920
FXUS66 KSGX 301610
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
910 AM PDT Sun Jun 30 2024

.SYNOPSIS...
Warmer today with highs well above normal. A slight cooldown on
Monday will be short- lived before a warming trend sets in across
the region for the rest of the week and into next weekend. A
prolonged period of hot weather will exacerbate any heat impacts
this week. Areas of night and morning low clouds and fog will
continue along the coast and far western valleys through the week.

&&

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

.Morning Update...
Good morning, SoCal! Mostly clear skies are abundant this morning
with low clouds clearing toward the beaches in the next couple of
hours as our morning sounding shows near a 10C inversion. Should
be another beautiful beach day out there with highs in the 70s
from Huntington to Aliso down to Moonlight and the dog beaches of
Ocean Beach and Coronado. A warmer day is ahead for those across
the western valleys with 90s and low 100s from the Inland Empire
to the foothills of San Diego County. HREF probabilities increase
cloud coverage mostly after sunset near the coast into adjacent
valleys overnight.

The afternoon sea breeze will increase west and
southwest winds with NBM projecting moderate to high probabilities
of seeing winds over 25 MPH; same probabilities for winds over 35
MPH through passes. Cumulus may form over the southern mountains
this afternoon as moisture from Mexico tries to make its way
north, but lack of forcing/instability and PWAT values near to
below one inch, yields a high chance for dry conditions. Dry
conditions look to last awhile after this as high pressure moves
into the region with hot conditions away from the coast through
the upcoming week.

.Previous Discussion (309 AM)...

High pressure aloft building in from the east today will bring
widespread warming to the region. High temperatures will be around
5 to 10 degrees above normal, with the greatest departure from
normal in the far inland valleys where highs will be in the low
100s. Low deserts will see highs of around 110 to 114 degrees, and
the high deserts will be in the low 100s. The marine layer will
help moderate temperatures at the coast into the western valleys,
where highs will be in the upper 70s to around 90. An Excessive
Heat Warning remains in effect for the low deserts. There is
around 10 percent chance of showers and thunderstorms in the
southern portions of the San Diego County mountains and deserts
this afternoon. The 00Z run of the HRRR did show at least light
showers over our area, but later runs now keep any activity south
of the border, so our chances are dwindling.

Brief minor cooling occurs on Monday as an upper trough moves
inland across the West Coast, though high temperatures will remain
a few degrees above normal. The upper level high off the West
Coast very slowly shifts eastward over CA and eventually into the
Great Basin through the week as it steadily strengthens. This will
bring a prolonged heat wave to the region with a degree or two of
warming each day through Thursday, followed by another 2 to 4
degrees of warming on Friday, which is currently forecast to be
the hottest day. Ensemble guidance is still showing a bit of
spread with the placement of the upper high, especially beyond
Thursday, and to a lesser degree, the strength of the high. This
brings in some uncertainty in the high temperature forecast,
though even the lower end of the range is still quite hot. With
the EC ensemble coming more in line with the GEFS in terms of the
strength of the high, overall temperatures have trended upward for
Fri and Sat. NBM now shows a 22 percent chance of Palm Springs
hitting 120 or more by Friday, increasing to 25 percent on
Saturday. Saturday and Sunday are even more uncertain as there is
the potential for a short wave to drop through the interior west,
pushing the upper high back westward and bringing cooling, or at
least not as hot, weather here, but this only accounts for around
20-40 percent of the ensemble space depending on the day, with the
remaining members having the upper high persisting somewhere
across CA into the Great Basin. The Excessive Heat Warning remains
in place for the lower deserts through Friday, with an Excessive
Heat Watch for the high deserts for Tuesday through Friday.
Additional heat products may be needed for other inland areas
late in the week.

Aside from the heat, some mid-level moisture may make its way in
here around Wednesday as an upper low develops to our southwest.
However, at this time instability is very marginal with strong
capping from the nearby ridge, so thunderstorm chances remain
below 10 percent. Otherwise a continuation of night and morning
low clouds and fog will continue along the coast and occasionally
into the far western valleys as the marine layer persists. The
marine layer and onshore flow each day will help moderate
temperatures at the coast through the week.

&&

.AVIATION...
301550Z...Coast/Valleys...Low clouds cover much of the coast and
some portions of the coastal valleys, generally ~10-15mi inland in
spots. Bases are 600-1000 ft MSL with tops to 1200 ft MSL. Vis 3-5SM
in fog, with local vis 1SM on higher coastal terrain through 16Z.
Expect clearing to the coast by 17Z. Low clouds returning to coastal
areas after 06Z Monday with less coverage, and bases similar to this
morning or perhaps slightly lower, around 500-900 FT MSL.

Inland...Westerly winds gusting locally 25-30 knots through Cajon
and San Gorgonio Passes and into adjacent deserts again this
afternoon/evening. Mostly clear skies with unrestricted VIS today
except SCT100 after 18Z, mainly over mountains.

&&

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

&&

.BEACHES...
A long-period 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
current risks will also increase accordingly.


&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Watch from Tuesday morning through Friday evening
     for Apple and Lucerne Valleys.

     Excessive Heat Warning until 8 PM PDT Friday for Coachella
     Valley-San Diego County Deserts-San Gorgonio Pass Near
     Banning.

PZ...None.

&&

$$

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AVIATION/MARINE...Adams