FXUS66 KSGX 031204
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
400 AM PST THU DEC 3 2009

.SYNOPSIS...CLOUDS AND FOG WEST OF THE MOUNTAINS TODAY WILL DECREASE 
THIS AFTERNOON AND TONIGHT AS HIGH PRESSURE BUILDS. INCREASING 
OFFSHORE FLOW WILL BRING MOSTLY CLEAR SKIES FRIDAY ALONG WITH GUSTY 
WINDS THROUGH AND BELOW MOUNTAIN CANYONS AND PASSES. A SOUTHERN 
SHIFT IN THE JET STREAM WILL BRING INCREASING CHANCES FOR RAIN NEXT 
WEEK. 

&&

.DISCUSSION...FOR SOUTHWEST CALIFORNIA INCLUDING SAN DIEGO... 
ORANGE...SOUTHWEST SAN BERNARDINO AND WEST RIVERSIDE COUNTIES.

A STRATUS DECK BLANKETS THE COASTAL AND VALLEY ZONES THIS MORNING 
WITH A 3700 FOOT DEEP MARINE LAYER IN PLACE. INCREASING OFFSHORE 
FLOW FROM BUILDING HIGH PRESSURE OVER WYOMING WILL SHALLOW UP THE 
MARINE LAYER TONIGHT...WHICH WILL LIMIT THE INLAND EXTENT OF THE LOW 
CLOUDS. ANY CLOUDS FRIDAY MORNING IN THE COASTAL ZONES WILL 
DISSIPATE QUICKLY. 

OFFSHORE GRADIENTS ON FRIDAY MORNING WILL BE STRONG ENOUGH TO 
SUPPORT MODERATE OFFSHORE WINDS. THE 12Z FRIDAY 850 MB WINDS PEAK AT 
20-30 KTS. THERE IS ALSO A FAIRLY STEEP THERMAL GRADIENT SETTING UP 
OVER THE MOUNTAINS. EXPECT A PERIOD OF MODERATELY STRONG EAST WINDS 
FROM 20-30 MPH TO FUNNEL THROUGH THE MTN PASSES FRIDAY...GUSTING TO 
45 MPH AT TIMES. THIS WILL BE A FAIRLY SHORT WIND EVENT THAT WILL 
END FRIDAY EVENING. 

COLD AIR ADVECTION ON NORTHEAST WINDS FRIDAY WILL REALLY PUT A LID 
ON TEMPERATURES IN THE MOUNTAINS AND DESERTS. EXPECT HIGHS ONLY IN 
THE 50S IN THE HIGH DESERTS...THE 60S IN THE LOW DESERTS...AND THE 
40S AND LOW 50S IN THE MOUNTAINS. IN CONTRAST...DOWNSLOPE WARMING 
WILL PUSH TEMPERATURES INTO THE UPPER 60S AND 70S IN THE COASTAL 
ZONES. 

FRIDAY NIGHT WILL BE QUITE COLD WITH A VERY DRY AIRMASS AND LIGHTER 
WINDS PROMOTING RAPID COOLING AFTER SUNSET. VALLEY LOWS WILL FALL 
INTO THE 30S WITH TEMPS FALL NEAR 32 IN THE COLDEST AREAS. THE LOWER 
DESERTS WILL ALSO FALL INTO THE 30S AND LOW 40S. 

.LONG TERM OUTLOOK FOR NEXT WEEK...THE STORM DOOR WILL BE REPLACED 
BY A SCREEN DOOR THAT WILL ALLOW RAIN BACK INTO CALIFORNIA. A 
DECIDEDLY SOUTHERN SHIFT IN THE PACIFIC JET WILL BRING A SERIES OF 
POTENT...MOISTURE LADEN SHORTWAVES INTO CALIFORNIA NEXT WEEK. THE 
POSITION OF THE STORM TRACK WILL ULTIMATELY DETERMINE THE AMOUNT OF 
RAIN WE GET. THE FARTHER SOUTH IT GETS...THE BETTER OUR CHANCES. 
CENTRAL CALIFORNIA WILL GET MORE RAIN IF IT ENDS UP FARTHER NORTH. 
AS IT STANDS NOW...MONDAY AND TUESDAY SHOW A DECENT CHANCE AT RAIN 
WITH THE FIRST SHORTWAVE...WITH A SECOND STRONG SYSTEM AND MORE RAIN 
LATER IN THE WEEK. 

&&

.AVIATION...
030915Z...CURRENTLY A BROKEN-OVERCAST STRATUS LAYER WITH BASES  
FL020 AND TOPS FL035 IS OVER WATER AND EXTENDS INLAND TO THE COASTAL 
SLOPES OF THE MOUNTAINS. ABOVE FL035 SKIES ARE CLEAR SKIES UNDER 
BUILDING HIGH PRESSURE. WINDS ACROSS MOUNTAINS IN THE FL050-FL100 
LAYER ARE VEERING TO THE NORTHEAST BUT EXPECTED TO REMAIN BELOW 15 
KT UNTIL AFTER 04/0200 UTC. THE STRENGTHENING AND LOWERING 
SUBSIDENCE INVERSION WILL PUSH THE MARINE LAYER DEPTH DOWN TO FL020 
BY 04/0000 UTC...AROUND FL015 BY 04/0600...AND FL005 OR LESS BY 
04/1000 UTC. EXPECT AN EARLIER SCATTERING OUT OF STRATUS LAYER 
TODAY...GENERALLY 1700 UTC INLAND TO 1900 UTC COAST...WITH A RETURN 
OF BROKEN TO OVERCAST STRATUS AFTER 04/0000 UTC OVER WATER AND 
INLAND 10-15 MILES WITH A RETREAT OF CLOUDS SEAWARD AFTER 04/0600 
UTC. THERE MAY BE   A 1 OR 2 HOUR PERIOD OF VERY LOW 
CEILINGS/VISIBILITY AT COASTAL AIRPORTS BETWEEN 04/0600-1000 UTC 
UNTIL MARINE AIR IS COMPLETELY PUSHED OUT TO SEA.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...NONE. 

&&

$$

PUBLIC...MOEDE
AVIATION...BALFOUR