Excessive Heat and Heat in California, September 4 to 7, 2020

Area Forecast Discussion
National Weather Service Hanford CA
358 AM PDT Fri Sep 4 2020

.SYNOPSIS...Dangerous temperatures will impact the central
California interior for the upcoming Labor Day Holiday. Some
locations will be close or slightly above records, especially on
Sunday and Labor Day. Temperatures will slowly decrease by
Tuesday through next Thursday, but will remain above average.
Smoke from surrounding wildfire will continue to plague the area
for at least through Wednesday.

&&

.DISCUSSION...For today, high pressure will continue to slowly
strengthen over the four-corners. Afternoon high temperatures will
slightly increase for the West Side Hills and the Kern county
desert. An Excessive Heat Warning will begin this afternoon for
the Kern desert, where afternoon high temperatures will reach
between 105 to 115 degrees with poor overnight recoveries.
However, I have lower confidence for increasing temperatures in
both the valley and foothills. This is because smoke from the SQF
Complex wildfire will be more dense in these regions, which will
counteract any synoptic warming. This will especially be the case
from Tulare county northward to Merced county. As such, I have
lowered the NBM temperatures a few degrees for these areas.

From Saturday through Sunday, the aforementioned high pressure
over the four-corners will strengthen to an impressive, and very
anomalous 600 decameters. This high pressure will then start to
slightly weaken on Labor Day as a deep trough begins to swing
southward into the northern Great Basin. Temperatures through
Labor Day will ramp up for all locations across the central
California interior. An Excessive Heat Warning will take effect
Saturday afternoon for the West Side Hills, Southern San Joaquin
Valley, Southern Sierra Foothills, and portions of the Kern
County mountains. The Excessive Heat Warning for all areas will
remain in effect until Labor Day evening. Temperatures each day
for these locations will range from 100 to 110 degrees. Low
temperatures will range from 70 to 80 degrees, with urban areas
and foothill locations seeing the poorest overnight recoveries.

On Tuesday the prior mention trough will swing south through the
Great Basin. Synoptic cooling across the region will slowly lower
temperatures each day, but will remain above normal for mid-
september.

&&

.AVIATION...
Areas of MVFR visibility due to haze and smoke can be expected in
the San Joaquin Valley during the next 24 hours. Locally poor
visibility due to wildfire smoke will linger mainly over the
Tulare County mountains. VFR conditions will prevail elsewhere
over the central California interior during the next 24 hours.

&&

.AIR QUALITY ISSUES...
On Friday September 4 2020... Unhealthy in Kern County and Sequoia
National Park and Forest. Unhealthy for sensitive groups in
Fresno... Kings... Madera and Tulare Counties.
Further information is available at Valleyair.org

An Air Quality Alert issued by local Air Pollution Control
Districts is in effect for portions of the central California
interior for smoke due to area wildfires until fires are
extinguished. For details, please see SFOAQAHNX.

&&

.CERTAINTY...

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
www.weather.gov/hnx/certainty.html for additional information
an/or to provide feedback.

&&

.HNX WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning from 1 PM this afternoon to 9 PM PDT
Monday for CAZ198-199.

Excessive Heat Warning from 1 PM Saturday to 9 PM PDT Monday for
CAZ179>191-196-197.

&&

public/avn/fire wx...CMC
PIO/IDSS.............BS

weather.gov/hanford