AREA FORECAST DISCUSSION
FXUS66 KLOX 142358 AAA
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
400 PM PST THU JAN 14 2010

UPDATE FOR NEW AVIATION DISCUSSION

.SYNOPSIS...

A DRY AND WARM OFFSHORE WILL PREVAIL ACROSS THE AREA THROUGH FRIDAY
WITH SOME GUSTY NORTHEAST WINDS THROUGH AND BELOW PASSES AND
CANYONS. FROM SUNDAY THROUGH THE MIDDLE OF NEXT WEEK...A SERIES OF
POWERFUL WINTER STORMS IS EXPECTED TO BRING SIGNIFICANT
PRECIPITATION AND STRONG WINDS TO THE AREA.

&&

.SHORT TERM (TODAY-SATURDAY)...SATELLITE IMAGERY SHOWING MOSTLY CLEAR
SKIES ACROSS THE REGION TODAY UNDER THE INFLUENCE OF A DRY OFFSHORE
FLOW PATTERN. THE MAIN SHORT TERM WEATHER CONCERN WILL BE THE GUSTY
NORTHEAST WINDS BELOW PASSES AND CANYONS. TAKING A LOOK AT CURRENT
OBSERVATIONS...STILL SEEING SOME ISOLATED WIND GUSTS OVER 50 MPH
IN THE MOUNTAINS. STILL ENOUGH RESIDUAL UPPER LEVEL WIND SUPPORT
AND LOW LEVEL PRESSURE GRADIENT TO WARRANT AN EXTENSION OF THE
WIND ADVISORY THROUGH NOON FRIDAY. LATEST NAM MODEL INDICATES
A -5.3 MB GRADIENT BETWEEN LAX AND DAGGETT FOR FRIDAY MORNING.
THE OFFSHORE FLOW WILL BRING CONTINUED WARMING ON FRIDAY...WITH
WIDESPREAD TEMPERATURES INTO THE 70S.

WEAK UPPER LEVEL IMPULSE WILL MOVE INTO THE REGION ON SATURDAY...
BRINGING SOME CLOUDS AND COOLER TEMPERATURES TO THE REGION...WITH
A SLIGHT CHANCE OF SHOWERS NORTH OF POINT CONCEPTION SATURDAY
AFTERNOON INTO SATURDAY NIGHT.


.LONG TERM (SUNDAY-THURSDAY)...BIG CHANGES EXPECTED DURING
EXTENDED PERIOD AS A VERY WET AND UNSETTLED PATTERN IS EXPECTED
TO AFFECT THE REGION. A VERY STRONG WESTERLY JET STREAM WITH A 200
KNOT CORE IN THE EASTERN PACIFIC WILL LIKELY STEER A SERIES OF STORM
SYSTEMS INTO THE REGION SUNDAY THROUGH FRIDAY. EXTENDED MODELS
CONTINUE TO SHOW VARYING SOLUTIONS IN TIMING AND STRENGTH OF
INDIVIDUAL IMPULSES BUT THEY DO AGREE ON SIGNIFICANT AMOUNTS OF
PRECIPITATION. IN ADDITION TO THE STRONG JET DYNAMICS...THERE WILL
BE AMPLE SUBTROPICAL MOISTURE...WITH MAX PW VALUES OF 1.3 INCHES.
PER LATEST MODEL GUIDANCE AND COORDINATION WITH SURROUNDING
OFFICES...HAVE BUMPED UP RAINFALL TOTALS IN LATEST QPS PRODUCT.
CURRENT PROJECTIONS NOW INDICATE 4 TO 8 INCHES OF RAIN FOR COASTAL
AND VALLEY AREAS BETWEEN SUNDAY AND FRIDAY...WITH 8 TO 16 INCHES IN
THE FOOTHILLS AND MOUNTAINS. LOCAL AMOUNTS OVER 20 INCHES ARE QUITE
LIKELY IN FAVORED COASTAL SLOPE LOCATIONS.

