STORM2K

OUTHWEST CALIFORNIA AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
430 AM PST SUN JAN 31 2016

UPDATED AVIATION SECTION

.SYNOPSIS...

LOW PRESSURE WILL PASS OVERHEAD TODAY BRINGING WITH IT MODERATE TO
HEAVY RAIN...HIGH ELEVATION SNOW AND THE SLIGHT CHANCE OF
THUNDERSTORMS DURING THE DAY AND EARLY EVENING HOURS. DAMAGING GUSTY
WINDS WILL DEVELOP LATER IN THE AFTERNOON AND CONTINUE INTO MONDAY.
GENERALLY FAIR SEASONAL WEATHER IS FORECAST FOR THE REST OF THE WEEK.

&&

.SHORT TERM (TODAY AND MONDAY)... ALL EYES ON A POWERFUL STORM
ENERGIZED BY A 130+ KT JET THAT IS JUST OFF THE COAST AND MOVING
QUICKLY TO THE EAST. THE JET WILL SLOWLY SAG TO THE SOUTH DURING THE
DAY WHILE TAKING ON A CYCLONIC CURVE. ITS FINAL POSITION WILL BE
SOUTH OF THE AREA WHICH WILL PLACE SRN CA UNDER THE FAVORABLE LEFT
FRONT EXIT REGION. A WEAK SFC LOW WILL APPROACH PT CONCEPTION THIS
MORNING AND WILL THEN TRACK THROUGH VENTURA AND LA COUNTIES IN
DURING THE AFTERNOON. A COLD FRONT WILL MOVE THROUGH WITH THE SFC
LOW LATE THIS MORNING THROUGH MID AFTERNOON. THIS STORM WILL START
OUT AS A GOOD RAIN (AND SNOW ABOVE 6500 FEET) MAKER BUT WILL TURN
INTO A WIND MAKER LATE THIS AFTERNOON AND AS A PARTING SHOT IT WILL
BRING A PERIOD OF DECENT SNOW TO THE GRAPEVINE AREA OF I-5 EARLY
MONDAY MORNING.

RAIN...RAIN WILL MOVE INTO THE CENTRAL COAST BEFORE SUNRISE. THE
RAIN WILL THEN OVERSPREAD THE REST OF THE AREA DURING THE MORNING
HOURS. RAIN WILL TURN HEAVY ACROSS SLO AND SBA COUNTIES FROM MID TO
LATE MORNING AND WILL BE HEAVY ACROSS VTA AND LA COUNTIES LATE
MORNING TROUGH MID AFTERNOON. THE RAIN WILL QUICKLY TURN TO SHOWERS
BEHIND THE FRONT AND WILL DIMINISH. MOST AREAS WILL BE RAIN FREE BY
MID EVENING.

RAIN TOTALS...SLO AND SBA COUNTIES WILL SEE BETWEEN THREE QUARTERS
OF AN INCH TO AN INCH AND A HALF. FOR VTU/L.A. COUNTIES ABOUT 1 TO 2
INCHES WILL FALL EXCEPT UP TO 3.00 INCHES ON SOUTH FACING MOUNTAIN
SLOPES.

TSTMS...LOW LEVEL CONVERGENCE WITH THE SFC LOW AND FRONT...UPPER
LEVEL DIVERGENCE WITH THE STRONG JET STREAM ALOFT. 500 MB TEMPS
WILL BE NEAR MINUS 30 DEGREES. SOUTH OF POINT CONCEPTION THE LI`S DIP
TO -4. ITS HARD TO IMAGINE A SCENARIO WITH THESE PARAMETERS THAT
DOES NOT PRODUCE TSTMS...ESP SOUTH OF POINT CONCEPTION. THERE IS
ENOUGH TURNING IN THE LOWER ATMOSPHERE TO INCLUDE A RISK OF
WATERSPOUTS AND WEAK TORNADOS. MOS GUIDANCE BRINGS A NEAR UNHEARD OF
36 PERCENT CHC OF TSTMS TO SOME L.A. SITES. FORECAST NOW INCLUDES
CHANCE WORDING FOR TSTMS UP FROM SLIGHT CHC. THE TIME OF PEAK TSTM
PROBABILITY WILL BE FROM LATE MORNING TO MID AFTERNOON.

RAINFALL RATES...WILL BE UP TO A HALF INCH PER HOUR AWAY FROM
THUNDERSTORMS WHICH IS JUST ENOUGH TO BRING DEBRIS FLOWS TO THE
RECENT BURN AREAS. ANY THUNDERSTORM THAT FORMS WILL TAP INTO THE 1
INCH PRECIPITABLE WATER AND WILL LIKELY PRODUCE RAINFALL RATES IN
EXCESS OF AN INCH PER HOUR WHICH IS MORE THAN ENOUGH TO PRODUCE
FLASH FLOODS/DEBRIS FLOWS OVER THE RECENT BURN AREAS. A FLASH FLOOD
WATCH IS IN EFFECT FOR ALL OF THE RECENT BURN AREAS TODAY.

