533
FXUS66 KSGX 091031
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
331 AM PDT Tue Jul 9 2024

.SYNOPSIS...
The hottest days for the coast and valleys will be through
Thursday with not much change for the mountains and deserts. An
influx of monsoonal moisture over the weekend could bring a slight
chance of afternoon and early evening showers and thunderstorms
for the mountains and deserts. A gradual slow cooling trend will
begin around Friday and continue into next week with Monday high
temperatures within a few degrees of average. Night and morning
coastal low clouds will spread into portions of the western
valleys at times late each night.

&&

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

.SHORT TERM (Today through Thursday)...
The hottest days for the coast and valleys are expected for today
through Thursday. Wednesday is the most likely hottest day with
high temperatures for the inland valleys of 10 to 15 degrees above
average, to 108 to 112 in the far inland valleys. There will be
minor day to day differences in high temperatures for the
mountains and deserts with widespread Extreme Heat Risk for the
deserts. Night and morning coastal low clouds will spread into the
far western valleys at times late each night. There will also be
some afternoon clouds for the mountains.

&&

.LONG TERM (Friday through Monday)...
The center of high pressure over the southwest states will move
slowly toward the north and east and in combination with a weak
low pressure system off the California coast could draw some
monsoonal moisture into the area from the southeast over the
weekend. ECMWF ensemble output has the highest precipitable water
values for Imperial over the weekend with continuing spread in
the timing of drying for the early into the middle of next week.

There is a slight chance for showers and thunderstorms for the
mountains into the adjacent deserts each afternoon and early
evening over the weekend.

High temperatures will gradually cool through the weekend and
early next week with Monday high temperatures generally within a
few degrees of average.

The marine layer will continue to moderate the heating near the
coast with night and morning coastal low clouds extending into the
far western valleys at times late each night.

&&

.AVIATION...
090900Z...Coast/Valleys...Low clouds with bases 800-1200 feet
MSL and tops to 1600 feet will continue through 16Z-18Z Tue
within 25-30 miles of the coast, locally extending into far W and S
parts of the Inland Empire. Local VIS 3-5 miles in BR will occur in
the coastal valleys through 16Z Tue. Partial and limited clearing at
the beaches this afternoon. Low clouds and fog will be more patchy
tonight and early Wed and likely only spreading 10-15 miles inland.
Onset will be 01Z-04Z Wed near the coast with little change in cloud
heights.

Mountains/Deserts...Mostly clear skies with unrestricted VIS will
continue through Wed morning. Local west surface winds with gusts
25-35 knots will continue through 12Z Tue and again 23Z Tue-12Z Wed
through/east of mountain passes and the desert slopes with
associated weak to moderate up/downdrafts.

&&

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

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Warning from 11 AM this morning to 9 PM PDT
     Thursday for San Bernardino and Riverside County Valleys-
     The Inland Empire-San Diego County Valleys.

     Heat Advisory until 9 PM PDT Thursday for Riverside County
     Mountains-San Bernardino County Mountains.

     Heat Advisory from 11 AM this morning to 9 PM PDT Thursday for
     Orange County Inland Areas-Santa Ana Mountains and
     Foothills.

     Excessive Heat Warning until 9 PM PDT Thursday for San Diego
     County Mountains.

     Excessive Heat Warning until 9 PM PDT Friday for Apple and
     Lucerne Valleys-Coachella Valley-San Diego County Deserts-
     San Gorgonio Pass Near Banning.

PZ...None.

&&

$$

PUBLIC...17
AVIATION/MARINE...Maxwell