Sierra-at-Tahoe

000
FXUS66 KSGX 011204
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
504 AM PDT Sat Aug 1 2026

.SYNOPSIS... 
The heat is on across SoCal as high pressure strengthens over the
area through the weekend, leading to areas of moderate to major 
heat risk. The marine layer will stay thin through this period, 
where night and morning low clouds will cover the coast each day. 
The area of high pressure will weaken some into next week and may 
move further east. This pattern will bring slightly cooler weather
with a minimal chance for rainfall over the mountains.

&&

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

Today through tomorrow night...

The latest satellite imagery at midnight reveals that the marine 
layer continues to struggle over the inner socal bight waters, 
thanks partially in part to an eddy that has developed near Catalina 
and has helped to create a stronger offshore flow for San Diego 
County as a result. This is also helping to erode some of the marine 
layer that has already developed over Orange County, as SE'ly 
surface winds have picked up due to the coastal eddy. There will 
still likely be some additional low cloud development, and skies may 
periodically go broken right along the coastal areas through this 
morning, with ceilings hovering around 1000 ft MSL. Otherwise, 
mostly clear skies will prevail and set up for another very warm day 
with temperatures still running generally around 5 to 10 degrees 
above the average for this time of year. There has also been some 
recycled mid-level monsoonal moisture that has been streaming over 
the region this morning, which may allow for a very slight chance of 
a shower or two to develop over the mountains (likely only confined 
to the highest elevations), although confidence is low given the 
lack of instability over the region. Hi-res guidance also does not 
suggest much in the way of development later on, although given that 
there is some moisture present, and a monsoonal wave transitioning 
towards the area, which may help to destabilize the mid-levels later 
on, a possible shower or two cannot be ruled out. However, it is a 
lot less likely with very little instability aloft that these would 
become thunderstorms. Under a strengthening ridge, highs will still 
be running around 5 to 10 degrees above the seasonal average for 
this time of year for today.

By tomorrow, winds in the mid-levels will begin to shift to become 
more southwesterly, and draw in drier air along with it. This will 
help to impede the chance of afternoon shower and thunderstorm 
development over the mountains. The troughing upstream will also 
begin to influence the area with slightly lower heights that will 
begin a gradual cooling trend beginning tomorrow. There will also 
begin the presence of a more predominant onshore flow, and this will 
likely help to draw in the marine layer a little sooner, and with 
better coverage for the following night. In addition, this is also 
going to allow for winds to increase through San Gorgonio Pass, and 
along the desert slopes, with gusts up around 40 mph through the 
early evening. This will continue to likely be the case through 
Wednesday as stronger onshore flow remains in place.

Monday through Friday...

Subtle cooling will continue through the mid half of next week and 
conditions will remain dry, with temperatures still being above 
average. Thereafter, mid-level winds will begin to shift back to 
being from a more easterly direction, with better positioning of the 
high pressure center aloft to allow for some of these monsoonal 
waves to develop and advect moisture over our region. Temperatures 
will also start to gradually warm again during this period, with 
increased humidity values and an increasing chance of getting 
thunderstorm activity for our mountains and deserts (and possibly 
even all the way to the coastal locations, depending on the 
propagation of these monsoonal waves as they develop over the 
deserts to our southeast and then transition over our region. During 
this period, the marine layer will likely struggle to develop, given 
the increased mid to high level clouds moving overhead, in
addition, with better offshore flow overnight.

&&

.AVIATION...
010600Z....Coasts...Very patchy low clouds based around 1200ft MSL 
have developed offshore and along the coast. Brief CIGs have already 
been observed at KSAN and KCRQ and intermittent CIGs will likely 
persist through the next several hours as these patchy clouds move 
in and out. Guidance is indicating that clouds should become more 
consistent in coverage closer to 10-12z, with bases closer to 0800-
1100ft MSL and about 10 miles of inland extent. VIS restrictions to 
3-5SM expected over mesas and higher coastal terrain when clouds are 
present. Clouds will scatter out around 16z Saturday morning, with 
VFR prevailing into the afternoon. Similarly patchy low clouds will 
form locally along the coast after 06z Sunday, initially based at 
800-1100 ft MSL.

.Valleys/Mountains/Deserts...VFR conditions prevails throughout 
the period with FEW high clouds AOA 20000 feet MSL.

&&

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

&&

.BEACHES...
A southerly swell from now Tropical Storm Genevieve will generate 
surf of 4-6 feet with sets up to 7 feet for south facing beaches 
today and tonight before diminishing Saturday. This will create 
hazardous conditions for inexperienced swimmers. In addition, the 
high tide tonight will be near 6 feet. The combination of the high 
tides and elevated surf increases the risk of coastal flooding. For 
more details, check the Coastal Hazard Message.

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...High Surf Advisory until 5 PM PDT this afternoon for Orange 
     County Coastal Areas-San Diego County Coastal Areas.

     Heat Advisory until 8 PM PDT Sunday for Orange County Coastal 
     Areas-San Bernardino County Mountains-San Diego County 
     Coastal Areas.

     Extreme Heat Warning until 8 PM PDT Sunday for Apple and Lucerne 
     Valleys-Orange County Inland Areas-Riverside County 
     Mountains-San Bernardino and Riverside County Valleys-The 
     Inland Empire-San Diego County Mountains-San Diego County 
     Valleys-Santa Ana Mountains and Foothills.

     Extreme Heat Warning until 8 PM PDT Monday for Coachella Valley-
     San Diego County Deserts-San Gorgonio Pass near Banning.

PZ...None.

&&

$$

PUBLIC...Stewey
AVIATION/MARINE/BEACHES...Stewey