FXUS66 KLOX 061125
AFDLOX
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
315 AM PST SUN DEC 6 2009
.SYNOPSIS...
INCREASING ONSHORE FLOW AND A DEEPENING MARINE LAYER COULD PRODUCE
SOME AREAS OF LIGHT SHOWERS TODAY...ALONG WITH COLDER TEMPERATURES.
A COLD LOW PRESSURE SYSTEM WILL BRING WINDS...RAIN...AND MOUNTAIN
SNOW TONIGHT THROUGH TUESDAY MORNING. A SECOND SYSTEM WILL BRING
MORE RAIN TO THE AREA ON THURSDAY.
&&
.SHORT TERM (TODAY-TUE)...
5000 FOOT MOIST LAYER HAS CREATED NUMEROUS CLOUD LAYERS BETWEEN 2500
AND 5000 FEET THIS MORNING OVER L.A. AND VENTURA COUNTIES. THERE IS
ENOUGH LIFT IN THE AREA TO SUPPORT LOCAL DRIZZLE OR LIGHT RAIN
ESPECIALLY NEAR THE FOOTHILLS. THE SUN WILL CONTINUE TO COOK UP
CLOUDS AND THE VLYS WILL STAY MOSTLY CLOUDY BUT THE COASTS WILL
LIKELY CLEAR. THERE HAS BEEN ENOUGH MIXING NORTH OF POINT CONCEPTION
TO KEEP THE SKIES CLEAR EXCEPT FOR THE INTERIOR VLYS WHERE SOME
CLOUDS ARE SLOPPING OVER FROM THE SAN JOAQUIN VLY.
A LOW PRESSURE SYSTEM CURRENTLY OVER OREGON WILL ROTATE DOWN THE
COAST TONIGHT AND WILL SET UP A MOIST WESTERLY FLOW PATTERN OVER
CALIFORNIA. AFTER MIDNIGHT A WEAK SURFACE LOW WILL DEVELOP WEST OF
POINT CONCEPTION. RAIN WILL MOVE INTO THE CENTRAL COAST AFTER
MIDNIGHT AND THERE WILL BE A CHANCE OF SOME WARM FRONTAL RAIN FOR
AREAS SOUTH OF POINT CONCEPTION.
RAIN WILL OVERSPREAD THE ENTIRE AREA MONDAY MORNING. RAINFALL WILL
PEAK IN INTENSITY NORTH OF POINT CONCEPTION IN THE MORNING AND
DURING THE AFTERNOON SOUTH OF POINT CONCEPTION. THIS WILL GENERALLY
BE A NON CONVECTIVE EVENT BUT THERE IS ENOUGH COLD AIR ALOFT TO
CREATE LOCAL POCKETS OF CONVECTION WITH ENHANCED RAINFALL RATES. IN
GENERAL PEAK RAINFALL RATES WILL BE NEAR A THIRD OF AN INCH PER HOUR
BUT THERE WILL LIKELY BE ISOLATED RAINFALL RATES OF UP TO A HALF
INCH PER HOUR. A FLASH FLOOD WATCH FOR THE BURN AREAS WILL LIKELY BE
ISSUED THIS AFTERNOON WHEN IT IS ABOUT 18 TO 24 HOURS AWAY FROM THE
PEAK RATES. THE BULK OF THE RAIN WILL BE DONE BY EARLY EVENING
MONDAY. RAINFALL AMOUNTS ARE EXPECTED TO RANGE BETWEEN
.50 AND 1.50 INCHES ACROSS MOST AREAS...WITH 1.50 TO 3.00 INCHES
EXPECTED ACROSS SOUTH AND SOUTHWEST FACING FOOTHILL AND MOUNTAIN
LOCATIONS. THE HIGHEST RAINFALL AMOUNTS ARE EXPECTED ACROSS LOS
ANGELES COUNTY...ESPECIALLY ACROSS THE SAN GABRIEL MOUNTAINS AND
ADJACENT FOOTHILLS.
SNOW WILL BE A MORE PROBLEMATIC FORECAST. SNOW LEVELS WILL START OUT
AROUND 6000 FEET BUT WILL LOWER TO AROUND 5000 FEET DURING THE DAY
EXCEPT ON THE FRONT RANGES WHERE SOUTH FLOW WILL BOOST SNOW LEVELS.
THERE IS A POTENTIAL FOR 12 TO 18 INCHES OF SNOW WITH THIS SYSTEM
ABOVE 6000 FEET AND A WINTER STORM WATCH IS CURRENTLY IN EFFECT FOR
MONDAY FOR THE MTNS OF L.A. AND VTA COUNTY.
