NATIONAL WEATHER SERVICE FORECAST DISCUSSION
Area Forecast Discussion
Issued by The National Weather Service
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170
FXUS66 KSTO 171158
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
358 AM PST Sun Feb 17 2019

.SYNOPSIS...
Cold disturbance will bring showers through Sunday. Heaviest
precipitation over the Sierra with significant travel issues
through this morning, gradually decreasing through the afternoon.
Dry Monday and Tuesday. A weak, cold system is possible Wednesday
and Thursday.

&&

.DISCUSSION...
Broad trough continues to dominate pattern across the West, with
a cold upper low from British Columbia dropping southward through
Northern California. Clouds with this system have spread across
the area, with light rain showers in the Valley and increasing
snow showers in the Sierra and foothills. Snow profiler in
Oroville shows snow levels in that area currently around 2500
feet. These will drop to around 1500-2000 feet for the Sierra as
the cold core passes through this morning, down to as low as 500
feet over Shasta County. Snow amounts in Shasta County should be
limited by moisture, though, with wet snow possible from around
a dusting to an inch. The Winter Storm Warning ends at 4 am, with
a Winter Weather Advisory for the Sierra taking effect and
continuing until 4 pm this afternoon, with another 5 to 7 inches
of snow accumulation possible. Most of this is expected in the
morning hours, gradually diminishing through the afternoon and
light lingering showers early this evening. The upper foothills
could see 1 to 4 inches of snow.

Dry weather returns for Monday and Tuesday with dry northerly flow
across the region and breezy northerly winds. Morning lows will
drop into the upper 20s to lower 30s. The northerly winds should
limit frost to some extent early Monday, with better chances on
Tuesday.

The next cool low drops down across the area Wednesday, bringing
widespread precipitation. Moisture amounts are limited, but snow
levels will be down into the foothills, so there are some travel
concerns. EK


.EXTENDED DISCUSSION (Thursday THROUGH Sunday)

Extended period starts out with a cold inside slider type system
dropping into the Great Basin on Thursday bringing a shower threat
to areas mainly east of the central valley. This system which
originated in the Gulf of Alaska will bring low snow levels again
with light snow possible down below 1000 feet. Impacts with this
system should be minor as QPF values with this dry system will be
minimal. At this time, Friday looks dry under northerly upper
flow and high pressure ridging. Temperatures warm on Friday but
cool airmass will keep daytime highs several degrees below normal.
Upper ridge breaks down quickly as next upper low pressure system
drops out of the Gulf of Mexico and approaches the Pacific
northwest coast on Saturday. Models differ on just how far south
precipitation will reach with GFS digging precipitation somewhat
farther south than ECMWF. Have split the differenct for now and
kept precipitation with this system mainly north of the
Sacramento area through Sunday. Snow levels with this system will
be more moderate than previous systems but still relatively low
and below 4000 feet.

&&

.AVIATION...

VFR conditions except brief MVFR/IFR conditions in showers through
18z. Southerly winds to 10 mph shifting to northerly after 18z
gusts to 20 to 30 mph.
&&

.STO WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 4 PM PST this afternoon for West
Slope Northern Sierra Nevada.

&&

$$
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