Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 031135
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
335 AM PST Sat Dec 3 2016

.SYNOPSIS...

A small upper level disturbance will bring chances for small
amounts of rain and snow to the upper Valley and northern
mountains Sunday and Monday. Colder air in the Valley could
result in near to below freezing overnight temperatures this
coming week.

&&

.DISCUSSION (Today through Tuesday)...

Main forecast concerns for the period starting this weekend
through Tuesday night are rain and snow chances to the northern
mountains and northern Valley, and low overnight temperatures
Monday and Tuesday near or slightly below freezing for the
Valley.

Dry weather influenced by an upper level high pressure system in
the eastern Pacific will prevail across the forecast area today.
Patchy fog and frost are possible in the lower San Joaquin valley
this morning, but will taper off quickly in the late morning as
temperatures begin to rise. High temperatures will rise to the
upper 50s and lower 60s for the valley and foothills, and 40s/50s
for the higher elevations, which is a few degrees above average
for this time of year.

A small weather disturbance will move across the Pacific Northwest
and will clip northern California Sunday through Tuesday. This
weather system will provide chances for rain and snow across
mainly across the northern mountains and the Sierra, but only
minor accumulations are expected at elevations higher than 1500
feet with 1-2 inches at most for higher peaks.

Colder air moving southward associated with the upper disturbance
will bring high and low temperatures between 5 and 10 degrees
below normal. Low overnight and early morning temperatures will be
near to slightly below freezing in the Valley, which could affect
sensitive vegetation and any crops that are still growing.
Confidence is increasing for sub freezing Valley temperatures
with good model agreement.

.EXTENDED DISCUSSION (Wednesday THROUGH Saturday)

Long range forecast starts out dry with upper level ridge axis
near the coast. Fair skies and cool airmass will allow for some
of the coolest morning lows of the season in the valley. Morning
lows could drop to below freezing especially in outlying areas.
Overnight lows on Thursday climb a few degrees as clouds
spill over the north state. This cloudiness is in advance of a
Pacific frontal band forecast to weaken the west coast ridge and
punch into Norcal early Thursday morning. Timing varies from
the extended models but it appears heavier precipitation will
occur sometime on Friday. Moderate precipitation is expected with
this system as it breaks down the upper ridge. Snow levels with
this system will be moderately high so travel impacts over the
Sierra will be possible. Weak upper ridge returns by next Saturday
for drying most areas. ECMWF keeps this ridging fairly flat so
have kept slight precipitation chances over the northern
mountains.

&&

.AVIATION...

VFR conditions for TAF sites next 24 hours. North to east winds
up to about 10 knots. Some gusts to 20 knots this morning west
side of Sacramento valley.

&&

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

$$


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