Lake San Marcos, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

481
FXUS66 KSGX 140413
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
913 PM PDT Sun Jul 13 2025

.SYNOPSIS...
A little warmer inland Monday. Gradual cooling back to near seasonal
averages expected for the middle to the end of the week. While
chances are still low and uncertainty remains, confidence is
increasing for the potential of monsoonal thunderstorms over the
mountains late in the week. Marine layer low clouds and patchy fog
will spread across the coastal areas and into the western valleys
during the nights and mornings.

&&

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

Satellite at 9 PM was showing low clouds along much of the coast.
The 00Z sounding from KNKX showed the marine layer depth to be
around 1500 ft with low clouds expected to make it into portions the
valleys overnight. There is a potential for showers and
thunderstorms over the mountains Thursday through Sunday. While
uncertainty remains in the details, latest guidance is starting to
indicate Friday and Saturday afternoons being the most likely days
for shower and thunderstorm activity.

From previous discussion...

The dominant ridge will remain centered about 135 miles west
southwest of San Diego through Monday. This will allow inland
temperatures to rise by a few degrees above what they were the last
couple of days. Temperatures Monday in the mountains and deserts
will be several degrees above seasonal averages while west of the
mountains, temperatures will be near to a few degrees below seasonal
averages. This is mostly due to a relatively shallow but persistent
marine layer, with low clouds and patchy fog in the coastal areas
and western portions of the inland valleys each night and morning.
On Monday, a couple of inverted troughs in the southeast flow on the
southern side of the east-west oriented ridge axis will bring some
monsoonal moisture into SoCal but the threat of afternoon convection
will be low because the moisture will be limited and mostly above
10,000 ft, although a stray shower or tstm can`t be ruled out
altogether.

For Tuesday through the end of the week, model solutions begin to
diverge significantly introducing more uncertainty into the forecast
but in general, the dominant high pressure ridge will be weakened
and displaced eastward towards the Four Corners as a low pressure
system moves inland over the Pacific Northwest. During this time,
temperatures will begin to trend generally lower even as conditions
become drier for Tuesday and Wednesday. For Thursday through the
weekend, an increasing number of solutions across model platforms
are indicating an increase in monsoonal moisture with a
corresponding increase in the chances for afternoon showers and
thunderstorms, mainly in the mountains. This change in the pattern
will likely continue the trend toward lower temperatures for the
mountains and deserts.

&&

.AVIATION...
140340Z....Coast/Valleys...Low clouds with bases 1000-1500 ft MSL
and tops to 2000 ft MSL filling in along the coast through 08Z then
spreading 20-25 mi inland by 11Z. Clouds likely reaching the far
southern and western portions of the Inland Empire again with a 30%
chance of CIGs at KONT 12-16Z. Clouds clearing inland 15-17Z and
near the coast 17-19Z, though there is a 60% chance of CIGS
continuing along the immediate coast of southern Orange County and
San Diego County through the afternoon. Low clouds beginning to
spread back into the coastal areas 15/00-03Z with similar bases and
tops.

Mountains/Deserts...Scattered shallow Cu possible over the mountain
ridges Monday afternoon. Otherwise clear with unrestricted vis
through Monday evening.

&&

.MARINE...
No hazardous marine conditions expected through Friday.

&&

.BEACHES...
A moderate period south-southwesterly swell (2-3 feet at 15-17
seconds) will generate elevated surf and a high risk of rip currents
on Wednesday and Thursday. Surf of 3-5 feet expected with sets to 6
feet possible, primarily on southerly facing beaches. Swell and surf
will begin to lower on Friday.

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.

&&

$$

PUBLIC...CO/PG
AVIATION/MARINE/BEACHES...SS