Forecast Discussion

FXUS66 KSGX 242028

Area Forecast Discussion
National Weather Service San Diego CA
128 PM PDT Mon Jun 24 2024

Hot conditions will continue in the deserts through Thursday, with a
gradual cooling west of the mountains into the the middle of the
week. There is a slight chance of showers and thunderstorms for the
mountains into the High Desert this afternoon and early evening with
decreasing chances for Tuesday afternoon. Dry conditions expected
for the middle of the week into the weekend, with marine layer low
clouds and fog returning to the coast and portions of the valleys.



Visible satellite imagery at 1:30 PM was showing cumulus
developing along the mountains, but so far no precipitation or
lightning has been detected. Similar to yesterday, the convection
will likely start late in the afternoon. The places most likely to
see shower or thunderstorm activity will be along the convergence
boundaries in the mountains and High Desert. Chances of isolated
showers and thunderstorms are in the forecast for Tuesday
afternoon in similar locations, but chances are lower due to
gradually decreasing moisture.

Temperatures in the valleys and mountains this afternoon are
running 3 to 7 degrees cooler than 1:30 PM yesterday afternoon.
The immediate coast and deserts are running a few degrees warmer
than 1:30 PM yesterday afternoon. Areas west of the mountains are
expected to see additional cooling into Tuesday and Wednesday.
Highs in the deserts will fluctuate a few degrees each day through
Thursday before a couple degrees of cooling is expected for

One of the main drivers of the elevated heat risk this weekend was
the above average low temperatures. Low temperatures will gradually
decrease through much of this week. This will help decrease the heat
risk in the deserts Friday and Saturday even though high
temperatures will only decrease a degree or two. Additional warming
is expected by next weekend with the greatest warming for the coast
and valleys on Saturday and for the deserts on Sunday. There is
still some uncertainty surrounding the forecast for next weekend
into early next week, largely centered around how ridges building in
the Southeast and over the East Pacific will interact with the
trough moving through the Pacific Northwest this weekend. The
temperature spread is most noticeable for the valleys with narrower
spread for the deserts.


241955Z...Coast/Valleys...FEW-SCT clouds at/above 10,000 ft MSL and
unrestricted vis through this evening. There is a 15-25 percent
chance of low clouds with bases 1000 ft MSL or less developing along
the San Diego County coast after 09Z Tue.

Mountains/Deserts...There is a 10-15 percent chance of TSRA over the
San Bernardino Mountains and portions of the high desert this
afternoon, with CB bases near 10,000 ft MSL and tops to 25,000 ft
MSL. Gusty outflow winds and reduced vis in RA VCTY TSRA. Otherwise
FEW-SCT clouds at/above 10,000 ft MSL and unrestricted vis through
Tue night.


No hazardous marine conditions are expected through Friday.


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


CA...Excessive Heat Warning until 8 PM PDT Thursday for Apple and
     Lucerne Valleys-Coachella Valley-San Diego County Deserts-
     San Gorgonio Pass Near Banning.