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SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
900 PM PDT FRI APR 17 2015

.SYNOPSIS...

THE HIGH AND OFFSHORE FLOW WILL BRING ABOVE NORMAL TEMPERATURES INTO 
SATURDAY. THEN ONSHORE FLOW WILL RETURN BY SUNDAY WITH A MARINE 
LAYER AND COOLING...AND TEMPERATURES SHOULD DROP TO NORMAL BY 
MONDAY. A COLD LOW PRESSURE SYSTEM WILL ARRIVE BY WEDNESDAY WITH 
POSSIBLE PRECIPITATION THROUGH FRIDAY.

&&

.SHORT TERM (TONIGHT-MON)...CLEAR SKIES PREVAILED ACROSS THE 
FORECAST AREA THIS EVENING. PATCHY LOW CLOUDS AND DENSE FOG IS 
EXPECTED TO DEVELOP ALONG THE L.A. COUNTY COAST AND PARTS OF THE 
CENTRAL COAST LATE TONIGHT INTO SAT MORNING....OTHERWISE THE MOSTLY 
CLEAR SKIES WILL CONTINUE THRU TONIGHT. GUSTY W TO NW WINDS ACROSS 
PARTS OF THE AREA EARLY THIS EVENING WILL DIMINISH AND TURN WEAKLY 
OFFSHORE LATE TONIGHT INTO SAT MORNING. 

A LARGE UPPER LEVEL LOW CENTERED OVER COLORADO THIS EVENING WILL 
MOVE SLOWLY E THRU SAT...WITH WEAK UPPER LEVEL RIDGING PERSISTING 
ALONG AND OFF THE CA COAST DURING THE PERIOD. WEAK UPPER LEVEL 
TROFFINESS WILL DEVELOP OVER THE AREA SAT NIGHT AND SUN...THEN 
LINGER OVER THE AREA THRU MON. GENERALLY WEAK FLOW CAN BE EXPECTED 
NIGHT AND MORNING HOURS...WITH DECENT ONSHORE FLOW EACH AFTERNOON 
AND EARLY EVENING THRU MON OVER SWRN CA. THERE SHOULD ALSO BE AN 
EDDY DEVELOPING DURING THE OVERNIGHT HOURS DURING THE WEEKEND. IT 
LOOKS LIKE VARYING AMOUNTS OF LOW CLOUDS AND FOG SHOULD DEVELOP SAT 
NIGHT INTO SUN MORNING FOR THE COAST AND SOME ADJACENT VLYS S OF 
POINT CONCEPTION...WITH NIGHT AND MORNING LOW CLOUDS ALSO POSSIBLE 
ALONG THE CENTRAL COAST. MORE EXTENSIVE LOW CLOUDS AND FOG SHOULD 
DEVELOP SUN NIGHT INTO MON MORNING FOR THE COAST AND ADJACENT VLYS. 
OTHERWISE...MOSTLY CLEAR SKIES WILL CONTINUE ACROSS THE REGION THRU 
MON....EXCEPT FOR AFTERNOON CLOUDS MAINLY IN MTNS ON MON. THERE WILL 
ALSO BE INCREASED INSTABILITY AND COLDER AIR ALOFT ON MON...WITH THE 
SLIGHT CHANCE OF AN AFTERNOON TO EARLY EVENING THUNDERSTORM FOR THE 
VTU COUNTY MTNS. TEMPS ARE FORECAST TO CONTINUE SEVERAL DEGREES 
ABOVE NORMAL THRU SUN...EXCEPT TURNING COOLER BACK TO NEAR NORMAL 
NEAR THE COAST FOR SUN. TEMPS WILL BE SLIGHTLY COOLER ACROSS THE 
AREA FOR MON...BUT REMAIN A FEW DEGREES ABOVE NORMAL FOR INTERIOR 
AREAS.

***FROM PREVIOUS DISCUSSION***

.LONG TERM (TUE-FRI)...THE TROF WILL DEEPEN THE MIDDLE AND END OF 
NEXT WEEK, THOUGH MODELS STILL SHOWING ENOUGH VARIANCE IN THE 
MOISTURE AND TRACK OF THE INDIVIDUAL WAVES TO MAKE THE EXTENDED 
FORECAST ONE OF SIGNIFICANT UNCERTAINTY. SEEMS LIKE A GOOD CHANCE OF 
SHOWERS SOMETIME BETWEEN WEDNESDAY AND FRIDAY, BUT MOISTURE IS 
FAIRLY LIMITED AND THE TRACK MAY ULTIMATELY FAVOR BETTER CHANCES FOR 
AREAS EAST AND SOUTH OF OUR FORECAST AREA. IT'S A PRETTY COLD SYSTEM 
WITH 500 MB TEMPS AROUND -25, BUT UNCERTAINTY WITH THE TRACK OF THE 
COLDEST AIR ON DAYS 6-8 OF THE FORECAST IS KEEPING ME FROM GOING ANY 
HIGHER WITH POPS OR ADDING THUNDERSTORMS AT THIS TIME. 

&&

.AVIATION...17/2355Z.

AT 2245Z...THE MARINE INVERSION AT KLAX WAS AROUND 650 FEET DEEP. 
THE INVERSION TOP WAS AT 2500 FEET WITH A TEMPERATURE OF 21 DEG C.

