Dense Fog in California, December 22, 2016

Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
420 AM PST Thu Dec 22 2016

.SYNOPSIS...A storm system over northern Baja will bring
light rain to the Kern County mountains and desert this
morning followed by clearing skies later today as the storm
moves into Arizona. Otherwise, dry weather can be expected
across much of central California through tonight. A cold
Pacific storm will bring rain and mountain snow to the district
Friday through Saturday.

&&

.DISCUSSION...A closed low currently situated off the coast of
northern Baja brought subtropical moisture much farther northward
than originally anticipated during the past 24 hours. While the
deepest moisture stayed south of our CWA, the storm brought
measurable rain to the Kern County mountains and desert. Rain
amounts so far have ranged from just a few hundredths to nearly
a quarter of an inch in this region. This low is progged to open
up and lift into Arizona later today, but until it does so, this
system will continue to bring light rain to the Kern County mtns
and desert through at least this morning. Skies will gradually
clear in these areas this afternoon into early this evening as
drier air infiltrates Kern County. Higher clouds associated with
this low currently extend as far north as Fresno County and will
help mitigate dense fog development in the southern San Joaquin
Valley through the post dawn hours today. Otherwise, a short
wave ridge aloft will build into central California during the
next 12 to 18 hours and remain in control through tonight.

The next storm upstream is handled very well by the models and
will begin to impact our CWA Friday morning, first with an
increase in clouds followed by wet weather generally north of
Kern County Friday afternoon. As the storm approaches, a healthy
barrier jet will become established along the east side of the
San Joaquin Valley by midday Friday. Before the onset of rain,
southeast winds will become rather gusty in the north valley
Friday, especially in Merced County. A powerful 110+ knot jet to
the south of this storm will move over the central California
interior Friday afternoon and produce generous lift and healthy
orographic precipitation along the west slopes of the Sierra
which will continue through Friday night. A drenching rain is
expected in the lower elevations from this storm system, the
brunt of which will occur Friday evening into Saturday morning.
As the upper level trough associated with this storm sytem moves
inland over central California during the midday hours Saturday,
steady precip will turn showery.  Snow levels will fall rather
abruptly in the mountains, too, down as low as 2500 feet in the
Sierra and 3500 feet in the Tehachapi mountains by Saturday
morning. This will obviously significantly impact holiday
travelers through the Kern county mountain passes Saturday
where accumulating snow could produce potentially long delays
and very slick road conditions. Otherwise, this will be a banner
storm for heavy snow in the Sierra with up to 3 feet possible
over the highest elevations by late Saturday. Residents in the
Sierra foothills above 2500 feet could wake up to a light dusting
of snow Saturday morning. Rain in the lower elevations could be
heavy enough to cause localized flooding Friday evening and
night. Additionally, the atmosphere may become unstable enough
for the development of isolated thunderstorms with small hail
in the San Joaquin valley and adjacent foothills Saturday.
Confidence was too low to add thunderstorms to the valley forecast
this morning, but it is something we'll have to monitor during
the first part of this weekend. Saturday will also be blustery
with brisk westerly winds possibly gusting to advisory levels in
the Kern County mountains and desert.

The models shift the upper level trough eastward into the Great
Basin Saturday evening. Residual snow showers will occur in the
upslope regions of the CWA during this time while the rest of
the district begins to dry out. Christmas Day will be dry,
however clouds could linger into the midday hours along the
west facing slopes of the Sierra and the north facing slopes of
the Tehachapi mountains.

There is much better model agreement with the storm that follows
early next week, which now looks as though it will remain offshore
and hug the California coast Sunday night through Monday. Unless
there is a slight shift eastward in the track of this storm, most
if not all of the central California interior will remain dry
through Monday. Otherwise, the storm will bring little more than
some mid and high clouds to the district.

In the 5 to 7 day period, the models forecast an eastpac ridge to
build into the Golden State. Dry weather will prevail during this
period with the return of night and morning fog in the San Joaquin
Valley and otherwise milder afternoon temperatures, especially
over the higher terrain.

&&

.AVIATION...
Areas MVFR and local IFR/LIFR conditions in fog and mist until 20z
Thursday in the San Joaquin Valley and again from 06z through 12z
Friday. MVFR in ceilings and visibility in showers across the Kern
County desert area through 00z Friday. Potential mountain
obscurations in precipitation across the Kern County mountains
through 00z Friday. Otherwise VFR conditions will prevail over the
central California interior during the next 24 hours.

&&

.AIR QUALITY ISSUES...
On Thursday December 22 2016... Unhealthy for sensitive groups in
Fresno... Kern... Kings... Madera and Tulare Counties.
Firepalce/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 Storm Warning from 10 AM Friday to 4 PM PST Saturday
CAZ096-097.

&&

public...Durfee
avn/fw...JDB
synopsis...Durfee

weather.gov/hanford