Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 061226
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
426 AM PST Tue Dec 6 2016

.SYNOPSIS...
Cold overnight temperatures again tonight. A return to wetter
weather is expected Wednesday through Saturday.

&&

.DISCUSSION...
Clouds are moving out of the region as the latest frontal system
pushes south. With generally light winds, areas of frost and
patchy fog have developed in the Central Valley. Temperatures are
running colder north of Sacramento where skies have been mostly
clear overnight while readings are milder across the northern San
Joaquin Valley. Current temperatures are in the teens and 20s in
the mountains and in the 30s across the Sacramento Valley with
lower 40s around Stockton and Modesto.

Another weak system brushes across NorCal today and will bring
some light snow showers to the northern mountains and northern
Sierra Nevada. Skies will clear tonight, and temperatures will
likely be the coldest of the season so far.

At this time, widespread morning lows around the freezing mark are
expected in the Central Valley with some of the colder spots
dipping into the upper 20s. The durations at or below freezing
should not exceed several hours for most locations. Mountain
valley lows will get very cold dipping into the single digits and
teens. There looks like high clouds drifting over the region by
Wednesday morning should help to mitigate the low temperatures and
prevent them form dipping colder than freezing in many places.

The cold morning lows will be short lived as a stronger more
significant system moves into the region Wednesday night into
Thursday. Snow levels should be low to start Wednesday night but
rise on Thursday to near or just above pass levels by mid to late
morning. The focus of where the heavier precip will occur into
Friday continues to vary depending on which model you examine with
the GFS remaining generally the wettest.

Nevertheless, appears transition back to a wetter pattern for
NorCal commences late this week.

&&

.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)
Unsettled pattern looks to continue through much of the extended
period. Model solutions diverge from Friday night with the ECMWF
showing an additional wave of precipitation, perhaps substantial,
during the day Saturday, while GFS remains mostly dry outside a
few Sierra showers. Given such a large difference, have hedged
toward a blend of solutions with precipitation over most of the
area, until solutions are better aligned. Snow levels may drop
lower with this wave should it occur which would further impact
weekend mountain travel.

Next wave moves across the area late Sunday or overnight with a
more subtropical influence. The GFS is much wetter with this wave
vs the drier ECMWF. Regardless, looks like best chance for
widespread precip across the area comes Monday and Tuesday. Snow
levels around 3500 feet across northern mountains and 4500 to 5500
feet in the Sierra on Monday, then increasing into Tuesday with
the warm air advection.   JClapp/CEO

&&

.AVIATION...
Areas of Valley MVFR and local IFR to LIFR in BR/FG again this
morning generally south of MYV. Light northerly flow under 10 kts
thru the period. JClapp

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Freeze Watch from late tonight through Wednesday morning for
Central Sacramento Valley-Clear Lake/Southern Lake County-
Motherlode-Northeast Foothills/Sacramento Valley-Northern
Sacramento Valley-Northern San Joaquin Valley-Southern
Sacramento Valley.

&&

$$


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