AREA FORECAST DISCUSSION

AREA FORECAST DISCUSSION

FXUS66 KLOX 062236
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
230 PM PST SUN DEC 6 2009

.SYNOPSIS...
A COLD LOW PRESSURE SYSTEM WILL BRING WINDS...RAIN...AND LOW
ELEVATION SNOW TO THE AREA TONIGHT THROUGH TUESDAY MORNING. A SERIES
OF SYSTEMS WILL BRING MORE CHANCES OF RAIN TO THE AREA FROM
WEDNESDAY NIGHT THROUGH THE WEEKEND. TEMPERATURES WILL REMAIN WELL
BELOW SEASONAL NORMALS THROUGH THE WEEK...COLDEST MONDAY AND TUESDAY.

&&

.SHORT TERM (TODAY-WEDNESDAY)...
CLOUDY AND COLD CONDITIONS ONCE AGAIN TODAY AS THAT WINTER FEELING
BEGINS TO SET IN. MODERATE ONSHORE GRADS ARE PRODUCING BREEZY WINDS
ONCE AGAIN IN THE LA MTNS AND DESERTS...BUT SHOULD STAY A TOUCH
UNDER ADVISORY STRENGTH.

TIME TO ROLL-UP THE SLEEVES AND DIVE INTO OUR UPCOMING SYSTEM. THE
VERY COLD UPPER LEVEL LOW JUST NOW GETTING INTO NORTHERN CALIFORNIA
WILL CONTINUE TO INTENSIFY OVERNIGHT...PRODUCING A 150+KT JET BY
MON AFTERNOON. THIS SYSTEM IS STILL ON TRACK TO BRING WIDESPREAD
MODERATE PRECIPITATION TO THE REGION BEGINNING LATE TONIGHT AND
CONTINUING THROUGH MONDAY EVENING. AS THE LOW RETROGRADES TO THE
WEST...THE JET WILL PRODUCE STRONG SOUTHWESTERLY FLOW...ESPECIALLY
OVER LA AND VTU COUNTIES. THIS FLOW WILL PICK UP A LARGE BLOB OF
MILD MOISTURE CURRENTLY ABOUT 700 MI WEST OF LOS ANGELES. WITH
PLENTY OF LIFT DUE TO THE WARM AIR ADVECTION...THIS MOISTURE WILL
RESULT IN WIDESPREAD 0.5-1.5 INCHES OF RAIN OVER THE COASTS AND
VALLEYS...WITH 1-3 INCHES IN THE MTNS AND FOOTHILLS. DUE TO THE
LOCATION OF THE MOISTURE FEED...THE SOUTHERN AREAS WILL RECEIVE THE
JUICIEST AIR...AND LOCAL AMOUNTS UP TO 4 INCHES ARE POSSIBLE OVER
THE SAN GABRIEL RANGE. WILL BE ISSUING A FLASH FLOOD WATCH FOR THE
LA COUNTY BURN AREAS AS A RESULT...AS RAINFALL RATES COULD GET
PRETTY CLOSE TO USGS THRESHOLDS. THE STATION AND MORRIS BURN AREAS
ARE OF MOST CONCERN. LEFT THUNDERSTORMS OUT OF FORECAST AS LAPSE
RATES LOOK FAR FROM IMPRESSIVE...BUT WITH THE JET DYNAMICS...ONE OR
TWO CELLS COULD POP UP AND WOULD ONLY HEIGHTEN THE RISK OF FLASH
FLOODING. THE SNOW WILL BE TRICKY TO FORECAST...AS INITIALLY SNOW
LEVELS WILL RANGE BETWEEN 3500-4500 FEET MON MORNING...BUT SHOULD
RAISE TO 5000-6000 FEET AS THE MILDER AIRMASS OFF THE COAST COMES
IN. THIS SHOULD MELT MOST OF ANY SNOW THAT FELL BELOW 5000 FEET OR
SO...BUT AREAS ABOVE 6000 FEET SEE THE SNOW FALLING THROUGHOUT THE
PERIOD. DUE TO THE JUICY AIRMASS...THE SNOW COULD BE HEAVY ABOVE
6000 FEET...WHERE SNOW TOTALS OF 1-2 FEET ARE POSSIBLE...ESPECIALLY
OVER THE HIGHER SAN GABRIEL RANGE. THE PREVIOUS WINTER WATCH HAS
BEEN CONVERTED TO A WARNING TO ACCOUNT FOR THE HEAVY SNOW AND STRONG
WINDS. SPEAKING OF THE WINDS...DUE TO THE STRONG JET ALOFT AND THE
COLD AIR ALOFT...GUSTY WINDS ARE EXPECTED MONDAY AFTERNOON...BUT
ESPECIALLY MONDAY NIGHT AS THE MAIN FRONT PASSES THROUGH. WIDESPREAD
WIND ADVISORIES ARE EXPECTED AND WILL LIKELY BE ISSUED TONIGHT. THE
MTNS...SBA SO COAST AND ANTELOPE VALLEY WILL FEEL THE STRONGEST
WINDS...AND A HIGH WIND WATCH HAS BEEN ISSUED FOR THAT.

