Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 262314
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
314 PM PST Fri Dec 26 2014

.Synopsis...
Mainly dry weather will continue for the next few days, with
north winds and frosty overnight lows. Stronger north winds and a
few mountain showers may be possible for early/middle next week.

&&

.Discussion...
Northern California remains under dry northerly flow between a
strong eastern Pacific ridge and deep trough over the Rockies. An
impressive amount of subsidence is noted on WV satellite imagery,
allowing for clear skies and locally breezy north winds especially
along the western Sacramento Valley. Temperatures this afternoon
are being buoyed by some adiabatic warming (downslope effect) with
northerly winds, with mid to upper 50s across the Valley and 30s
and 40s over the mountains.

Pressure gradients are forecast to relax later this evening and
especially tonight. The combination of lighter winds and clear
skies will allow for strong radiational cooling, and will likely
lead to the coldest temperatures of the season thus far. Look for
lows to drop down to around or slightly below freezing across the
Valley and foothills. 10s and 20s are forecast for the mountains
and colder mountain basins. A frost advisory has been issued for
Saturday morning, with tonight expected to be the first widespread
frost of the season across the Valley.

Dang

&&


.Extended Discussion (Tuesday through Friday)

The extended forecast continues to look cool with breezy north
winds on Tuesday. There is little potential for precipitation
except for light snow showers up in the Sierra Tuesday.

A cold trough originates from Alaska/northwestern Canada and drops
down through northern California Tuesday. This system deepens and
spreads westward over the area, bringing cold air into the region.
Lower level thickness values bottom out Wednesday and/or Thursday.
Breezy winds are expected on Tuesday into Wednesday, and will
likely reach wind advisory levels with sustained winds of 25 mph
and stronger gusts. The winds should keep the atmosphere mixed in
the Valley and limit frost and colder temperatures.

This system has little moisture to work with, so snowfall amounts
in the Sierra should be light. Snow levels could be low enough to
allow some light snow showers/flurries into the foothills by
Tuesday.

By Wednesday/Thursday, the trough closes off and drops to the
south and east. Winds weaken allowing colder temperatures in the
Valley. The best chance for frost and freezing valley temperatures
will likely be Thursday/Friday mornings when winds subside,
especially on the less windy eastern side of the valley. Highs in
the mountains will remain quite cold through the later half of
the week. The new year should start out dry, with no significant
precipitation events in sight.

&&

.Aviation...

VFR conditions this evening, with some patchy fog developing after
06z south of KMYV. Local breezy northly windw gusting to 25kt through
the afternoon becoming light tonight. Clearing skies Saturday
afternoon with light northerly winds. EK


&&

.STO Watches/Warnings/Advisories...
frost advisory from 4 am to 9 am pst saturday carquinez strait
and delta...central sacramento valley...northern sacramento
valley...northern san joaquin valley...southern sacramento
valley.

&&

$$






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