Area Forecast Discussion
Issued by NWS Sacramento, CA

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000
FXUS66 KSTO 252341
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
341 PM PST Tue Nov 25 2014

.Synopsis...
Dry and mild weather is expected through Thanksgiving as high
pressure covers the region. Rain is expected to return to the
region by late Friday and continue into early next week. Snow
across the mountains is likely to cause travel difficulties for
the holiday weekend and into early next week.

&&

.Discussion...
Strengthening upper level ridging is going to bring continued mild
weather to the area through Thanksgiving. Afternoon temperatures
will peak well above normal levels on Wednesday, with slightly
cooler highs on Thursday as high clouds begin to spread in. There
could be some patchy morning fog/mist in the Valley and mountain
valleys Wednesday and possibly again early Thursday.

A weak wave will bring some precipitation gradually spreading
into the area from north to south Friday. Models have trended a
little slower with this system. The precipitation should be
mainly north of I80 during the day and should have limited impact
on travel. More substantial moisture arrives on Saturday, with
some accumulating snow beginning early Saturday, with more
significant amounts late Saturday through early Sunday. Snow
levels are projected to drop to around 6000-7000 feet on Saturday
and then down to around 6000 feet by early Sunday. Snow amounts
Saturday should generally be relatively light. More impactful snow
is possible Saturday night into early Sunday. Holiday travelers,
especially those going over Sierra passes, should closely monitor
the forecast as it evolves over the next several days. EK

&&

.Extended Discussion (Saturday through Tuesday)

Development of a deep...closed upper-level low off the CA coast
during the holiday weekend promises to bring significant rain/mtn
snow to interior Norcal into early next week. A strong probability/
measure of predictability is forecast by the NCEP 15 days 500 mbs
height ensemble for this scenario to unfold. While there is a high
degree of confidence in a multi-day precip event for Norcal...model
differences in timing could result in greater or lesser impacts. For
now...the heaviest QPF is expected to occur from Sun nite into
Mon...or near the end of the holiday weekend during the mass
return/exodus of the public. A high probability of an inch or more
of precip is forecast for the Shasta Co area...and Siernev for the
Sat...Sun...Mon periods...with the highest probabilities in the
latter two periods.

Due to the slower timing of the models...Norcal will be in the WAA
zone ahead of the upper low early in the weekend and we have
adjusted the snow levels upwards to account for this timing. In the
later periods...there is more uncertainty in the timing and amount
of QPF into Tue due to the slower movement of the ECMWF positively-
tilted trof. The GFS may be too progressive with the trof and the
slower timing of the GEM/ECMWF for lingering precip into at least
Tue morning is preferred.    JHM

&&

.Aviation...

VFR SKC with light winds tonight thru Wed with the exception of
early morning fog/ST and local IFR/LIFR conditions in the Central
Vly and mtn valleys/basins.

&&

.STO Watches/Warnings/Advisories...
None.
&&

$$






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