857
FXUS66 KSGX 021552
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
852 AM PDT Tue Jul 2 2024

.SYNOPSIS...
A long-duration heat wave will continue inland through at least
the weekend. Friday and Saturday are expected to be the hottest
days for most areas with the only relief from the heat toward the
coast. The marine layer will slow the warming near the coast with
night and morning coastal low clouds spreading into the western
valleys late each night.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

The marine layer deepened and the actual low cloud deck thickened
early this morning. That extended the low clouds as far as Chino.
The clouds will clear efficiently this morning, but the strong
marine inversion could prevent full clearing from some beaches
today. The marine layer will get more shallow for the rest of the
week, with less nocturnal coverage. But the coastal low clouds are
a minor issue. The inland heat warrants most of our attention for
the coming week. A strong upper ridge develops Wednesday just off
the coast and spills into CA and the West Friday and Saturday.
And I do mean strong; heights reach 600 decameters over NorCal
Thursday through Sunday. Friday and Saturday right now appear the
be the hottest days. Heat warnings are in effect in all desert
regions through next Tuesday. Heat Warnings are in effect for
mountains and inland valleys Friday and Saturday. And Heat
Advisories are in effect for inland Orange County and the Santa
Ana Mountains Friday and Saturday. This heat wave will be
significant and long- lasting even for early July. Temps at night
will not cool off much, so the accumulated heat risk will add to
the stress on humans. For added detail on the anomalous nature of
this heat event at Palm Springs, check out the CLIMATE section
below. Max temps today through Thursday will range from 2 to 12
degrees above normal, with the greatest anomalies in the desert.
On Friday and Saturday, the hottest days, max temps will range
from 6 to 15 degrees above normal. That puts Palm Springs up to
122, flirting with the highest temps on record. There are some
hints that the monster ridge weakens slightly next week, but also
some other hints that the excessive heat could persist
relentlessly until further notice.

&&

.AVIATION...
021530Z...Coast/Valleys...Low clouds eroding fairly quickly out of
inland valleys this morning, with bases 800-1600 ft MSL and tops to
1900 ft MSL. Most areas will continue to clear to coast through 18Z
with associated improving VIS. Low clouds returning vcnty coastal
TAF sites 3Z-6Z this evening with similar to lower cigs, eroding
again Wed 15-18Z.

Mountains/Deserts...Mostly clear skies with unrestricted VIS will
continue through this evening. West winds will return to the desert
slopes and through San Gorgonio Pass this afternoon/evening but will
be generally weaker, with most gusts 25 kt or less.

&&

.MARINE...
No hazardous marine conditions are expected through Saturday.

&&

.BEACHES...
A swell of 2-3 feet from 190 degrees with a period of 16-18 seconds
will arrive at SoCal beaches as early as Wednesday morning, peak
Friday and gradually subside next Sunday. This may lead to elevated
surf with breaking wave heights of 6-7 feet, mainly on exposed south
and southwest-facing beaches in Orange County. Rip and longshore
current risks will be high the second half of this week.

&&

.CLIMATE...
This could be an historic heat wave for portions of the lower
deserts in terms of consecutive days of very hot high
temperatures.

For Palm Springs, NBM is forecasting 11+ consecutive days with
high temperatures of 115 or higher, 10+ consecutive days with 117
or higher, and 8 consecutive days with 119 or higher.

The existing records for Palm Springs are 9 consecutive days of
115+ in 2023, 5 consecutive days of 117+ in 1958, and 3
consecutive days of 119+, most recently in 2021.

The all-time record high temperature for Palm Springs is 123,
occurring most recently on June 17th, 2021. NBM has a 14 percent
chance on Friday and 20 percent chance on Saturday of tying the
existing record. NBM has a 7 percent chance on Friday and 8
percent chance on Saturday of breaking that record.

As for daily high temperature records for Palm Springs, NBM has a
69 percent chance on Friday and 78 percent chance on Saturday of
tying or breaking the existing high temperature records for those
dates and a 55 percent chance on Monday.

As for record warm daily minimum temperatures for Palm Springs,
NBM has a 77 percent chance on Friday and 90 percent chance on
Saturday of tying or breaking the existing records.

&&

.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Warning from 11 AM Friday to 9 PM PDT Saturday
     for Riverside County Mountains-San Bernardino County
     Mountains-San Bernardino and Riverside County Valleys-The
     Inland Empire-San Diego County Mountains-San Diego County
     Valleys.

     Heat Advisory from 11 AM Friday to 9 PM PDT Saturday for Orange
     County Inland Areas-Santa Ana Mountains and Foothills.

     Excessive Heat Warning from 11 AM this morning to 9 PM PDT
     Tuesday for Apple and Lucerne Valleys.

     Excessive Heat Warning until 9 PM PDT Tuesday for Coachella
     Valley-San Diego County Deserts-San Gorgonio Pass Near
     Banning.

PZ...None.

&&

$$

PUBLIC...MM
CLIMATE...17
AVIATION/MARINE/BEACHES...CSP