
AFDLOX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA  
433 AM PDT MON APR 21 2025  
   
SYNOPSIS
 
21/405 AM.  
 
ONSHORE FLOW WILL STRENGTHEN THROUGH THE WEEK AND BRING A COOLING  
TREND THROUGH FRIDAY. NIGHT THROUGH MORNING LOW CLOUDS AND FOG  
WILL BE A STAPLE OF THE FORECAST, STRUGGLING TO CLEAR FROM  
BEACHES EACH DAY. NIGHT THROUGH MORNING DRIZZLE IS POSSIBLE TOWARD  
MID-TO-LATE WEEK AS THE MARINE LAYER DEPTH DEEPENS SUBSTANTIALLY.  
GUSTY ONSHORE WINDS ARE POSSIBLE ACROSS THE INTERIOR PORTIONS FOR  
THE LATTER HALF OF THE WEEK.  
 

 
   
SHORT TERM (TDY-WED)
 
21/405 AM.  
 
ONSHORE FLOW IS STRENGTHENING EARLY THIS MORNING AS BROAD WEAK  
TROUGHING DEVELOPS OVER THE WEST COAST. SURFACE PRESSURE GRADIENTS  
ARE TRENDING ABOUT A MILLIBAR MORE STRONGLY ONSHORE. CLOUDS ARE  
WELL-ENTRENCHED ALONG THE CENTRAL COAST BUT STRUGGLING TO FORM  
INSIDE THE SOUTHERN CALIFORNIA BIGHT AND ALONG THE SOUTH COAST OF  
CALIFORNIA DUE TO HIGH CLOUDINESS ALOFT PLAYING TRICKS ON THE  
MARINE LAYER DEPTH. AS THE MORNING PROGRESSES, HIGH CLOUDS SHOULD  
LESSEN IN COVERAGE AND ALLOW FOR BETTER LOW CLOUDS COVERAGE INTO  
THE BIGHT AND THE LOS ANGELES AND VENTURA COUNTY COAST.  
 
ONSHORE FLOW WILL CONTINUE TO STRENGTHEN THROUGH THE PERIOD AS  
WEAK TROUGHING WILL REMAIN ANCHORED OFF THE WEST COAST. LOW CLOUDS  
AND FOG WILL BECOME MORE ENTRENCHED TONIGHT AND INTO TUESDAY  
MORNING AS ONSHORE FLOW STRENGTHENS. THE MARINE LAYER DEPTH WILL  
DEEPEN EACH NIGHT AND MORNING, DEEPENING FROM AROUND 700 FEET AT  
KLAX THIS MORNING TO NEAR 2000 FEET DEEP BY TUESDAY MORNING, THEN  
TO NEAR 2500 FEET DEEP BY WEDNESDAY MORNING. CLOUDS SHOULD MAKE A  
RETURN TO THE LOS ANGELES AND VENTURA COUNTY VALLEYS TONIGHT AND  
INTO TUESDAY MORNING. PATCHY LATE NIGHT AND EARLY MORNING DRIZZLE  
CANNOT BE RULED OUT TONIGHT AND INTO TUESDAY MORNING, BUT THERE  
IS A HIGHER CHANCE ON TUESDAY NIGHT AND INTO WEDNESDAY MORNING.  
 
WITH THE STRONGER ONSHORE TRENDS TAKING SHAPE EACH DAY, LOW  
CLOUDS AND FOG WILL LIKELY STRUGGLE TO CLEAR FROM THE BEACHES AND  
IMMEDIATE COAST OVER THE COMING DAYS. AS A RESULT, TEMPERATURES  
WILL BE BELOW SEASONAL NORMALS FOR THIS TIME OF YEAR, ESPECIALLY  
AT THE BEACHES AND NEAR THE COAST.  
   
LONG TERM (THU-SUN)
 
21/402 AM.  
 
ONSHORE FLOW AND A DEEP MARINE LAYER WILL BE THE MAIN STORY  
THROUGH FRIDAY. NIGHT THROUGH MORNING LOW CLOUDS AND FOG WITH  
DRIZZLE WILL LIKELY PUSH WELL INTO THE COASTAL SLOPES OF THE  
MOUNTAINS. THE FORECAST ENSEMBLES ALL ADVERTISE MUCH COOLER  
CONDITIONS LINGERING WITH TEMPERATURES BELOW SEASONAL NORMALS INTO  
LATE WEEK. GUSTY ONSHORE WINDS, EACH AFTERNOON AND EVENING ACROSS  
THE INTERIOR PORTION, COULD REACH ADVISORY LEVELS IN THE  
FOOTHILLS OF THE ANTELOPE VALLEY, ESPECIALLY IF 10 MB ONSHORE  
GRADIENTS DEVELOP.  
 
