Frost Advisory 4, NWS Los Angeles, CA

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
120 PM PST THU JAN 10 2013

.SYNOPSIS...

A LARGE UPPER LEVEL TROUGH WILL BRING WINDY AND MUCH COLDER
CONDITIONS TO THE AREA THROUGH FRIDAY. SCATTERED SNOW SHOWERS ARE
POSSIBLE OVER NEAR THE GRAPEVINE. BREEZY AND COLD CONDITIONS
WILL PERSIST THROUGH THE WEEKEND...WITH MUCH BELOW NORMAL
TEMPERATURES INCLUDING OVERNIGHT FROSTS AND FREEZES IN MANY AREAS.
UNSEASONABLY COOL TEMPERATURES WILL LINGER MONDAY...BUT THEN A
WARMUP SHOULD OCCUR BY THE MIDDLE OF NEXT WEEK AS HIGH PRESSURE AND
OFFSHORE FLOW DEVELOPS.

&&

.SHORT TERM (TODAY-SUN)...TODAY'S WEATHER TURNED OUT PRETTY MUCH
SPOT ON WITH EXPECTATIONS. FRONT PASSED THROUGH IN THE MORNING WITH
SHOWERS MOSTLY CONFINED TO AREAS NORTH OF PT CONCEPTION, THE
GRAPEVINE, AND EASTERN LA COUNTY. AMOUNTS WERE LIGHT, MOSTLY A FEW
HUNDREDTHS, EXCEPT A LITTLE HIGHER IN THE EASTERN SAN GABRIELS WHERE
UPSLOPE FLOW AND A LITTLE ENHANCEMENT LATE IN THE MORNING BROUGHT
THE NUMBERS UP THERE.

PRECIP THREAT IS ENDING FOR THE MOST PART AS WE TRANSITION TO A
COLD/BREEZY NORTHWEST FLOW PATTERN THROUGH THE WEEKEND. THAT
NORTHWEST FLOW WILL INTERACT WITH LINGERING MOISTURE NEAR THE
GRAPEVINE THROUGH EARLY FRIDAY SPAWNING SOME SCATTERED SNOW SHOWERS
THERE WITH MINIMAL ACCUMULATIONS. OTHERWISE JUST WINDY AND COLD
TONIGHT AND FRIDAY. WINDS WILL LIKELY KEEP TEMPERATURES FROM
DROPPING TOO LOW TONIGHT, THOUGH CENTRAL COAST AND THE OJAI VALLEY
AREAS WILL LIKELY GET TO OR JUST BELOW THE FREEZING MARK TONIGHT AND
FROST ADVISORIES HAVE BEEN POSTED THERE.

WINDS ADVISORIES ARE UP FOR MUCH OF THE REMAINING CWA THROUGH AT
LEAST THIS EVENING. WARNING LEVEL WIND GUSTS ARE POSSIBLE OVER THE
HIGHER MOUNTAIN PEAKS THROUGH FRIDAY MORNING. STRONG NORTHWEST FLOW
ALOFT EXPECTED TO CONTINUE THROUGH FRIDAY NIGHT AND SOME ADVISORIES
MAY NEED TO BE EXTENDED ANOTHER 12-24 HOURS.

LATE FRIDAY NIGHT THE FLOW SHIFTS MORE TO THE NORTHEAST AND WEAKENS,
ALLOWING TEMPERATURES TO DROP EVEN FURTHER. IN FACT, SAT IS EXPECTED
TO BE THE COLDEST MORNING OF THE SEASON FOR THE ENTIRE AREA. MID 20S
ARE LIKELY ACROSS MANY COASTAL VALLEY AREAS AND POSSIBLY THE CENTRAL
COAST AS WELL. CLOSER TO THE BEACH TEMPS WILL BE A LITTLE WARMER,
BUT EVEN VENTURA AND SRN SB COAST LOWS ARE EXPECTED TO DROP IN THE
LOWER 30S AND POSSIBLY UPPER 20S. LA COAST SHOULD STAY 34 OR ABOVE
BUT COULD STILL SEE SOME PATCHES OF FROST IN THE COLDER AREAS. A
SERIES OF FREEZE WATCHES AND FROST AVISORIES WILL BE ISSUED WITH THE
AFTERNOON FORECAST. OVERNIGHT LOWS SUNDAY EXPECTED TO BE VERY
SIMILAR TO SAT SO MORE FREEZE/FROST HEADLINES LIKELY TO BE NEEDED.

