Area Forecast Discussion
Issued by NWS San Joaquin Valley, CA

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243
FXUS66 KHNX 180943
AFDHNX

Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
243 AM PDT Mon Sep 18 2017

.SYNOPSIS...
Mainly average temperatures are expected for today before a
trough moves through the region by Tuesday morning and lowers
temperatures a little. A second and stronger trough will arrive
Thursday with temps falling even lower, or well below average, and
high elevation precipitation. Breezy to gusty winds will be
possible at times, especially through the favored passes leading
to the coastal and desert areas during Thursday and Thursday
evening.

&&

.DISCUSSION...A weak high pressure ridge will continue for today;
afterward, a trough pattern will prevail for the rest of the
week. Onshore flow will also help to keep temperatures in check
today, so we expect similar or slightly lower highs. Temperatures
rose into the lower 90s in the warmest locations yesterday,
although they are expected to rise into the upper 80s today and
mainly the lower to mid-80s through the next couple of days. A
low pressure system will also pass over northern CA and the
Pacific Northwest tonight into Tuesday, so temperatures will be
noticeably cooler as a more northwesterly flow sets up. Onshore
flow with this first system may bring enough low to mid-level
moisture to produce cloud cover over the west/northwest-facing
slopes, especially in Kern County by late tonight into Tuesday
morning.

The big upcoming weather change is in store for Thursday and into
Friday (just in time to begin Fall) as a strong trough of low
pressure prevails over much of the Western United States. Much
cooler temperatures, or around 15 degrees below average are
expected by Thursday. Daytime highs will struggle to reach above
the mid-70s in the lower elevations. It looks like snow levels
will fall to around 8,000 feet or a little lower over the Sierra
Nevada. Westerly winds will likely pick up over much of the
region, and the strongest winds will develop through and below the
passes and canyons along the west side of the San Joaquin Valley
and the Kern County mountain/desert areas. At this time, it is
possible local advisory-level winds could materialize in the
favored passes. Overall, models have been consistent in the
development of this low pressure trough, especially over the past
couple of days. While this is not an unusual pattern for early
Fall, these will be the coolest temperatures we have seen since
Spring.

As for the weekend, temperatures will gradually warm closer to
average as a ridge of high pressure builds just off the West
Coast. Will keep the forecast dry for this period.



&&

.AVIATION...
Areas of smoke from wildfires will continue to produce MVFR
visibility over the southern Sierra Nevada and adjacent foothills.
Otherwise, VFR conditions can be expected over 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 high.

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...BSO
avn/fw...JEB
synopsis...BSO

weather.gov/hanford



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