Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA

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957
FXUS66 KHNX 061230
AFDHNX

Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
430 AM PST Tue Dec 6 2016

.SYNOPSIS...
Areas of fog will dissipate across the San Joaquin Valley this
morning. Otherwise, dry conditions will prevail through
Wednesday. A low pressure system will spread precipitation into
the area with a chance of rain and mountain snow Thursday into
Friday. An unsettled pattern continues through the weekend with
another chance of precipitation north of Fresno early next week.

&&

.DISCUSSION...
Fog has become dense in parts of the San Joaquin Valley early
this morning, especially along highway 99. The densest fog as of
4 am was in the Fresno area where visibility was down to 1/8 mile
at the airport. As the sun begins to rise, the dense fog may
expand with many areas experiencing very low visibility. Thus a
dense fog has been issued for the San Joaquin Valley until 10 am.

&&

.PREV DISCUSSION... /issued 306 AM PST Tue Dec 6 2016/

DISCUSSION...
A low pressure system moving through the Pacific Northwest brought
high clouds over central California Monday night. Despite the high
clouds, there was enough low level moisture for fog to form in the
San Joaquin Valley. The fog may be dense in a few areas this
morning. The fog is expected to burn off this morning with scattered
high clouds expected through the afternoon as the low drops into
the Great Basin. As it does so, winds will become gusty across the
mountain and desert areas of Kern County today through this
evening. At this time, it looks like winds will remain below
advisory criteria.

This system will also push some cooler air into our area and will
less high cloud cover tonight, some patchy fog and patchy frost
are possible in the San Joaquin Valley by Wednesday morning.

The northern jet stream will remain active this week with a low
pressure system in the Gulf of Alaska sending a series of
shortwaves into the Pacific Northwest and Northern California.
There are quite a bit of model differences with the timing of the
shortwaves coming into California. But models are in good
agreement that the first of these waves will move into Northern
California Wednesday, with some precipitation making it south into
Central California Wednesday night mainly north of Fresno. As
this wave continues to move inland, the precipitation will spread
a little farther south on Thursday, but still remain north of Kern
County. A second wave will keep the precipitation chances going
Thursday night into Friday. The best chance of significant
precipitation will be from Merced to Yosemite. Snow levels will
begin around 6000 feet Wednesday night, but will rise to around
8000 feet by Thursday.

There is still a lot of uncertainty regarding how much precipitation
our area will receive. At this time the RFC QPF progs are
indicating up to around an inch and a half of liquid precipitation
between Wednesday Night and Friday Night for Yosemite National Park
with only a quarter of an inch by the time you move south to
Sequoia/Kings Canyon National Park. In the San Joaquin Valley,
rainfall amounts are expected to range from around a half an inch
in Merced County to 2 to 3 tenths of an inch near Fresno and only
a few hundredths in northern Kern County. Confidence in these
amounts is still fairly low and they are subject to change based
on how far south the deeper moisture aligns itself later this
week.

Models are having much more difficulty with the timing of systems
after Friday. The GFS brings another system in to California
Friday night into Saturday morning, while the ECMWF holds it off
until Saturday and Saturday night. Have kept low chance pops going
through the weekend due to this uncertainty. Ensemble means are
indicating the storm track shifts a bit further north early next
week, but with an atmospheric river type pattern setting up. This
would bring precipitation across northern California Monday and
Tuesday, with the possibility of some rain spreading across the
northern part of the district from Merced to Yosemite.

&&

.AVIATION...
Across the San Joaquin Valley, areas of IFR visibilities due to mist
with local LIFR/VLIFR in fog through 18Z Tuesday. Areas of MVFR in
haze after 18Z, then local IFR/LIFR in mist/fog after 06Z Wednesday.
Otherwise, VFR conditions can be expected elsewhere across the
central California interior during the next 24 hours.

&&

.AIR QUALITY ISSUES...
On Tuesday December 6 2016... 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 medium.
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...
Dense Fog Advisory until 10 AM PST this morning CAZ089>092.

&&

$$

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