Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 281841
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1041 AM PST SAT FEB 28 2015

.SYNOPSIS...

A COLD LOW PRESSURE SYSTEM WILL BRING SHOWERS AND MOUNTAIN SNOW TO
SOUTHWEST CALIFORNIA THIS WEEKEND...ALONG WITH A SLIGHT CHANCE OF
THUNDERSTORMS. AFTER A BRIEF BREAK...ANOTHER COLD SYSTEM WILL BRING
SIMILAR WEATHER TO THE AREA LATE MONDAY MORNING THROUGH EARLY
TUESDAY. DRY WEATHER IS EXPECTED LATE TUESDAY THROUGH FRIDAY. THERE
WILL BE A WARMING TREND...WITH DAYTIME TEMPERATURES NEAR OR ABOVE
NORMAL BY THURSDAY.

&&

.SHORT TERM (TODAY-MON)...

MAIN UPDATE THIS MORNING WAS TO DECREASE THE POPS AND CLOUD COVER
FOR THE MORNING HOURS BASED ON CURRENT SATELLITE AND RADAR TRENDS.
NOT EXPECTING MUCH SHOWER ACTIVITY FOR AREAS S OF THE MOUNTAINS THIS
MORNING DUE TO NW FLOW ALOFT. CLOUD COVERAGE AND RAIN CHANCES WILL
INCREASE THIS AFTERNOON AS THE UPPER LOW THAT IS CURRENTLY OVER
NORTHERN CA CONTINUES TO MOVE S. DAYTIME SURFACE HEATING WILL ALSO
HELP SHOWERS TO DEVELOP...AS THIS WILL BE A CONVECTIVE SCENARIO WITH
COLD AIR MOVING IN ALOFT. COULD EVEN BE SOME ISOLATED THUNDERSTORMS
N OF POINT CONCEPTION TODAY...WHERE THERE IS SOME WEAK INSTABILITY.

***FROM PREVIOUS DISCUSSION***

THE UPPER LOW WILL SLOWLY DROP SWD TO NEAR POINT CONCEPTION LATE
TONIGHT...MOVE VERY LITTLE ON SUNDAY...THEN PUSH SLOWLY INTO
LOS ANGELES COUNTY SUNDAY NIGHT. THIS WILL MAINTAIN A MOIST AND
UNSTABLE AIRMASS ACROSS THE REGION...SO EXPECT QUITE A BIT OF SHOWER
ACTIVITY OVERNIGHT THROUGH SUNDAY NIGHT...WITH A SLIGHT CHANCE OF
TSTMS. THE TEMPERATURE PROFILE THROUGH THE ATMOSPHERE WILL BE
FAVORABLE FOR SOME SMALL HAIL...AND INDEED...THIS HAS BEEN REPORTED
ACROSS NRN CA. ANY THUNDERSTORM THIS AFTERNOON THROUGH SUNDAY
EVENING WILL HAVE THE CAPABILITY OF PRODUCING SMALL HAIL AND HEAVY
DOWNPOURS. WHILE SHOWERS MAY OCCUR ANYWHERE AT ANY TIME...IT APPEARS
THAT THE BEST CHANCES OF ORGANIZED SHOWER ACTIVITY WILL BE TONIGHT
ACROSS L.A. COUNTY AND EASTERN VTU COUNTY AS SOME LOW LEVEL SWLY
FLOW DEVELOPS...AND SUNDAY AFTERNOON AND EVENING AS THE UPPER LOW
MOVES OVERHEAD. DUE TO THE SHOWERY NATURE OF THE PRECIPITATION...
RAINFALL TOTALS THROUGH SUNDAY NIGHT WILL BE HIGHLY VARIABLE...BUT
IN GENERAL...EXPECT TOTALS OF ONE QUARTER TO ONE HALF INCH...
EXCEPT ONE HALF INCH TO ONE INCH ACROSS THE MOUNTAINS...THE SAN
GABRIEL VALLEY...AND POSSIBLY PORTIONS OF THE REMAINDER OF THE L.A.
COUNTY VALLEYS AND THE VALLEYS OF ERN VTU COUNTY. LOCAL TOTALS UP TO
2 INCHES ARE POSSIBLE IN THE SAN GABRIEL MOUNTAINS AND FOOTHILLS.

SNOW WILL BE AN ISSUE FOR TRAVELERS THIS WEEKEND. SNOW LEVELS ARE
EXPECTED TO LOWER TO 5000 FEET LATE TODAY...THEN TO BETWEEN 3500 AND
4000 FEET LATE TONIGHT OR EARLY SUNDAY...THEN LINGER AT THOSE LEVELS
INTO SUNDAY NIGHT. SNOW MAY WELL AFFECT TRAVEL ACROSS HIGHER
PORTIONS OF INTERSTATE 5...HIGHWAY 14 AND HIGHWAY 33...ESPECIALLY
LATE TONIGHT THROUGH EARLY MONDAY. HAVE EXPANDED WINTER WEATHER
ADVISORIES TO INCLUDE THE MOUNTAINS OF SANTA BARBARA COUNTY. ON
AVERAGE...EXPECT A TOTAL OF 4 TO 8 INCHES OF SNOW BETWEEN 5000 AND
6500 FEET...WITH TOTALS OF 8 TO 12 INCHES ABOVE 6500 FEET...AND 2 TO
4 INCHES BETWEEN 4000 AND 5000 FEET. THERE COULD BE LOCAL TOTALS AS
HIGH AS 18 INCHES ACROSS PORTIONS OF THE SAN GABRIEL MOUNTAINS...OR
HIGHER ELEVATIONS IN VTU COUNTY. WAS STRONGLY CONSIDERING UPGRADING
TO A WINTER STORM WARNING...BUT HAVE DECIDED AGAINST IT...SINCE THE
SNOW ACCUMULATIONS MAY NOT MEET THE REQUIRED TOTALS IN ANY 12 OR 24
HOUR PERIOD. LATER SHIFTS MAY WELL HAVE TO UPGRADE DEPENDING UPON
SHOWER DEVELOPMENT.

