Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 290508
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
1008 PM PDT FRI AUG 28 2015

.SYNOPSIS...
Approaching Pacific storm will move through Saturday bringing
cooler temperatures and some precipitation...mainly north of
Interstate 80. Dry Sunday through next week with below normal
temperatures.

&&

.DISCUSSION...
Rain band still off the northern California coast will progress
east to the coastal range by early morning and through Shasta
county mid morning. Best rain chances will be from Chico north
with not much more than sprinkles south. Delta Breeze has been
slow to get going...but is starting to crank with 30 mph gusts
through the delta. This will lead to cooler overnight
lows...despite not currently being much cooler versus yesterday.

&&

.PREVIOUS DISCUSSION... PACIFIC FRONTAL SYSTEM IS APPROACHING THE
WEST COAST AND WILL BRING SOME PRECIPITATION TO NORTHERN
CALIFORNIA LATE TONIGHT INTO SATURDAY. SATELLITE IMAGERY SHOWING
BAROCLINIC ZONE MOVING INSIDE 130 W AND BECOMING MORE N-S ORIENTED
WHICH WILL SLOW EASTWARD PROGRESSION. A SECOND LOW PRESSURE AREA
IS DIGGING FROM THE GOA AND WILL DRAW THE STORM NE INTO ITS FLOW
AS ASSOCIATED SURFACE LOW DEEPENS. BLENDED TPW REVEALING
ASSOCIATED MOISTURE PLUME OF 1.5+ INCHES ALONG FRONT HAS NARROWED.
MODEL PRECIP BEGINS SPREADING INTO WESTERN PORTIONS OF INTERIOR
NORCAL AROUND 12Z SATURDAY THEN MOVES THROUGH TOMORROW AS
BAROCLINIC ZONE WEAKENS AND MOISTURE PLUME DECREASES. AS A RESULT,
QPF CONTINUES TO LOOK LIGHT WITH PRECIP GENERALLY NORTH OF I-80
AND GREATEST AMOUNTS (AROUND A THIRD OF AN INCH OR LESS) OVER THE
COASTAL RANGE AND WESTERN SHASTA MOUNTAINS. BREEZY SOUTHERLY WIND
TONIGHT OVER THE NORTHERN HALF OF INTERIOR NORCAL AS FRONT
APPROACHES. WINDS PEAK TOMORROW MORNING AS THE FRONT MOVES
THROUGH, BUT SPEEDS ARE FORECAST TO REMAIN BELOW ADVISORY
CRITERIA. SYNOPTIC COOLING AND CLOUDINESS SATURDAY WILL RESULT IN
HIGH TEMPERATURES 10 TO 15 DEGREES BELOW TODAY WITH LOWER TO MID
80S FOR THE CENTRAL VALLEY AND 50S TO 70S FOR THE MOUNTAINS AND
FOOTHILLS.

ISOLATED LINGERING SHOWERS POSSIBLE OVER THE EASTERN MOUNTAINS
TOMORROW EVENING, THEN DRIER WEATHER SUNDAY AND MONDAY AS LONG
WAVE TROUGHING CONTINUES OVER THE EASTERN PACIFIC. HIGH
TEMPERATURES WILL WARM A FEW DEGREES SUNDAY AND AGAIN MONDAY BUT
WILL CONTINUE BELOW NORMAL FOR LATE AUGUST.

PCH

.EXTENDED DISCUSSION (Tuesday THROUGH Friday)

NorCal will remain under the influence of a large scale trough
pattern through the extended forecast. Trough forecasted to dig
southward and move across the region for the end of the week. The
GFS is hinting at some precipitation across far northern CA
Thursday into Friday but ECMWF remains dry. Have kept dry forecast
through the end of the period due to model differences. High temperatures
will continue to be below normal. Wednesday and Thursday look
like the coolest days with highs 4 to 13 degrees well below
normal. IDM


&&

.AVIATION...

VFR conditions continue for TAF sites. Winds will continue to
pick up this evening into Saturday as trough moves through. Winds
will be southwesterly at 10-15 knots with gusts up to 25 knots.
Increasing cloud cover will accompany the system. Chance for brief
periods of showers and MVFR conditions after 15Z Saturday for
northern SAC valley.


&&

.STO WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$


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