680  
FXUS66 KLOX 260341  
AFDLOX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA  
841 PM PDT MON OCT 25 2021  
   
SYNOPSIS
 
25/820 PM.  
 
MOSTLY CLEAR SKIES ARE EXPECTED ACROSS SOUTHWEST CALIFORNIA  
TONIGHT AS A STORM SYSTEM MOVES EAST OF THE AREA. HIGH PRESSURE  
WILL BEGIN TO BUILD OVER THE REGION ON TUESDAY FOR A WARMING  
TREND THAT WILL EXTEND INTO THURSDAY. COOLER TEMPERATURES AND A  
RETURN OF COASTAL OVERNIGHT AND EARLY MORNING CLOUDS ARE EXPECTED  
LATE IN THE WEEK.  
 

 
   
SHORT TERM (MON-THU)
 
25/808 PM.  
 
***UPDATE***  
 
TODAY'S STORM SYSTEM IS MOVING SOUTHEAST OF THE AREA THIS  
EVENING.THE RADAR SHOWS ISOLATED SHOWERS OVER KERN COUNTY,  
CURRENTLY DISSIPATING AS THEY MOVE TOWARD THE NORTH SLOPES OF  
VENTURA COUNTY, AND THIS COULD MAINTAIN SOME CLOUDINESS IN THAT  
AREA THROUGH LATER TONIGHT. OTHERWISE, MOST AREAS ARE NOW CLEAR  
WITH ADDITIONAL LINGERING CLOUDS OVER EASTERN LA COUNTY.  
 
RAINFALL TOTALS GENERALLY RANGED FROM 1 TO 5 INCHES OVER SAN LUIS  
OBISPO AND SANTA BARBARA COUNTIES (HIGHEST IN THE SLO COASTAL  
HILLS AND THE SANTA YNEZ RANGE) TO 0.50 TO 3 INCHES OVER VENTURA  
AND LA COUNTIES. THE ANTELOPE VALLEY HAD MUCH MORE VARIABLE  
AMOUNTS, RANGING FROM 0.11 AT LAKE PALMDALE TO 0.68 AT POPPY PARK.  
 
NORTHERLY SURFACE GRADIENTS BEHIND THE FRONT ARE CAUSING GUSTY  
WEST TO NORTHWEST WINDS TO FILL IN ACROSS THE AREA, STRONGEST OVER  
THE ISLANDS WITH GUSTS UP TO 40 MPH, OTHERWISE 25 TO 30 MPH IN  
AREAS PRONE TO WEST TO NORTH WINDS SUCH AS THE SBA SOUTH COAST,  
I-5 CORRIDOR AND ANTELOPE VALLEY.  
 
A MOSTLY CLEAR NIGHT IS EXPECTED, ALTHOUGH SOME WIND SHELTERED  
VALLEYS COULD SEE SOME FOG FORMATION DUE TO WEST GROUND AND GOOD  
RADIATIONAL COOLING.  
 
***FROM PREVIOUS DISCUSSION***  
 
HIGH PRESSURE BEGINS BUILDING OVER THE AREA ON TUESDAY FOR  
SLIGHTLY WARMER TEMPERATURES AND UNDER SUNNY SKIES. GUSTY  
NORTHWEST WINDS WILL CONTINUE SOME MOUNTAIN AREAS, STRONGEST  
TUESDAY EVENING. IN CONJUNCTION WITH THE BUILDING HIGH PRESSURE, A  
SURFACE HIGH PRESSURE BUILDS OVER THE GREAT BASIN WHICH WILL  
BRING ABOUT SOME WEAK OFFSHORE GRADIENTS TO THE FORECAST AREA ON  
WED AND THU. ONLY EXPECTING PEAK NORTHEAST WINDS EACH DAY IN LA  
AND VTU COUNTIES TO GUST AROUND 35, MAYBE 40 MPH, BUT NOT  
EXPECTING ANYTHING SIGNIFICANT. THERE WILL ALSO BE SOME GUSTY  
NORTHEAST WINDS THROUGH SLO COUNTY ON WEDNESDAY. TEMPERATURES WILL  
WARM INTO THE 80S THROUGH THE VALLEY AREAS ON THE COASTAL SIDE OF  
THE MOUNTAINS ON BOTH WED AND THU, WITH THU BEING THE WARMEST DAY  
OF THE 7 DAY FORECAST.  
   
