706
FXUS66 KSGX 221000
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
300 AM PDT Sat Jun 22 2024

.SYNOPSIS...
High pressure building over the Southwest will bring hot weather to
the valleys, mountains and deserts through the middle of next week.
A shallow marine layer will moderate temperatures near the coast. A
surge of monsoon moisture tonight and Sunday will bring higher
humidity and a slight chance for showers and thunderstorms.

&&

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

The summer solstice on Friday, the day with the most daylight,
brought with it a hot day. The high was 113 at Palm Springs and 112
at Ocotillo Wells, 97 at the Victorville, and 99 in Johnson Valley
in the High Desert. The heat also filtered in the Inland Empire with
a high of 95 at San Bernardino and 98 at Hemet. Today will be hotter
as the upper ridge over Texas backbuilds westward toward New Mexico
and Arizona, raising 850 mb temperatures from 24.5C Friday to 28C
today. That will translate to highs near 115 in the Lower Deserts,
from 100 to 105 in the High Deserts, and from 98 to 104 in the
Inland Empire.

A modest surge of mid-level moisture the southeast flow around the
upper ridge tonight and Sunday will raise Precipitable Water values
to 1.75" in the Lower Deserts, 1.25" in the west of the mountains
and 1" in the mountains. A weak shortwave coupled with the heat of
the day will generate mid-level lapse rates of 7.7C/km Sunday
afternoon and raise CAPE values to 500-600 J/kg. This is when the
chances for scattered convection will be greatest. Thunderstorm
chances dwindle Sunday night but isolated convection is again
possible Monday, mainly over the San Bernardino Mountains and High
Deserts.

Next week will be hot in the valleys, mountains and deserts with the
ridge of high pressure anchored over the Four Corners region. An
Excessive Heat Warning is in effect for the deserts through Thursday
evening. Coastal areas will be spared the searing heat by a shallow
marine layer.  On Friday and Saturday the ridge weakens ahead of a
Pacific trough that will bring a few degrees of cooling to the
region.

&&

.AVIATION...
220900Z...Coast/Valleys...Low clouds increasing in coverage at this
hour with bases around 1000 ft MSL and tops to 1400 ft MSL. Inland
spread will be restricted to the coastal areas and the western
portions of the San Diego County valleys. CIG impacts currently at
KSAN and KCRQ. 35-45 percent chance for CIG impacts at KSNA between
13Z and 15Z. Bases could briefly drop below 1000 ft MSL 12Z-15Z.
Local VIS 1-3SM on elevated coastal terrain. Clearing to the coast
14Z-16Z.

Mountains/Deserts...Clear with unrestricted VIS through today.

&&

.MARINE...Tropical moisture is expected to arrive tonight
through Sunday morning. The moisture is enough with a weak
disturbance to bring a threat for widely scattered lightning and
brief showers tonight through Sunday. See the Marine weather
statement for more information.

&&

.BEACHES...
There is a slight chance of thunderstorms tonight through Sunday
which could produce cloud-to-ground/cloud-to-water lightning
strikes. Chances of a lightning strike near any particular beach are
currently 20 percent or less tonight and Sunday. Rain showers will
generally be brief and light to moderate.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory from 10 AM this morning to 8 PM PDT Sunday for
     Orange County Inland Areas-San Bernardino and Riverside
     County Valleys-The Inland Empire-San Diego County Valleys.

     Heat Advisory from 10 AM this morning to 8 PM PDT this evening
     for Riverside County Mountains-San Bernardino County
     Mountains-San Diego County Mountains.

     Excessive Heat Warning from 10 AM this morning to 8 PM PDT
     Thursday for Apple and Lucerne Valleys-Coachella Valley-San
     Diego County Deserts-San Gorgonio Pass Near Banning.

PZ...None.

&&

$$

PUBLIC...Moede
AVIATION/MARINE/BEACHES...PG