Winter Storm Warning 11, NWS Sacramento, CA

Area Forecast Discussion
National Weather Service Sacramento CA
343 AM PST Thu Nov 29 2018

.SYNOPSIS...
Wet pattern continues through the weekend with several weather
systems forecast to affect the region. A stronger system moves
through today with valley rain, mountain snow, thunderstorms and
gusty southerly winds. That will be followed by a colder system
over the weekend.

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.DISCUSSION...
Cold front moving through early this morning accompanied by a
narrow band of heavy rain. Fortunately, the lines of heavier
showers have mostly missed the recent burn scars (Carr and Camp
Fires) so far. Earlier in the night, a large area of moderate
rain occurred ahead of the cold front bringing a half inch to an
inch of rain to areas north of I-80. The lines of heavier showers
are now moving into the foothills and Sierra east of the Central
Valley, and their relatively fast movement to the east will limit
more significant flooding. An urban and small stream flood
advisory continues for much of the area through 6 AM.

Gusty southerly winds continue, especially right ahead of the
cold front where gusts of 35 to 45 mph are likely early this
morning. Winds may subside a bit for an hour or so behind the
front, but the potential for some strong gusts will continue
through the morning.

Much of the valley may see a relative respite from precipitation
(just some scattered showers) during the morning commute hours,
but it's still looking like another significant line of showers
and thunderstorms will spread inland by mid to late-morning as the
surface and upper low approach.

Will continue the winter storm warning through early Friday (for
up to 2-3 feet over the higher Sierra) with snowfall rates
expected to increase. The flash flood/debris flow watch for the
Camp, Mendocino Complex and Carr, Hirz-Delta fires has been
extended through today as the threat for stronger convection will
linger across much of the region until about sunset.

Mostly a dry day and more settled weather on Friday (although
some lingering showers are possible over the Sierra) before the
next Pacific Storm moves through Norcal Friday night and Saturday.
Snow levels will be lower with this colder system (between 3500
and 4000 feet over the Sierra), and even though the QPF will be
lower, significant snow is expected, especially at lower
elevations, and therefore mountain travel impacts are likely.
Preliminary snowfall amounts of around a foot at 4500 feet with
18-20 inches along the crest. Some lingering showers possible over
the mountains Sunday.

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.EXTENDED DISCUSSION (Monday THROUGH Thursday)
Extended models aim the next Pacific Frontal system into Norcal
early next week but differ on timing a bit. Will to mention cool
and unsettled weather. Snow levels come up a bit as a Pacific low
starts to move onshore but still fairly low for this time of year
at between 3000 and 4000 feet. QPF and snow levels would indicate
mountain travel impacts again by mid week but continued poor model
run to run consistency makes for low confidence in details.

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.AVIATION...
Areas of locally heavy rain will impact NorCal through 12Z,
becoming mostly scattered through 00Z Friday. MVFR/IFR conditions
expected in rain showers. Strong southerly winds 15-25 kts, gusts
to 35 kts. An Airport Weather Warning has been issued for SCK due
to sustained winds potentially exceeding 24 kt through 16Z. HEC

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.STO WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through this afternoon 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-Western Plumas County/Lassen
Park.

Winter Storm Warning until 4 AM PST Friday for West Slope
Northern Sierra Nevada-Western Plumas County/Lassen Park.

Wind Advisory until noon PST today for Carquinez Strait and
Delta-Central Sacramento Valley-Motherlode-Northern San Joaquin
Valley-Southern Sacramento Valley.

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