524
FXUS66 KSGX 261029
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
329 AM PDT Wed Jun 26 2024

.SYNOPSIS...
There will be overall slight cooling of high temperatures through
Friday with a little greater cooling of low temperatures. Night
and morning coastal low clouds will increase in coverage and
spread gradually farther into the valleys through Friday. There
will be warming for the weekend with Sunday high temperatures
around 5 to locally 10 degrees above average, to around 115 for
the lower deserts and around 100 for the most inland valleys. This
may be followed by very slight cooling into the middle of next
week.

&&

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

.SHORT TERM (Today through Friday)...
Satellite imagery shows some mid clouds spreading northwestward
across the area. Though still fairly patchy, there`s greater
coverage of low clouds over the coastal waters and into portions
of coastal San Diego County into the western valleys. The local
NAM-bounded WRF shows a weak coastal eddy for tonight into
Thursday morning and again for Thursday night into Friday morning
with night and morning coastal low clouds becoming more widespread
and spreading farther into the valleys.

High temperatures for the coast into the valleys will be a few
degrees cooler today, otherwise just a slight overall cooling
trend in high temperatures through Friday along with some drying
for late in the week.

&&

.LONG TERM (Saturday through Tuesday)...
With the drying, temperatures for Friday night will not be quite
as warm. High temperatures will warm for Saturday and Sunday with
Sunday high temperatures around 5 to locally 10 degrees above
average, to around 115 in the lower deserts and around 100 for the
far inland valleys. With the drying and with the resulting overnight
temperatures not being quite as warm, the heat risk for the
deserts may decrease just enough to fall below Excessive Heat
Warning criteria for Friday and Saturday. However, with the
warming during the weekend, excessive heat could return for the
deserts on Sunday and continue at least into the middle of next
week.

&&

.AVIATION...
260850Z...Coast/Valleys...Areas of stratus with bases 1300-1800 ft
MSL and tops to 2000 ft MSL continuing to develop across the coastal
areas and far western valleys this morning. There is a 30-40 percent
chance of CIGS at KSNA 12-15Z. Clouds clearing to the coast 15-18Z.
More widespread low clouds redeveloping this evening, beginning to
move back into the coastal areas after 27/02Z and spreading 15-20 mi
inland by Thu morning. Little change in bases/tops tonight.
Otherwise FEW-SCT clouds at/above 15,000 ft MSL through Thu morning.

Mountains/Deserts...SCT Cu with bases near 10,000 ft MSL developing
across the mountain crests this afternoon, dissipating by sunset.
Otherwise FEW-SCT clouds at/above 15,000 ft MSL through Thu morning.
West winds with sfc gusts 25-40 kt developing across the mountains
and deserts this afternoon and evening, strongest through the
passes. MOD up/downdrafts over and east of the mountains.

&&

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

&&

.CLIMATE...
Precipitable water is the water through the entire depth of the
atmosphere above a location if that water were all precipitated
out as rain. For San Diego for June, the existing record for
highest precipitable water from a sounding occurred on June 9th,
2015 for the 12Z NKX sounding at 1.75 inch. The second greatest
was for a sounding on June 30th at 1.61 inch. The climatological
average for San Diego increases from 0.70 inch at the beginning
of June to 0.84 inch at the end of June.

Beginning on June 23rd of this year, there have now been 5
soundings from NKX that have exceeded the previously second
highest precipitable water for June, but not quite reached the
record of 1.75 inch. Those soundings have had PW values of 1.7,
1.7, 1.69, 1.68, and 1.65 inches. This is probably most notable in
that there is nothing in the existing climatological record of
sustained precipitable water values this high for the month of
June. The main impact has probably been in keeping overnight
temperatures warmer. Over the past three days, there have been 28
daily records tied or broken for warmest low temperature.
Soundings for San Diego go back to around 1956.

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
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.

PZ...None.

&&

$$

PUBLIC/CLIMATE...17
AVIATION/MARINE...SS