Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 022352

Area Forecast Discussion
National Weather Service Sacramento CA
352 PM PST Fri Dec 2 2016

Breezy north winds will decrease Saturday. Morning low temperatures
will be chilly, with warming daytime temperatures into the weekend.
Light showers and cooling temperatures Sunday into Monday mainly
north of Sacramento and over the northern Sierra. Turning much
colder Tuesday through mid week. Valley minimum temperatures
dropping to near freezing Tuesday through Thursday. A chance of rain
or mountain snow again by the end of the week.

Gusty/breezy Nly winds continued over Norcal today due to increasing
anticyclonic flow and subsidence in the wake of short wave energy
that moved through Norcal earlier today and in conjunction with
surface high pressure over the Great Basin. As the surface high
sinks Swd across the Great Basin tonite, the Nly gradients will
slacken while the Ely gradients continue. This should allow winds
to decouple in the Vly while katabatic/downslope winds continue
over the Sierra. Decoupling of the winds in the Valley along with
clear skies and strong radiational cooling should lead to another
chilly nite. Although most of the valley will see drying from the
Nly winds, the guidance suggests some return flow from the Great
Basin high will shift winds lightly to the SEly which will slightly
raise dewpoints by Sat morning. Although fog is unlikely, we can`t
rule out the possibility of some frost in outlying areas mainly E
side of the Nrn SJV Sat morning and perhaps in SErn Sac Co.

Increased ridging over Norcal on Sat will lead to a strong temp and
subsidence inversion over the CWA and the formation of thermal belts
roughly in the 1500-5000 ft level. The greatest warming will likely
be in the Nrn Sac Vly and in the thermal belt areas where maxes
could be some 6-12 degrees above normal.

The upper ridge weakens on Sunday as a weak trof moves across the
Pac NW ahead of a low pressure system dropping SEwd from the GOA.
This will bring a chance of light precip to the Nrn mountains. Model
guidance has been trending farther N and a bit slower with precip
holding off until Sun afternoon/Sun nite over our Nrn mtns. This
trof moves through early in the day with most of Mon dry in our
CWA. This will be a precursor to the GOA low dropping into the Great
Basin bringing colder (wetter?) wx to our area early next week.  JHM


A few showers may linger during the day Tuesday across the
northern mountains as weak wave passes across the region. Colder
air entrenched within system may drop snow levels to around 2000
feet but wave looks fairly moisture starved. Maybe an inch or two
of snow accumulation but not expecting major impacts at this
point. Wednesday looks dry as ridging briefly builds in across the
region. Wednesday morning lows will hover near the freezing mark
across most of the Valley with teens to 20s across higher
elevations. 12z runs of the GFS and ECMWF have come into better
agreement regarding the end of the week, but substantial timing
differences still remain. Regardless, better confidence that wet
system will move across the area sometime later Thursday into
Friday. Associated moisture plume may allow for decent
precipitation accumulations, especially across the mountains.
Something to watch going forward as weekend travel may be



VFR conditions for TAF sites next 24 hours. Gusty northerly winds
for Valley terminals will gradually subside this evening to less
than 10 kts through remainder of period.


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