Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA

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256
FXUS66 KHNX 191302
AFDHNX

Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
455 AM PST Mon Feb 19 2018

.SYNOPSIS...Unseasonably cold weather will continue over the
central California interior through at least Wednesday in the
wake of a storm system over the Great Basin. Temperatures
will slowly moderate later this week. Isolated snow showers
will occur over the foothills and mountains today and could
return to the high Sierra during midweek.

.DISCUSSION...Cold air continues to advect southward over the
central California interior early this morning and snow levels
are falling accordingly. As of this writing, snow levels range
from about 2000 feet over the northern part of the CWA to btwn
3500 and 4500 feet in the Tehachapi mountains. Composite radar
is currently detecting spotty light precipitation over the Sierra
and a scattering of instability showers over the coastal waters
where cold air has moved over the relatively warmer waters of
the ocean. Precipitation, albeit light and widely scattered,
will be mostly confined to the mountains today. However, with
unusually low snow levels, local accumulations of a dusting to
an inch or two are possible through early this evening and at
elevations as low as 1500 feet. This not only includes the
Sierra foothills but also the foothill region west of I-5
today where roads wind through the coastal ranges. Most of the
high resolution models pick up on this with spotty light qpf
in these regions. Additionally blustery winds will continue
through and below the Kern county mountain passes into early
this evening. A few RAWS stations reported wind gusts as high
as 80 mph earlier this morning but these are stations in
remote locations. Nonetheless, westerly winds will blow rather
briskly in this region and frequently gust as high as 55 mph
until they finally diminish early this evening. Northwesterly
winds will ramp up over the western third of the San Joaquin
Valley by midday today as the core of the upper level jet moves
over this part of the CWA. This northerly jet will transport
drier air into the central California interior by tonight and
Tuesday, and the advection of this drier air should finally
scour clouds out of the upslope regions of the CWA tonight.
Once valley and desert winds abate early this evening (by or
shortly after sunset), temperatures will drop like a rock.
Thermometer readings are destined to bottom out in the mid
teens to lower 20s in the Kern county desert by daybreak
Tuesday and will end up below the freezing mark for a few
to several hours over much of the San Joaquin Valley.
Definitely a critically cold night ahead for livestock,
pets, outdoor pipes, and lastly valley vegetation which has
experienced an earlier than usual Spring bloom. The nights
that follow do not look to be as cold as tonight, thanks in
part to an increase in clouds, but nonetheless colder than
normal with some frost.

Now to the broader picture. A very deep upper level trough
will be centered over the Great Basin for the next several
days. This will keep the Golden State locked in a prevailing
northerly flow aloft with a continuation of below normal
temperatures through the week. That`s the simple part of
the pattern. What complicates it is the fact that there will
be weak upper level disturbances embedded in the northerly
flow aloft that move southward through the CWA. While each
of these features will be limited on moisture, they will
bring a good amount of mid and high clouds into the central
California interior at times beginning Wednesday. Timing their
arrival and departure will be next to impossible in an otherwise
brisk flow aloft. Otherwise, these systems will bring a slight
chance of generally light precip with their passage. The first of
these systems will move through late Wednesday and bring a slight
chance of light snow to the Sierra. The next disturbance will be
right on its heels and will bring a chance of light precip just
about anywhere over the CWA from late Thursday through Friday.
Afterward, the models forecast more of a zonal flow aloft to become
established over central California with dry weather. Temperatures
will slowly moderate in the 5 to 7 day period.

&&

.AVIATION...
Strong surface winds with gusts to 45 knots will continue across the
Kern County Mountains and Deserts through 00Z Tuesday, with possible
IFR conditions in blowing dust over the Mojave Desert. Increasing
clouds over the region this evening with clouds and showers
obscuring the mountains after 02Z Monday. Otherwise, VFR conditions
will prevail across the Central CA Interior during the next 24
hours.

&&

.AIR QUALITY ISSUES...
None.

&&

.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 Weather Advisory until 3 AM PST Tuesday CAZ095.

Winter Weather Advisory until 4 PM PST this afternoon CAZ093-094.

Hard Freeze Warning from midnight tonight to 8 AM PST Tuesday
CAZ089>092.

Freeze Watch from late Tuesday night through Thursday morning
CAZ089>092.

Wind Advisory until 4 PM PST this afternoon CAZ098-099.

&&

$$

public...Durfee
avn/fw...Bean
synopsis...Durfee

weather.gov/hanford



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