Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 220357
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
857 PM PDT Tue Oct 21 2014

.Synopsis...
Dry zonal flow will persist through tomorrow afternoon with some
high clouds at times. An elongated frontal system impacts Northern
CA with potential rain from Wednesday night into the weekend.
Chances for the areas south of the I-80 corridor to receive
precipitation increase Friday night and Saturday. Significant
rainfall is possible over the far northern sections of the state
through Saturday.

&&

.Short Term Discussion (Today through Friday)...
Zonal dry flow will continue with just some high clouds moving
through the area. through Wednesday. Temperatures will cool in the
valley tonight into the 40s and lower 50s for the valley and in
the 30s for the mountain valleys.

A low pressure area in the gulf of Alaska will start to spread
precipitation along the northwest coast late Wednesday and into
the far northern interior sections of the state Wednesday night
into Thursday. Late Wednesday night and Thursday is when chances
increase mainly for areas north of I-80. This will be the first
wave of precipitation to move into California.

As the low deepens on Thursday night into Friday out over the
Pacific a second front forms and becomes a little bit more
oriented north to south and is slowing down. This looks like it
may result in mainly dry conditions for the interior sections
Thursday night and Friday. Friday night and Saturday is when the
front pushes inland given areas the greatest chance of widespread
rain over the entire interior along with some higher elevation
snow and windy conditions.

.Extended Discussion (Saturday through Tuesday)

GFS/EC/GEM in fairly good agreement with timing of Pacific frontal
system early in the extended. Front progged through Interior
NorCal Friday night into Saturday morning followed by associated
upper trough Saturday. Differences do exist with QPF with GFS
advertising about double the amount of precip compared to the EC.
Models currently not showing a lot of post-frontal instability but
the pattern suggests it, and thus will need to consider adding
mention of thunderstorms as the event draws near. Lingering threat
of showers Saturday night then slight chance over the Shasta
mountains Sunday. Below normal temperatures expected over the
weekend with mid 60s to lower 70s for the Central Valley and 40s
to 60s for the mountains and foothills. Some accumulating snow
possible Saturday with snow levels ranging from around 6500 ft in
the Shasta mountains, and 7000 to 8000 ft from Lassen Park to
Sierra Nevada.

Dry weather Monday as weak ridging moves through then models
suggest potential for some light WAA precip over northern portions
of the CWA Tuesday.



&&

.Aviation...

Wly flow alf with VFR conds ovr Intr NorCal nxt 24 hrs. Sfc wnds
genly aob 10 kts.

&&

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

$$







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