Area Forecast Discussion
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FXUS66 KSTO 221217

Area Forecast Discussion
National Weather Service Sacramento CA
417 AM PST Fri Nov 22 2019

Dry weather with mild daytime temperatures and light winds through
the weekend. Breezy conditions over the Sacramento Valley on
Monday with the potential for a significant winter storm by
Tuesday into the Thanksgiving holiday. Much cooler temperatures in
store for next week.


Satellite imagery this morning shows continued mid to low level
cloud cover over the Sierra and foothills, generally from Plumas
County southward. Current temperatures are quite chilly across
the region with Valley temperatures in the mid 30s to low 40s and
mountains temperatures in the teens to low 30s.

A weak low pressure system will remain over the Eastern Pacific
generally west of the California Coast through the weekend. Weak
high pressure will build over NorCal north of this offshore low.
Quiet weather is expected with mainly light winds and dry
conditions. Daytime temperatures will rise slightly each day,
especially over the northern Sacramento Valley and mountains.
Above normal daytime temperatures expected ranging around 7 to 15
degrees above normal as Valley temperatures rise to the upper 60s
to low 70s and mountains in the 50s to low 60s. Overnight lows
will still fall to near or below normal due to light winds and
little cloud cover.

Ensembles continue to depict the pattern beginning to change
Monday as a series of weather systems are forecast to impact the
West Coast next week. For NorCal, a weak weather system moves
east of California into the Great Basin on Monday which will
create gusty northerly winds across the Valley and wind prone
mountain areas. There could be an increased fire weather concern
with these winds as vegetation remains very dry and daytime
humidity Monday are currently forecast in the upper teens to 20s.
However, overnight humidity recoveries will be moderate with most
locations in the 40s to 70s except for a few localized areas in
the upper 30s. Daytime temperatures will begin to cool Monday,
especially in the northern Sacramento Valley and mountains where
temperatures are forecast to drop around 5 to 10 degrees from
Sunday. Cooler and wet weather return Tuesday with a strong
weather system possibly bringing our first significant winter
storm leading into the Thanksgiving holiday. HEC


Cool and wet weather is expected from Tuesday through the
Thanksgiving holiday period.

A strong and rather cold system from western Canada will drop
southward into the region bringing widespread precipitation
starting on Tuesday and impacting the region through Friday.
Confidence is increasing that this will be a significant system
bringing heavy snow to the Sierra, bringing travel disruption
during the busiest period of the year. While model ensembles show
a range of possibilities, the most likely storm total amounts
(Tue-Fri) at this point appear to be up in the general range of
1-3 feet at pass levels. Cold air with this system could bring
some accumulating snow to 2500 feet, potentially lower in heavier
convective showers. Anyone considering travel mountain travel
around Thanksgiving should closely monitor the forecast.

Valley temperatures are going to be cooler than they have been in
a long time, with highs on Wednesday and Thursday (Thanksgiving)
only reaching the low 50s! Rainfall amounts in the Valley, Delta,
and lower foothills are currently estimated to be in the half
inch to inch range. There could be thunderstorms with this system
as the cold core moves through Wednesday and Thursday, though,
which could bring locally higher amounts. Confidence in timing and
details remain uncertain at this time, so will leave out of the
forecast for now. The current track of the low along the suggests
higher potential along the west side of the forecast area. EK


VFR conditions, winds generally less than 10 kts expected. Local
MVFR conditions possible in BR over Northern San Joaquin Valley
this morning.



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