Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA

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FXUS66 KHNX 181247
AFDHNX

Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
441 AM PST Sun Feb 18 2018

.SYNOPSIS...A southward moving cold front will bring an
unseasonably cold air mass into the central California interior
by this evening. Blustery winds will accompany the change to
colder weather this afternoon through Monday and snow showers are
possible in the mountains and foothills by this evening. Below
freezing temperatures are likely in the San Joaquin Valley Tuesday
morning and Wednesday morning. Colder than normal weather will
continue for the remainder of the week.

&&

.DISCUSSION...Our long spell of mild, Springlike weather will
come to an abrupt end later today. Although the cold front that
heralds the arrival of an unseasonably cold air mass will be
moisture starved initially, it will blast southward through
central California later this afternoon on the heels of a strong
northerly jet originating in Western Canada. It`s first impacts
will be strong, gusty winds in the wake of this front which will
gust to 55 mph or locally higher through and below the Kern
county mountain passes later today and tonight. The upper level
storm that trails behind this Arctic front will settle southward
into the Great Basin tonight and Monday (Washington`s Birthday).
While the trajectory of this low as an inside slider would favor
a relatively dry weather scenario for us, there will be at least
one or two upper level disturbances in the northerly flow aloft
that will produce some instability showers over mainly the
higher terrain tonight through Monday. That`s where the second
impact comes into play...very low snow levels, which means any
precip that falls will be in the frozen form down to elevations
as low as 1500 feet tonight into Monday evening. Although QPF
amounts will be light, there could be a dusting to as much as
an inch or two of snow accumulating down to this elevation,
and that`s a big deal...enough to warrant a winter weather
advisory in the Sierra foothills. Similar amounts could fall
to and below pass level in the Kern county mountains tonight
through Monday evening and could seriously impact travel over
the Grapevine, through all of the passes and on secondary
roads. To make matters worse, brisk winds will also continue
through this region and pose an additional hazard to the
snow and ice. A Winter weather advisory was also launched for the
Kern county mountains accordingly. If motorists have travel plans
through the Grapevine this weekend, best to do so before sunset
and before wintry weather moves in later this evening.

By Monday night, winds will tame considerably across much of
the CWA and skies will be clearing in the mountains and be clear
elsewhere. This will set the stage for a hard freeze in the San
Joaquin Valley early Tuesday morning. We`re pretty confident
that minimum temperatures will be below 28 degrees in several
valley locations before daybreak Tuesday, which at this time
appears as though it will be the coldest morning in this spell
of unseasonably cold weather. Obviously this will not only
have an impact on frost sensitive plants, but pets and pipes
as well. Otherwise, the overall weather pattern will remain
colder than normal as the mean upper level trough anchors itself
over the Great Basin through the week. The models are now
forecasting additional short wave impulses embedded in the
north to northwest flow aloft to trek through the CWA next
week which will greatly complicate sky cover and ultimately
overnight min temps. If mid level moisture advects into
central California in the northwesterly flow aloft, it would
mitigate the threat of freezing temperatures in the San Joaquin
Valley Wednesday morning and Thursday morning. But confidence
is really low during this period, so we will have to monitor
the upper level pattern for any upstream ripples. At this point,
we are keeping the Freeze Watch for the San Joaquin Valley in
effect for those particular mornings.

In summary, it looks like colder than normal weather will grip the
central California interior for much of the next 7 days. I`m
one meteorologist that`s going to spend some time today looking for
the winter coat and gloves that I packed away when the first of
those many balmy days occurred early this month.

&&

.AVIATION...
Strong surface winds with gusts to 45 knots developing after 22Z on
Sunday across the Kern County Mountains and Deserts. IFR conditions
in Blowing Dust will be also be possible across the Mojave Desert
after 22Z Sunday. Increasing clouds this afternoon with clouds and
showers obscuring the mountains after 00Z 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 from 9 PM this evening to 3 AM PST
Tuesday CAZ095.

Wind Advisory from 3 PM this afternoon to 9 PM PST this evening
CAZ095.

Winter Weather Advisory from 6 PM this evening to 4 PM PST
Monday CAZ093-094.

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

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

Wind Advisory from 3 PM this afternoon to 4 PM PST Monday
CAZ098-099.

&&

$$

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

weather.gov/hanford


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