Frost Advisory 9, NWS Los Angeles, CA

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
250 PM PST MON DEC 10 2007

.SHORT TERM (TODAY-THURSDAY)...
TEMPS TRENDING ABOUT EQUAL TODAY FROM SUNDAYS HIGHS...EXCEPT FOR
SOME WARMING SEEN IN THE MOUNTAINS. OFFSHORE GRADS PEAKED THIS
MORNING AROUND -2.1 MB LAX-DAG AND HAVE SINCE GONE NEUTRAL. WINDS
HAVE DIED DOWN FROM EARLIER THIS MORNING...WITH A FEW PLACES STILL
GUSTING NEAR 30 MPH. FURTHER WEAKENING IS EXPECTED THROUGH EARLY
THIS EVENING...BUT THEN RESTRENGTHEN SHOULD BE REALIZED AFTER
MIDNIGHT.

A 547 DM CUTOFF LOW HAS BEEN PATIENTLY SPINNING JUST OFF BAJA WHILE
A 546 DM UPPER LEVEL TROUGH DIGS SOUTH THROUGH CANADA AND INTO
IDAHO. THIS LOW TO THE NORTH WILL CONTINUE TO SAG DOWN SOUTH WHILE
THE CUTOFF NUDGES NORTHWARD. THESE TWO SYSTEMS WILL MEET AND MERGE
OVER ERN CALIFORNIA BY TUESDAY MORNING. MODELS HAVE COME INTO PHASE
WITH THE LOCATION OF THIS RESULTING TROUGH. SOLID NORTHERLY FLOW TUE
MORNING WILL BRING SOME MOISTURE IN FROM THE NORTH AND POSSIBLY
ALLOW SOME MOISTURE TO WRAP AROUND FROM THE EAST. THIS WILL CREATE A
POSSIBILITY OF SOME LIGHT RAIN AND SNOW SHOWERS IN THE LA/VTU
MOUNTAINS TUESDAY MORNING AND AFTERNOON...WITH THE BEST CHANCE OVER
THE NORTHEAST FACING SLOPES OF THE SAN GABRIELS. SNOW LEVELS WILL
INITIALLY BE AS LOW AS 4000 FT IN THE MORNING...BUT SHOULD RAISE
SOME IN THE AFTERNOON. ANY PRECIP CHANCES SHOULD BE GONE BY TUESDAY
EVENING AS THE LOW SHIFTS EASTWARD.

THE FLOW ALOFT ALONG WITH A RESTRENGTHENING SURFACE HIGH OVER UTAH
WILL ALLOW FOR GUSTY NORTH TO NORTHEAST FLOW TO RESTRENGTHEN ONCE
AGAIN OVERNIGHT. WINDS WILL INCREASE OVER THE MOUNTAINS FIRST
TONIGHT...THEN WORK THEIR WAY TO THE SURFACE THROUGH THE MORNING.
WIND SPEEDS SHOULD BE NEAR ADVISORY LEVELS FOR THE MOUNTAINS AND
VALLEYS BY NOON ON TUESDAY...WITH THE POSSIBILITY OF VTU COAST
INCLUDED IN THE MIX. THE AIRMASS WILL BE QUITE COOL AND THERE IS NOT
MUCH WARMING EXPECTED WITH THE OFFSHORE FLOW. DESERTS AND MOUNTAINS
WILL BE QUITE COOL TUE. IN ADDITION...MORNING LOWS WILL BE COOL
EXCEPT IN THE WINDIER AREAS.

WEDNESDAY AND THURSDAY WILL SEE SOME WARMING PRETTY MUCH EVERYWHERE
AS OFFSHORE FLOW CONTINUES. WINDS WILL BE A TAD WEAKER...LIKELY
BELOW ADVISORY LEVELS. AIRMASS WILL WARM WITH THE ADDITIONAL
COMPRESSIONAL WARMING...AND NEAR NORMAL TEMPS ARE EXPECTED TO RETURN
TO THE REGION BY THURSDAY. A VERY WEAK SHORTWAVE MOVES DOWN THE CA
COAST ON WED...AND MODELS HAVE BEEN STRUGGLING WITH THE TIMING OF IT
TO NO SURPRISE. NO PRECIP IS EXPECTED DUE TO THE VERY WEAK NATURE
AND LACK OF MOISTURE ASSOCIATE WITH IT...BUT SOME PARTLY CLOUDY MID
TO HIGH LEVEL CLOUDS MAY RESULT WEDNESDAY NIGHT AND THURSDAY.

.LONG TERM (FRIDAY-MONDAY)...
FRIDAY AND SATURDAY WILL CONTINUE TO BE OFFSHORE WITH WEAK RIDGING
ALOFT. THIS SHOULD RESULT IN MOSTLY CLEAR SKIES AND NEAR NORMAL
TEMPS. A 516 DM LOW IS EXPECTED TO FORM JUST THE CANADIAN COAST ON
FRIDAY THEN SLOW MOVE SOUTHEASTWARD. ALTHOUGH THERE IS SOME
DISCREPANCIES WITH THE TIMING AND EXTENT OF THE MOISTURE...THERE IS
GOOD AGREEMENT FOR THIS FAR OUT AS TO THE FORMATION AND MOVEMENT OF
THIS SYSTEM. A SERIES OF FRONTS IS PROGGED TO STEM FROM THIS
SYSTEM...WHICH WILL BRING POSSIBILITIES OF RAIN AND SOME SNOW TO THE
MOUNTAINS SUNDAY AND MONDAY. MONDAY LOOKS TO BE TO BEST CHANCE AT
THIS POINT...BUT BEING SO FAR OUT I WOULD NOT HANG MY HAT ON THE
TIMING JUST YET. WITH THAT SAID...IT DOES LOOK GOOD FOR SOME PRECIP
EARLY NEXT WEEK.

&&

.AVIATION...AT 1750Z...OR 0950 PST...VIRTUALLY CERTAIN CLEAR SKIES
WILL PERSIST BELOW 12KFT OVER KLAX AND KBUR. THERE IS A CHANCE MID
LEVEL CIG WILL DEVELOP OVER LA COUNTY...MOISTURE IS EXPECTED TO
SKIRT THE AREA WHILE A SHORT WAVE CURRENTLY OVER IDAHO ACCELERATES
SOUTH AND CIGS MAY DEVELOP AROUND SUNRISE TUE.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY (SEE LAXNPWLOX).

&&

PUBLIC...KITTELL
AVIATION...FORWOOD

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