338  
FXUS66 KLOX 171720  
AFDLOX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA  
1020 AM PDT SAT AUG 17 2019  
   
SYNOPSIS
 
17/654 AM.  
 
TEMPERATURES WILL BE COOLER THIS WEEKEND THEN WARMER NEXT WEEK  
WITH THE HIGHEST READINGS MIDWEEK. OVERNIGHT AND MORNING LOW CLOUDS  
AND FOG WILL CONTINUE IN COASTAL AND ADJACENT VALLEY AREAS THROUGH  
MONDAY THEN WILL BE PRIMARILY ALONG THE COAST THROUGH WEDNESDAY.  
 

 
   
SHORT TERM (TDY-MON)
 
17/903 AM.  
 
THE MARINE INVERSION THIS MORNING WAS NEAR 2600 FT DEEP AT LAX. LOW  
CLOUDS WERE QUITE WIDESPREAD THIS MORNING, EXTENDING FROM THE COAST  
WELL INTO THE VLYS AND EVEN INTO SOME LOWER COASTAL SLOPES. THE LOW  
CLOUDS ARE FORECAST TO CLEAR BACK TO THE COAST BY MIDDAY WITH LOW  
CLOUDS PROBABLY LINGERING AT SOME OF THE BEACHES THRU THE AFTERNOON  
THANKS TO GOOD ONSHORE GRADIENTS, WHICH ARE EXPECTED TO BE AROUND  
+9.2 MB AT 00Z ACCORDING TO THE LATEST NAM. OTHERWISE, MOSTLY SUNNY  
SKIES WILL PREVAIL ACROSS THE REGION THRU THE AFTERNOON.  
 
THE GOOD ONSHORE GRADIENTS WILL PROMOTE GUSTY S TO W WINDS ACROSS  
MUCH OF THE FOOTHILLS, MTNS AND DESERTS THIS AFTERNOON. TEMPS WILL  
BE MUCH COOLER ACROSS THE FORECAST AREA AS WELL, WITH HIGHS EXPECTED  
TO REACH ONLY INTO THE 80S IN THE WARMER VLYS AND LOWER MTNS, ALTHO  
THE ANTELOPE VLY SHOULD STILL WARM INTO THE 90S THIS AFTERNOON.  
TEMPS OVERALL ACROSS THE REGION TODAY WILL BE 6-12 DEG BELOW NORMAL  
FOR THIS TIME OF YEAR.  
 
AN UPPER LEVEL TROF WILL PERSIST ALONG AND OFF THE CA COAST TODAY  
THRU SUN, WITH H5 HEIGHTS IN THE 586-588 DM RANGE. A LARGE UPPER  
LEVEL HIGH OVER THE SOUTHERN PLAINS WILL START TO SLOWLY EXPAND W  
AND INTO SRN CA SUN NIGHT AND MON, WITH H5 HEIGHTS EXPECTED TO  
INCREASE TO 590-591 DM FOR MON AFTERNOON. A DRY SW FLOW ALOFT WILL  
PREVAIL FOR THE MOST PART THRU THE PERIOD.  
 
THE MARINE INVERSION IS EXPECTED TO BE SLIGHTLY LOWER TONIGHT INTO  
SUN MORNING, THEN SHRINK TO ABOUT 1500-1800 FT OR SO SUN NIGHT INTO  
MON MORNING. EVEN SO, PLENTY OF NIGHT AND MORNING LOW CLOUDS AND FOG  
WILL AFFECT THE COASTAL AREAS INTO PORTIONS OF THE ADJACENT VLYS  
DURING THE PERIOD. LOW CLOUDS AND FOG WILL LIKELY AFFECT THE SALINAS  
RIVER VLY FOR THE LATE NIGHT AND MORNING HOURS AS WELL THRU MON  
MORNING. OTHERWISE, MOSTLY CLEAR SKIES WILL CONTINUE ACROSS SWRN CA  
THRU MON.  
 
