Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 210410
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
910 PM PDT MON APR 20 2015

.SYNOPSIS...

LOW CLOUDS...FOG...AND POSSIBLE DRIZZLE ARE EXPECTED BY TUESDAY
MORNING...MOSTLY ALONG THE COAST AND VALLEYS. THE LOW PRESSURE SYSTEM
WILL CONTINUE TO BRING A SLIGHT CHANCE OF SHOWERS AND ISOLATED
THUNDERSTORMS TO MAINLY VENTURA AND LOS ANGELES COUNTIES ON
TUESDAY...THEN ANYWHERE WEDNESDAY AFTERNOON THROUGH FRIDAY NIGHT.

&&

.UPDATE...

INFRARED SATELLITE IMAGERY INDICATE A TROUGH OF LOW PRESSURE ABOUT
300 MILES SOUTHWEST OF LOS ANGELES. ALL MODEL SOLUTIONS INDICATE
THIS TROUGH MOVING INTO THE SOUTH COAST BASIN THROUGH TUESDAY
MORNING WHILE DEEPENING SLIGHTLY. WITH THE TROUGHS CUTOFF
NATURE...MOVEMENT CAN BE SOMEWHAT UNPREDICTABLE DESPITE MODEL
AGREEMENT. MODELS TEND TO FOCUS THE BEST MOISTURE AND INSTABILITY
OVER VENTURA COUNTY...BUT IT IS POSSIBLE THAT THE SYSTEM COULD
DRIFT FARTHER SOUTH AND PUT LOS ANGELES COUNTY INTO THE MIX. POPS
AND CLOUD COVER HAVE BEEN BUMPED UP FOR AREAS SOUTH OF POINT
CONCEPTION ALONG WITH MENTIONS FOR A SLIGHT CHANCE OF SHOWERS AND
THUNDESTORMS.

WITH MODERATELY STRONG ONSHORE FLOW IN PLACE...A DEEP MARINE LAYER
NEAR 2000 FEET THIS EVENING SHOULD DEEPEN TO BETWEEN 2500 AND 3000
FEET THROUGH TUESDAY MORNING. ENOUGH INSTABILITY WITH THE
TROUGH COULD LIFT THE MARINE LAYER STRATUS DECK AND SQUEEZE OUT
DRIZZLE OR LIGHT SHOWERS. MENTIONS OF PATCHY DRIZZLE HAS BEEN
EXPANDED ACROSS THE AREA TONIGHT AND INTO TUESDAY MORNING IN THE
CURRENT PACKAGE FOR ALL COASTAL AND VALLEY AREAS. INSTABILITY
MOVING OVER THE AREA AROUND 12Z COULD SQUEEZE OUT SOMETHING OUT OF
THE MARINE LAYER. NAM BUFR TIME HEIGHT SECTIONS INDICATE
MEASURABLE DRIZZLE FOR A MAJORITY OF AIRPORT LOCATIONS THROUGHOUT
SOUTHERN CALIFORNIA.

&&

.PREV DISCUSSION...

SHORT TERM...WEDNESDAY AND THURSDAY WILL SEE A MORE UNIFORM NORTH
FLOW ACROSS THE AREA BUT WEAK DISTURBANCES WILL ROTATE SOUTH FROM
THE SIERRA AND ADDITIONAL THUNDERSTORMS WILL BE POSSIBLE FOR THE
VENTURA AND LA MOUNTAINS EACH AFTERNOON. TEMPERATURES WILL BE
STUNTED NEAR OR SLIGHTLY BELOW NORMAL THROUGH MOST OF THE WEEK AS
THIS UNSETTLED PATTERN LINGERS AND ONSHORE GRADIENTS REMAIN
STRONG.

