Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 212239
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
339 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)...
Weak ridging over the area bringing mostly sunny skies and dry
weather today. Temperatures warming into the upper 60s to low 70s
in the Valley and mid 40s to low 60s in the mountains this
afternoon which is several degrees below normal for this time of
year. Temperatures will be a few degrees warmer on Wednesday with
highs in the 70s in the Valley and 50s and 60s in the mountains,
which is near normal for this time of year. The weak ridge shifts
east as the trough deepens late Wednesday. Precipitation is
expected to enter the Coastal range around Wednesday evening and
spread southeast to around the I-80 corridor on Thursday morning.
Precipitation will continue on Thursday...mainly North of I-80.
The trough continues to deepen along the west coast on Friday. The
front may become more north- south oriented oriented on Friday
continuing the rain along the coastal range and Shasta county but
not much farther east. Snow levels are expected to generally be
above 8500 feet Thursday and Friday. The trough moves onto the
coast Saturday spreading the chance of precipitation across all of
interior Northern California.

.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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