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fxus66 ksto 192341 
afdsto

Area forecast discussion
National Weather Service Sacramento California
341 PM PST Tue Nov 19 2019



Synopsis...
pattern transitioning to breezy to windy conditions, cooler
temperatures and possible showers over mainly the Sierra Nevada
south of I-80.

&&

Discussion...
the upper level trough is showing up nicely on water vapor and is
currently still an open wave along the California coast. Over the next
few hours we will see this trough close off near Monterey and drop
south into socal by Wednesday mid morning. Showers have started
to develop mainly along the Sierra crest and are quickly pushing
east with the strong westerly flow. As the trough closes off
easterly flow will develop and that will favor precip on The East
Slope of the Sierra. Last several runs of the hrrr show a band of
light to moderate precip pushing over I-80 and Highway 50 and
pushing down the slope to the east of Placerville and Auburn in
the 7 PM to midnight range. This is somewhat of an outlier at this
time as the href along with other models favor that band setting
up to the south of Highway 50. It is something that will have to
be monitored this evening as snow levels will be falling to just
below pass level. Current thinking is 1-2" will be possible over
I-80 and Highway 50 this evening into the overnight with the
higher snow totals staying to the south where a Winter Weather
Advisory is in effect.

The bigger impact from this system will be the cooler
temperatures and an increase in northerly wind that will develop
across a large part of the area overnight and continue into
Thursday as the surface gradient tighten. The period of strongest
northerly winds are expected Wednesday afternoon as subsidence
and upper level support increase. Gusts of 40-50 mph will be
possible in the Sacramento Valley and surrounding terrain north of
Sacramento.

Shower chances will push south on Wednesday and will continue to
favor The East Slope of the Sierra but light activity will be
possible in our area mainly near the crest south of 50. Snow
levels will be dropping down to around 5500 feet by Wednesday
afternoon and we could see some light accumulation down to that
elevation but it should remain minor.

Winds will die down quickly Thursday mid morning into the
afternoon and we will see an upper level low set up over the
Pacific on Friday. This will keep clouds in our forecast along
with the cooler but still a bit above average temperatures. Light
winds will continue on Friday.

-Cjm

&&

Extended discussion (saturday through tuesday)...

To start the weekend, the region will feature an eastward
extending ridge with a closed low positioned well off the Southern
California coast. Perhaps a few additional clouds are possible
although this should not hinder temperatures much. Valley High
temperatures will easily reach the mid to upper 60s with even a
couple 70 degree readings in the upper Sacramento Valley. This is
still quite warm for mid-November with departures from climatology
on the order of 5 to 10 degrees. Although ridging will allow
optimal radiational cooling at night to keep readings closer to
average.

Moving to next week, global ensembles continue to favor a ridge
centered over the east Pacific (i.E., 140w longitude) while
longwave troughing extends over the western/central U.S. Models
remain Adamant about a sharpening shortwave sweeping across the
central Great Basin into The Four Corners. This pattern would
support another bout of gusty northerly winds on Monday into early
Tuesday. With extremely dry fuels in place, elevated fire weather
concerns are nearly a given if this setup were to become reality.
Looking further beyond, another trough may reach the West Coast
by mid-week although impacts remain unclear given increasing model
uncertainties. ~Bro

&&

Aviation...

VFR conditions the next 24 hours with winds increasing from north
to south during the overnight hours. Krdd and krbl can expect
northerly wind gusts in excess of 30 knots by around 12z
Wednesday. Breezy conditions are likely over the Sacramento taf
sites starting by 15z Wednesday with slightly lighter winds down
into the upper San Joaquin Valley. ~Bro

&&

Sto watches/warnings/advisories...
red flag warning from 4 am Wednesday to 7 am PST Thursday for
central Sacramento Valley in Glenn, Colusa, Yuba, northern
Sutter, and Butte County below 1000 ft-eastern Mendocino nf-
eastern portion of Shasta/Trinity nf-Lake County portion of lake-
Napa-Sonoma unit-northern Sacramento Valley to southern Tehama
County line below 1000 ft-northern Sierra foothills from 1000 to
3000 ft. Includes portions of Shasta-Trinity and Butte units-
northern Sierra including Lassen np and Plumas and Lassen nf/S
west of the Sierra crest (west of Evans Peak-Grizzly Peak-
beckworth peak)-southeast edge Shasta-Trinity nf and western
portions of Tehama-Glenn unit-southern Sacramento Valley in Yolo-
Sacramento far western Placer, southern Sutter and Solano County
below 1000 ft.

Wind Advisory from 4 am to 10 PM PST Wednesday for central
Sacramento Valley-Clear Lake/Southern Lake County-mountains
southwestern Shasta County to Northern Lake County-northeast
foothills/Sacramento Valley-northern Sacramento Valley-Shasta
Lake area / northern Shasta County-southern Sacramento Valley-
western Plumas County/Lassen park.

Winter Weather Advisory until 7 PM PST Wednesday for West Slope
northern Sierra Nevada.

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