AT THIS TIME...THE TIMING OF THE STRONGEST IMPULSES APPEAR TO BE
MONDAY AFTERNOON/EVENING AS WELL AS LATE WEDNESDAY INTO THURSDAY.
DURING THIS TIME...MODEL CROSS SECTIONS SHOW DEEP MOISTURE...STRONG
LIFT...AND STRONG SOUTHERLY WINDS (50 KNOTS OR GREATER) IN THE
BOUNDARY LAYER. THE SOUTHERLY WINDS WILL LIKELY BRING SIGNIFICANT
OROGRAPHIC ENHANCEMENT OF RAINFALL ACROSS SOUTH FACING SLOPES. MAX
RAINFALL RATES DURING BOTH OF THESE STRONG IMPULSES COULD BE AROUND
1 INCH PER HOUR...ESPECIALLY ACROSS SOUTH FACING SLOPES. IT IS ALSO
IMPORTANT TO NOTE THAT CONVECTIVE PARAMETERS SHOW THE POTENTIAL FOR
EMBEDDED THUNDERSTORMS AT TIMES DURING THE WEEK...WITH RAINFALL
RATES POSSIBLY EXCEEDING 1 INCH PER HOUR. THE PROJECTED RAINFALL
TOTALS AND INTENSITIES WILL BRING A SIGNIFICANT THREAT FOR
FLASH FLOODING AND DEBRIS FLOWS IN THE BURN AREAS. IF THE
STRONGER SYSTEM PANS OUT FOR THE LATE WEDNESDAY INTO EARLY
THURSDAY TIME FRAME...THERE MAY ALSO BE MAIN STEM RIVER
FLOODING ISSUES.

OTHER BIG STORY WITH THESE STORMS WILL BE STRONG SOUTHERLY WINDS.
AT THIS TIME...APPEARS THAT THE STRONGEST WINDS WILL OCCUR
ON WEDNESDAY...WHICH COULD BRING WIDESPREAD GALE FORCE WINDS
ACROSS THE COASTAL WATERS AND DAMAGING WINDS ACROSS SOME OF THE
LAND ZONES. THE STRONG WINDS WILL LIKELY BRING SIGNIFICANT WIND
WAVES. THIS IN COMBINATION WITH LARGE WESTERLY SWELL WILL LIKELY
BRING HIGH SURF CONCERNS...ALONG WITH THE POTENTIAL FOR COASTAL
FLOODING ISSUES. FOR MORE INFORMATION ON THE DEVELOPING SITUATION
ACROSS THE COASTAL WATERS...PLEASE REFER TO THE LATEST MARINE
PRODUCTS THROUGH THE WEEKEND.

THE SNOW LEVELS ARE GENERALLY EXPECTED TO RANGE BETWEEN 4000 AND
6000 FEET THROUGH THE WEEK. AS THE STRONG SOUTHERLY WINDS AFFECT
THE AREA ON MONDAY AND WEDNESDAY...SNOW LEVELS WILL LIKELY RISE.
THESE SERIES OF STORMS COULD BRING SEVERAL FEET OF NEW SNOW TO THE
MOUNTAINS...ESPECIALLY AT THE RESORT LEVELS ABOVE 6000 FEET.

&&

.AVIATION...14/2355Z...GENERALLY HI CONFIDENCE IN THE CURRENT TAF
PACKAGE. THERE IS A 30 PERCENT CHANCE KPRB MAY NOT HAVE LIFR
CONDITIONS LATE TONIGHT INTO FRI MORNING. OTHERWISE VFR CONDITIONS
WILL PREVAIL AT THE AIRFIELDS THRU FRI. LOW LEVEL WIND SHEAR WILL BE
POSSIBLE EARLY THIS EVENING AT KVNY THANKS TO CONTINUED GUSTY
NORTHERLY CANYON WINDS IN THE VICINITY.

KLAX AND KBUR...HI CONFIDENCE IN CURRENT TAFS.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY (SEE LAXNPWLOX).
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).
HIGH SURF ADVISORY (SEE LAXCFWLOX).
HIGH RIP CURRENT RISK (SEE LAXSRFLOX).
SPECIAL WEATHER STATEMENT (SEE LAXSPSLOX).

&&