LONG TERM...INCREASING MODEL AGREEMENT OF ANOTHER FAST-MOVING
SYSTEM DROPPING DOWN THE COAST DEEPENING THE TROUGH OVER
CALIFORNIA ON FRIDAY. THERE IS EVEN SIGNS OF ANOTHER CUT-OFF LOW
FORMING ACROSS THE SAN JOAQUIN VALLEY LATE FRIDAY. THIS WILL
CONTINUE A THREAT OF MOUNTAIN SHOWERS AND POSSIBLY THUNDERSTORMS
THROUGH FRIDAY. SATURDAY WILL LIKELY BE A TRANSITION DAY BETWEEN
THE EXITING TROUGH AND BUILDING HIGH PRESSURE AND THE START OF A
WARMING TREND. HIGH PRESSURE RIDGE WILL CONTINUE TO BUILD THROUGH
MONDAY WITH TEMPERATURES EDGING TOWARD 80 DEGREES OR SO IN THE
WARMER VALLEYS AND ANTELOPE VALLEY.

&&

.AVIATION...21/0028Z.

AT 2335Z...THE MARINE LAYER WAS 1900 FEET DEEP AT KLAX AND THE TOP
OF THE INVERSION WAS 2700 FEET WITH A TEMPERATURE OF 16 DEGREES C.

MVFR CONDITIONS WILL SPREAD INTO MOST COASTAL AND VALLEY TERMINALS
THROUGH 09Z. THERE IS A CHANCE OF IFR CONDITIONS BETWEEN 10Z AND 16Z
IN DRIZZLE. MVFR CONDITIONS WILL LIKELY LINGER LATER ON TUESDAY.
THERE IS A CHANCE OF MVFR CONDITIONS THROUGHOUT THE DAY AT COASTAL
AND VALLEY TERMINALS.

KLAX...VFR CONDITIONS ARE EXPECTED THROUGH AT LEAST 04Z. THERE IS A
30 PERCENT CHANCE OF MVFR CONDITIONS BETWEEN 02Z AND 04Z. MVFR
CONDITIONS SHOULD SPREAD IN BETWEEN 04Z AND 06Z. THERE IS A 40
PERCENT CHANCE OF IFR CONDITIONS BETWEEN 10Z AND 16Z DUE TO POSSIBLE
DRIZZLE. MVFR CONDITIONS WILL LINGER THROUGH AT LEAST 20Z. THERE IS
A 30 PERCENT OF MVFR CONDITIONS LINGER THROUGHOUT TUESDAY AFTERNOON.

KBUR...VFR CONDITIONS ARE EXPECTED THROUGH AT LEAST 07Z. THERE IS A
30 PERCENT CHANCE OF MVFR CONDITIONS BETWEEN 06Z AND 08Z. MVFR
CONDITIONS SHOULD SPREAD AROUND 08Z. THERE IS A 40 PERCENT CHANCE OF
IFR CONDITIONS BETWEEN 10Z AND 16Z DUE TO POSSIBLE DRIZZLE. MVFR
CONDITIONS WILL LINGER THROUGH AT LEAST 18Z. THERE IS A 30 PERCENT
OF MVFR CONDITIONS LINGER THROUGHOUT TUESDAY AFTERNOON.

&&

.MARINE...20/900 PM.

HIGH CONFIDENCE THAT WINDS WILL REMAIN BELOW SCA THRESHOLDS THROUGH
TUESDAY AFTERNOON...ASIDE FROM THE POSSIBILITY OF A FEW GUSTS UP TO
25 KNOTS NEAR POINT CONCEPTION THIS EVENING. HIGH PRESSURE 1000 NM
WEST OF SAN FRANCISCO WITH A WEAK UPPER LOW MOVING OVER THE COASTAL
WATERS TONIGHT INTO TUESDAY. NORTHWEST WINDS ARE EXPECTED TO
INCREASE TO NEAR-SCA SPEEDS TUESDAY NIGHT INTO WEDNESDAY...THEN
DIMINISH AGAIN ON THURSDAY AS ANOTHER WEAK UPPER LOW CROSSES THE
AREA. NORTHWEST WINDS ARE EXPECTED TO INCREASE MORE STRONGLY OVER
THE OUTER WATERS FRIDAY INTO SATURDAY AS THE EAST PACIFIC HIGH MOVES
CLOSER TO THE CALIFORNIA COAST.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

PUBLIC...HALL/BOLDT
AVIATION...HALL
MARINE...SMITH
SYNOPSIS...B/HALL

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