FXUS66 KSTO 090009
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
405 PM PST TUE DEC 8 2009

.SHORT TERM DISCUSSION (TONIGHT THROUGH FRIDAY NIGHT)...
STRATOCUMULUS CLOUDS BETWEEN 5000 AND 7000 FEET HAVE SPREAD INTO THE 
DELTA AND NW SAN JOAQUIN VALLEY THIS AFTERNOON.  THE DECK IS 
BECOMING MORE CELLULAR AND ERODING AS WE GET LATER IN THE DAY.  TIME 
HEIGHT VERTICAL PROFILE FROM THE GFS KEEPS THE CLOUDS IN THE AREA 
UNTIL NEAR 6Z.  THE HIGH CLOUDS ASSOC WITH THE SYSTEM OVER THE 
PACIFIC ARE RUNNING INTO A NW-SE ORIENTATED DEFORMATION ZONE NEAR 
THE CAL COAST. MOSTLY CLEAR IF NOT CLEAR SKIES ARE STILL IN ORDER 
FOR GOOD RADIATIONAL COOLING TONIGHT.  FROST WILL FORM IN THE 
CENTRAL VALLEY WHILE FOG WILL LIKELY FORM IN THE MOUNTAIN VALLEYS TO 
INCLUDE THE BURNEY BASIN...QUINCY BASIN AND THE CLEAR LAKE AREA.  
BLACK ICE WILL ALSO BE A FACTOR OVERNIGHT AS RECENT RAIN AND SOME 
MELTING SNOW FROM TODAY FREEZES.  ROADS IN THE SNOW COVERED AREAS 
WILL BE THE MOST IMPACTED.  BELOW IS A LIST OF RECORD TEMPS AND A 
FEW ARE EXPECTED TO BREAK.

RECORD LOWS FOR DEC 9TH:
REDDING             21/1972
RED BLUFF           21/1972
MARYSVILLE          20/1972
SACRAMENTO DTS      23/1932
SACRAMENTO EXEC     21/1972
VACAVILLE           19/1932
STOCKTON            23/1972
MODESTO             22/1972
AUBURN AIRPORT      16/1972
BLUE CANYON          3/1972

THE NEXT WET WEATHER IMPACTS THE AREA THU AFTERNOON WITH LIGHT 
PRECIP AND INCREASES TOWARD SAT.  THE UPPER LEVEL FLOW WILL BE 
RELATIVELY ZONAL WITH GOOD OROGRAPHIC LIFT PERPENDICULAR TO THE 
SIERRA WHICH MAY KEEP CONTINUOUS CLOUDS AND/OR PRECIP OVER THE 
SIERRA.  HOWEVER...THE CENTRAL VALLEY WILL NOT LIKELY EXPERIENCE 
CONTINUOUS RAIN.  THE SYSTEM WILL BE WARMER IN NATURE WITH SNOW 
LEVELS STARTING AROUND 3000 FT AND CLIMBING TO 4000 FT.  ALSO THE 
SNOW TO LIQUID RATIO WILL BE LOWER THAN THE 18-20:1 RATIO FROM THE 
DEC 7 STORM.    JMC
 

.EXTENDED DISCUSSION (SATURDAY THROUGH TUESDAY)...
WHAT COULD BE A MUCH WETTER AND MILDER SYSTEM IS FORECAST TO IMPACT 
INTERIOR NORCAL ON SATURDAY AND INTO SUNDAY ACCORDING TO THE MEDIUM 
RANGE MODELS. A STRONG NW TO SE ORIENTED JET STREAM OF 130+ KTS IS 
FORECAST TO PASS JUST SOUTH OF INTERIOR NORCAL WHICH WILL TEND TO 
SHUNT THE PW PLUME S OF OUR CWA ON SAT...BUT THE GFS/ECMWF INCREASE 
PCPN IN OUR FORECAST AREA WITH THE DYNAMICS OF THE UPPER LOW AS IT 
MOVES OVER THE AREA JUST N OF THE UPPER JET. THE GFS VERTICAL CROSS 
SECTIONS REVEAL OMEGA OF 20 UBAR/S OVER NORCAL BY MIDDAY SAT...VERY 
STRONG UPWARD MOTION. LOWER LEVEL SLY FLOW IS FORECAST TO INCREASE 
TO 40-45 KTS SO IT COULD ALSO BE A VERY BREEZY/WINDY DAY...WITH 
FAVORABLE OROGRAPHICS IN THE SIERNEV AS WELL. SNOW LEVELS EXPECTED 
TO RANGE IN THE 4500 TO 5000 FT LEVEL. CERTAINLY APPEARS AS IF 
WINTER STORM CRITERIA WILL BE MET/EXCEEDED FROM THIS STORM IN OUR 
NRN SIERNEV. PCPN AND WIND WILL DECREASE ON SUN...AND DIMINISH SUN 
NITE ON MON AS THE SYSTEM MOVES SE OF THE AREA. BEHIND THIS 
SYSTEM...A HIGHLY AMPLIFIED RIDGE IS FORECAST TO BUILD ALONG THE W 
COAST ON MON GIVING NORCAL A DRY PERIOD. AS USUAL FOR THIS TIME OF 
YEAR AND WITH INCREASING SUBSIDENCE...VALLEY FOG IS EXPECTED TO 
REFORM MON MORNING. AN ELONGATED OR SPLITTING FRONTAL SYSTEM IS 
FORECAST TO MOVE INTO THE PAC NW AND N COAST DURING THE DAY ON 
TUE.    JHM

&&

.AVIATION...
GENERALLY VFR CONDITIONS EXPECTED IN THE VALLEY THROUGH WEDNESDAY 
WITH PERIODS OF HIGH CLOUDS AND LIGHT WINDS. ALTHOUGH A BATCH OF LOW 
CLOUDS WITH BASES AROUND 6000 FEET ARE CURRENTLY IN THE BAY AREA AND 
MAY MOVE WEST INTO THE SACRAMENTO AND STOCKTON AREAS THIS EVENING. 
LOCAL MVFR CONDITIONS ARE POSSIBLE IN THE SACRAMENTO AREA AND THE 
NORTHERN SAN JOAQUIN VALLEY AFT 08Z UNTIL 18Z WITH BR. SUB-FREEZING 
SFC TEMPERATURES ARE EXPECTED AGAIN WEDNESDAY MORNING.

&& 

.STO WATCHES/WARNINGS/ADVISORIES...
FREEZE WARNING FROM 2 AM TO 9 AM PST WEDNESDAY FOR SACRAMENTO 
VALLEY... DELTA AND NORTHERN SAN JOAQUIN VALLEY AND SURROUNDING 
FOOTHILLS INCLUDING SOUTHERN LAKE COUNTY GENERALLY BELOW 2000 FEET.

&&

$$