Dense Fog in California, December 5 to 7, 2016

Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
215 PM PST Mon Dec 5 2016

.SYNOPSIS... A cooler airmass will push into the area through
midweek, but dry conditions will prevail through Wednesday
afternoon. A low pressure system will spread precipitation into
the area by Wednesday Night with better chances of rain and
mountain snow on Thursday and Friday. Another system will bring a
chance of precipitation to the area on Sunday.

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.DISCUSSION...The Eastern Pacific ridge that had prevailed over
our area retrograded westward overnight as a cold upper low has
dropped into the PAC NW. This resulted in increased high clouds
for our area today. Some fog formed in the valley overnight, but
the fog lifted into a stratus deck which has persisted into the
afternoon in a line from northwestern Kern County northward to
eastern Merced County although visible imagery is indicating that
the stratus deck is finally dissipating.

Meanwhile the low is progged by the 12Z WRF to drop into the
eastern Great Basin on Tuesday. Moisture from this system will
remain well to the north of our area, but it will heal push some
cooler air into our area and bring enough mixing to inhibit
widespread fog formation in the San Joaquin Valley. Some patchy
frost is possible in the San Joaquin Valley on Wednesday morning
but increased cloud cover by Wednesday Night will keep
temepratures in the valley above the freezing mark on Thursday
morning.

The models have been consistently trending faster with the arrival
of the deeper moisture and precipitation into central CA on
Wednesday Night and have therefore increased precipitation
chances and sky cover for Wednesday Night as chances of
precipitation will be possible from Fresno County northward. Snow
levels will range from 5000 to 6000 feet on Wednesday Night, but
are expected to rise up to around 8000 feet by Thursday as sub-
tropcial moisture get pulled up into Central CA as a strong upper
low approaches the PAC NW coast. Additional shortwave energy is
expected to push through Norcal through Friday evening which will
keep a possibility of precipitation going for our area with the
exception of the Kern County Deserts. While confidence has
improved for the potential of precipitation for our area most
noticeably from Fresno County northward, there is still a lot of
uncertainty dealing with how far south the precipitation band will
extend and with regard to how much precipitation our area will
receive. At this time the RFC QPF progs are indicating up to an
inch and a half of liquid precipitation between Wednesday Night
and Friday Night for Yosemite Park with lesser amounts further
south in the Southern Sierra Nevada. The central San Joaquin
Valley is progged to valley is progged to pick up some rainfall as
well with up to half an inch in Merced County and a quarter inch
of rainfall near Fresno. Further south not much rainfall is
anticipated with up to around a tenth of an inch progged for the
south San Joaquin Valley. This is subject to change based on how
far south the deeper moisture aligns itself later this week and
some uncertainty still remains.

Shortwave ridging is progged for Saturday although a few showers
cannot be ruled out. Another shortwave is progged to push through
Norcal on Sunday and bring chances of precipitation to our area.
Ensemble means are indicating the storm track shifts further north
early next week so we are anticipating drier conditions by next
Monday.

&&

.AVIATION...Local areas of IFR/MVFR visibilities due to haze,
fog, and low stratus near Merced through early Monday afternoon.
Otherwise, VFR conditions can be expected across the central
California interior during the next 24 hours.

&&

.AIR QUALITY ISSUES...On Monday December 5 2016... Fireplace/Wood
Stove Burning Status is: No Burning Unless Registered in Fresno...
Kern... Kings... Madera 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...NONE.

&&

public...DS
avn/fw...Rowe
synopsis...DS

weather.gov/hanford