FXUS66 KLOX 220419
AFDLOX
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
815 PM PST MON DEC 21 2009
.SYNOPSIS...
A LOW PRESSURE SYSTEM PASSING TO OUR EAST WILL BRING A CHANCE OF SHOWERS
TONIGHT INTO EARLY TUESDAY...FOLLOWED BY STRONG WINDS AND COLD
TEMPERATURES. THE REST OF CHRISTMAS WEEK LOOK FOR MOSTLY CLEAR SKIES
AND A WARMING TREND. A STORM SYSTEM MAY APPROACH EARLY NEXT WEEK
WITH A CHANCE OF RAIN AND A COOLING TREND.
&&
.SHORT TERM (TONIGHT-THU)...A COLD LOW PRESSURE SYSTEM CURRENTLY
CENTERED OVER NORTHERN OREGON IS EXPECTED TO TRACK SOUTHEASTWARD
ACROSS INTERIOR CALIFORNIA AND NEVADA ON TUESDAY. A WEAK COLD FRONT
CURRENTLY CENTERED ACROSS SBA COUNTY WILL SWEEP THROUGH THE FORECAST
AREA TONIGHT. DOPPLER RADAR IMAGERY AND AUTOMATED RAIN GAUGES SHOWED
LIGHT SHOWER ACTIVITY ACROSS SLO AND SBA COUNTIES THIS EVENING...WITH
ACCUMULATIONS GENERALLY UNDER A TENTH OF AN INCH SO FAR. AS THE SYSTEM
ROUNDS SOUTH OF POINT CONCEPTION...THERE IS GENERALLY EXPECTED TO BE
FURTHER WEAKENING...WITH THE EXCEPTION OF LA COUNTY WHERE MODELS CONTINUE
TO SHOW MORE FAVORABLE CYCLONIC ONSHORE LOW LEVEL FLOW WHICH COULD
GIVE BETTER CHANCE OF MEASURABLE SHOWERS...ESPECIALLY IN THE SAN
GABRIEL MOUNTAINS AND VALLEY. ALSO...NORTHWEST FLOW WILL PROVIDE
MORE FAVORED UPSLOPE FLOW ACROSS NORTH FACING MOUNTAIN SLOPES LATER
TONIGHT INTO TUESDAY MORNING. SNOW LEVELS ARE EXPECTED TO LOWER
RAPIDLY BY TUESDAY MORNING...GENERALLY RANGING BETWEEN 3000 AND 4000
FEET. ANY SNOW ACCUMULATIONS ARE EXPECTED TO BE 2 INCHES OR
LESS...BUT INTERSTATE 5 NEAR THE GRAPEVINE COULD DEFINITELY BE
IMPACTED.
MAIN IMPACTS OF THIS SYSTEM WILL BE STRONG WINDS AND COLDER
TEMPERATURES. HIGH WIND WATCHES POSTED LAST NIGHT ARE BEING
CONVERTED TO WARNINGS IN EVENING UPDATE. PER PREVIOUS FORECAST
THINKING...HAVE BUMPED UP START TIMES A BIT FOR WARNING PRODUCT...
WITH STRONG AND POTENTIALLY DAMAGING WINDS STARTING AS EARLY AS
MID MORNING TUESDAY FOR THE MOUNTAINS AND ANTELOPE VALLEY. 00Z
NAM CONTINUES TO ADVERTISE VERY STRONG UPPER LEVEL WIND SUPPORT
AND SUBSIDENCE WITH THIS EVENT...WITH 700 MB WINDS RANGING BETWEEN
60 AND 80 KNOTS FOR A LARGE PORTION OF THE FORECAST AREA FROM LATE
TUESDAY MORNING INTO TUESDAY EVENING! STRONG LIKELIHOOD OF DAMAGING
WIND GUSTS OF 60 TO 70 MPH ACROSS THE MOUNTAINS AND ANTELOPE
VALLEY...WITH ISOLATED GUSTS TO 80 MPH POSSIBLE IN FAVORED LOCATIONS
THROUGH THE INTERSTATE 5 CORRIDOR...SUCH AS WHITAKER PEAK. DUE TO
THE NORTHWEST TO NORTH ORIENTATION OF THE FLOW...OTHER AREAS THAT
HAVE BEEN INCLUDED IN THE HIGH WIND WARNING FOR DAMAGING GUSTS TO 60
MPH INCLUDE THE SANTA BARBARA SOUTH COAST...SANTA CLARITA
VALLEY...AND SAN FERNANDO VALLEY. AS WE DRAW CLOSER TO THE EVENT...
