552
FXUS66 KSGX 071909
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
1209 PM PDT Thu May 7 2026

.SYNOPSIS...
Above average temperatures will prevail through the remainder of the
forecast period. Warmest conditions will be Sunday through Tuesday
with areas of moderate HeatRisk expected in the valleys and major
HeatRisk in the low deserts. The marine layer and weak onshore flow
will keep coastal areas cooler. A gradual cooling trend expected for
next Tuesday through Thursday although conditions will remain above
average. Dry conditions will prevail through the forecast period.

&&

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

Highs today are expected to be a few degrees warmer than yesterday
along the coast and 7 to 13 degrees warmer than yesterday for inland
locations. This warming will push temperatures to above average.
Above average temperatures will continue through next Thursday. Weak
onshore flow will be maintained, which will help moderate
temperatures along the coast and portions of the western valleys.
Additionally, areas of at least patchy low clouds and fog are
expected to be present along the coast potentially into portions of
the western valleys at times through the forecast period.

An upper level ridge of high pressure will expand over California
and strengthen early next week. This will bring temperatures 15 to
20 degrees above average for the far inland valleys, mountains, and
deserts on Monday, which continues to be forecast as the hottest day
of the week. Current forecast has moderate to major HeatRisk in the
low desert, with minor to moderate in the valleys and High Desert
Sunday through Tuesday. Ensemble guidance from the ECMWF and GEFS
continue to align with solutions from NBM guidance, even though the
deterministic NBM is still skewed towards the maximum values of the
EC and GEFS guidance, especially for Monday. The geographical
proximity of the deserts to the center of the high pressure
increases confidence in the temperature forecast for that area.
There still remains some uncertainty on how warm it will get west of
the mountains as prevailing onshore flow will spread cooler coastal
air inland with the afternoon sea breeze. The spread between the
10th and 90th percentile of the NBM guidance in the Inland Empire
for Monday is about 8 degrees which would be a difference of
highs in the low 90s (10th percentile solution) or reaching 100
(90th percentile solution) at the hottest locations.

By Tuesday, most of the ensemble guidance indicates the ridge aloft
will weaken, which will bring a few degrees of cooling to areas west
of the mountains. For the deserts, there is less confidence in a
substantial cooling on Tuesday. NBM spread in 10th and 90th
percentile in temperatures is 8 to 10 degrees which is a difference
between highs in the upper 90s/low 100s (10th percentile) and
105 degrees or warmer (90th percentile). The upper level pattern
becomes more uncertain for next Wednesday and Thursday, with some
solutions maintaining weak ridging and others showing weak
troughing. Current forecast has gradual cooling from Tuesday
through next Thursday. Dry conditions will prevail through the
forecast period.

&&

.AVIATION...
071745Z...Coast...Low clouds are just about cleared from the entire
coastline and should hang just offshore today. More widespread and
cohesive low clouds 800-1300ft MSL will move ashore after 02Z and
locally inland overnight. There`s a 20% chance of reaching KONT by
13Z Friday. Vis reduced 2-4SM for coastal terrain and in valleys,
with 4-6SM for coastal areas. Chance of IFR CIGs at KSAN after 06Z
around 50%, chance of MVFR > 85%. Clearing will occur between 15-17Z
Friday.

Valleys/Mountains/Deserts...Mostly clear and VFR with only FEW
clouds around 10,000ft MSL over mountains 18-00Z today. Strong
westerly winds with gusts 25-35 kts develop after 23Z through
mountain gaps into deserts, continuing into early Friday.

&&

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

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Extreme Heat Watch from Sunday morning through Tuesday evening
     for Coachella Valley-San Diego County Deserts-San Gorgonio
     Pass near Banning.

PZ...None.

&&

$$

PUBLIC...CO
AVIATION/MARINE...Zuber

NWS San Diego (SGX) Office