Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 312242

342 PM PDT Fri Oct 31 2014

A cold front is impacting NorCal through this evening. Rain and
mountain snow with isolated thunderstorms will impact Halloween
activities this evening. Showers are expected behind the front on
Saturday then end Sunday. Drier and milder weather next week.


Rain, from sprinkles to light & moderate rain, continues to impact
interior NorCal this afternoon and will continue this evening.
The 20z HRRR model is consistent with earlier runs showing the
main rain band pushing into the Sierra by 5-6 pm then reaching
pass levels by 10 pm. Another important note is that the Northern
Sacramento Valley still has the best chance for thunderstorm
development later this afternoon into evening. This latest HRRR
run shows the typical convergence line setting up between Red
Bluff and Redding crossing I-5 during early evening hours (5-9 pm).
Rain totals in the valley remain impressive with some
locations getting up towards 0.75" and most snow amounts above
6000 ft should range between 6-10".

Even though some valley locations will see breaks in the rain, it
won`t be completely dry this evening. Trick-or-Treaters need to
be prepared for wet conditions and should seek shelter if
thunderstorms are nearby. Roads will be slick from the rain and
motorists in the Sierra need to be prepared for winter driving

Showery conditions will linger into Saturday after the main
frontal band passes east with some mountain showers persisting
into early Sunday morning. With all this moisture and cold morning
temperatures, there could be some patchy fog development during
the very early morning hours on Sunday. It`s tricky to say how
widespread the fog could be or how long it will last because
northerly winds will also develop Sunday morning. Even light
northerly winds (around 5 mph or higher) can inhibit fog.

Daytime highs over the weekend will be cool with valley highs only
warming into the mid 60s for much of our CWA. By Monday, dry
weather with a warming trend will settle in for the rest of the week.


.Extended Discussion (Tuesday through Friday)

High pressure ridging along the west coast will be the dominant
weather feature through the extended period. Daytime highs will
climb Tuesday and Wednesday before stabilizing Thursday and
Friday. In any case, max temperature will be around 5 degrees
above normal. Extended models do move a weak system over the north
end of the ridge and into the Pacific Northwest on Thursday
according to the ECMWF. On the other hand, the GFS and GEM are a
bit slower (12-18 hrs) and weaker with this wave. We compromised
with the models and meshed with our neighboring coastal offices on
introduced and slight chance of precip over the Coastal Mountains
Wed night into Thu night.    JClapp



Periods of MVFR/IFR conditions are expected across the Valley in
rain. A few thunderstorms can`t be ruled out this afternoon and
evening across the Valley. IFR/LIFR conditions expected over the
mountains with snow levels dropping to ~5000 ft tonight.
Scattered showers expected to continue across the area tonight.

South winds expected to increase to 15 kt late this afternoon
and evening as front passes, becoming lighter overnight. Over the
mountains, SW wind gusts 35 to 50 kt possible through tonight.



.STO Watches/Warnings/Advisories...
winter weather advisory until 2 pm pdt saturday above 6000 feet
in the western plumas county/lassen park.

winter storm warning until 2 pm pdt saturday above 6000 feet in
the west slope northern sierra nevada.


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