THE ONSHORE FLOW WILL SLOWLY DECREASE THRU THE PERIOD, WITH THE LAX-  
DAG FORECAST GRADIENT (NAM) EXPECTED TO BE ABOUT +8.3 MB SUN  
AFTERNOON, AND +7.3 MB MON AFTERNOON. SOME GUSTY S-W AFTERNOON AND  
EVENING WINDS WILL CONTINUE FOR THE FOOTHILLS, MTNS AND DESERTS EACH  
DAY, WITH SOME GUSTY NW WINDS FORECAST FOR THE CENTRAL COAST.  
 
TEMPS ARE EXPECTED TO REMAIN ABOUT 6-12 DEG BELOW NORMAL FOR MANY  
AREAS ON SUN, THEN WARM SLIGHTLY TO ABOUT 2-7 DEG BELOW NORMAL FOR  
MON. THE WARMEST VLYS AND LOWER MTNS SHOULD REACH THE 80S ON SUN,  
AND MID 80S TO LOW 90S MON. THE ANTELOPE VLY SHOULD BE IN THE 90S  
EACH DAY.  
   
LONG TERM (TUE-FRI)
 
17/313 AM.  
 
BY TUESDAY THE UPPER-LEVEL HIGH WILL PUSH FURTHER WEST AND HGTS  
WILL RISE TO 594 DM OVER SRN CA. THE ONSHORE FLOW TO THE EAST  
WILL BE WEAK AND OFFSHORE FLOW WILL DEVELOP FROM THE NORTH. THIS  
WILL GREATLY REDUCE THE MARINE LAYER STRATUS PATTERN AND WILL  
BRING ANOTHER 3 TO 6 DEGREES OF WARMING TO ALL AREAS.  
 
SIMILAR TO THIS WEEK'S WARM UP, WEDNESDAY AND THURSDAY WILL BE THE  
WARMEST DAYS AND IF THE FORECAST REMAINS VALID THERE WILL BE A  
NEED FOR HEAT PRODUCTS. HGTS WILL REMAIN NEAR 594 DM, OR ABOUT 5  
DM HIGHER THAN NORMAL. WEAK ONSHORE FLOW TO THE EAST AND 2 TO 3 MB  
OFFSHORE FLOW FROM THE NORTH IS EXPECTED. THERE WILL BE MINIMAL  
MORNING STRATUS. TEMPERATURES WILL JUMP ANOTHER 4 TO 8 DEGREES AND  
WILL BE ABOVE NORMAL ALMOST EVERYWHERE. THE RIDGE WILL BREAK DOWN  
A LITTLE ON THURSDAY WHICH WILL DROP MAX TEMPS BY 2 TO 4 DEGREES.  
 
THE RIDGE BREAKS DOWN FURTHER NEXT FRIDAY AND THE ONSHORE FLOW  
BEGINS TO REASSERT ITSELF. THE MARINE LAYER AND THE ATTENDANT  
MARINE LAYER STRATUS WILL BEGIN TO REDEVELOP. MAX TEMPS WILL FALL  
ANOTHER 2 TO 5 DEGREES.  
 
STILL TRACKING A TROPICAL SYSTEM FORECAST TO DEVELOP AROUND  
SOUTHERN BAJA CALIFORNIA FRIDAY AND MOVE TO THE NORTH. THE  
MOISTURE AND SWELL FROM THIS SYSTEM COULD AFFECT SRN CA'S WEATHER  
DURING THE WEEK OF THE 26TH.  
 

 
   
AVIATION
 
17/1720Z.  
 
AT 1615Z, THE MARINE INVERSION AT KLAX WAS BASED AT 2700 FEET.  
THE TOP OF THE INVERSION WAS 4500 FEET WITH A TEMPERATURE OF  
23 DEGREES CELSIUS.  
 
