Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 311726

1026 AM PDT Fri Oct 31 2014

A cold front will impact interior NorCal today and tonight
bringing rain and mountain snow with isolated thunderstorms.
Much cooler temperatures are also expected. Showers are expected
behind the front on Saturday then end Sunday. Drier and milder
weather next week.


The rain has moved inland and several locations in our CWA are
getting sprinkles to light & moderate rain. High resolution models
show that the main band of precipitation will be fairly
centered over NorCal from Redding down into Sacramento and into
the Bay Area by noon. The latest HRRR model this morning is
indicating that the main rain band will be pushing into the
eastern side of the valley into the Sierra by 5-6 pm. Which means
some valley locations could start seeing breaks in the rain, but
it won`t be completely dry. Another important note from the HRRR is
that the Northern Sacramento Valley could have the best chance
for thunderstorm development later this afternoon into evening.
Rain totals in the valley are fairly impressive with some
locations getting up towards 0.75" and most snow amounts above
6000 ft should range between 6-10".

Our main message has not changed: Very wet today with snow in
the Sierra by 5-6 pm. Trick-or-Treaters need to be prepared for
wet conditions and need to 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 conditions.

.Previous Discussion...
As the front moves into the Sierra late this afternoon
and tonight...higher elevations will see snowfall. Snow levels by
early this evening are forecast to drop to pass levels then
expected to continue to drop to as low as 4500-5000 feet on
Saturday as cooler air behind the front moves into the region. The
main frontal band shifts east of the state by mid day Saturday
with showers likely to continue through the day as the main upper
low crosses the north state. Cool temperatures continue on
Saturday with daytime highs as much as 10 degrees below normal.
Sierra showers end on Saturday night as the upper flow becomes
more anti-cyclonic behind a retreating upper level trough. High
pressure building over the eastern Pacific and west coast will
bring clearing skies on Sunday and the beginning of a warming
trend that should last through most of next week. By Monday...High
pressure building over the west coast will bring still warmer
temperatures with daytime highs climbing to just below normal.


.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 warning to several degrees above normal.
Extended models now move a weak system over the north end of the
ridge and into the Pacific Northwest on Thursday. Operational
ECMWF would bring light precipitation across much of the forecast
area but for now...have gone with the GEM and GFS models which
keep precipitation just north of the CWA. Extended models now in
good agreement in keeping some form of ridging over the west coast
through the end of next week so extended period remains dry with
slightly above normal temperatures.


A mix of VFR/MVFR/IFR conditions across the forecast area this
morning as a cold front moves inland. Steady rain has already developed
near KRDD-KRBL and KVCB-KSUU. Some sprinkles have started in the
Sac Metro region, but expect steadier rain near Sacramento and
Stockton TAF sites between 20-22z. 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 from ~7500 ft this morning to ~5000 ft tonight. Scattered
showers expected to continue across the area tonight.

South winds up to 15 kt expected to continue across the Valley
through this afternoon, becoming lighter overnight. Over the
mountains, SW wind gusts up to 50 kt possible through tonight.



.STO Watches/Warnings/Advisories...
winter weather advisory from 5 pm this afternoon to 2 pm pdt
saturday above 6000 feet in the western plumas county/lassen

winter storm warning from 5 pm this afternoon to 2 pm pdt
saturday above 6000 feet in the west slope northern sierra


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