FXUS66 KSTO 252343
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
330 PM PST FRI DEC 25 2009

.DISCUSSION...
UPPER LEVEL RIDGE CENTERED VERY NEARLY OVERHEAD THIS MORNING 
BRINGING MAINLY CLEAR SKIES AND GENERALLY LIGHT WINDS ACROSS 
INTERIOR NORTHERN CALIFORNIA. DOWNSLOPING WINDS CONTINUE DOWN 
FAVORED SIERRA CANYONS...THOUGH HAVE TAPERED OFF CONSIDERABLY OVER 
THE LAST 12 TO 24 HOURS AS OFFSHORE GRADIENT HAS WEAKENED. 
TEMPERATURES ACROSS THE FORECAST AREA ARE RUNNING A FEW DEGREES 
WARMER THAN 24 HOURS AGO.

A FEW MORE HOURS OF CLEAR SKIES BEFORE WE START TO SEE INCREASING 
CLOUDINESS ASSOCIATED WITH AN UPSTREAM TROUGH...CURRENTLY NEAR 130W. 
FOG MAY BE A BIT MORE PREVALENT LATE TONIGHT INTO SATURDAY MORNING 
THAN THE LAST FEW NIGHTS AS LOW LEVEL FLOW REVERSES AND BECOMES MORE 
SOUTHERLY...ALLOWING BETTER RH RECOVERIES. 

THE FOCUS THEN SHIFTS TOWARDS THE UPSTREAM WEATHER SYSTEM. CONTINUE 
TO SEE QUITE A BIT OF MODEL UNCERTAINTY WITH THIS WEATHER 
SYSTEM...WITH THE GFS AND NAM SPLITTING THE SYSTEMS ENERGY AS IT 
APPROACHES THE COAST AND LEAVING MOST OF THE INTERIOR DRY. THE ECMWF 
HAS STUCK TO ITS GUNS AND BRINGS A SOGGY SOLUTION TO THE FORECAST 
AREA SATURDAY NIGHT INTO SUNDAY. THE CANADIAN NOW APPEARS TO BE A 
COMPROMISE SOLUTION BETWEEN THE TWO. WITH THIS FORECAST 
PACKAGE...OPTED TO INCREASE THE CHANCE OF PRECIPITATION ALONG THE 
COASTAL RANGE AND NORTHERN MOUNTAINS WITH THIS STORM...AND LEFT THE 
REST OF THE FORECAST AREA RELATIVELY UNCHANGED WITH HOPES THAT 
MODELS WILL COME INTO BETTER ALIGNMENT SOON. IN ANY SCENARIO...ANY 
PRECIPITATION WILL LIKELY BE LIGHT AS DYNAMICS ARENT GREAT AND 
AVAILABLE MOISTURE WILL BE MEDIOCRE AT BEST.

A QUICK MOVING SHORTWAVE WILL MOVE IN BEHIND THIS EARLIER SYSTEM AND 
HELP REINFORCE THE SPLIT FLOW...FORCING THE UPPER LOW SOUTHWARD 
TOWARD BAJA. MONDAY APPEARS TO BE A DRY DAY AS WEAK HIGH PRESSURE 
BUILDS INTO NORTHERN CALIFORNIA. ANOTHER SYSTEM WILL APPROACH THE 
AREA TOWARDS THE END OF THE SHORT TERM. DANG 

.EXTENDED DISCUSSION (MONDAY NIGHT THROUGH SATURDAY)...

...THE EXTENDED PERIOD OF THE FORECAST BEGINS WITH A VERY WEAK 
WEATHER SYSTEM MOVING ACROSS THE NORTHERN PART OF CALIFORNIA TUE 
THROUGH TUE NIGHT. EXTENED MODELS GENERALLY AGREE ON THE TIMING AND 
WEAKNESS OF THE SYSTEM. EXPECT LITTLE IN THE WAY OF MEASURABLE 
PRECIPITATION OUTSIDE OF THE COASTAL RANGE AND SIERRA.  BY WED 
MODELS SHOW A UPPER RIDGE OF HIGH PRESSURE WEST OF THE WEST COAST. 
THIS WILL RESULT IN GENERALLY DRY AND SEASONABLY COOL CONDITIONS 
OVER THE REGION...WITH PERHAPS...SOME CHILLY AND FOGGY MORNINGS IN 
THE VALLEY. LATE IN THE WEEK MODELS INDICATE THE RIDGE SHIFTING 
INLAND WITH A WEATHER SYSTEM CROSSING THE AREA JUST TO THE NORTH.  
THIS SYSTEM IS CURRENTLY FORECAST TO BE A BIT STRONGER THAN THE 
EARLY WEEK SYSTEM...BUT STILL NOT A MAJOR WEATHER PRODUCER. BOTTOM 
LINE IS GENERALLY UNREMARKABLE WEATHER DURING THE UPCOMING 
WORKWEEK...WITH THE THREAT OF SOME RATHER LIGHT PRECIPITATION TUE 
AND TOWARD FRI...AND THAT MAINLY NORTH OF THE I80 CORRIDOR. DK2

&&

.AVIATION...
GENERALLY VFR CONDITIONS ACROSS THE AREA THROUGH SATURDAY  
EXCEPT FOR AREAS OF MVFR CONDITIONS DUE TO BR AND ISOLD LIFR 
CONDITIONS DUE TO FOG AFT 08Z UNTIL AROUND 18Z ON SATURDAY IN THE 
SACRAMENTO AREA AND THE NORTHERN SAN JOAQUIN VALLEY. 

&&

.STO WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$