MONDAY NIGHT WILL BE A VERY TRICKY FORECAST. THE RAIN WILL TAPER OFF
TO SHOWERS AND THEN END OVERNIGHT OVER MOST AREAS. THE NORTH SLOPES
WILL BE THE BIG EXCEPTION WHERE STRONG NORTH FLOW WILL PILE UP THE
CLOUDS AND KEEP A CHANCE OF SNOW SHOWERS GOING ALL NIGHT. COLD AIR
WILL PLUNGE INTO THE AREA LOWERING THKNS TO 534 DM. THIS COLD AIR
WILL BE ACCOMPANIED BY STRONG WINDS AND WIND ADVISORIES MAY BE
NEEDED IN THE AREAS FAVORED BY NORTH WINDS. SNOW LEVELS WILL FALL TO
2000 FEET OR LOWER AND THE I-5 CORRIDOR WILL BE IMPACTED ALL NIGHT.
THE WINDS WILL KEEP OVERNIGHT LOW FROM FALL TOO FAR BUT ANY WIND
SHELTERED AREAS MAY SEE LOWS WELL BELOW NORMAL. FREEZING FOG WILL BE
POSSIBLE IN THE INTERIOR VALLEYS AND BLACK ICE COULD FORM IN ANY
INTERIOR WIND SHELTERED AREAS.
A LITTLE RIDGE BUILDS IN TUESDAY. AND SKIES WILL BE AT WORST PARTLY
CLOUDY SAVE THE NORTH SLOPES WHERE CLOUDS AND SNOW SHOWERS WILL
CONTINUE THROUGH THE DAY. IT WILL BE BREEZY. DESPITE THE INCREASED
SUNSHINE IT WILL BE A COLD DAY WITH THKNS VALUES ONLY AROUND 545 DM.
.LONG TERM (WED-SAT)...
ALL MDLS ARE NOW DELAYING THE LATER WEEK STORM SYSTEM AND WEDNESDAY
NOW LOOKS LIKE A PRETTY NICE DAY WITH MOSTLY SUNNY OR AT WORST
PARTLY CLOUDY SKIES. THKNS WILL BUMP UP TO ABOUT 552 DM AND WHILE
MAX TEMPS WILL NOT REACH SEASONAL NORMS THEY WILL BE CLOSE.
EC AND GFS ARE NOW BACKING OFF OF THE THURSDAY/FRIDAY EVENT WITH THE
06Z GFS COMING IN WITH ONLY A WEAK SYSTEM. BOTH THE EC AND THE GFS
STILL AGREE THAT IT WILL RAIN THURSDAY AND THURSDAY NIGHT BUT THE
STORM NO LONGER LOOKS LIKE A HUGE RAIN MAKER. THIS OF COURSE COULD
CHANGE IN THE VERY NEXT MDL RUN. DESPITE THE LACK OF CONFIDENCE ON
HOW MUCH RAIN WILL FALL IT DOES LOOK LIKELY THAT SOME RAIN WILL FALL
EVERYWHERE ON THURSDAY.
THERE IS A CHANCE THAT A SECONDARY IMPULSE WILL KEEP THE RAIN GOING
INTO FRIDAY EVEN IF IT DOES NOT RAIN IT LOOKS LIKE IT WILL BE MOSTLY
CLOUDY AND COOL.
YET ANOTHER SYSTEM IS PROGGED IN FOR THE WEEKEND. THE MDLS ARE
CONTINUOUSLY MOVING THE AXIS OF THE STORM WITH SOME RUNS SO FAR
NORTH THAT WE WOULD GET LITTLE MORE THAN A BRIEF SHOWER AND OTHER
RUNS PLACING THE STORM TRACK RIGHT THROUGH POINT CONCEPTION. BROAD
BRUSHED SOME CLOUDS AND POPS INTO THE FORECAST AND WILL SEE HOW THIS
SYSTEM EVOLVES.
&&
.AVIATION...
06/1130Z
5000-6000 FOOT MOIST LAYER WILL GENERATE LOW VFR OCNL HIGH MVFR
THROUGH NOON. LIGHT RAIN OR DRIZZLE AT TIMES ACROSS THE FOOTHILLS
AND POSSIBLY OVER THE REST OF THE COAST AND VLYS AS WELL. SOME
CLOUDS ARE POSSIBLE OVER THE DESERTS AS WELL. CLOUDS WILL START TO
INCREASE AGAIN SUNDAY NIGHT AND LOWER THROUGH THE NIGHT LEADING TO A
CHANCE OF RAIN AFTER MIDNIGHT SOUTH OF POINT CONCEPTION AND A 60
PERCENT CHANCE OF RAIN NORTH OF POINT CONCEPTION.
KLAX ...RANDOM LAYERS OF CLOUDS BETWEEN 025 AND 045 THROUGH THE
MORNING. THERE IS A 30 PERCENT CHANCE OF EAST WINDS UNDER 8KT FROM
12Z-16Z. A 10 PERCENT CHANCE OF A LIGHT SHOWER OR SOME DRIZZLE IN
THE MORNING.
KBUR...RANDOM LAYERS OF CLOUDS BETWEEN 025 AND 045 THROUGH
THE DAY. A 20 PERCENT CHANCE OF A LIGHT SHOWER OR SOME DRIZZLE
THROUGH THE DAY.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH (SEE LAXWSWLOX).
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).
MARINE WEATHER STATEMENT (SEE LAXMWSLOX).
SPECIAL WEATHER STATEMENT (SEE LAXSPSLOX).
&&
$$
PUBLIC...RORKE
AVIATION...KAPLAN
SYNOPSIS...B
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