Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 302206

306 PM PDT Thu Oct 30 2014

A cold front will impact interior NorCal Friday into Saturday.
The front will bring rain, mountain snow, cooler temperatures, and
a slight chance of thunderstorms. Snow levels will lower to around
5000-6000 ft by early Saturday morning. Showers are expected
behind the front on Saturday then end Sunday. Drier and milder
weather early next week.


.Short Term Discussion (Tonight through Sunday)...
Have made some changes to this afternoon`s forecast. Latest models
are showing higher snow levels, slower timing, and that the
greater snow impacts will be farther south than anticipated. We have
cancelled the Winter Storm Watch for Western Plumas County and
Lassen Park. Parts of Lassen Park (especially the peak of Mt.
Lassen) will still see some snow, but the coverage is not very
widespread. The Western Sierra slopes south of Plumas county will
have greater snow impacts so we upgraded the Winter Storm Watch
for that region to a Warning. The other changes to this Warning are
that we raised the elevation to above 6000 ft (the Watch was
at 5000 ft) and adjusted the timing from 5 pm Friday through 2 pm
Saturday. Motorists in the Sierra need to be prepared for winter driving.

The big focus is how will the weather impact Halloween. First off,
the forecast continues to call for a wet day across NorCal with a
slight chance of thunderstorms. The brunt of precipitation in the valley is
still on track to arrive before 5 pm, but light rain will continue
during typical Trick-or-Treating hours. If you are at higher
elevations, expect rain to turn to snow above 6000 ft sometime
after 5 pm. Bottom line: have an umbrella, be careful driving as
roads will be slick, and stay sheltered if you hear thunder or see
lightning nearby.

Daytime highs on Halloween will be notably cooler than the past
couple of days. Valley highs will be in the low to upper 60s while
mountain regions peak in the 50s. After 5 pm, temperatures during
Trick-or-Treat hours will be: Valley - upper 50s to low 60s,
Mountains - 40s to 50s.

Showers are likely to continue on Saturday but are expected to
diminish by late morning/early afternoon. Saturday highs under
the cooler airmass are forecast to be about 10 degrees below
normal. Lingering light showers along the Sierra could continue
into Sunday morning, but rebuilding high pressure will end precipitation
by Sunday afternoon. Sunday highs will start to move upward again
as a warmer and drier trend settles in for the first half of next week.

.Extended Discussion (Monday through Thursday)
High pressure ridging along the west coast will be the dominant
weather feature through the extended period. Daytime highs will
slowly be climbing Monday through Thursday reaching to around
normal. Extended models move a weak system over the north end of
the ridge and into the Pacific Northwest around Tuesday but keep
any precipitation north of the forecast area. Therefore...extended
period remains dry for now. Extended models hinting at a return to
a wetter pattern towards the end of next week but have been rather
inconsistent both run to run and model to model so confidence in
this change not especially high at this time.


VFR conditions expected to continue the next 18 hours. A frontal
system will begin to approach the area tonight, with light showers
spreading across the Coastal Range after midnight tonight and into
Valley toward sunrise and after. Southerly winds dominating Fri
ahead of front. SW mountain wind gusts up to 30 kt will be



.STO Watches/Warnings/Advisories...
Winter Storm Warning from 5 pm Friday to 2 pm PDT Saturday above
6000 feet in the west slope Northern Sierra Nevada.


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