SNOW...SNOW LEVELS WILL START OUT FAIRLY HIGH (BETWEEN 6500 AND 7000
FEET) TODAY AND THIS IS WHERE THE BULK OF THE SNOW WILL FALL. SNOW
LEVELS WILL RAPIDLY FALL TO 4000 FEET BY EARLY EVENING AND THEN ALL
THE WAY TO 25O0 FEET BY MONDAY MORNING. WHILE THE FORECAST STORM
TOTALS ABOVE 6500 FEET OF 1 TO 2 FEET SEEM IMPRESSIVE THE MOST
IMPORTANT ASPECT WITH THE SNOW FROM THIS EVENT WILL BE THE OVERNIGHT
SNOW SHOWERS THAT WILL OCCUR WITH THE UPSLOPE FLOW ON THE NORTH
SLOPES OF THE MTNS. IT IS LIKELY THAT THE I-5 HIGHWAY WILL SEE 3 TO
6 INCHES OF SNOW IN THE GORMAN AREA BY MONDAY MORNING. 6 TO 12
INCHES OF SNOW WILL LIKELY FALL BETWEEN 5000 AND 6500 FEET. A WINTER
STORM WARNING COVERS THE VTA AND LA MTNS FOR THE COMBINATION OF
HEAVY SNOW AND VERY STRONG WINDS.

WINDS...THE WINDS MAY WELL TURN OUT TO BE THE DEFINING FEATURE OF
THIS SYSTEM. MDL GUIDANCE IS SHOWING WIND SPEED VALUES THAT ONLY ARE
SEEN ONCE A DECADE. STRONG SOUTH WINDS WILL DEVELOP AHEAD THE FRONT
AND WILL LIKELY CREATE ADVISORY LEVEL GUSTS ACROSS SOME OF VENTURA
COUNTY AND MOST OF LA COUNTY. THE STRONG WINDS WILL LIKELY CREATE A
MOUNTAIN WAVE OVER THE LAKE PALMDALE AREA AND BRING VERY STRONG WIND
GUSTS TO THE AREA. LOS ANGELES INTERNATIONAL AIRPORT WILL LIKELY HAVE
VERY STRONG CROSS WINDS WHICH WILL HAVE QUITE THE NEGATIVE IMPACT ON
FLIGHT OPERATIONS. THE REAL WINDS WILL MOVE IN BEHIND THE FRONT.
THESE WINDS WILL BE BOOSTED BY A STRONG PRESSURE GRADIENT...ALL
SORTS OF COLD AIR ADVECTION AND AN INCREDIBLE AMOUNT OF UPPER LEVEL
WIND SUPPORT PROVIDED BY THE OVERHEAD JET. EVERY AREA OF THE
FORECAST AREA WILL SEE AT LEAST ADVISORY LEVEL WINDS TO 50 MPH AND
THE MTNS INCLUDING THE SANTA MONICA AS WELL AS THE SANTA CLARITA VLY
WILL SEE WARNING LEVEL WIND GUSTS IN EXCESS OF 60 MPH. THE HIGHER
MOUNTAIN ELEVATIONS ABOVE 6000 FEET WILL LIKELY SEE SOME GUSTS AS
HIGH AS 80 MPH. THE WINDS WILL CONTINUE THROUGH MONDAY MORNING
BEFORE DIMINISHING SOME. THE MOUNTAINS WILL LIKELY NEED WIND
ADVISORIES THROUGH TUESDAY. THE WINTER STORM WARNING INCLUDES THE
STRONG WINDS FOR THE LA AND VTA MTNS.

.LONG TERM (TUE-SAT)... THE EXCITEMENT QUICKLY FADES TUESDAY AS A
RIDGING PATTERN SETS UP OVER THE WEST COAST. IT WILL BE DRY THROUGH
THE PERIOD. IT WILL BE PARTLY CLOUDY AT TIMES AS A FEW WEAK SHORT
WAVES TRY TO UNSUCCESSFULLY PUSH THROUGH THE RIDGE. MAX TEMPS WILL
MOSTLY BE ABOVE NORMAL BY THURSDAY. THE MOUNTAIN AREAS WILL NEED
WIND ADVISORIES FOR EARLY TUESDAY.

&&

Ntxw wrote:The Sierras are in really good shape. They will only continue to benefit which is more beneficial to SoCal IMO. Watering their lawns rains isn't as important as building their snowpack in the high Sierras.