128
FXUS66 KSGX 031607
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
907 AM PDT Wed Jul 3 2024

.SYNOPSIS...
A long-duration heat wave will continue for the deserts through at
least much of next week. 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 dominant synoptic-scale feature through the forecast period
will be strong high pressure, currently along the California
coast, slowly building in and becoming anchored over the Western
US. This will favor an extended stretch of hot and dry weather
across much of the Western US, away from the immediate coast line
where marine layer low clouds each morning and daily sea breezes
will keep temperatures relatively cool.

Highs today will be generally be 2-7 degrees warmer than
yesterdays highs, topping out 5-10 degrees warmer than average
for early July. Temperatures tomorrow remain relatively steady,
perhaps a degree or two warmer/cooler depending on location.
Friday and Saturday look to be the overall peak of this heat
event, when highs along and near the coast top out 5-10 degrees
above normal, while highs across all other inland areas range from
10-18 degrees warmer than seasonal average! Some areas in the
Coachella Valley and San Diego County Deserts, as well as
localized areas in the mountains and coastal valleys, look to set
multiple daily high temperature records. Friday in Palm Springs
will be an exceptional case, when the all-time daily high
temperature record of 123 degrees will be challenged.

Despite the numbers and stats just provided, there will
undoubtedly be at least a few thoughts and mindsets of, 70s and
80s along the coast and almost 100 inland isnt irregular, its
summer, just turn on the A/C, the last of which isnt an option
for every coastal resident and certainly isnt the case for
outdoor workers and unhoused populations. It definitely isnt an
option if ones A/C equipment fails. And, lets be real. A bunch
of folks are likely going to be outside for the holiday, in the
heat, playing games, grilling, and drinking alcohol. All of this
is a recipe for dehydration (not to mention sunburn) if you arent
careful and mixing in a water here and there, as well as re-
applying sunscreen. The fact of the matter is, heat is the most
frequent cause of weather-related illnesses and deaths, and we
have an abundance of it coming in. Were gonna take this incoming
heatwave seriously.

Excessive Heat Warnings remain in effect for all desert zones,
and are likely to remain in place through at least early next
week. Excessive Heat Warnings also go into effect for the
mountains of San Bernardino/Riverside/San Diego Counties, the
Inland Empire, and the San Diego County Inland Valleys on
Friday/Saturday, while Heat Advisories are hoisted for Inland
Orange County and the Santa Ana Mountains on Friday/Saturday as
well. There will be a slight drop in high temperatures on Sunday,
followed by a relatively steady high temperature forecast for
early next week. Keep in mind, its still going to be rather hot,
with highs each day topping out 5-10 degrees warmer than seasonal
averages per latest latest NBM guidance and derived HeatRisk
guidance. The aforementioned tools suggest that an extension of
all heat warning/advisory products through more of next week very
well may be warranted.

What must absolutely not be lost in this story are the overnight
low temperatures in the deserts. Lows in the Coachella Valley and
San Diego County Deserts look to routinely only fall into the
middle to upper 80s overnight while the High Deserts see lows in
the middle to upper 70s, providing little to no overnight relief
and added stress on power grids.


&&

.AVIATION...
031530Z...Coast/Valleys...Latest satellite imagery shows low clouds
already eroding quickly west towards the coast. Reported bases this
morning were 800-1300 ft MSL with tops to 1200-1700 ft MSL. Clearing
to beaches will continue through 17Z. Low clouds returning with
similar bases and inland extent after 05-08Z Thu.

Mountains/Deserts...Mostly clear skies with unrestricted VIS will
continue through this evening. Local south/west winds near 20-30 kts
at times through the San Gorgonio Pass and above the Cajon Pass 22Z
Wed-06Z Thu.

&&

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

&&

.BEACHES...
A swell of 2-3 feet from 190 degrees with a period of 16-18 seconds
will build into SoCal today through the weekend, peaking Friday into
Saturday. This will lead to elevated surf with breaking wave heights
up to 7 feet, mainly on exposed south and southwest-facing beaches
in Orange County. Rip and longshore current risks will be high as
well now through next Monday.

&&

.FIRE WEATHER...
The long-duration period of hot and dry weather across Southern
California will aid in a persistent downward trend in both dead
and live fuel moisture. As evidenced by the recent Kitchen,
McCain, and numerous other fires, local grass fuels are cured and
very available to burn. The primary factors limiting any more
critical fire weather potential are a lack of strong winds
(outside of the typical diurnally-driven winds) any given day, as
well as live fuel moisture. In other words, theres still plenty
of green as opposed to brown vegetation in the trees and brush.
Live fuel moisture will, however, be steadily dropping/drying out
as we head through the weekend and into early next week. This will
increase the ability of larger fuels (especially dead/dry and
brown fuels) like brush, chaparral, and trees to burn. Energy
Release Components, which can be thought of as somewhat of an
available energy for a fire to burn, are steadily trending
upward toward the 40th percentile and expected to approach the
45th-50th percentile next week. In other words, fuels are finally
drying out back to normal levels for July, after being below
normal for so long following this winters precipitation.

With fuels becoming drier and more receptive to burning, residents
need to exercise additional caution with this year`s 4th of July
fireworks. If possible, please leave the fireworks shows to
professional displays where firefighting resources are likely
already on site. Please also take extra caution to ensure that any
grills are kept far away from any potential grass/brush that
would be receptive to burning.

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement from Thursday morning through Sunday
     afternoon for Orange County Coastal Areas-San Diego County
     Coastal Areas.

     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 until 9 PM PDT Wednesday for Apple and
     Lucerne Valleys-Coachella Valley-San Diego County Deserts-
     San Gorgonio Pass Near Banning.

PZ...None.

&&

$$

PUBLIC/FIRE WEATHER...Adams
AVIATION/MARINE...MM