Area Forecast Discussion
Issued by NWS Sacramento, CA

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000
FXUS66 KSTO 260506
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
906 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...
High pressure ridge will remain in place for Wednesday.
Temperatures will warm slightly for most locations over today.
Overnight dew points are up by several degrees so a few patches of
fog will be possible for the late night and early morning hours
over the Southern Sacramento and Northern San Joaquin Valley and
delta region.

For Wednesday night and Thursday morning the dew points should
come up a little but there should be a lot of high clouds that
could help to prevent a lot of fog from forming but patchy still
looks possible. For Thanksgiving the high pressure ridge will
begin to break down and shift eastward. Some precipitation will be
possible over the far northwestern part of the state.

On Friday there are timing differences but models do agree on
bringing precipitation to the coastal range and far northern part
of the interior. There is agreement on a jet moving over the far
north so would not be surprised to see some rain start early during
the day on Friday for the Northern Sacramento Valley. Snow levels
will be high for the onset of precipitation through Friday daytime
but may lower below major pass trans-sierra levels Friday night to
impact travel with snow. For Sacramento area and south the models
are pointing towards the start of rain from the evening hours to
late at night or early Saturday morning for the far southern
sections of the CWA.

&&

.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 (60-70% chance)
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. Last nite`s GFS
shows a more substantial TPW plume to work with than the GEFS
ensemble and we are leaning wetter in the EFP due to the slower
timing and multi-day precip event.
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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