Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 251748 AAA
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1047 AM PDT SAT APR 25 2015

.SYNOPSIS...
A FAST-MOVING COLD FRONT WILL MOVE THROUGH THE AREA TODAY...BRINGING
SHOWERS TO PARTS OF THE REGION...ESPECIALLY NORTH OF POINT
CONCEPTION. GUSTY WEST WINDS AHEAD OF THE FRONT WILL SHIFT TO THE
NORTH TONIGHT. A WARMING AND DRYING TREND IS EXPECTED THROUGH EARLY
NEXT WEEK AS OFFSHORE FLOW DEVELOPS AND HIGH PRESSURE BUILDS ALOFT.
A COOLING TREND IS LIKELY FOR THE SECOND HALF OF NEXT WEEK.

&&

.SHORT TERM (TODAY-MON)...FAST MOVING COLD FRONT BRINGING SOME LIGHT
TO MODERATE RAIN ACROSS PORTIONS OF SAN LUIS OBISPO AND SANTA BARBARA
COUNTIES. HIGHEST RAINFALL TOTALS SO FAR HAVE BEEN ACROSS THE
NORTHERN COASTAL AND FOOTHILL PORTIONS OF SLO COUNTY...WHERE AMOUNTS
HAVE RANGED BETWEEN .33 AND .66 INCHES AS OF 9 AM. ONE HOUR RAINFALL
RATES UP TO
.25 INCHES PER HOUR HAVE BEEN OBSERVED IN THIS AREA THIS MORNING.
WHILE THE BULK OF THE RAINFALL IS STILL EXPECTED TO FALL ACROSS
AREAS NORTH OF POINT CONCEPTION...LATEST 12Z NAM MODEL SOLUTIONS
SHOWING ENOUGH LIFT AND MOISTURE TO POTENTIALLY
SQUEEZE OUT A FEW BRIEF SHOWERS FOR SOME AREAS SOUTH OF POINT
CONCEPTION...INCLUDING THE SBA SOUTH COAST...MOUNTAINS...AND
ANTELOPE VALLEY. 12Z NAM MOS GUIDANCE ALSO SUPPORTS THESE HIGHER
POPS...WHICH HAS BEEN REFLECTED IN MORNING UPDATE. WHILE COASTAL AND
VALLEY PORTIONS OF VENTURA COUNTY WILL PROBABLY NOT SEE MUCH IN THE
WAY OF SHOWERS...SOME WEAK CYCLONIC FLOW WILL BRING A BETTER CHANCE
OF SHOWERS TO LA COUNTY THIS AFTERNOON (ESPECIALLY THE SAN GABRIEL
MOUNTAINS AND ADJACENT FOOTHILLS). SNOW LEVELS ARE EXPECTED TO RANGE
BETWEEN 6000 AND 7000 FEET.

MAIN IMPACT OF THIS WEATHER SYSTEM WILL BE INCREASING WINDS.
INITIALLY...WILL SEE INCREASING SOUTHWEST TO WEST WINDS AHEAD OF THE
FRONT WITH LAX-DAGGETT GRADIENT ALREADY AT +6.6 MB. WINDS EXPECTED TO
PICK UP SHARPLY THIS AFTERNOON ACROSS THE MOUNTAINS...ANTELOPE
VALLEY...AND MANY COASTAL AREAS. WIND ADVISORIES AND HIGH WIND
WARNINGS HAVE BEEN POSTED FOR SEVERAL PORTIONS OF THE FORECAST AREA.
THE FOCUS OF THE STRONGEST WINDS THIS AFTERNOON INTO THE EARLY
EVENING WILL LIKELY BE THE ANTELOPE VALLEY...WHERE THERE COULD BE
DAMAGING WIND GUSTS TO 60 MPH ALONG WITH AREAS OF REDUCED
VISIBILITIES IN BLOWING DUST. BY TONIGHT...THE FLOW WILL SHIFT TO A
NORTHWEST DIRECTION BEHIND THE FRONT WITH STRONGER WINDS EXPANDING
TO THE INTERSTATE 5 CORRIDOR AND THE SANTA YNEZ RANGE. WILL NEED TO
CONSIDER ADDING WIND ADVISORIES TO THE SANTA CLARITA VALLEY AND SAN
FERNANDO VALLEY FOR SUNDAY MORNING AS THE NORTHERLY WINDS EXPAND
SOUTH FROM THE I-5 CORRIDOR.

*** FROM PREVIOUS DISCUSSION ***

AS FAR AS THE SKY CONDITIONS AND TEMPERATURES...LINGERING LOW LEVEL
MOISTURE WILL KEEP A STRATOCU DECK ACROSS THE LA/VTU COUNTY
TODAY...THEN SCOUR OUT AS THE STRONGER W TO NW WINDS MOVE INTO THE
REGION LATE THIS AFTERNOON OR EVENING HOURS. SKIES WILL BECOME
MOSTLY CLEAR TONIGHT...EXCEPT FOR SOME LOW CLOUDS BANKING UP AGAINST
THE NORTHERN SLOPES OF THE MOUNTAINS INTO SUNDAY MORNING. HIGH TEMPS
WILL BE FAIRLY SIMILAR TODAY AS YESTERDAY. EXPECT MOST COAST AND
VALLEYS TO REMAIN IN THE 60S WITH A FEW SITES POSSIBLY REACHING 70
DEGREES. THERE WILL BE BETTER WARMING ON SUNDAY AS THE UPPER TROUGH
MOVES IN TO THE FOUR CORNERS REGION. HEIGHTS AND THICKNESS LVLS WILL
RISE AS THE BEGINNING OF A RIDGE DEVELOPS OVER THE EASTERN PAC ON
SUNDAY. HIGH TEMPS WILL BE UP 4 TO 8 DEGREES IN MOST AREAS.

