Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA

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FXUS66 KHNX 212120

Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
120 PM PST Wed Feb 21 2018

.SYNOPSIS...A cold weather system will drop into Central
California from the north on Thursday and Friday bringing a
chance of low elevation snow to the mountains and foothills
with a slight chance of rain to the San Joaquin Valley.
Additionally, winds will be rather strong over the Kern County
Mountains and Desert areas. High pressure will then rebuild
over the weekend before another cold low pressure area arrives
on Monday.


.DISCUSSION...Mainly sunny skies over the forecast area outside
of the Sierra, where quite a cumulus field has formed in the
afternoon heating. Expect these clouds to dissipate with loss of
sun late this afternoon leaving skies mainly clear over the entire
area tonight. It will be another rather chilly night however high
clouds from the next storm system now dropping south from
Vancouver Island will arrive overnight and keep lows several
degrees warmer than this morning.

Forecast models continue to bring the above mentioned low pressure
system southward and into the area on Thursday with precipitation
progged to begin in the Yosemite area by later in the morning and
then spreading south down the Sierra during the afternoon. As the
vorticity center approaches in the afternoon and evening, lower
elevations will likely see a burst of light rain and elevations
above 1500 to 2000 feet will likely see some light snow. This is a
reinforcing shot of very cold air and ahead of the approaching
cold front, winds will pick up especially over the Kern County
Mountains and Desert areas. MOS guidance for Lancaster and Edwards
suggests wind advisory levels will be achieved during the day and
through the evening and an advisory will be posted accordingly.

Although very cold, the continental polar airmass is dropping
from Western Canada and has limited moisture. Forecast rain and
snow amounts are rather light, however with snow falling at very
low elevations where it is a rare occurrence, any snow may cause
some travel problems. By Thursday evening the front will move in
the Kern County Mountains and winds aloft will align with the San
Emigdio Range west of Interstate 5 and the Tehachapi Mountains to
produce some enhanced precipitation due to orographic lift.
Forecast grids at this time have 1-2 inches of snow possible down
to around 2000 feet on the north and northwest facing slopes with
dusting amounts elsewhere. This scenario, may cause some travel
concerns for the Grapevine if the heaviest snow falls along
Interstate 5 corridor and will be monitored closely to see if any
winter weather advisories are needed. The one area that looks to
remain dry in this pattern is the Kern County Desert where
downsloping winds will likely evaporate any snow that falls over
the eastern slopes of the mountains.

By Friday morning the low pressure area is progged to move rapidly
east with all upslope precipitation coming to an end over Kern
County. With high pressure beginning to rebuild over the area from
the north in the wake of the low exiting, the cold airmass and
lighter winds on Friday night and Saturday morning will set the
stage for another round of very cold lows. Current forecast grids
suggest lots of upper 20s in the agriculturally sensitive San
Joaquin Valley thus interests should monitor the weather and take
protective action if necessary.

Forecast models keep the area cold, but dry on Sunday then bring
yet another southward diving cold Canadian weather system into the
forecast area on Monday and Tuesday. The track of this system as
of today shows some promise of drifting offshore which would
indicate more significant precipitation amounts but we will see.
High pressure is then progged to rebuild by the middle of next
week however the flow remains northerly and will be cool.


Mountain obscurations over the Southern Sierra Nevada after 18z Thu.
Otherwise VFR conditions expected across the remainder of the
Central CA Interior during the next 24 hours.





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 for additional information
an/or to provide feedback.


.HNX Watches/Warnings/Advisories...
Wind Advisory from 10 AM to 10 PM PST Thursday CAZ095-098-099.



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