Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 200950
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
250 AM PDT Wed Sep 20 2017

.SYNOPSIS...
Cooler weather continues this week with a chance of showers into
Thursday.

&&

.DISCUSSION...
Western North America trough continues to evolve with the initial
wave from earlier this week now lifting out through the northern
Great Plains while the next wave drops south off the PacNW coast.
Across interior NorCal, skies are partly to mostly cloudy to the
north of I-80 while they`re clear to the south. Radar indicates
showers have so far been remaining over northwest California.

Current temperatures range from the mid 30s to mid 40s in the
mountain valleys to the mid 50s to mid 60s in the Central Valley.

The upper trough is forecast to deepen across NorCal over the next
24 hours pushing another cold front southward later today and this
evening. Most precipitation is expected over the mountains as the
front moves through, but some sprinkles or light showers may
brush through portions of the valley as well. QPF will be light,
generally less than a third of an inch across the higher
elevations and less than a tenth of an inch elsewhere.

Colder air will move into the region tonight behind the front
lowering snow levels to around 5500-6500 feet. Even a few inches
of snowfall accumulation will be possible across the higher peaks.

Temperatures will be well below average (10-20 degrees) across
the region the next few days with highs only in the 70s across the
Central Valley through Friday.

Dry and milder weather returns for the weekend.

&&

.EXTENDED DISCUSSION (Sunday THROUGH Wednesday)
High pressure returns to northern California this weekend with
dry conditions and a warming trend to the afternoon temperatures.
High temperatures Saturday will remain below normal, but
temperatures Sunday into early next week will return to normal or
slightly above normal. Breezy north and east valley and ridgetop
winds can be expected for the weekend and into next week.

&&

.AVIATION...
VFR conditions for the valley terminals for the next 24 hours
with light winds. Chances for light mountain rain showers and
increasing clouds tonight and Wednesday.

&&

.STO WATCHES/WARNINGS/ADVISORIES...None.

&&

$$



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