OVERALL, MODERATE CONFIDENCE IN 18Z COASTAL/VALLEY TAFS AND HIGH  
CONFIDENCE IN DESERT TAFS. CURRENT MVFR CIGS WILL DISSIPATE BY  
NOON WITH VFR CONDITIONS FOR ALL SITES THIS AFTERNOON. FOR  
TONIGHT, HIGH CONFIDENCE IN RETURN OF STRATUS/FOG TO ALL COASTAL  
AND VALLEY SITES, BUT ONLY MODERATE CONFIDENCE IN TIMING.  
 
KLAX...OVERALL, MODERATE CONFIDENCE IN 18Z TAF. HIGH CONFIDENCE IN  
VFR CONDITIONS THIS AFTERNOON. FOR TONIGHT, HIGH CONFIDENCE IN  
RETURN OF MVFR CIGS, BUT ONLY MODERATE CONFIDENCE IN TIMING (COULD  
BE +/- 2 HOURS OF CURRENT 04Z FORECAST).  
 
KBUR...OVERALL, MODERATE CONFIDENCE IN 18Z TAF. HIGH CONFIDENCE IN  
VFR CONDITIONS THIS AFTERNOON. FOR TONIGHT, HIGH CONFIDENCE IN  
RETURN OF STRATUS, BUT ONLY MODERATE CONFIDENCE IN TIMING (COULD  
BE +/- 2 HOURS OF CURRENT 07Z FORECAST). THERE IS A 40% CHANCE  
OF IFR CIGS 07Z-12Z.  
 

 
   
MARINE
 
17/815 AM.  
 
FOR THE OUTER WATERS, MODERATE TO HIGH CONFIDENCE IN CURRENT  
FORECAST. THERE IS HIGH CONFIDENCE IN WINDS AND SEAS REMAINING  
BELOW SMALL CRAFT ADVISORY (SCA) LEVELS TODAY THROUGH SUNDAY.  
ON MONDAY, THERE IS A 50% CHANCE OF SCA LEVEL WINDS DEVELOPING  
(ESPECIALLY ACROSS THE SOUTHERN WATERS) THEN A 70% CHANCE OF SCA  
LEVEL WINDS TUESDAY AND WEDNESDAY.  
 
FOR THE INNER WATERS NORTH OF POINT SAL, MODERATE TO HIGH  
CONFIDENCE IN CURRENT FORECAST. THERE IS HIGH CONFIDENCE THAT  
WINDS AND SEAS WILL REMAIN BELOW SCA LEVELS TODAY THROUGH MONDAY.  
THERE IS A 60% CHANCE OF SCA LEVEL WINDS DURING THE AFTERNOON AND  
EVENING HOURS OF TUESDAY AND WEDNESDAY.  
 
FOR THE INNER WATERS SOUTH OF POINT CONCEPTION, MODERATE TO HIGH  
CONFIDENCE IN CURRENT FORECAST. IN GENERAL, THERE IS HIGH  
CONFIDENCE THAT WINDS AND SEAS WILL REMAIN BELOW SCA LEVELS  
TODAY THROUGH WEDNESDAY. THE ONLY EXCEPTION WILL BE THE WESTERN  
HALF OF THE SANTA BARBARA CHANNEL WHERE THERE IS A 60% CHANCE OF  
SCA LEVEL WINDS DURING THE LATE AFTERNOON AND EVENING HOURS MONDAY  
THROUGH WEDNESDAY.  
 

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

 
 
.HAZARD POTENTIAL OUTLOOK (MON-FRI).  
 
HOT TEMPERATURES COULD LEAD TO HEAT ADVISORIES FOR SOME INLAND  
AREAS NEXT WEDNESDAY AND POSSIBLY THURSDAY. OTHERWISE, NO  
SIGNIFICANT HAZARDS ARE EXPECTED THROUGH THE PERIOD.  
 

 
 

 
 
PUBLIC...SIRARD/RORKE  
AVIATION...RAT  
MARINE...RAT  
SYNOPSIS...KJ  
 
WEATHER.GOV/LOSANGELES  
 
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