FXUS66 KSGX 191622
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
922 AM PDT Fri Jul 19 2024

.SYNOPSIS...
High pressure over the Southwest will bring a more stable and
slightly drier atmosphere through the weekend with very hot days
and very warm nights for inland areas. Moderate to major heat risk
is expected in the valleys and mountains with major to extreme
heat risk for the deserts. A return of greater monsoonal moisture
will bring more humid conditions for the early and middle part of
next week along with a chance for mainly afternoon showers and
thunderstorms for the mountains and deserts. Coastal low clouds
will continue to develop at times during nights and mornings.

&&

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

Low clouds were later to cover coastal areas last night and
earlier to clear out. San Diego cleared out even before sunrise.
So we can see that the high pressure aloft is putting pressure on
the marine layer, causing it to back off in spatial and temporal
coverage. Expect this weaker marine layer as coastal clouds
diminish in time and space, with less uniform coverage for the
coming week. Despite its weakened state, a strong marine
inversion will make clearing at the beaches a temporary or short-
lived condition. The bigger story is the inland heat for the next
several days. Inland heat risk will be high to extreme through at
least Sunday. The high overnight temperatures are probably more
responsible than the high afternoon temperatures for creating that
high heat risk. The high pressure aloft weakens very slightly
Sunday and Monday, so temperatures will come down a couple
degrees. But the high pressure appears to strengthen again Tuesday
and Wednesday and dew points come up to keep those nights extra
warm. So not much cooling is happening early next week. Monsoon
moisture already decreasing today will continue that trend for the
weekend for no legitimate chances of thunderstorms. The moisture
begins to increase again Monday for marginal chances of
thunderstorms Monday afternoon in the mountains, followed by more
moisture and instability Tuesday and Wednesday afternoons for a
higher chance across mountains and deserts. The moisture appears
to retreat again Thursday and Friday for decreasing chances. The
consensus of most guidance for late next week is to break down the
high pressure ridge with an amplifying trough on the West Coast,
although many Euro ensemble members hang on to stronger high
pressure. We expect some cooling trend toward next weekend, but
how much is uncertain.

&&

.AVIATION...
191615Z...Coast/Valleys...Low clouds will continue to clear to the
coast through 18Z with bases 700-1000 ft MSL and tops to 1500 ft MSL
and local VIS 2-4 miles in BR/HZ. Local BKN clouds will continue
this afternoon at the beaches with VFR conditions elsewhere. Stratus
will be slow to develop this evening with TEMPO BKN conditions
within 5 miles of the coast 00Z-06Z Sat, then stratus spreading up
to 15 miles inland 06Z-12Z Sat with bases 600-1000 ft MSL and tops
to 1200 ft MSL and local VIS 1-3 miles over higher coastal terrain
08Z-16Z Sat. Most areas will clear 15Z-17Z Sat.

Mountains/Deserts...There is a slight chance of TSRA over the
mountains and adjacent deserts 20Z today-02Z Sat with CB bases
around 10000 ft MSL and tops to 35000 ft MSL, along with local
surface gusts to 40 knots and strong UDDFS. Otherwise, mostly clear
skies with unrestricted VIS will prevail through Sat morning.

&&

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

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory until 9 PM PDT Sunday 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.

     Excessive Heat Warning from 11 AM Saturday to 9 PM PDT Sunday
     for Apple and Lucerne Valleys.

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

PZ...None.

&&

$$

PUBLIC...MM
AVIATION/MARINE...Maxwell