421
FXUS66 KSTO 080000
AFDSTO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
330 PM PST SAT NOV 7 2009
DISCUSSION
DEWPOINTS ARE DROPPING IN NORTH BREEZES AS SURFACE HIGH PRESSURE
BUILDS INTO NORTHERN CALIFORNIA. TEMPERATURES WILL COOL RAPIDLY
AFTER SUNSET AND A CHILLY NIGHT IS ON TAP ACROSS THE REGION. AREAS
AWAY FROM THE CITIES COULD SEE OVERNIGHT MINIMUMS NEAR OR BELOW
FREEZING. THE 18Z MODELS AND 12Z WRF HAD SOMEWHAT MILDER OVERNIGHT
LOWS THAN PREVIOUS RUNS. ADDITIONALLY A MASS OF HIGH CLOUDS APPEARS
HEADED FOR CENTRAL CALIFORNIA ON THE SATELLITE. THESE MAY HAVE
LITTLE IMPACT ON TEMPERATURES HOWEVER. A FROST ADVISORY WAS ISSUED
EARLIER FOR THE ENTIRE SACRAMENTO VALLEY AND THE NORTHERN SAN
JOAQUIN VALLEY 3AM-9AM. THE ADVISORY IS MAINLY FOR AREAS EAST OF
HIGHWAY 99 AND AWAY FROM METROPOLITAN AREAS. COLD SENSITIVE FRUITS
AND TREES SUCH AS APRICOTS...PEARS...GRAPES AND FIGS SHOULD BE
PROTECTED FROM COLD TEMPERATURES TONIGHT.
OTHERWISE THE PATTERN AMPLIFIES OVER THE NEXT FEW DAYS WITH A MEAN
RIDGE OVER THE CENTRAL U.S. AND THE PERSISTENT RIDGE NEAR THE
DATELINE. WITH THIS WAVELENGTH IT WILL BE DIFFICULT TO GET GOOD
STORMS INTO CALIFORNIA. SUNDAY WILL BE A NICE DAY AFTER A CHILLY
START. TEMPERATURES IN THE MOUNTAINS WILL ALSO BE SEVERAL DEGREES
MILDER AS HIGH PRESSURE BUILDS IN ALOFT. CLOUDS WILL INCREASE AHEAD
OF A SPLITTING SHORTWAVE MONDAY. SOUTHWEST WINDS WILL PICK UP IN THE
MOUNTAINS BUT THE VALLEYS SHOULD STILL HAVE A NICE DAY WITH
TEMPERATURES REMAINING IN THE 60S. THE COLD FRONT WILL MOVE ONTO THE
NORTHERN COAST MONDAY NIGHT BUT FORECAST MODELS WEAKEN IT RAPIDLY AS
IT DROPS SOUTH...SIMILAR TO THE LAST SYSTEM. THE GFS AND THE NAM
BOTH HANG THE FRONT UP NEAR THE COASTAL RANGE TUESDAY...KEEPING THE
PRIMARY THREAT OF PRECIPITATION NORTH OF I-80. SG
EXTENDED DISCUSSION (WEDNESDAY THROUGH SATURDAY)
UPPER LEVEL
TROUGH OF LOW PRESSURE WILL GRADUALLY MOVE ACROSS THE REGION ON
WEDNESDAY AND THURSDAY. MODELS ARE STILL HAVING SOME ISSUES WITH
THE TIMING AND STRENGTH OF THIS SYSTEM. THEREFORE...CONFIDENCE IS
STILL RELATIVELY LOW AS TO HOW MUCH PRECIPITATION WILL MAKE IT INTO
NORTHERN CALIFORNIA...BUT HAVE AT LEAST A SLIGHT CHANCE FOR THE
VALLEY AND CHANCE OF THE MOUNTAINS. HIGH PRESSURE WILL BRIEFLY
BUILD BACK OVER THE REGION ON FRIDAY...BEFORE THE NEXT SYSTEM HEADS
TOWARDS NORTHERN CALIFORNIA ON SATURDAY. PALMER
AVIATION
A FEW LOW CLOUDS WILL REMAIN OVER THE SIERRA AND
NORTHERN MOUNTAINS THROUGH THIS EVENING...WITH AREAS OF MVFR CIGS
POSSIBLE THROUGH 00Z. OTHERWISE...EXPECT VFR CONDITIONS TO PREVAIL
THROUGH THE NEXT 24 HOURS.
STO WATCHES/WARNINGS/ADVISORIES
NONE.
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