FXUS66 KSGX 190420
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
920 PM PDT Thu Jul 18 2024

.SYNOPSIS...
Hot conditions are expected this weekend. Moderate to major heat
risk is expected in the valleys and mountains and major to extreme
heat risk is expected in the deserts. Slight chances of
thunderstorms will linger in the mountains Friday afternoon, with
dry conditions expected this weekend. Shower and thunderstorm
chances return to the mountains Monday. Areas of night and morning
coastal low clouds will continue to extend into the western valleys
at times late each night.

&&

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

A few isolated thunderstorms developed over the mountains and High
Desert this afternoon. Rainfall was even measured near Mt. Laguna
ranging from 0.25 to 0.38 inches. Thunderstorm chances will decrease
Friday through the weekend. Thunderstorm chances will increase again
Monday through Thursday. With the lack of monsoonal moisture,
another hot weekend is expected. Make sure to stay hydrated and to
avoid strenuous outdoor activities during the hottest parts of
the day if you can.

From previous discussion issued at 2 PM Thu July 18...

High pressure over the four corners will migrate westward over the
southern Great Basin and strengthen Friday into Saturday.
That will bring us the warming (and warning) trend we've been
talking about for several days. Excessive Heat Warnings are up for
the deserts: Fri-Sun for the low desert and Sat-Sun for the high
desert. Heat Advisories are up for the valleys and mountains Fri-
Sun. High temperatures inland will reach up to 10 degrees above
normal, exceeding 115 in parts of the low desert and 105 in the high
desert and parts of the Inland Empire. The strong high pressure
bringing our weekend heat will weaken just a little Monday, which
will tamp down temperatures a few degrees. Some of the extended
guidance and ensembles show the high strengthening again the middle
of next week, which would mean hotter inland weather again. Over the
next several days, coastal low cloud coverage overall will be less
uniform, less extensive, and with less duration. However, the strong
marine inversion will make clearing at the beaches somewhat iffy.
Late next week there is growing consensus in guidance that the
strong upper high will eventually relent as a trough pattern
amplifies along the West Coast. That would sweep away the monsoon
moisture and bring, dare I say it, cooler weather.

&&

.AVIATION...
190400Z...Coast/Valleys...Low clouds will spread up to 10 miles
inland through 07Z Fri and 20 miles inland by 12Z Fri with bases
900-1300 ft MSL and tops to 1500 ft MSL. Local VIS 3-5 SM will
occur over higher coastal terrain 08Z-16Z Fri, along with local
terrain obscurations 03Z-17Z Fri. Most areas will clear 15Z-18Z Fri,
with some lower ceilings remaining near the coast.

Mountains/Deserts...ISOLD-SCT TSRA will occur in Friday afternoon
with CB bases again around 10000 ft MSL and tops to 35000 ft MSL and
be accompanied by local VIS reductions in +RA, along with lightning,
surface gusts to 40 kt, and strong UDDFS. Otherwise, occasional SCT-
BKN clouds at/above 10000 ft MSL will prevail through Fri.

&&

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

&&

.BEACHES...
Long period 3 foot SSW swell (200-210 degrees) will bring elevated
surf of 3-5 feet with sets up to 6 feet into Friday along south and
southwest facing beaches in both Orange and San Diego counties with
a high risk for rip currents. The period and swell will decrease
Friday, but the rip current risk will remain high.

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory from 11 AM Friday to 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 from 11 AM Friday to 9 PM PDT Sunday for
     Coachella Valley-San Diego County Deserts-San Gorgonio Pass
     Near Banning.

PZ...None.

&&

$$

PUBLIC...CO
AVIATION/MARINE/BEACHES...Suk