Area Forecast Discussion
Issued by NWS Sacramento, CA

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822
FXUS66 KSTO 080509
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
909 PM PST Wed Dec 7 2016

.SYNOPSIS...
An active wet pattern begins today and continues into next week.

&&

.DISCUSSION...
Rain and low elevation snow continue to move through the region.
Over the north end of the valley lots of reports this evening of
rain/snow mix that for the most part is not sticking in the
valley. We did get one report of a half inch of snow 3 miles west
of Red Bluff this evening, 3 inches of snow at Sims at 2500 feet
and Fall River Mills had 3 inches of snow. The coldest air should
be about over with warmer air expected to start to move into the
region albeit a very very slow modification overnight. The
morning is when the warmer air really starts to move into the
region. The one issue of concern that differs from the current
forecast is with the Burney Basin where there is a chance that
freezing rain may become an issue Thursday morning.

Further south snow levels are near 4000 ft with several inches of
snow above 5000 ft. Snow levels will rise faster overnight than
over the north. Several inches of additional snow is likely near
the crest tonight. Snow levels will rise above pass level during
the day.

A very moist zonal flow pattern will stay with us the next couple
of days and bring decent amounts of rain to the region. The snow
levels look like they will lower just enough Thursday night and
Friday to impact the Trans-Sierra roadways over the higher
elevations. Several feet of new snow over the peaks will likely
occur through Saturday.

&&
.EXTENDED DISCUSSION (Sunday THROUGH Wednesday)


Unsettled pattern will continue through the extended period.
Forecast confidence is low on Sunday given different weather
scenarios. Long range models have different outcomes at this
point, with the GFS bringing another wave of precipitation. For
now, current forecast is a blend of solutions given model
differences.

Forecast models indicate a moisture plume approaching the area
Monday into Tuesday. This should result in widespread
precipitation across our CWA. The GFS is wetter and spreads
precipitation further south compared to the ECMWF. Warm air
advection should rise snow levels to 8000 feet or higher by
Tuesday. Main dynamics shift to the north by Wednesday, so
precipitation coverage should be limited to the northern portions
of our CWA. Guidance suggests another round of widespread
precipitation by Thursday so stay tuned for updates. Temperatures
could be a few degrees above normal by the end of the forecast
period.

&&

.AVIATION...


MVFR cigs/vis likely across TAF sites with local IFR in the
northern Sacramento Valley as a storm system moves through. IFR
conditions over the Sierra after about 02z. Southerly winds will
increase especially over the northern Sierra with gusts up to 30
mph.


&&

.STO WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 10 AM PST Thursday for West Slope
Northern Sierra Nevada-Western Plumas County/Lassen Park.

Winter Weather Advisory until 10 AM PST Thursday for Shasta Lake
Area / Northern Shasta County.

&&

$$



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