Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 272227

Area Forecast Discussion
National Weather Service Sacramento CA
327 PM PDT Thu Oct 27 2016

Wet and unsettled weather into early next week as several weather
systems move across the area. The most impactful system should be
Sunday with snow possible at Sierra pass level.


Numerous showers ongoing this afternoon over NorCal rainfall
amounts have generally been light with valley amounts less than
0.20...except over portions of Shasta county where 1-2 inches has
fallen. Main rain band taking shape over the San Joaquin valley
extending to Monterey and offshore. This band will lift north
through the evening and spread over the southern half of the
Sacramento valley overnight. Heaviest activity should be from 10pm
tonight-11am as low pressure wave rides northeast along stalled
frontal boundary and entrains left over moisture from Hurricane
Seymour. This will bring valley rain amounts to an inch or more
with up to 2 inches over the mountains. Snow levels will remain
quite high given the sub-tropical origin of the system and not
expecting any snow accumulations. Forecast confidence is high with
overnight and Friday timing and precip amounts.

Showers will continue into Saturday, but there will also be
breaks in the not a complete wash out. The best precip
chances will shift over the mountains and Shasta county where up
to an inch could fall. Snow levels remain high above 8000 feet.

A colder system will drop south from the Gulf of Alaska Sunday
with significant precip and lower snow levels. Models have been
gradually trending lower with snow levels and current thinking
brings them down to 6000 feet during the day. In this scenario rain
would change to snow during the day over the Sierra impacting pass
level travel. Have issued a winter storm watch above 6000 feet for
6-12 inches at pass level and several feet at higher peaks
including Lassen park. Thunderstorms also look possible with a
good shear profile and instability for storm organization and
small hail threat. Confidence in Sunday`s system is medium and
some adjustments to this forecast may occur...especailly snow



Forecast model agreement continues to be good in bringing another
disturbance into northern California early next week, although the
forecast path and progression of the weather feature remains
uncertain at this time. High temperatures will run about 5 to 10
degrees cooler than average early to mid week with chances for
rain showers and snow at higher elevations.


A majority of visibility and ceiling conditions will be MVFR/IFR
for the TAF sites as light rain continues across northern
California for the next 24 hours. Wind gusts up to 20 kts at times
for some terminals in the valley and foothills through this


Winter Storm Watch from late Saturday night through Sunday
evening for West Slope Northern Sierra Nevada-Western Plumas
County/Lassen Park.


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