Alpine, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

047
FXUS66 KSGX 100949
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
249 AM PDT Sun Aug 10 2025

.SYNOPSIS...
Hot weather will continue inland through Wednesday, followed by
gradual cooling for the remainder of the week. There is a 15-20
percent chance of showers and thunderstorms over the central and
southern San Diego County mountains and adjacent desert slopes as
well as the Santa Rosa Mountains this afternoon. Areas of low
clouds and fog will reach into the far western valleys each night
and morning through early next week, deepening further late next
week.

&&

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

Low clouds are a little slower to fill in this morning, but should
spread into the far western valleys and northern Orange County by
sunrise, then clearing back to the coast by late morning. Further
east, mid level clouds are developing over the Imperial Valley and
heading towards our forecast area as outflow from earlier
convection over the Sonoran Desert lifts northwards. Dew points in
the low deserts remain in the low 60s, but no signs of a true
gulf surge yet except in Yuma where winds just picked up and their
dew point jumped up to 76F. High-res guidance does show moisture
increasing across the low deserts later this morning and mid-level
moisture still in place. The moisture in the deserts will mainly
act to suppress high temperatures once again while making it more
humid. Forecast soundings show more favorable conditions for
showers/thunderstorms (15-20% chance) over the Santa Rosa and
central/southern San Diego County mountains this afternoon,
possibly drifting onto the desert mountain slopes. Once again, the
bulk of the convection will be south of the border. Mid-level
moisture begins to decrease on Monday, ending any thunderstorm
chances for the remainder of the week as it only continues to get
drier.

Weaker ridging will be in place over the region today for minor
cooling. The ridge rebuilds from the north Monday and Tuesday for
some warming inland, though areas west of the mountains may not
see much change thanks to a persistent marine layer and afternoon
sea breezes moderating temperatures. Hi-res guidance shows gulf
surges into the lower deserts each night, which will likely limit
daytime temperatures but keep overnight lows elevated. Overall
HeatRisk remains high across the lower deserts with areas of
moderate HeatRisk in the mountains, high desert, and Inland Empire
through Tuesday.

The upper ridge is eventually replaced with long-wave troughing
along the West Coast Thursday into the weekend, though ensembles
are in disagreement with the amplitude of this trough and
therefore how much cooling will occur. Current NBM forecast has
temperatures dropping to around 5-10 degrees below normal by
Saturday.


&&

.AVIATION...
100945Z....Coasts/Valleys...Low clouds based 800-1200 ft MSL
covering most coastal areas currently. Expecting a relatively
uniform 15 miles of inland extent by 13z Sunday. Scattering back to
the beaches by 17-18z Sunday morning. Clouds likely sticking over
nearshore waters and along the beaches across San Diego County, with
full clearing for Orange County beaches. Clouds return to coastal
San Diego County around 02-04z Monday with similar to slightly lower
bases. Spreading northward and about 10 miles inland overnight.

Mountains/Deserts...VFR conditions continuing through Sunday
evening. Isolated Cu above 15,000ft MSL over mountains of San
Diego County and Riverside County Sunday afternoon 19z-01z with
5-15% chance of TSRA. Gusty winds near any storms.

&&

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

&&

.BEACHES...
Long period (16-17 second) southwesterly (200-220 degree) swell will
move into coastal waters late Sunday allowing for elevated surf and
high rip current risk from Monday onward. Surf of 3 to 6 feet with
the highest sets along south and southwest facing beaches.

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory until 8 PM PDT Monday for Riverside County
     Mountains-San Bernardino County Mountains-San Bernardino
     and Riverside County Valleys-The Inland Empire-San Diego
     County Mountains.

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

PZ...None.

&&

$$

PUBLIC...SS
AVIATION/MARINE/BEACHES...KW