FXUS66 KSTO 101120

Area Forecast Discussion
National Weather Service Sacramento CA
320 AM PST Mon Dec 10 2018

Series of weak storms will pass over Norcal over the next several
days but precipitation and impacts will be minimal with each of
them. Valley fog will continue to be possible between systems.


Radar shows spotty light precipitation across interior NorCal
spreading southward with the weakening cold front early this
morning. Temperatures are milder compared to 24 hours ago and only
patches of fog are present in the valley from around the
Sacramento area southward. Current temperatures range from the mid
teens to 20s in the mountain valleys to the upper 30s to mid 40s

The front will continue to weaken as it moves south into the San
Joaquin Valley by this afternoon. Very light (generally less than
a tenth of an inch), though spotty, amounts of precipitation will
be possible today with around an inch or so of snow possible over
the mountains. Clearing develops by this evening except for some
lingering showers across the northern Sierra.

Developing north winds will limit widespread fog chances tonight
and Tuesday morning, though some patchy fog could develop along
the more sheltered east side of the Valley. Dry weather is
expected Tuesday, but warm-advection ahead of a fast-moving system
will result in increasing cloudiness during the afternoon. The
brunt of that system will affect the PacNW, though some light
precipitation will be possible across the far northern portion of
the forecast area on Tuesday night as it skirts by to the north.

Stronger ridging will result in dry and milder weather Wednesday
and Thursday, and northerly flow is expected to be strong enough
to limit extensive fog development (particularly early Wednesday).


Mid range models in a little better agreement in bringing a
Pacific Frontal band through Norcal during the day on Friday. QPF
values are not especially high with this one but snow levels are
low enough that some mountain travel impacts are likely. May see a
brief break in precipitation Saturday as flat upper ridge slides
quickly across the west coast but overrunning precipitation could
still bring a few showers north of Sacramento. Next Pacific storm
system moves quickly into norcal next Sunday. ECMWF a bit slower
than GFS with this one bringing this system into norcal Sunday
night. Models diverge going into early next week with varying
amounts of upper ridging so uncertainty remains high for this time
period. Daytime temperatures will remain around normal throughout
the extended period with occasional breezy south winds as weather
systems progress though.


MVFR/IFR visibilities and ceilings this morning as weak frontal
band moves through. Improving conditions after about 18z KRDD to
about 00z Tuesday KSAC and southward. Fog and haze returning after
about 06z tonight. Winds generally north less than 15 knots.




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