Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA

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628
FXUS66 KHNX 182255
AFDHNX

Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
255 PM PST Sat Nov 18 2017

.SYNOPSIS...
Onshore flow across the area this weekend will provide seasonal
temperatures and dry conditions along with the possibility of
valley morning fog. Weak cold front will clip Yosemite on Monday
with a few showers possible. Upper level ridge will build in with
a warm up through next weekend as temperatures reach above normal
levels and the area remains dry.

&&

.DISCUSSION...
Upper level disturbance from earlier this week continues to push
across the Midwest as higher pressure builds onto the West Coast.
Due to mixing of the atmosphere from strong winds aloft (as
observed at Vandenberg and wind profilers from across the valley)
fog had a very difficult time developing this morning over the San
Joaquin Valley. Yet, the strong winds did provide the south-end
and east- side of the valley with upslope low clouds that
restricted visibility to a few hundred feet. Current satellite and
surface observations show that skies have just about cleared out
with a few patches remaining in the Porterville area. Therefore,
with the clear skies this afternoon, radiational cooling will
likely support better fog development this evening with a better
potential toward Sunday morning. Yet, short range meso-scale
models are not very aggressive at producing widespread valley fog
overnight and only form patches along the Highway 99 corridor from
Atwater to Delano. Will take a more aggressive tone and expect
wider coverage and spot that may reach less then 2 miles.

Another concern in the short term will be the minimum temperatures
across the Mojave Desert. Saturday morning saw a few spot reach
the freezing mark (mainly around Edwards AFB). As dew point
temperatures continue to drop today to values below 32 degrees,
the potential for freezing will increase tonight. At this point,
will expect patches of temperatures ranging from 28 to 32 degrees
over areas mainly east of Highway 14 at Edwards and
Inyokern/Ridgecrest. Will message out the potential for frosty
conditions from 4 AM PST to around 9 AM PST on Sunday. Models then
show a more defined ridge pattern over the West Coast on Sunday
which has been steering the next storm further and further
northward with each successive run. Therefore, scaled back on the
precipitation potential across Central California for the Monday
time frame. While the Yosemite area will receive additional
orographic lift during the event, very weak lift will exist
elsewhere for any chances of measurable precipitation. This
scenario agrees well with both probabilistic and deterministic
models.

In the long term, models continue to improve on a strong ridge
pattern solution for the Thanksgiving day period. Model
temperature statistics now indicating max temperature in the lower
to mid 70s across the San Joaquin Valley during Thanksgiving Day.
The only problem with having such a strong ridge will be the
stable atmosphere below it. This will lead to persistent episodes
of possible dense fog across the valley. Even with limited
precipitation from the latest storms, the ridge pattern will lead
to a growing inversion that will trap to necessary ingredients for
persistent fog into next weekend.

&&

.AVIATION...
Local IFR in fog across the San Joaquin Valley with a possibility
of LIFR conditions from 08Z until 18Z Sunday. 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...
None.

&&

$$

public...Molina
avn/fw...BSO
synopsis...Molina

weather.gov/hanford



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