THERE WILL BE A SIGNIFICANT WARM UP ON MONDAY OF 8 TO 15 DEGREES AS
THE UPPER RIDGE AXIS MOVES OVER MUCH OF CALIFORNIA. AT THE LOWER
LEVELS...A STRONGER SURFACE OFFSHORE GRADIENT SETS UP BETWEEN NRN
NEVADA AND SO CAL. THEREFORE EXPECT OFFSHORE WINDS TO DEVELOP ACROSS
THE USUAL WIND PRONE AREAS OF L.A./VENTURA COUNTIES MONDAY MORNING.
IN FACT...BOTH THE NAM AND GFS ARE INDICATING GOOD UPPER LVL SUPPORT
ON MONDAY WHICH SHOULD ENHANCE THE WIND GUSTS TO A LOW END ADVISORY
LEVEL WIND EVENT.


.LONG TERM (TUE-FRI)...
OFFSHORE WINDS WILL BE MUCH WEAKER ON TUESDAY DUE TO A WEAKER
OFFSHORE SURFACE GRADIENT AND LACK OF UPPER SUPPORT. HOWEVER THE
WEAK OFFSHORE FLOW WILL KEEP VERY WARM TEMPS OVER SOUTHERN
CALIFORNIA. THIS SHOULD BE THE WARMEST DAY OF THE WEEK WITH HIGHS
REACHING THE MID TO UPPER 80S IN MANY VALLEY AND SOME COASTAL AREAS.
THE CENTRAL COAST WILL SEE HIGH TEMPS INTO THE LOWER 80S AS WELL
TUE. THE AMPLIFIED RIDGE OVER THE ENTIRE WEST COAST WILL BEGIN TO
PUSH EAST AS ANOTHER UPPER TROUGH ROTATES INTO THE EASTERN PAC. THIS
WILL BE THE START OF A COOLING TREND WEDNESDAY...MAINLY ALONG THE
COAST INITIALLY WEDNESDAY...WITH MARGINAL COOLING CONTINUING ACROSS
THE ENTIRE FORECAST AREA THU/FRI. EXPECT A RETURN OF THE MARINE
LAYER IN SOME FASHION WEDNESDAY MORNING...BECOMING MORE WIDESPREAD
LATE IN THE WEEK.

&&

.AVIATION...25/1800Z.

MID/UPPER LEVEL TROUGH OF LOW PRESSURE OVER THE AREA WILL CONTINUE
MOVING EAST AND A RIDGE OF HIGH PRESSURE OVER THE EASTERN PACIFIC
WILL APPROACH THE AREA. UPPER LEVEL STRONG NORTH WINDS WILL BECOME
MODERATE NORTH AFTER 26/11Z WHILE MID LEVEL MODERATE TO STRONG
NORTHWEST WINDS BECOME MODERATE NORTH AFTER 26/19Z. MID/UPPER LEVEL
MOISTURE WILL EXIT THE AREA WHILE AREAS OF LOWER LEVEL MOISTURE
LINGERS AFTER 26/00Z. FREEZING LEVEL WAS APPROXIMATELY 8KFT THIS
MORNING AND WILL DIFFER BY PLUS 3KFT SUNDAY MORNING.

MARINE LAYER AT LAX AT 1625Z IS NONE.

KLAX...SURFACE WIND 27022G32KT LIKELY BETWEEN 25/21-26/05Z.
OTHERWISE BROKEN/OVERCAST MID/UPPER LEVEL CLOUD FIELD BECOMING
SCATTERED AFTER 26/00Z.

KBUR...CHANCE CIGS 025 AT TIMES BETWEEN 25/18-25/20Z OTHERWISE
CHANCE CIGS 035-040 THROUGH 26/00Z AND CHANCE -RA AT TIMES BETWEEN
25/20-26/00Z.


VIRTUALLY CERTAIN - 95-100%
VERY LIKELY       - 80-95%
LIKELY            - 60-80%
CHANCE            - 30-60%
VERY UNLIKELY     - 20% OR LESS

&&

.MARINE...25/900 AM...
IT IS LIKELY NORTHWEST WINDS WILL CONTINUE TO INCREASE AND GALE
FORCE GUSTS WILL EXIST FROM PIEDRAS BLANCAS TO SAN CLEMENTE ISLAND
LATE TONIGHT THROUGH LATE SUNDAY NIGHT. THE PERIOD WITH THE PEAK
WINDS AND MOST WIDESPREAD IS LIKELY SUNDAY AFTERNOON THROUGH SUNDAY
EVENING. SCA CONDITIONS WILL LIKELY EXIST 0-10 NM SLO COUNTY AS WELL
AS IN SANTA BARBARA BASIN TO SAN PEDRO BASIN THIS AFTERNOON THROUGH
SUNDAY EVENING. STEEP COMBINED SEAS WILL LIKELY BUILD TO 9 TO 12
FEET IN THE OUTER WATERS AND 6 TO 8 FEET IN THE NEAR SHORE BASINS
THIS AFTERNOON AND SUBSIDE SUNDAY NIGHT.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING (SEE LAXNPWLOX).
HIGH WIND WATCH (SEE LAXNPWLOX).
GALE WARNING (SEE LAXMWWLOX).
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).

&&

$$

PUBLIC...GOMBERG/KAPLAN
AVIATION/MARINE...30
SYNOPSIS...SUKUP

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