HI CONFIDENCE IN THE 00Z TAFS WITH VFR CONDITIONS AT ALL AIRFIELDS 
THRU SAT AFTERNOON. HOWEVER...PATCHY LOW CLOUDS AND DENSE FOG IS 
EXPECTED TO BE IN AND AROUND KSMX...KLGB AND KLAX LATE TONIGHT INTO 
SAT MORNING...WITH A 10-20 PERCENT CHANCE OF LIFR CONDITIONS AT 
TIMES BETWEEN ABOUT 11Z AND 16Z. GUSTY W WINDS AT KLAX WILL DIMINISH 
THIS EVENING. NW WINDS AT KVNY AND KBUR WILL DIMINISH THIS 
EVENING...WITH A 10-20 PERCENT CHANCE OF LOW LEVEL WIND SHEAR THRU 
EARLY THIS EVENING.

KLAX...HI CONFIDENCE IN THE 00Z TAF WITH VFR CONDITIONS EXPECTED 
THRU SAT EVENING. HOWEVER...PATCHY LOW CLOUDS AND DENSE FOG IS 
EXPECTED TO BE IN AND AROUND THE AIRFIELD EARLY SAT MORNING...WITH A 
10-20 PERCENT CHANCE OF LIFR CONDITIONS AT TIMES BETWEEN ABOUT 13Z 
AND 16Z. GUSTY W WINDS WILL DIMINISH THIS EVENING.

KBUR...HI CONFIDENCE IN THE 00Z TAF WITH VFR CONDITIONS THRU SAT 
AFTERNOON. NW WINDS TO ABOUT 15 KT AT THE AIRFIELD WILL DIMINISH 
THIS EVENING...WITH A 10-20 PERCENT CHANCE OF LOW LEVEL WIND SHEAR 
THRU EARLY THIS EVENING.

&&

.MARINE...17/800 PM.

MODERATE CONFIDENCE THAT SMALL CRAFT ADVISORY CONDITIONS DUE TO 
HAZARDOUS SEAS WILL CONTINUE ACROSS THE NORTHERN TWO THIRDS OF THE 
OUTER WATERS THROUGH LATE TONIGHT...BUT SEAS MAY SUBSIDE BELOW 10 
FEET SEVERAL HOURS EARLIER. HIGH CONFIDENCE THAT GUSTY ONSHORE WINDS 
NEARSHORE OVER THE SOCAL BIGHT WILL CONTINUE TO SUBSIDE OVERNIGHT. 

A MARINE WEATHER STATEMENT HAS BEEN ADDED FOR AREAS OF DENSE FOG FOR 
THE NORTHERN TWO-THIRDS OF THE OUTER WATERS. THERE IS A CHANCE OF 
AREAS OF DENSE FOG FOR THE INNER WATERS OVER THE SAN PEDRO CHANNEL 
AFTER 08Z TONIGHT.

&&

.FIRE WEATHER...17/1215 PM
OFFSHORE WINDS MUCH LIGHTER ACROSS DISTRICT THIS MORNING...WITH 
FASTER ONSET OF ONSHORE WINDS ACROSS THE COAST AND SOME COASTAL 
VALLEYS AS OF NOON. ONSHORE WINDS EXPECTED TO SPREAD ACROSS ALL 
VALLEY AREAS THROUGH THE AFTERNOON...REACHING THE MOUNTAINS AND 
ANTELOPE VALLEY BETWEEN 2 PM AND 6 PM. HIGH RESOLUTION WRF MODEL 
INDICATING STRONGEST ONSHORE WIND PUSH EXTENDING FROM SANTA CLARITA 
VALLEY THROUGH HIGHWAY 14 CORRIDOR INTO THE ANTELOPE VALLEY...WHERE 
GUSTS BETWEEN 20 AND 25 MPH WILL BE COMMON...AND ISOLATED GUSTS AS 
HIGH AS 30 MPH IN THE FOOTHILLS OF THE ANTELOPE VALLEY. 
MEANWHILE...A WARM AND DRY AIR MASS REMAINS IN PLACE ACROSS THE 
REGION TODAY. MANY INTERIOR SECTIONS WILL SEE HIGH TEMPERATURES IN 
THE 80S TODAY WITH HUMIDITIES BETWEEN 7 AND 12 PERCENT. THE 
COMBINATION OF GUSTY ONSHORE WINDS...WARM TEMPERATURES...AND LOW 
HUMIDITIES WILL BRING ELEVATED FIRE DANGER TO THE 
VALLEYS...MOUNTAINS...AND ANTELOPE VALLEY THIS AFTERNOON AND 
EVENING. A SLIGHTLY STRONGER ONSHORE PUSH IS EXPECTED FOR SATURDAY 
AFTERNOON AND EVENING. WHILE HUMIDITIES WILL BE SLIGHTLY HIGHER 
TOMORROW...THERE WILL STILL CONTINUE TO BE AN ELEVATED FIRE DANGER 
ACROSS THE MOUNTAINS AND ANTELOPE VALLEY WHERE HUMIDITIES BETWEEN 10 
AND 20 PERCENT WILL BE COMMON.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).
HIGH SURF ADVISORY (SEE LAXCFWLOX).
BEACH HAZARDS STATEMENT (SEE LAXCFWLOX). 

&&

$$

PUBLIC...SIRARD/MW
AVIATION...SIRARD
MARINE...SMITH
FIRE...GOMBERG
SYNOPSIS...SETO

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