Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 201100

Area Forecast Discussion
National Weather Service Sacramento CA
300 AM PST Mon Nov 20 2017

Weather system will bring rain chances to the region today. Mainly
dry weather is then expected for the remainder of the week with
rain chances limited to the northern mountains.


Cloudy skies across interior NorCal as the next weather system
moves into the region. Measurable rain has so far been limited to
the Coast Range where amounts up to two tenths of an inch have
been reported since late Sunday evening. So far, only sprinkles
have been occurring over the Sacramento Valley and far northern
Sierra Nevada.

Current temperatures are considerably milder compared to 24 hours
ago and range from the upper 30s and lower 40s in the mountain
valleys to the upper 40s and lower 50s in the Central Valley.

Mostly light precipitation is expected across interior NorCal
today as we catch the tail end of a system moving through the
PacNW. Satellite imagery shows a wide plume of deep moisture (TPW
of around 1.5 inches) moving up from the southwest. Warm-advection
and terrain will be the main forcing mechanisms as the cold front
remains to the north, and precip in the valley will occur mainly
to the north of Sacramento. Heaviest amounts will be in the
mountains where up to an inch may occur into this evening. Snow
levels will remain above 10K feet.

Dry weather returns Tuesday and Wednesday as high pressure
strengthens over the West ahead of the deepening trough over the
Gulf of Alaska. Temperatures will be unseasonably mild with upper
60s and lower 70s expected through the Central Valley (around 10
degrees above average).

Another weak system will move through the ridge on Thanksgiving
and may bring even lighter QPF (than the current system) to far
northern California.


Weak system will be exiting the area on Friday with a few
lingering showers across mountains. Snow levels will remain high,
so not expecting any impact there, other than some wet roads. Rest
of the extended period characterized by high model uncertainty.
ECMWF and GFS out of phase with subsequent waves, leading to low
confidence in timing and extent of precipitation for the weekend
into early next week. ECMWF fairly wet for Sunday into Monday
while GFS holds off until Monday night-Tuesday. Have left low
chance pops across much of the area through the period until
better agreement is shown. As it stands now, snow levels look high
(above 8-9K feet through the weekend), then perhaps dropping
below pass levels by Monday. Will be something to watch depending
on which solution verifies. Temperatures will remain mild through
the period, around 4-10 degrees above normal for this time of


Showers possible today with areas of MVFR conditions from time to
time in heavier showers. Winds generally 10 kts or less.




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