WHILE THE FORECAST ENSEMBLES AGREE WELL THROUGH FRIDAY, THE  
ENSEMBLE SPREAD STARTS TO WIDEN OVER NEXT WEEKEND AND INTO NEXT  
WEEK. CLUSTER ANALYSIS FAVORS TROUGHING LINGERING OVER THE REGION  
INTO FRIDAY OR SATURDAY, THEN THE CLUSTERS START TO DIVERGE.  
THEREAFTER, THE MOST LIKELY SCENARIO SUGGEST RIDGING ALOFT  
BUILDING, GIVING A 56 PERCENT CHANCE OF OCCURING. EPS FORECAST  
ENSEMBLES LEAN TOWARD WARMING FOR NEXT WEEKEND IN THE MAXIMUM  
TEMPERATURE MEANS. THE FORECAST GOES WITH NBM VALUES FOR THE  
CURRENT TIME.  
 

 
   
AVIATION
 
21/1133Z.  
 
AT 1100Z AT KLAX, THE MARINE INVERSION WAS AROUND 700 FEET DEEP.  
THE TOP OF THE INVERSION WAS 2100 FEET WITH A TEMPERATURES OF  
18 DEGREES CELSIUS.  
 
OVERALL FOR 12Z TAF PACKAGE, HIGH CONFIDENCE IN DESERT TAFS WITH  
MODERATE CONFIDENCE FOR COASTAL/VALLEY SITES. LOWER CONFIDENCE FOR  
COASTAL/VALLEY SITES DUE TO UNCERTAINTIES WITH THE MARINE LAYER  
STRATUS. MODERATE CONFIDENCE IN TIMING OF FLIGHT CATEGORY CHANGES  
(+/- 3 HOURS OF CURRENT FORECASTS) FOR TAFS NORTH OF POINT  
CONCEPTION. FOR SITES SOUTH OF POINT CONCEPTION, THERE IS A 50%  
CHANCE OF VFR CONDITIONS OR IFR/LIFR THIS MORNING.  
 
KLAX...MODERATE CONFIDENCE IN 12Z TAF. THERE IS A 50% CHANCE THAT  
IFR CONDITIONS DO NOT DEVELOP 12Z-17Z. FOR TONIGHT, MODERATE  
CONFIDENCE IN RETURN OF CIG/VSBY RESTRICTIONS AS WELL AS TIMING OF  
FLIGHT CATEGORY CHANGES (+/- 3 HOURS OF CURRENT FORECASTS). NO  
SIGNIFICANT EASTERLY WIND COMPONENT IS EXPECTED.  
 
KBUR...OVERALL, MODERATE CONFIDENCE IN 12Z TAF. THROUGH THIS  
EVENING, HIGH CONFIDENCE IN VFR CONDITIONS. FOR TONIGHT, MODERATE  
CONFIDENCE IN RETURN OF IFR CONDITIONS WITH MODERATE CONFIDENCE IN  
TIMING (+/- 3 HOURS OF CURRENT 10Z FORECAST).  
 

 
   
MARINE
 
21/1258 AM.  
 
FOR THE OUTER WATERS, MODERATE TO HIGH CONFIDENCE IN CURRENT  
FORECAST. THROUGH TONIGHT, THERE IS A 10-20% CHANCE OF SMALL CRAFT  
ADVISORY (SCA) LEVEL WINDS, MAINLY AROUND POINT CONCEPTION. FOR  
TUESDAY, THERE IS A 30-50% CHANCE OF SCA LEVEL WINDS ACROSS ALL  
THE OUTER WATERS. FOR WEDNESDAY THROUGH FRIDAY, THE CHANCES FOR  
SCA LEVEL WINDS INCREASE TO 60-80%.  
 
FOR THE INNER WATERS NORTH OF POINT SAL, MODERATE TO HIGH  
CONFIDENCE IN CURRENT FORECAST. TODAY THROUGH TUESDAY, HIGH  
CONFIDENCE IN WINDS AND SEAS REMAINING BELOW SCA LEVELS. FOR  
WEDNESDAY THROUGH FRIDAY, THERE IS A 50-60% CHANCE OF SCA LEVEL  
WINDS, MAINLY IN THE LATE AFTERNOON AND EVENING HOURS.  
 
FOR THE INNER WATERS SOUTH OF POINT CONCEPTION, MODERATE TO HIGH  
CONFIDENCE IN CURRENT FORECAST. TODAY THROUGH FRIDAY, HIGH  
CONFIDENCE IN WINDS AND SEAS REMAINING BELOW SCA LEVELS ACROSS  
MOST AREAS. THE ONLY EXCEPTION WILL BE THE WESTERN HALF OF THE  
SANTA BARBARA CHANNEL WHERE THERE IS A 40-60% CHANCE OF SCA LEVEL  
WINDS WEDNESDAY THROUGH FRIDAY, MAINLY DURING THE LATE AFTERNOON  
THROUGH EVENING HOURS.  
 

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

 
 

 
 
PUBLIC...HALL  
AVIATION...RAT  
MARINE...RAT  
SYNOPSIS...HALL  
 
WEATHER.GOV/LOSANGELES  
 
EXPERIMENTAL GRAPHICAL HAZARDOUS WEATHER OUTLOOK AT:  
HTTPS://WWW.WEATHER.GOV/ERH/GHWO?WFO=LOX  
 
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