Heat in California, June 23 to 27, 2020

Name: Heat in California, June 23 to 27, 2020
Start: 2020-06-23T10:00
End: 2020-06-27T19:00
Location: California

June 23 to 27, 2020 · NWS HNX · 11 events in 11 counties and zones

The toll

Deaths: 1
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.

A large upper ridge built into central California on June 22 and strengthened over the area on June 23 resulting in widespread triple digit heat across the San Joaquin Valley between June 23 and June 27. Afternoon highs in the valley ranged between 100 and 104 degrees at most locations between June 23 and June 26 and were mainly between 104 and 108 degrees on June 27 before temperatures cooled on June 28 and 29 following the passage of a strong cold front. At least one fatality could be attributed to the heat as a 27 year old man working on the Fresno State Universtiy water tower was overcome by heat stroke on June 25.

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 Jun 23, 1:45 AM PST, 8 hours 15 minutes earlier.

Area forecast discussion, Jun 23, 1:45 AM PST, 8 hours 15 minutes before

Area Forecast Discussion
National Weather Service Hanford CA
245 AM PDT Tue Jun 23 2020

.SYNOPSIS...
A heat wave will impact Central California today through
Saturday. High temperatures will be above the century mark
in the San Joaquin Valley, lower foothills and the Kern
county desert each day through the period. A cooling trend
will occur Sunday into early next week accompanied by locally
gusty winds.  Isolated afternoon thunderstorms are possible
near the Sierra crest today through Thursday.

&&

.DISCUSSION...This first week of Summer will certainly live up to
its reputation over the central California interior. It's nothing
terribly exceptional for this time of year. Marine stratus is
hugging the central California coast in its typical "June Gloom"
fashion...That's just one indicator that the interior valleys are
in for a hot day. It's only going to get a little hotter in the
days ahead as a strong upper level ridge of high pressure remains
in control. Although this ridge splits into two pieces later this
week with one center over the Eastern Pacific and the other over
northern Baja, the ridge will remain in control through Saturday
and keep temperatures a good 7 to 12 degrees above normal over the
CWA. That means triple digit heat will be commonplace each and
every afternoon through Saturday in the San Joaquin Valley, lower
foothills and the Kern County desert.

This will undoubtedly be our longest stretch of triple digit heat
yet this year. Although we're not expecting high temperature
records to be broken during this hot spell, its longevity will
stress heat sensitive individuals as the week progresses. A heat
advisory is in effect, accordingly, for the San Joaquin Valley and
Sierra foothills through Saturday. Temperatures will be especially
slow to cool in the urban areas each night and will drop no lower
than the 70s for the remainder of this week. Thermometer readings
could top 105 degrees in the hottest locations of the valley and
desert this week as well. A buildup of cumulus clouds near the
Sierra crest during the next few afternoons could grow into
isolated thunderstorms, so hikers in the back country should keep
this in mind and be prepared to seek shelter where skies turn
threatening.

Relief from this heat wave, thankfully, is on the horizon. A
noticeably cooler airmass will be swept into the CWA later this
weekend in the wake of a dry cold frontal passage Sunday. The
models forecast a rather deep upper level trough to settle
southward out of western Canada in the 5 to 7 day period. As a
closed low positions itself over the Pacific Northwest early next
week, it will produce a robust onshore flow across central
California. Gusty westerly winds could materialize as early as
Saturday evening through and below the coastal ranges and the Kern
county mountain passes. Gusty winds will likely persist in these
regions through Monday. High temperatures Sunday will finally
return to seasonable levels. Further cooling Monday will bring
afternoon temperatures to several degrees below normal with little
change in high temperatures next Tuesday. If the marine layer deepens
significantly along the central coast by then, high temperatures in
the San Joaquin valley and lower foothills may be no higher than the
mid 80s early next week.

Until then, however, residents in the valley, lower foothills and
desert should keep heat safety tips in mind. If you have to be
outdoors during the hottest part of the day, wear a hat, sunscreen
and light colored, loose fitting clothing and, most importantly,
stay hydrated!

&&

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

&&

.AIR QUALITY ISSUES...
On Tuesday June 23 2020... Unhealthy for sensitive groups in
Fresno... Kern 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...
Heat Advisory from noon today to 8 PM PDT Saturday for
CAZ180>191.

&&

synopsis...Durfee
public/aviation/fw...Durfee
PIO/IDSS...Molina

weather.gov/hanford