SHOWERS WILL DECREASE ACROSS THE REGION SUNDAY NIGHT...AND MAY END
JUST ABOUT EVERYWHERE. HOWEVER...ANOTHER COLD UPPER LOW DROPPING
RAPIDLY SOUTHWARD WILL CAUSE SHOWERS TO BECOME LIKELY AGAIN MONDAY
AFTERNOON...WITH SHOWERS CONTINUING MONDAY NIGHT. THAT SYSTEM WILL
ALSO HAVE LOW SNOW LEVELS...AND PROBABLY ALSO A SLIGHT CHANCE OF
TSTMS. THAT SYSTEM WILL MOVE A BIT FASTER...BUT MAY ALSO TRACK A BIT
FARTHER OFF THE COAST...SO IT MAY PICK UP MORE MOISTURE. SHOWERS
SHOULD WIND DOWN IN MOST AREAS LATE MON NIGHT. MAX TEMPERATURES WILL
BE WELL BELOW NORMAL THROUGH MONDAY.

.LONG TERM (TUE-FRI)...THERE COULD BE A FEW LINGERING SHOWERS
TUE...BUT THAT IS LOOKING LESS AND LESS LIKELY. HEIGHTS WILL REBOUND
TUE AFTERNOON...AND WITH SOME SUNSHINE...EXPECT AT LEAST A BIT OR
WARMING. THE 06Z GFS NOW SHOWS A WEAK IMPULSE DROPPING SWD INTO THE
REGION ON WED...AND THAT WAS NOT ON THE PREVIOUS RUN. NO SHOWER
EXPECTED...BUT IT COULD KEEP MAX TEMPS ON THE COOL SIDE. AN UPPER
RIDGE AND HIGHER HEIGHTS WILL BRING WARMER WEATHER THU AND
FRI...WITH DAYTIME TEMPS LIKELY ABOVE NORMAL.


&&

.AVIATION...28/1800Z...

MID/UPPER LEVEL TROUGH CENTER OVER CENTRAL/NORTHERN CALIFORNIA WILL
SHIFT SOUTH. UPPER LEVEL STRONG WEST-SOUTHWEST WINDS WILL BECOME
STRONG SOUTHWEST WHILE MID LEVEL MODERATE WEST WINDS BECOME LIGHT TO
MODERATE SOUTHWEST AFTER 01/05Z OVER THE AREA. FREEZING LEVEL WAS
APPROXIMATELY 6KFT THIS MORNING AND WILL DIFFER BY MINUS 1KFT SUNDAY
MORNING. ISOLATED THUNDERSTORMS WITH TOPS APPROXIMATELY 30KFT ARE
EXPECTED TO MOVE EAST-NORTHEAST AFTER 01/05Z.

MARINE LAYER AT LAX AT 1715Z IS NONE.

KLAX...CHANCE CIGS 030 AT TIMES THROUGH 28/20Z THEN CHANCE CIGS 030
AND -SHRA BETWEEN 01/03-01/11Z. CHANCE CIGS 030-035 AND -TSRA
BETWEEN 01/11-01/15Z THEN CHANCE CIGS 035-040 THEREAFTER.

KBUR...CHANCE CIGS 025 THROUGH 28/19Z THEN CHANCE CIGS 035 BETWEEN
29/19-01/11Z. CHANCE -TSRA CIGS 030 BETWEEN 01/11-01/15Z.

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

&&

.MARINE...28/900 AM...

THERE IS A CHANCE SMALL CRAFT ADVISORY CONDITIONS WILL PERSIST
THROUGH EARLY THIS AFTERNOON IN THE INNER AND OUTER WATERS SOUTH OF
THE NORTHERN CHANNEL ISLANDS. OTHERWISE ISOLATED THUNDERSTORMS ARE
EXPECTED THROUGH MONDAY MORNING. THE THUNDERSTORMS WILL MOVE
WEST-SOUTHWEST AROUND 28 KT TODAY THROUGH THIS AFTERNOON THEN AS THE
TROUGH AXIS SETTLES OVER THE AREA TONIGHT THROUGH SUNDAY NIGHT THE
STORMS SOUTH OF POINT CONCEPTION WILL MOVE NORTHEAST 25 KT AND MOVE
SOUTHWEST AROUND 15 KT NORTH OF POINT CONCEPTION. A SWELL GENERATED
IN THE SOUTHERN HEMISPHERE WITHIN 190-210 DEGREES RELATIVE TO
VENTURA COUNTY LAST TUESDAY IS EXPECTED TO ARRIVE NEXT WEEK TUE
THROUGH WEDNESDAY.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY (SEE LAXWSWLOX).
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).
HIGH RIP CURRENT RISK (SEE LAXSRFLOX).
MARINE WEATHER STATEMENT (SEE LAXMWSLOX).

&&

$$

PUBLIC...SUKUP/DB
AVIATION...30
MARINE...30
SYNOPSIS...SMITH

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