FXUS66 KLOX 290343
AFDLOX
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
745 PM PST SAT NOV 28 2009
.SYNOPSIS...
LINGERING SHOWERS WILL CONTINUE OVER EASTERN SECTION OF LOS ANGELES
COUNTY TONIGHT OTHERWISE COOL AND BREEZY CONDITIONS WILL AFFECT THE
AREA TONIGHT AND SUNDAY AS A COLD LOW PRESSURE SYSTEM MOVES EAST OUT
OF THE AREA. A SLIGHT WARMING TREND WITH OFFSHORE WINDS WILL PERSIST
INTO MID WEEK AS HIGH PRESSURE BUILDS OVER AND ALONG THE WEST COAST.
&&
.SHORT TERM (TONIGHT-TUE)...AN UPPER LEVEL LOW SPINNING OVER INLAND
SOUTHERN CALIFORNIA THIS EVENING WAS CONTINUING TO BRING SCATTERED
SHOWERS TO THE ANTELOPE VALLEY FOOTHILLS...THE SAN GABRIEL MTNS AND
SAN GABRIEL VALLEY THIS EVENING...WITH SNOW LEVELS AROUND 4500 FT OR
SO. ANOTHER COUPLE OF INCHES OF SNOW WILL BE POSSIBLE OVERNIGHT
MAINLY IN THE SAN GABRIEL MTNS AND A WINTER WEATHER ADVISORY WILL
REMAIN IN EFFECT FOR THIS AREA THRU 4 AM. PLEASE SEE LAXWSWLOX FOR
DETAILS. THE UPPER LOW WILL MOVE FURTHER S AND AWAY FROM THE
DISTRICT OVERNIGHT...WITH THE CHANCES OF SHOWERS ENDING FOR THE MOST
PART OVER EASTERN L.A. COUNTY BY SUNRISE. THERE WILL ALSO CONTINUE
TO BE A SLIGHT CHANCE OF A THUNDERSTORM THIS EVENING OVER THIS AREA
AS WELL. OTHERWISE...THE MAIN AFFECT OF THE EXITING UPPER LOW IS THE
INCREASE IN NE WINDS THROUGH AND BELOW THE PASSES AND CANYONS OF
L.A./VTU COUNTIES OVERNIGHT. A WIND ADVISORY IS IN EFFECT FOR THE
EASTERN VALLEYS OF VTU COUNTY...THE SANTA CLARITA AND SAN FERNANDO
VALLEYS IN L.A. COUNTY...AS WELL AS THE L.A. COUNTY MOUNTAINS LATER
TONIGHT INTO SUNDAY. PLEASE SEE LAXNPWLOX FOR DETAILS ON THE WIND
ADVISORIES.
THE UPPER LEVEL LOW WILL DRIFT INTO NORTHERN BAJA SUN MORNING THEN E
INTO NW MEXICO BY MON MORNING. AN UPPER LEVEL RIDGE WILL BUILD INTO
NORTHERN CA BY LATE SUN THEN INTO CENTRAL CA FOR MON. THE UPPER
RIDGE WILL THEN WEAKEN MON NIGHT AND TUE...WITH A A BROAD NW FLOW
ALOFT OVER SRN CA DURING THE PERIOD. EXCEPT FOR THE SLIGHT CHANCE OF
A LINGERING SHOWER OVER THE L.A. COUNTY MTNS EARLY SUN...DRY WEATHER
CAN BE EXPECTED ACROSS THE ENTIRE FORECAST AREA SUN THRU TUE. GUSTY
NE OFFSHORE FLOW WILL AGAIN AFFECT PORTIONS OF VTU/L.A. COUNTIES SUN
NIGHT INTO MON MORNING...WITH WINDS POSSIBLY APPROACHING ADVISORY
LEVELS AT TIMES IN THE MTNS. GRADIENTS WILL TURN MUCH WEAKER INTO
TUE MORNING WITH SOME ONSHORE FLOW DEVELOPING TUE AFTERNOON. MOSTLY
CLEAR SKIES ARE EXPECTED TO PREVAIL IN ALL AREAS THRU THE PERIOD.
TEMPS ACROSS THE REGION ARE FORECAST TO WARM TO NEAR NORMAL FOR
SUN...AND TO A COUPLE OF DEGREES ABOVE NORMAL FOR MON BEFORE COOLING
BACK TO AROUND OR SLIGHTLY BELOW NORMAL FOR TUE.
...FROM PREVIOUS DISCUSSION...
.LONG TERM (WED-SAT)...MODELS STILL VERY DIVERGENT WITH 18Z GFS
TRENDING TO TAKE EASTERN PACIFIC SYSTEM FOR WEDNESDAY SOUTH OF THE
REGION WHILE THE 12Z ECMWF WEAKENS THIS SYSTEM AND MOVES IT INTO THE
PACIFIC NW. CONFIDENCE UNFORTUNATELY REMAINS LOW ON A GOOD SOLUTION
FOR THE END OF THE WEEK SO HAVE GONE CLOSE TO CLIMATOLOGY BUT HAVE
HELD OFF ON RETURNING THE MARINE LAYER TO COASTAL AREAS FOR NOW.
MODELS SUGGEST WITH WEAK SURFACE FLOW ON WEDNESDAY THIS MAY BE THE
RETURN DAY BUT 18Z GFS BUILDS A SURFACE HIGH INTO THE GREAT BASIN ON
THURSDAY FOR WEAK OFFSHORE FLOW. WAIT AND SEE PLAN UNTIL MORE
CONTINUITY EXISTS AMONGST THE MODELS APPEARS MOST PRUDENT AT THIS
POINT.
&&
.AVIATION...28/2350Z...HI CONFIDENCE IN THE CURRENT TAFS. THERE WILL
BE SOME CLOUDINESS AT TIMES TONIGHT OVER THE ANTELOPE VALLEY AND THE
L.A. COUNTY COAST AND VALLEYS...BUT ANY CIGS SHOULD REMAIN VFR.
KLAX...HI CONFIDENCE IN CURRENT TAF.
KBUR...HI CONFIDENCE IN CURRENT TAF. SOME GUSTY N WINDS WILL
DIMINISH THIS EVENING.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY (SEE LAXWSWLOX).
WIND ADVISORY (SEE LAXNPWLOX).
SMALL CRAFT ADVISORY (SEE LAXCWFLOX).
HIGH SURF ADVISORY (SEE LAXCFWLOX).
HIGH RIP CURRENT RISK (SEE LAXSRFLOX).
&&
$$
PUBLIC...SIRARD/TRM
AVIATION...SIRARD
SYNOPSIS...TRM/MEIER
WWW.WEATHER.GOV/LOSANGELES
