Heat in California, May 31, 2021

Name: Heat in California, May 31, 2021
Start: 2021-05-31T10:00
End: 2021-05-31T19:00
Location: California

May 31, 2021 · NWS HNX · 11 events in 11 counties and zones

A very strong upper ridge built inland into California during the Memorial Day holiday weekend resulting in temperatures rising to near record levels across the San Joaquin Valley and the West Side Hills by Memorial Day (May 31). Several stations across these areas had maximum temperatures exceed the century mark on May 31 prompting the issuance of Excessive Heat Warnings and the opening of…

The toll

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 11

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS HNX wrote it up.

What forecasters said that day

The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Hanford, CA wrote its last area forecast discussion before the first event at May 31, 4:26 AM PST, 5 hours 34 minutes earlier.

Area forecast discussion, May 31, 4:26 AM PST, 5 hours 34 minutes before

Area Forecast Discussion
National Weather Service Hanford CA
526 AM PDT Mon May 31 2021

.SYNOPSIS...Dangerously hot temperatures will impact much of
interior central California today through Wednesday. Temperatures
will be as much as 15-20 degrees above normal with some locations
in the San Joaquin Valley reaching or exceeding record highs.
temperatures will be lower for the latter part of the week into
early next week but will still be around 8 to 14 degrees above
normal for early June.

&&

.DISCUSSION...
High temperatures Sunday were up a few degrees from the previous
day as a shortwave trough continues to move away and a high
pressure ridge edges in from the Pacific. The ridge will continue
to build over the region for the next couple of days and
temperatures will climb further today through Tuesday. Blended
model guidance predicts high temperatures in the San Joaquin
Valley and adjacent foothills and west side hills will jump as
much as 8 to 12 degrees from yesterday's highs and rise a couple
of more degrees Tuesday. This will lead to triple digit readings
at most locations in this area today and Tuesday, with records
reached or exceeded at some locales. This is the first significant
heat event of the year and has prompted am Excessive Heat Warning
for today and Wednesday as widespread areas of moderate to high
heat risk will exist in these temperatures.

A developing northeast Pacific trough will begin to weaken the
ridge by Wednesday and high temperatures will start a downward
trend. This downward trend will start slowly, with temperatures
Wednesday only down a degree or so from Tuesday, except around
Merced County where a few more degrees of cooling is expected. A
Heat Advisory will be in effect for this "cooler" area Wednesday,
while an Excessive Heat Warning will be in effect Wednesday for
the remainder of the currently warned area.

Model solutions begin to diverge after Wednesday with the exact
details of the evolution of the trough, but generally indicate
some version of a closed low developing off the California coast
while shortwave energy rotates through to our north. In this
pattern, our triple digit highs will come to an end, as guidance
gives around an 80 to 100 percent chance that highs will be less
than 100 degrees. Although temperatures will be lower for the end
of the week into early next week, they will still run around 8-14
degrees above normal for early June.

Conditions will be generally dry through the period, except
blended model guidance suggests a slight chance for some showers
and possibly a few thunderstorms over the Sierra Thursday.

&&

.AVIATION...VFR conditions will prevail across the Central CA
interior through at least the next 24 hours.

&&

.AIR QUALITY ISSUES...
On Monday May 31 2021... Unhealthy for sensitive groups in
Fresno... Kern... Kings and Tulare Counties and Sequoia National
Park and Forest.
Further information is available at Valleyair.org

&&

.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.html for additional information
an/or to provide feedback.

&&

.HNX WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning from noon today to 8 PM PDT Tuesday for
CAZ179>191.

Heat Advisory from noon to 8 PM PDT Wednesday for CAZ180-181-190.

Excessive Heat Warning from noon to 8 PM PDT Wednesday for
CAZ179-182>189-191.

&&

public...JEB
aviation....JEB

weather.gov/hanford