FXUS66 KSTO 081727
AFDSTO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
925 AM PST TUE DEC 8 2009
.UPDATED DISCUSSION...
THE FORECAST FOR TONIGHT AND INTO WEDNESDAY MORNING LOOK GOOD AS FAR
AS THE TEMPS AND FREEZE WARNING. A WEAK SHORT WAVE SKIRTS NORTHEAST
CAL TONIGHT AND MODELS HINTS AT SOME LOW CLOUDS AT 4000 TO 5000
FT...BUT ALL LEVEL APPEAR TO BE DRY. SO I DO NOT SEE 5000 FT
STRATUS FORMING...IF ANY IT SHOULD BE A MID OR HIGH LEVEL CLOUD. AT
ANY RATE...WE DO NOT EXPECT ANY SIGNIFICANT CLOUDS.
THE NEXT WET WEATHER IMPACTS THE AREA THU NIGHT WITH LIGHT PRECIP
AND INCREASES INTO SAT. FRI MAY SEE A FEW BREAKS IN THE PRECIP.
THE SYSTEMS WILL BE WARMER IN NATURE WITH SNOW LEVELS STARTING
AROUND 3000 FT AND CLIMBING TO 5000 FT. JMC
.PREVIOUS DISCUSSION 400 AM PST...
COLD UPPER TROUGH IS MOVING THROUGH THE SOUTHWEST EARLY THIS MORNING
WITH SUBSIDENCE IN ITS WAKE ACROSS NORCAL. SKIES HAVE CLEARED ACROSS
THE ENTIRE REGION. WINDS ARE GENERALLY LIGHT AND WILL ALLOW
TEMPERATURES TO CONTINUE TO DROP OFF UNTIL AFTER SUNRISE. 4 AM
VALLEY TEMPERATURES ARE IN THE LOWER TO MID 20S...SO SOME UPPER
TEENS MINIMUMS WILL BE POSSIBLE ESPECIALLY IN THE NORTH VALLEY WHERE
DEWPOINTS ARE THE LOWEST (10-15 DEGREES). MOUNTAIN READINGS ARE
MAINLY IN THE TEENS WITH SOME OF THE MOUNTAIN VALLEYS DOWN AS LOW AS
0 TO -10 DEGREES.
WATER VAPOR IMAGERY SHOWS ANOTHER IMPULSE OFF THE OREGON COAST THAT
WILL SLIDE SOUTHEAST INTO FAR NORTHERN CALIFORNIA TODAY PERHAPS
BRINGING A FEW CLOUDS AND ANOTHER REINFORCEMENT OF COLD DRY AIR.
THIS FEATURE MOVES EAST TONIGHT WITH GENERALLY CLEAR SKIES EXPECTED
ACROSS THE REGION...BUT NAM CROSS-SECTIONS CONTINUE TO INDICATE
POTENTIAL FOR SOME STRATUS TO FORM IN THE CENTRAL VALLEY THIS
EVENING AND MIX OUT LATE TONIGHT AS STRONGER SUBSIDENCE RETURNS. NOT
EXPECTING THIS TO HAVE MUCH IMPACT ON MINIMUM TEMPERATURES
TONIGHT...PERHAPS A FEW DEGREES WARMER...BUT STILL VERY COLD AND
FREEZE WARNING HAS BEEN ISSUED FOR TONIGHT FOR THE VALLEY AND
FOOTHILLS.
TROUGH EDGES EASTWARD WEDNESDAY AS FLAT RIDGE MOVES OVERHEAD. MODELS
BRING NEXT SYSTEM ONSHORE NORCAL LATE THURSDAY AND THURSDAY NIGHT...
BUT WEAKEN IT DRAMATICALLY AS IT MOVES INLAND INTO THE RIDGE. HIGH
CLOUDINESS EXPECTED TO INCREASE AHEAD OF THIS SYSTEM AS EARLY AS
LATE WEDNESDAY AND WILL POTENTIALLY LEAD TO A LITTLE MILDER
OVERNIGHT TEMPERATURES WEDNESDAY NIGHT INTO EARLY THURSDAY.
&&
.EXTENDED DISCUSSION (SATURDAY THROUGH TUESDAY)...
MEDIUM RANGE MODELS IN FAIRLY GOOD AGREEMENT WITH A SHORTWAVE
BRINGING VERY WET CONDITIONS FOR THE WEEKEND. THIS SYSTEM HAS 700 MB
TEMPERATURES AROUND -8 C SO EXPECT SNOW LEVELS TO BE QUITE A BIT
HIGHER THAN SEEN RECENTLY...AT AROUND 4500 FEET. THERE IS THE
POTENTIAL FOR SIGNIFICANT MOUNTAIN SNOW AT HIGHER LEVELS AND VALLEY
RAIN. THE GFS IS QUICKER TO MOVE THE SYSTEM OUT WITH A RIDGE
BUILDING IN ON MONDAY...WHILE THE ECMWF AND THE GEM ARE A LITTLE
SLOWER AND LINGER SOME SHOWERS INTO EARLY MONDAY. ANOTHER SYSTEM
ARRIVES ON TUESDAY TO CONTINUE THE WET PATTERN. SNOW LEVELS RISE
FURTHER WITH THIS WARM SYSTEM AND SHOULD BE OVER 5000 FEET.
&&
.AVIATION...
VFR MAINLY SKC CONDITIONS AND LIGHT WINDS EXPECTED TO CONTINUE
THROUGH TONIGHT OVER INTERIOR NORCAL TAF SITES. AN EXCEPTION WILL BE
LINGERING LOCAL MVFR CONDITIONS IN BR OVER THE NORTHERN SAN JOAQUIN
VALLEY UNTIL 18Z. SUB-FREEZING MIN TEMPS SHOULD WARM ABOVE FREEZING
AFTER 18Z. ANOTHER COLD...MAINLY CLEAR NITE EXPECTED OVER INTERIOR
NORCAL TONITE...WITH PATCHY MVFR VSBYS IN MORNING BR/HZ.
&&
.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.
&&
$$
