Scientific Forecaster Discussion
fxus66 khnx 191100
Area forecast discussion
National Weather Service San Joaquin Valley - Hanford California
300 am PST Sat Jan 19 2019
Synopsis...high pressure will strengthen over the area today and
tonight before a fast moving weather disturbance moves through
on Sunday afternoon and Sunday night. High pressure will then
rebuild for much of next week for dry weather.
Discussion...high pressure is currently pushing inland into CA,
but the building ridge is somewhat dirty with overriding mid/high
moisture streaming into norcal and infrared imagery and metars are
indicating mid level clouds are present north of Fresno County.
The mid level moisture and dynamics to our north have inhibited
widespread fog from forming overnight as what had been
anticipated for the San Joaquin Valley. Fog loop imagery is
indicating a narrow strip of fog extending from near Kingsburg
southward to Buttonwillow. There has been a patch of fog near
Tehachapi overnight as well. With fog coverage in the valley not
being as extensive as indicated, we will revisit the dense fog
advisory issued by the day shift on Friday for much of the San
Joaquin Valley later this morning. With clear skies and low level
moisture present in the South Valley would not be surprised if
areas of dense fog form in the south San Joaquin Valley later this
morning. The fog will likely be mixed out by this afternoon with
shortwave energy to our north providing for a mixing mechanism.
This afternoon will likely be mostly sunny and mild from Fresno
County southward while mid/high clouds will be present north of
The ridge is progged to move further inland tonight then break
down on Sunday as a strong low pressure system takes aim at the
Oregon coast. Fog coverage in the valley on Sunday will be less
extensive, but some patches of dense fog will be possible in the
South Valley in the morning. Meanwhile, increased clouds and
precipitation chances will spread southward through California during the
day on Sunday as the low moves inland and pushes a frontal
boundary into our area. A period of light to moderate rain and
higher elevation snow is anticiapted Sunday afternoon through
Sunday night with snow levels expected to be around 7000 feet. The
bulk of the precipitation is expected on Sunday evening and quantitative precipitation forecast
progs are now showing half and inch to an inch of liquid
precipitation for the southern Sierra Nevada from Kings Canyon
northward while a quarter to half and inch is expected further
south in Tulare County. Rain shadowing will keep amounts in the
San Joaquin Valley lower, but a few hundredths to a tenth of an
inch of rain can be expected in much of the valley as well as
across the Kern County mountains.
The cold front with this system is expected to plunge through our
area late Sunday night ands early Monday which will likely
produce strong wind gusts in the normally wind prone area below
the passes in the Kern County mountains and deserts. Cooler
temperatures will be noticed on Monday behind the front and
daytime temperatures in the valley will be closer to seasonal
normals while the snow level lowers to near 4000 feet in residual
upslope showers in the mountains. Upslope clouds might persist
along the south end of the San Joaquin Valley and the valley
facing slopes of the southern Sierra Nevada through Tuesday
morning in some locations.
The medium range models are in good agreement with building a
large high amplitude upper ridge into California on Tuesday and this
feature will keep dry conditions across our area through the
remainder of next week and into next weekend as the ridge persists
across the western Continental U.S.. mostly clear skies and mild temperatures
will prevail across the mountains and deserts while long duration
fog and stratus prevail in the San Joaquin Valley as a result of
strong inversion conditions and light winds.
Aviation...MVFR visibilities in mist should fall to IFR to LIFR
visibilities in mist and fog by 14z at mer, mce, and visible. These
IFR to LIFR visibilities at mer, mce, and visible should persist until
about 17z. MVFR visibilities in mist at fat and bfl until 17z.
VFR conditions will prevail in the central California interior
from late this morning into Saturday night. Areas of fog may form
in the San Joaquin Valley after 08z Saturday night.
Air quality issues...none.
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.Html for additional information
an/or to provide feedback.
dense fog advisory until 11 am PST this morning caz089>092.