Area Forecast Discussion
Issued by NWS Sacramento, CA

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000
FXUS66 KSTO 251700
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
900 AM PST Sun Jan 25 2015

.Synopsis...
Dry weather with areas of night and morning valley low clouds and
fog through Monday. Temperatures expected to remain well above
normal through Monday in fog-free areas. Light precipitation is
possible Tuesday and Wednesday.

&&

.Discussion...
Strong ridge continues over the area with clear skies other than
the footprint of fog and stratus in the Central Valley. Appears
visibilities this morning are lowest in the valley from about
Sacramento north to Red Bluff with several sites reporting less
than 1/4 mile visibility. Dense Fog Advisory has been issued for
this area until 11 AM.

We hold out hope for an earlier fog dispersal today as strong
offshore flow continues (Reno to Sacramento gradient is over 8
mbs), though not quite as strong as yesterday morning, and morning
profiler data indicates the depth of the fog/stratus is several
hundred feet less than Saturday. North valley likely to be
considerably cooler than Saturday as gradients have reversed and
Redding won`t see as much north wind today.

Updates out shortly.

&&

.Previous Discussion...
Strong upper level ridge of high pressure has moved over northern
California this morning. Skies are mostly clear again early this
morning, except for the persistent fog and low clouds across the
Central Valley. North to northeast winds across parts of the area
have steadily weakened, with a light SE wind now being favored
across much of the Valley. This is helping to push the fog and low
clouds northward, and it wouldn`t be surprising to see some fog
reach Redding by morning. Visibilities are hovering at around 1/4
mile, which is not as dense as the last several nights.

Fog and low clouds will again be slow to clear out across much of
the Valley today, with many locations struggling to climb out of
the 50s. The Northern Sac Valley and foothills should again warm
up nicely today, with highs in the mid to possibly upper 70s.

The upper ridge will shift east into the Great Basin on Monday,
allowing for some synoptic cooling. Fog should again be prevalent
in parts of the Central Valley however. We should also begin to
see increasing high cloud cover later on in the day as a system
off the Baja California coast moves northward.

The aforementioned system will skirt by the area on Tuesday. This
system is weak at best, bringing little impact to the area
(mostly to the Sierra). Models are now in pretty good agreement,
showing the best chance of precipitation occurring on Tuesday.
The Sierra will likely see some precipitation, with a inch or so
of snow possible above 6000 ft. Parts of the Valley may see a
sprinkle or light shower, but odds don`t look great at this
point.

Showers may linger over the mountains through Tuesday night, with
dry weather expected on Wednesday.

&&

.Extended Discussion (Thursday through Sunday)...
An upper level ridge of high pressure over the Pacific Northwest
and Norcal will bring fair skies and well above normal
temperatures to most of the CWA through the extended period. An
area of surface high pressure moving through the Pacific Northwest
into the northern Great Basin will create mainly north to east
winds over the forecast area with these winds becoming breezy at
times. The tightest surface gradients and therefore the likely
strongest winds are forecast for late Friday on through the
weekend. Northerly winds in the teens are forecast for the valley
during this time with some sustained winds in the 20 mph range
over the Sierra. A weak low pressure system centered off the coast
of Baja will linger there through most of the extended period.
This system may pivot a few light showers up the Sierra bringing a
slight chance of showers over the crest Friday and Saturday
south of Tahoe. Otherwise...this system is not expected to have a
significant impact on the forecast area during the extended period.

&&

.Aviation...
Valley VLIFR/LIFR conditions in fog and low ceilings most of
valley, except KRDD, through the morning hours. The nrn SJ valley
has less fog, but still has LIFR ceilings. Fog/ceilings will erode
from edge, especially the north and west sides by late morning.
LIFR in nrn SJ valley will likely stay into aftn. Clouds tops
012-015 based on visible Sutter Buttes. Winds below 10 knots lower
elevations with NE-E winds gusting to 20 to 35 knots over higher
elevations. JClapp

&&

.STO Watches/Warnings/Advisories...
dense fog advisory until 11 am pst this morning central
sacramento valley...northern sacramento valley...southern
sacramento valley.

&&

$$




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