Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA

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FXUS66 KHNX 181758
AFDHNX

Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
958 AM PST Thu Jan 18 2018

.UPDATE...Extended Dense Fog Advisory for San Joaquin Valley
through Noon.

&&

.SYNOPSIS...
A system will move through the region beginning today increasing
chances for precipitation through Saturday and bringing cooler
temperatures. Dry conditions will return late saturday through
Sunday. Precipitation chances will again be increased beginning
Monday.

&&

.DISCUSSION...We extended Dense Fog Advisory for the San Joaquin
Valley through Noon today, as areas of dense fog and low clouds
are expected to remain for next couple of hours. There are some
visibility reports at 1/8 mile as of 10 AM, and a few locations
may still be a little lower. The low pressure system continues to
slowly move southward over northern California today and is
expected to arrive in our forecast area by the afternoon.
Otherwise, low clouds will persist until the arrival of this
system.

&&

.PREV DISCUSSION...
The San Joaquin Valley fog pattern in place the last several days
will be interrupted with a system moving into central California
beginning today. This will not be a blockbuster of a storm,
however it will bring the region some needed precipitation. The
majority of the precipitation will fall over the higher elevations
of the Sierra Nevada as the main drive will be orographical in
nature. As the westerly flow to the south of the low pressure
system centered over northern California moves southward the
moisture streaming into the system will begin to first drop in the
highest elevations near Yosemite. Winds will be gusty above 6000
feet. Snow levels will begin very high around 9500 feet today and
will drop to around 5000 feet by Saturday morning as the trough
moves southward. Snowfall will be moderate with many locations
above 6000 feet seeing 5 to 10 inches and localized amounts of
around a foot will be possible. Especially near the crest areas.
Mountain snowfall will trend less the further south you go along
the ridge. Therefore opted to just include the areas from Yosemite
to Tulare county in the Winter Weather Advisory that is in place
from 10 AM today until 4 AM Saturday. Precipitation across the SJV
will remain on the light side and amounts less than a quarter of
an inch will be the rule rather than the exception.

The main question with the upcoming system will be how far south
the trough will drop. This is where the forecast becomes tricky as
if the low moves eastward quicker than expected the Kern County
mountain areas may not see much. Therefore, the bust potential is
high for this part of the forecast. We have held off on hoisting
any products for the meantime and will allow the day shift a
chance to monitor and fire when it sees the whites of its eyes. If
the storm moves further southward, snowfall in the higher
elevations of the Kern County mountains will be possible and could
make a mess of the Grapevine and Tehachapi passes.

A break in the action will take place on Sunday when chances will
once again be increased beginning Monday as another weak system
skirts the area. Amounts at this time are expected to be on the
light side.
&&

.AVIATION...
Widespread IFR and LIFR conditions until 19Z today. Afterward, areas
of MVFR conditions in clouds and mist/haze with patches of IFR
conditions persisting over the San Joaquin Valley. VFR/MVFR
conditions over the higher terrain of the Sierra Nevada will become
IFR with mountain obscuration in clouds and precipitation after
00Z Friday. Elsewhere, VFR conditions will prevail during the next
24 hours.

&&

.AIR QUALITY ISSUES...
On Thursday January 18 2018... Fireplace/Wood Stove Burning
Status is: No Burning Unless Registered in Fresno... Kern...
Kings... Madera... Merced and Tulare Counties. Further information
is available at Valleyair.org

&&

.CERTAINTY...

The level of certainty for days 1 and 2 is high.
The level of certainty for days 3 through 7 is medium.

Certainty levels include low...medium...and high. Please visit
www.weather.gov/hnx/certainty.php for additional information
an/or to provide feedback.

&&

.HNX Watches/Warnings/Advisories...
Winter Weather Advisory until 4 AM PST Saturday ABOVE 6000 FEET
FOR THE CAZ096.

Dense Fog Advisory until noon PST today CAZ089>092.

&&

$$

public...Andersen/BSO
avn/fw...DCH
synopsis...Andersen

weather.gov/hanford


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