Area Forecast Discussion
Issued by NWS Sacramento, CA

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000
FXUS66 KSTO 191122
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
422 AM PDT Thu Oct 19 2017

.SYNOPSIS...
Increasing clouds and cooler temperatures today. Rain chances
along with high mountain snow and gusty winds this evening and
Friday. This will be followed by a warming trend early next week
with above normal temperatures through the week.

&&

.DISCUSSION...
Pacific frontal system now moving into the Pacific Northwest will
be moving into northwest California this afternoon. Increasing
cloud cover and increased onshore flow along with airmass cooling
will bring 10 degrees or more of cooling today. By this afternoon
the coastal range will see a chance of light rain. Southwest flow
aloft and orographics will bring a slight threat of showers over
the northern Sierra and southern Cascades. Main frontal band moves
through during the nighttime hours tonight will bring a good
chance of rain to most of the cwa with snow at the higher
elevations. Expected rainfall amounts in the valley range fairly
light at about 1/10th to 3/10ths of an inch. Orographics over the
Sierra could squeeze out over an inch of precipitation. Tightest
surface pressure gradient will be this evening. Could see winds at
wind advisory criteria especially over the Sierra Cascade range
but the stronger winds will likely be relatively short lived.
Front shifts east of the CWA by Friday morning with shower threat
ending most locations. Upper troughing will continue to feed cool
air into the region so highs on Friday will range from 10 to 15
degrees below normal. Upper ridging begins to build over the
eastern Pacific Friday afternoon with continued ridging on
Saturday. Disturbances slipping over this ridge will bring a
threat of showers to the northern zones through Saturday. Clearer
skies and warming airmass will bring daytime highs up to close to
normal for this time of year by Sunday afternoon. This warming
trend will continue going in to next week.

&&

.EXTENDED DISCUSSION (Monday THROUGH Thursday)

Upper level ridge persists next week maintaining a dry and warm
pattern for our CWA. Daytime highs will range 6-14 degrees above
normal during the extended forecast period. Valley highs will stay
in the low to mid 80s while mountain highs range 60s and 70s. JBB

&&

.AVIATION...

VFR conditions with light winds...local HZ/FU MVFR visibility is
possible in the Delta and surrounding terminals this morning.
Valley and ridge winds will increase this afternoon, especially
over the ridgetops and north Sacramento Valley. Gusts at TAF sites
could range between 15-25 kts in the afternoon/evening hours, then
decrease after 06z. Precipitation will move into interior NorCal
around 00z and impact TAF sites through Friday morning with MVFR
ceilings possible at times. JBB


&&

.STO WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 11 PM this evening to 11 AM PDT
Friday for West Slope Northern Sierra Nevada.

&&

$$



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