LATER SHIFTS WILL LIKELY NEED TO POST WIND ADVISORIES FOR MANY OTHER
PORTIONS OF THE SOUTHLAND.
THE OTHER BIG WEATHER CONCERN WILL BE AN INFLUX OF MUCH COLDER AIR
INTO THE REGION TUESDAY NIGHT. AT THAT TIME...THE ONLY THREAT OF
PRECIPITATION WILL BE ALONG THE NORTH SLOPES NEAR THE KERN COUNTY
LINE...WHEN SNOW LEVELS COULD FALL AS LOW AS 2000 FEET. WINDS ARE
EXPECTED TO DIMINISH SOMEWHAT ACROSS THE REGION LATE TUESDAY
NIGHT...SO SUB-FREEZING TEMPERATURES WILL DEFINITELY BE A CONCERN
FOR WIND PROTECTED AREAS. MANY PORTIONS OF THE ANTELOPE
VALLEY...CUYAMA VALLEY...AND INTERIOR VALLEYS OF SLO COUNTY ARE
EXPECTED TO SEE MINIMUM TEMPERATURES FALL TO THE LOWER TO MID
20S...BUT THOSE LOCATIONS HAVE ALREADY EXPERIENCED
TWO OR MORE HARD FREEZES THIS SEASON...SO NO FREEZE WATCH WILL BE
POSTED. OTHER WIND PROTECTED AREAS MAY REQUIRE FROST ADVISORIES...
WITH TEMPERATURES FALLING TO THE UPPER 20S TO MID 30S ACROSS MOST OTHER
COASTAL AND VALLEY LOCATIONS (WITH THE EXCEPTION OF THE LA COASTAL
PLAIN).
*** FROM PREVIOUS DISCUSSION ***
AN UPPER RIDGE WILL BE BUILDING OVER THE AREA WED AND THU FOR A
SLIGHT WARMING TREND. WEAK TO MODERATE OFFSHORE FLOW WILL HELP WARM
TEMPS AT LOWER ELEVATIONS BUT IT WILL TAKE A COUPLE DAYS TO FULLY
RECOVER FROM THE COLD AIR THAT THIS CURRENT TROF WILL LEAVE BEHIND.
AS A RESULT, HIGHS PROBABLY WON'T BOUNCE BACK TO NORMAL UNTIL THU AT
THE EARLIEST. WINDS PROBABLY NOT STRONG ENOUGH FOR ADVISORIES BUT
THE USUAL FAVORED SANTA ANA WIND LOCATIONS WILL LIKELY SEE GUSTS
INTO THE 40S.
.LONG TERM (FRI-MON)...NICE WEATHER TO CONTINUE RIGHT ON THROUGH
CHRISTMAS DAY AND INTO SAT WITH DAYTIME HIGHS HOVERING NEAR TO
SLIGHTLY ABOVE NORMALS. MODELS IN DECENT AGREEMENT SUNDAY AND MONDAY
SHOWING AN UPPER LOW UNDERCUTTING THE RIDGE ACROSS THE ERN PACIFIC,
BUT BIG DIFFERENCES EXIST WITH THE TRACK OF THE LOW. THE GFS IS
ACTUALLY THE WETTER MODEL BY FAR WITH A VERY SIGNIFICANT SYSTEM
MOVING ONSHORE AS EARLY AS SUNDAY. THE ECMWF AND CANADIAN MODELS
TAKE THE LOW SOUTH INTO NRN MEXICO AND ACTUALLY MISS SO CAL
COMPLETELY. SO WE'LL HAVE TO SEE HOW THIS PLAYS OUT OVER THE NEXT
SEVERAL DAYS. FOR NOW I'VE KEPT IN A GENERIC SLIGHT CHANCE OF
SHOWERS FOR SUN AND MON SINCE AT THIS TIME ANY OF THOSE MODEL
SOLUTIONS ARE EQUALLY PLAUSIBLE SCENARIOS.
