Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 271203
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
403 AM PST Fri Feb 27 2015

.Synopsis...
A weather system will move into the area today, leading to cooler
and wetter weather into the weekend. The potential exists for snow
impacting some travel in the mountains above 3500 feet, and more
so above 6000 feet.

&&

.Discussion...
An upper level trough is currently situated off the Washington
coast, with northwesterly flow persisting aloft across California.
A series of vorts has begun to move across portions of the area,
and mosaic radar imagery shows a few showers over the Great Basin
and far NW California. Across our forecast area however, primarily
clear skies and generally light winds continue.

The aforementioned trough will continue to shift southward through
the course of the day. Look for precipitation to begin filling in,
especially along the mountains starting around midday into the
afternoon and evening. The latest NMM/ARW runs continue to show an
unstable atmosphere this afternoon, and we`ve opted to expand the
"slight chance of thunderstorms" area across the Sacramento Valley
and adjacent Sierra foothills. Still believe accumulating small
hail to be the greatest convective threat, but can`t rule out a
brief funnel cloud either. Given the convective nature of today`s
precipitation, showers could be hit- or-miss especially across the
lower elevations.

The greatest overall impact with this system will likely be wintry
travel across the Sierra. Still expecting roughly 4-8" of snow
accumulation above 5500 ft this afternoon through Saturday, with
up to a foot at the highest elevations. Snow levels should begin
around 5500 ft, lowering to about 4000 ft by Saturday. Given the
high traffic volume across the Sierra on Fri/Sat, some spinouts,
slower travel, and chain controls should be expected.

The upper low shifts overhead Saturday, and moves south Saturday
night. Some northerly winds should begin to develop along the
northern CWA by Saturday afternoon. Often times this focuses
convection along the Coastal Range and the Sierra, with less for
the Valley. Regardless, showery precipitation should continue
through Saturday, and gradually diminish from north to south
Saturday evening and into Sunday.

Sunday currently looks dry across interior Northern California,
although some locally breezy north winds are likely. The next
system will be quick on its heels, with an elongated N-S vort
moving through the area Monday. This should be a drier system than
today`s, although some showers are possible especially over the
Sierra.

Dang

&&


.Extended Discussion (Tuesday through Friday)

Shower activity will continue into Tuesday but diminish by
Tuesday night. Snow levels will rise on Tuesday becoming
4000-5000 ft. Northerly winds will be breezy in the valley with
gusty downslope (easterly) winds along the Sierra on Tuesday as
the system tracks across our region. Ridging will dominate the
west coast again on Wednesday putting our CWA back into a drier
and warmer pattern with light winds through Friday. JBB


&&

.Aviation...

Cold front will move into the region today bringing breezy and wet
weather today into the weekend. Valley afternoon/evening thunderstorms
possible today and Saturday. Bulk of the rain/snow will occur
after 18z this afternoon. VFR conditions this morning with
MVFR/IFR conditions in rain/snow showers and thunderstorms for
afternoon/evening hours. Snow levels will be around 5500 ft today
lowering to around 3500 ft by Saturday. Winds should be breeziest
between 18-00z with gusts in the valley up to 25 kts possible. JBB


&&

.STO Watches/Warnings/Advisories...
winter weather advisory from 1 pm this afternoon to 1 pm pst
saturday above 5500 feet in the west slope northern sierra
nevada...western plumas county/lassen park.

&&

$$








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