Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 282210
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
310 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...
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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