&&
.AVIATION...22/0400Z
BEST THREAT OF LIGHT SHOWERS THIS EVENING WILL CONTINUE TO BE ACROSS
KSBP...KPRB...AND KSMX. 15-30 PERCENT CHANCE OF -SHRA ELSEWHERE
AS SYSTEM MOVES SOUTH AND EAST OVERNIGHT. MVFR CIGS/VIS COULD FORM
LATER TONIGHT WITH THE ADDED MOISTURE...BUT CONFIDENCE IS LOW. KPRB
COULD SEE LIFR CONDITIONS AFTER 10Z...BUT DEPENDS ON WHEN NORTHERLY
WINDS INCREASE. IF THEY ARE DELAYED...FG LIKELY. WIDESPREAD AND
STRONG W-NW WINDS ON TUE...WITH LLWS CONCERNS.
KLAX...BRIEF LIGHT SHOWER COULD AFFECT KLAX BETWEEN 09Z AND 14Z...
WITH POTENTIAL FOR BRIEF MVFR CIGS/VIS DURING THAT TIME. STRONG WEST
WINDS EXPECTED TUE...PEAKING WITH GUSTS INTO 30-35KT RANGE BETWEEN
21Z AND 00Z. BY TOMORROW EVENING...DIRECTION EXPECTED TO BE NORTHWEST
TO NORTH...WITH POTENTIAL FOR GUSTS OVER 30 KNOTS CONTINUING BETWEEN
00Z-06Z.
KBUR...BRIEF LIGHT SHOWER COULD AFFECT KBUR BETWEEN 09Z AND
14Z...WITH POTENTIAL FOR BRIEF MVFR CIGS/VIS DURING THAT TIME.
NORTHWEST WINDS EXPECTED TO PICK UP BY LATE TUESDAY MORNING INTO
TUESDAY EVENING...WITH GUSTS GENERALLY IN THE 20 TO 30 KNOT RANGE.
WITH STRONG FLOW EXPECTED ABOVE THE SURFACE...LLWS MAY BE CONCERN
DURING THIS TIME.
&&
.MARINE...
WIDESPREAD GALE FORCE WINDS EXPECTED ACROSS THE COASTAL WATERS TUESDAY
INTO TUESDAY EVENING. GUSTS OVER 40 KNOTS CAN BE EXPECTED IN FAVORED
LOCATIONS...INCLUDING PORTIONS OF THE SBA CHANNEL. CURRENT BUOY REPORTS
STILL SHOWING 6 TO 7 FOOT SWELL ACROSS INNER COASTAL WATERS THIS
EVENING. WITH THE THREAT OF HIGH WIND WAVE ACTIVITY TUESDAY AFTERNOON
INTO TUESDAY EVENING...WILL KEEP HIGHER THAN NORMAL SURF PRODUCT THROUGH
THAT TIME...WITH LATER SHIFTS POSSIBLY NEEDING TO UPGRADE TO A HIGH
SURF ADVISORY. MARINE INTERESTS SHOULD BE PREPARED FOR STEEP WIND
WAVES ON TUESDAY...WITH PERIODS UNDER 7 SECONDS. FOR MORE
INFORMATION ON MARINE PRODUCTS...PLEASE REFER TO THE LATEST
LAXMWWLOX AND LAXCFWLOX PRODUCTS.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING (SEE LAXNPWLOX).
GALE WARNING (SEE LAXMWWLOX).
HIGHER THAN NORMAL SURF (SEE LAXCFWLOX).
HIGH RIP CURRENT RISK (SEE LAXSRFLOX).
SPECIAL WEATHER STATEMENT (SEE LAXSPSLOX).
&&
$$
PUBLIC...GOMBERG/WOFFORD
AVIATION...GOMBERG
SYNOPSIS...GOMBERG
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