Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 210523 AAA
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1020 PM PDT SAT SEP 20 2014

UPDATED AVIATION SECTION

.SYNOPSIS...

A WARMING TREND IS EXPECTED THROUGH EARLY NEXT WEEK AS UPPER LEVEL
LOW PRESSURE MOVES EAST AND HIGH PRESSURE RETURNS. HIGH PRESSURE
WILL ALSO SHRINK THE MARINE LAYER AND FORCE THE NIGHT THROUGH
MORNING LOW CLOUDS AND FOG OUT OF SOME VALLEYS EARLY NEXT WEEK.
COOLER WEATHER WILL RETURN LATER NEXT WEEK AS A BROAD TROUGH OF LOW
PRESSURE APPROACHES FROM THE WEST.

&&

.UPDATE...

THE LATEST WATER VAPOR IMAGERY INDICATES AN UPPER-LEVEL CUTOFF
TROUGH OF LOW PRESSURE CENTERED NEAR CAMBRIA THIS EVENING. SOME
CONVECTION DEVELOPED MAINLY NORTH AND EAST OF THE AREA THIS
AFTERNOON AND EVENING...WITH ONLY A FEW TO SCATTERED CLOUDS OVER
THE MOUNTAINS AND ANTELOPE VALLEY. THE TROUGH WILL CONTINUE TO
MOVE TOWARDS THE NORTHEAST AND INTO THE GREAT BASIN BY SUNDAY
MORNING. A RIDGE OF HIGH PRESSURE NEAR 25 N AND 130 W WILL BUILD
IN AND STRENGTHEN THROUGH MONDAY. AS A RESULT...A WARMING TREND
WILL TAKE SHAPE ON SUNDAY...BECOMING MORE PRONOUNCED ON MONDAY AND
TUESDAY.

A WEAK MARINE INVERSION NEAR 2200 FEET AT KLAX THIS EVENING WILL
STRENGTHEN LATER TONIGHT AS TEMPERATURES START TO WARM IN THE
LOWER LEVELS OF THE ATMOSPHERE. THE MARINE LAYER STRATUS WILL
LIKELY BECOME WELL-ENTRENCHED TONIGHT...AND CLOUDS WILL LIKELY
STRUGGLE TO CLEAR ON SUNDAY. CLOUDS SHOULD HUG THE BEACHES INTO
THE AFTERNOON HOURS ON SUNDAY.

&&

.PREV DISCUSSION...

SHORT TERM...RIDGING ON MONDAY AND TUESDAY WILL BRING LESS OF A
MARINE LAYER...A WEAKER ONSHORE PRESSURE GRADIENT...AND MORE
WARMING.

LONG TERM...LITTLE CHANGE EXPECTED FROM TUESDAY TO WEDNESDAY.
RIDGE AXIS HAS SLID BY A BIT TO OUR EAST BUT STILL UNDER ITS
INFLUENCE FOR ABOVE NORMAL TEMPERATURES ALL BUT THE IMMEDIATE
CENTRAL COAST. LITTLE CHANGE IN THE MARINE LAYER EXPECTED. THEN ON
THURSDAY THE DEEP UPPER TROUGH MODELS HAVE BEEN FORECASTING FOR
THE END OF THE WEEK SHOULD BEGIN TO SHOW SOME INFLUENCE BY WAY OF
SLIGHTLY COOLER TEMPERATURES OVER SLO COUNTY. GFS AND ECMWF DIFFER
ON BOTH SPEED AND INTENSITY WITH THIS TROUGH AFTER THURSDAY. THE
GFS IS NOT AS DEEP WHILE ALSO MOVING IT THROUGH FASTER...BRUSHING
THE TROUGH AXIS BY THE AREA BY SATURDAY. MEANWHILE THE DEEPER AND
SLOWER ECMWF HAS THE TROUGH STILL WEST OF THE AREA ON SATURDAY.
ECMWF SOLUTION WOULD RESULT IN COOLER TEMPS ON SATURDAY. THE GFS
APPEARS TO HAVE BETTER RUN TO RUN CONSISTENCY SO IT`S FAVORED.
BOTH GFS AND ECMWF ESSENTIALLY SHOW A DRY TROUGH PASSAGE AS BOTH
KEEP PRECIP WELL EAST OF THE AREA. WOULD BE HARD TO IMAGINE AT
LEAST SOME SHOWERS SNEAKING INTO NORTHERN SLO COUNTY IF THE ECMWF
VERIFIES BUT KEPT ANY POPS OUT FOR NOW. HAVE PUT FRIDAY AS THE
COOLEST DAY AND SATURDAY`S TEMPS ARE A COMPROMISE BETWEEN THE
ECMWF AND GFS SOLUTION.

&&

.AVIATION...21/0520Z.
WIDESPREAD STRATUS WITH LOW MVFR TO HIGH IFR CONDS ON THE CENTRAL
COAST THIS EVENING. EXPECT STRATUS TO PUSH INTO MOST REMAINING
COASTAL AND VALLEY AREAS OVERNIGHT...WITH MOSTLY MVFR CONDS...EXCEPT
LOCAL IFR CONDS IN THE VLYS. SKIES SHOULD CLEAR SLOWLY SUNDAY
MORNING...BY EARLY AFTERNOON IN MOST AREAS. SOME CLOUDS MAY LINGER
NEAR THE COAST THRU THE DAY. EXPECT WIDESPREAD LOW MVFR TO LOCAL
IFR CONDS IN ALL COASTAL AND VLY AREAS SUNDAY NIGHT.

KLAX...MODERATE TO HIGH CONFIDENCE IN THE 06Z TAF. THERE IS A 20
PERCENT CHANCE THAT MVFR CIGS WILL PERSIST THROUGH SUNDAY
AFTERNOON.

KBUR...MODERATE CONFIDENCE IN THE 06Z TAF. THERE IS A 20 PERCENT
CHANCE THAT CIGS WILL NOT ARRIVE UNTIL AT LEAST 13Z. THERE IS A 20
PERCENT CHANCE THAT CONDS WILL BE IFR BETWEEN 11Z AND 16Z.

&&

.MARINE...20/800 PM.

THERE IS A 60% CHANCE NW WIND GUSTS UP TO 25 KT WILL DEVELOP IN THE
VICINITY OF THE CHANNEL ISLANDS DURING THE EVENING HOURS SUNDAY
THROUGH TUESDAY. A MODERATE (4-6 FT AT 13 SEC) NW SWELL FROM THE
GULF OF ALASKA WILL BEGIN TO MOVE INTO THE WATERS EARLY SUNDAY. THE
SWELL IS EXPECTED TO DIMINISH THROUGH TUESDAY. A STRONGER GULF OF
ALASKA LOW DEVELOPING MONDAY INTO TUESDAY WILL GENERATE A LARGE NW
SWELL FORECAST TO ARRIVE FROM 300-310 DEGREES WEDNESDAY
EVENING...PEAKING THURSDAY (8-10 FT AT 14 SEC) AND LINGERING THROUGH
FRIDAY. THERE IS A CHANCE THAT NW WINDS WILL INCREASE TO GALE FORCE
ON FRIDAY. THE SHORT PERIOD SEAS IN COMBINATION WITH LARGER NW SWELL
WILL LIKELY RESULT IN HAZARDOUS WIND AND SEA CONDITIONS LATE IN THE
WEEK.

&&

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

&&

$$

PUBLIC...HALL/JACKSON
AVIATION...DB
MARINE...SMITH
SYNOPSIS...SUKUP

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