Dense Fog in California, December 2, 2017

Area Forecast Discussion...UPDATED
National Weather Service San Joaquin Valley - Hanford CA
310 PM PST Fri Dec 1 2017

...UPDATED AIR QUALITY SECTION...

.SYNOPSIS...Dry weather and near normal temperatures will
continue over the area through Saturday. Sunday through Tuesday
will be cooler in the wake of a cold frontal passage Saturday
night.
&&

.DISCUSSION...Split zonal westerly flow prevailing over the
western CONUS with central CA in between the two storm tracks with
shortwave ridging prevailing over the region. Some patchy dense
fog formed this morning over the San Joaquin Valley which
dissipated by 1000 am. Hazy conditions have prevailed in the San
Joaquin Valley as a result of inversion conditions while some thin
high clouds associated with northern stream energy to our north
are pushing east across our area today as noted from satellite
imagery. Temperatures are trending upward slightly from yday as
some warming is taking place ahead of the system that is progged
to push through the PAC NW and Norcal on Saturday.

12Z WRF indicating the upper low will push into the PAC NW on
Saturday afternoon then slip southward into CA by Saturday Night.
Meanwhile, skies will remain mainly clear across our area except
for some thin high clouds until late Saturday so another night of
patchy fog is possible in the San Joaquin Valley where light
winds will also prevail, but whatever fog which does form should
burn off by late morning as the incoming system will provide for
some mixing.

The deeper moisture associated with this system is still expected
to clip the Yosemite Park area Saturday Night and early Sunday,
and will therefore keep mention of a slight chance to low chance
of precipitation for Yosemite Park for this time frame. Some
mid/high clouds will push through the remainder of our CWFA on
Saturday Night and Sunday and inhibit fog formation in the san
Joaquin Valley on Sunday morning.

WRF indicating a secondary shortwave dropping southward behind
the departing trough on Monday which will push a cold front
through our area. RH progs are indicating that this system is
moisture starved and will not produce any precipitation in our
area. However, it will provide for a brief period of gusty winds
Sunday Night and early Monday. Colder air will settle into our
are behind the front on Monday and with an offshore flow and clear
skies prevailing early next week, would not be surprised to see
some frost in the San Joaquin Valley on Monday morning and even
more so on Tuesday morning as winds become light on Monday Night.

The ensemble means are in good agreement in building a large dry
upper ridge off the western CONUS coast early next week then shift
the ridge inland slightly toward the middle of next week. This
will keep our area free of precipitation for the medium range
period and allow for some airmass moderation with slightly milder
temperatures. By late next week, a return of night and morning fog
is possible in the San Joaquin Valley as the prevailing airmass
warms and inversion conditions return.

&&

.AVIATION...Areas of MVFR in mist and haze with local IFR/LIFR
visibility in fog will occur in the San Joaquin Valley from 06z
through 18z Saturday. Otherwise, VFR conditions will prevail
over the central CA interior during the next 24 hours.

&&

.AIR QUALITY ISSUES...On Saturday December 2 2017... Unhealthy
for sensitive groups in Fresno... Kings and Tulare Counties.
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...NONE.

&&

public...DS
avn/fw...BSO
synopsis...DS

weather.gov/hanford