SKIES EXPECTED TO BE MOSTLY CLEAR FRI/SAT. ON SUNDAY THE MODELS ARE
SHOWING ANOTHER TROF DROPPING SOUTH THROUGH THE GREAT BASIN. THE GFS
HAS BEEN FARTHER WEST WITH IT THAN THE OTHERS BUT EVEN THAT MODEL
KEEPS THE AREA MOSTLY DRY. THE NAM SHOWS THE LOW DROPPING SOUTH
ALONG THE CA/NV BORDER WHILE THE EC IS MUCH FURTHER EAST. IT LOOKS
LIKE THE MAIN IMPACT FROM THIS SYSTEM WILL BE TO MAINTAIN A COOL,
NORTHERLY FLOW PATTERN OVER THE AREA, KEEPING HIGHS AND LOWS ABOUT
10 DEGREES BELOW NORMAL. KEEPING THE SUNDAY FORECAST DRY WITH JUST
SOME MID AND HIGH CLOUDS.

.LONG TERM (MON-THU)...STILL QUITE COOL MONDAY WITH YET ANOTHER
ROUND OF FROST/FREEZE HEADLINES POSSIBLE FOR THE MORNING. A SLIGHT
WARMUP EXPECTED BY TUESDAY AS THE RIDGE SLOWLY BUILDS IN FROM THE
WEST. OFFSHORE FLOW INCREASES TUESDAY THROUGH THU, POSSIBLY
GENERATING SOME NEAR ADVISORY LEVEL WINDS ACROSS VENTURA/LA COUNTIES
BY MID WEEK. HIGHS EXPECTED TO CLIMB TO ABOVE NORMAL LEVELS BY WED
OR THU WITH MID 70S POSSIBLE IN THE VALLEYS. RIDGE EXPECTED TO HOLD
RIGHT ON INTO NEXT WEEKEND FOR A LENGTHY DRY SPELL WITH TEMPS ABOVE
NORMAL.

&&

.AVIATION...10/1800Z.
A FEW STRAY SHOWERS LINGER...MAINLY NEAR THE MOUNTAINS AND
FOOTHILLS. OTHERWISE VFR TO OCCASIONALLY MVFR CONDITIONS PREVAIL
ACROSS THE AREA. VFR CONDITIONS WILL CONTINUE TONIGHT AND FRIDAY.
STRONG GUSTY WINDS WILL ALSO CONTINUE INTO THE EVENING BEFORE
SUBSIDING SOME OVERNIGHT. THERE WILL BE THE POSSIBILITY OF LOW LEVEL
WIND SHEAR AND TURBULENCE NEAR ANY TAF SITE THROUGH THIS EVENING.

KLAX AND KBUR...VFR TO OCCASIONALLY MVFR CONDITIONS WILL BECOME VFR
TONIGHT AND FRIDAY. GUSTY WINDS THROUGH THIS EVENING WILL CREATE
THE POSSIBILITY OF LOW LEVEL WIND SHEAR AND TURBULENCE.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING (SEE LAXNPWLOX).
COASTAL FLOOD ADVISORY (SEE LAXCFWLOX).
FREEZE WATCH (SEE LAXNPWLOX).
WIND ADVISORY (SEE LAXNPWLOX).
GALE WARNING (SEE LAXMWWLOX).
HIGH SURF ADVISORY (SEE LAXCFWLOX).
HIGH RIP CURRENT RISK (SEE LAXSRFLOX).
SPECIAL WEATHER STATEMENT (SEE LAXSPSLOX).

&&

PUBLIC...MW
AVIATION...SWEET
SYNOPSIS...SETO

WWW.WEATHER.GOV/LOSANGELES

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