MONDAY NIGHT INTO TUE WILL ALSO BE FULL OF INTEREST. IN ADDITION TO
THE STRONG NORTHERLY WINDS...MOISTURE WILL BANK UP ON THE NORTHERN
MTNS AND FOOTHILLS. WITH SNOW LEVELS PLUMMETING TO FAIRLY RARE
LEVELS OF 2000 FEET AND BELOW...EVEN THE ANTELOPE...SLO AND CUYAMA
VALLEYS COULD WAKE UP TO A WHITE TUESDAY. SNOW ADVISORIES MAY BE
NEEDED FOR THOSE AREAS. THE REST OF THE AREA WILL BE
COLD...ESPECIALLY THE WIND SHELTERED AREAS WHERE FROST AND FREEZE
CONCERNS COULD POP UP. CLOUDS SHOULD BE CLEARING OUT ON TUE...BUT
WILL REMAIN QUITE COLD WITH THE BITTERLY COLD AIRMASS. TUE NIGHT
LOOKS EVEN COLDER AS THE WINDS DIE AND THE SKIES CLEAR...AND MANY
FREEZE WARNINGS/FROST ADVISORIES ARE EXPECTED DURING THE COLDEST
NIGHT OF THE SEASON.

MODELS CONTINUE TO SLOW DOWN AND WEAKEN THE NEXT SYSTEM...AS WED DAY
LOOKS TO STAY DRY BUT STILL COLD.

.LONG TERM (THURSDAY-SUNDAY)...
THE NEXT SYSTEM NOW LOOKS TO PUSH IN WED NIGHT AND THU...BUT MODELS
CONTINUE TO TREND LESS AND LESS WITH THE PRECIP AMOUNTS. THERE IS
STILL A CONSIDERABLE AMOUNT OF UNCERTAINTY WITH THE AMOUNTS AS A
RESULT...BUT IT SHOULD RAIN AND IT WILL BE MUCH WARMER WITH HIGHER
SNOW LEVELS THAN MONDAYS SYSTEM. FRIDAY COULD STILL SEE A SHOWER OR
TWO...BUT LOOKS NOW TO BE THE BREAK BETWEEN THE SECOND AND THIRD
STORM. SAT IS LOOKING MORE AND MORE INTERESTING...BUT STILL A BIT
TOO EARLY TO GET TOO PRECISE ON. OVERALL...NEXT WEEKEND LOOKS
FAVORABLE FOR SOME MILD RAIN.

&&

.AVIATION...05/2325Z.
MID/UPPER LEVEL TROUGH OF LOW PRESSURE EXTENDING OVER THE ERN PAC
AND NRN CALIFORNIA WILL APPROACH THE AREA. MODERATE TO STRONG
RELATIVELY DRY MID/UPPER LEVEL WEST WINDS WILL BECOME MOIST AND
STRONG SOUTHWEST AFTER 07/12Z. FREEZING LEVEL AROUND 5KFT WILL
GRADUALLY ASCEND TO AROUND 7KFT AFTER 07/15Z.

KLAX...IT IS LIKELY CIGS WILL DESCEND TO AROUND 025 WITH 5SM -RA
WITH SFC WINDS 14015G20KT BY 07/17Z. IT IS LIKELY SFC WINDS WILL
BECOME 21020KT AFTER 07/22Z WITH CIGS ASCENDING TO AROUND 015 AND
VSBY 3SM RA BR.

KBUR...IT IS LIKELY CIGS WILL DESCEND TO AROUND 030 WITH RA- BY
07/11Z. OTHERWISE IT IS LIKELY CIGS AROUND 040 WILL PERSIST THROUGH
07/11Z.

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

.LOX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING (SEE LAXWSWLOX).
HIGH WIND WATCH (SEE LAXNPWLOX).
FLOOD WATCH (SEE LAXFFALOX).
GALE WATCH (SEE LAXMWWLOX).
HIGH RIP CURRENT RISK (SEE LAXSRFLOX).
MARINE WEATHER STATEMENT (SEE LAXMWSLOX).
SPECIAL WEATHER STATEMENT (SEE LAXSPSLOX).

&&