LONG TERM (FRI-MON)
 
25/219 PM.  
 
THE UPPER LEVEL RIDGE MOVES EAST OF THE AREA ON FRIDAY AS ANOTHER  
UPPER LEVEL TROUGH, THOUGH MUCH WEAKER THAN THE CURRENT TROUGH,  
MOVES INTO THE WEST COAST. THIS WILL BRING A RETURN TO ONSHORE  
FLOW, COOL TEMPERATURES FOR ALL BUT FAR INLAND AREAS, AND COASTAL  
STRATUS ON FRIDAY. BOTH THE EC AND GFS ENSEMBLES CONTINUE TO COOL  
THINGS ON SATURDAY AND SUNDAY, ALTHOUGH THE GFS ENSEMBLE WARMS  
THINGS A BIT ON MONDAY AS WEAK HIGH PRESSURE RETURNS.  
 

 
   
AVIATION
 
26/0018Z.  
 
AT 2214Z AT KLAX, THERE WAS NO MARINE LAYER NOR INVERSION.  
 
HIGH FORECAST FOR ALL TAF SITES EXCEPT MODERATE TO HIGH FORECAST  
FOR THE LA COUNTY SITES THROUGH THIS EVENING. A COLD FRONT WITH  
ASSOCIATED RAINFALL IS MOVING THROUGH EASTERN LA COUNTY AND IS  
EXPECTED TO BE OUT OF THE AREA BY 03Z-04Z. DURING THIS TIME, CIGS  
OVER LA COUNTY ARE VFR BUT OCCASIONAL MVFR CONDS AND VCSH WILL BE  
POSSIBLE THROUGH 04Z. FOLLOWING THE FRONT, INCREASING NW-N WINDS  
WILL AFFECT SOME SITES THROUGH TONIGHT.  
 
KLAX...MODERATE CONFIDENCE IN THE 00Z TAF 00Z-04Z, HIGH CONFIDENCE  
FOR THE REMAINDER OF THE PERIOD. THERE IS A 20% CHANCE OF SHOWERS  
AND MVFR CIGS THROUGH 04Z, THEN VFR CONDS EXPECTED THROUGH THE  
PERIOD. N WINDS UP TO 08KT EXPECTED OVERNIGHT.  
 
KBUR...MODERATE CONFIDENCE IN THE 00Z TAF 00Z-04Z, HIGH CONFIDENCE  
FOR THE REMAINDER OF THE PERIOD. THERE IS A 30% CHANCE OF SHOWERS  
AND MVFR CIGS THROUGH 04Z, THEN VFR CONDS EXPECTED THROUGH THE  
PERIOD. N WINDS UP TO 08KT EXPECTED OVERNIGHT.  
 

 
   
MARINE
 
25/828 PM.  
 
WIDESPREAD POST-FRONTAL GUSTY NORTHWEST TO WEST WINDS WILL  
CONTINUE THROUGH THIS (MONDAY) EVENING OVER NEARLY ALL WATERS,  
THEN GRADUALLY RETURN TO THEIR MORE TRADITIONAL OUTER WATER  
POSITION FROM THE CENTRAL COAST TO SAN NICOLAS ISLAND BY TUESDAY  
AFTERNOON AND REMAIN ABOVE SMALL CRAFT ADVISORY (SCA) LEVELS  
THROUGH WEDNESDAY NIGHT. NORTHEAST WINDS WILL FORM NEARSHORE TO  
THE CENTRAL COAST WEDNESDAY AND THURSDAY MORNINGS, WITH A 30  
PERCENT CHANCE OF REACHING SCA. SANTA ANA WINDS WILL ALSO LEAD TO  
A 20 PERCENT CHANCE OF SCA WINDS FROM VENTURA TO SANTA MONICA  
THURSDAY, WITH LITTLE TO NO CHANCE OF SIGNIFICANT IMPACTS TO  
AVALON.  
 
THE VERY LARGE NORTHWEST TO WEST SWELL THAT PEAKED LATE THIS  
(MONDAY) AFTERNOON HAS BEGUN ITS SLOW DOWNWARD TREND WHICH WILL  
CONTINUE THROUGH WEDNESDAY. HEIGHTS ARE STILL BETWEEN 17 AND 21  
FEET, AND ABOUT 6 FEET HIGHER THAN ANY OF THE COMPUTER  
PROJECTIONS, SO LESS CONFIDENCE THAN USUAL AS TO HOW FAST OR SLOW  
THIS SWELL WILL EVOLVE. SMALLER BUT STILL LARGER SWELLS OF 7 TO 9  
FEET ARE IMPACT THE INNER SOUTHERN WATERS, INCLUDING THE SANTA  
BARBARA CHANNEL AND SANTA MONICA BASIN. THIS IS ALSO HIGHER THAN  
THE PROJECTIONS, BUT NOT AS MUCH AS WHAT IS HAPPENING UP NORTH. ON  
TOP OF THIS SWELL, THERE IS A SHORT PERIOD WAVE CHOP FROM THE  
WIDESPREAD WINDS, THAT WILL LOWER INTO TUESDAY.  
 
WAVES THIS LARGE WILL POSE DANGERS TO ANY BOAT DRIFTING CLOSE TO  
THE SHORE, AS WELL AS THE HARBOR ENTRANCES AT MORRO BAY AND  
VENTURA WHERE BREAKING WAVES COULD FORM.  
 

 
   
BEACHES
 
25/818 PM.  
 
A HIGH SURF WARNING IS IN EFFECT FOR THE CENTRAL COAST THROUGH  
2 PM TUESDAY AFTERNOON, WITH SURF 15-20 FEET IN MOST AREAS,  
PEAKING NEAR 25 FEET ALONG THE MORE EXPOSED NW FACING BEACHES. THE  
WAVE MODELS UNDERESTIMATED THE NW SWELL HEIGHTS, WITH SOME BUOYS  
SHOWING SWELL 5-7 FEET HIGHER THAN THE ENP OR NWPS FORECAST. IN  
LIGHT OF THIS, DECIDED TO EXTEND THE HIGH SURF WARNING FOR AN  
ADDITIONAL 18 HOURS. HIGH ADVISORIES REMAIN IN EFFECT FOR THE  
REMAINDER OF THE COASTLINE THROUGH LATE TUESDAY NIGHT.  
 
LOW TO MODERATE CONFIDENCE IN THE WAVE FORECAST, WITH BUOYS  
CURRENTLY SHOWING HEIGHTS OF 17 TO 21 FEET OVER THE OUTER WATERS.  
WILL FOLLOW THE WAVE MODEL TREND OF DECREASING WAVE HEIGHTS, BUT  
THE TIMING IS LOWER CERTAINTY. THE NEARSHORE BUOYS ARE SHOWING  
BETTER MODEL FORECASTS, SO FEEL COMFORTABLE KEEPING FORECAST OF 6  
TO 12 FOOT SURF FOR THE VENTURA AND LA COAST, LARGEST NEAR VENTURA  
HARBOR.  
 
THE ENTRANCE OF MORRO BAY HARBOR COULD BE AFFECTED BY LARGE  
BREAKING WAVES THROUGH TUESDAY MORNING.  
 

 
   
LOX WATCHES/WARNINGS/ADVISORIES
 
 
CA...HIGH SURF WARNING IN EFFECT UNTIL 2 PM PDT TUESDAY FOR ZONES  
34-35. (SEE LAXCFWLOX).  
HIGH SURF ADVISORY IN EFFECT UNTIL 3 AM PDT WEDNESDAY FOR  
ZONES 39>41-87. (SEE LAXCFWLOX).  
PZ...SMALL CRAFT ADVISORY IN EFFECT UNTIL 3 AM PDT WEDNESDAY FOR  
ZONES 645-670-673-676. (SEE LAXMWWLOX).  
SMALL CRAFT ADVISORY IN EFFECT UNTIL 5 AM PDT TUESDAY FOR  
ZONES 650-655. (SEE LAXMWWLOX).  
 

 
 
.HAZARD POTENTIAL OUTLOOK (THU-MON).  
 
HIGH SURF AND DANGEROUS RIP CURRENTS WILL AFFECT AREA BEACHES  
THROUGH WEDNESDAY.  
 

 
 

 
 
PUBLIC...JACKSON/SMITH  
AVIATION...SMITH  
MARINE...SWEET  
BEACHES...SMITH  
SYNOPSIS...SMITH  
 
WEATHER.GOV/LOSANGELES  
 
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