Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 301111
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
411 AM PDT Fri Jul 30 2021

.SYNOPSIS...
Monsoonal moisture will bring a chance of mainly afternoon and
early evening showers and thunderstorms, mainly for the mountains
and deserts, through Saturday. Then drier and warmer for Sunday
through Thursday. Night and morning low clouds and fog will
continue for coastal areas.

&&

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

.SHORT TERM (Today through Sunday)...
Monsoonal moisture will spread north northwestward across the
area for today into Saturday with drier southwest flow aloft
for Saturday night and Sunday. There remains some spread in just
how much influx of monsoonal moisture will occur.

ECMWF ensemble members are still fairly dry. For Big Bear, about
half of ECMWF ensemble members have measurable rainfall this
afternoon, but amounts are light. Only two ensemble members have
measurable rainfall for Saturday. HREF remains more aggressive
with coverage and amounts for the mountains this afternoon and
again Saturday afternoon. There remain small chances for nocturnal
precipitation for tonight into Saturday morning, mainly for
portions of the mountains and deserts.

With an increase in moisture and clouds, most areas will be a few
degrees cooler than Thursday for today. High temperatures in the
lower deserts could be around 10 degrees lower than Thursday.
There will be slow warming for some areas on Saturday with greater
warming for inland areas on Sunday as drying occurs. For coastal
areas, night and morning low clouds and fog will continue.

&&

.LONG TERM (Monday through Thursday)...
High pressure aloft across the southwest states will bring warming
for inland areas into Wednesday and Thursday. The greatest warming
is expected in the deserts. For Wednesday and Thursday, high
temperatures for inland areas will be around 5 degrees above
average and within a few degrees of average for the coast into the
western valleys. For Wednesday and Thursday, high temperatures
will range from the mid 70s at the coast to around 112 in the
lower deserts. The marine layer and onshore flow will continue
night and morning low clouds and fog for coastal areas.

&&

.AVIATION...
301100Z...Coast/Valleys...Patchy low clouds with bases 500-1000 feet
MSL will move in and out of areas within 10 miles of the coast
through about 15-17Z before clearing. Vis restrictions of 2-4 miles
in BR/HZ where stratus nears higher coastal terrain. Somewhat lower
confidence on when low clouds will return tonight, though most
guidance is leaning toward a yet again patchy SCT-BKN pattern with
later timing after 06Z Tuesday.

Mountains/Deserts...SCT-BKN clouds at/above 20,000 ft MSL and
unrestricted vis through the morning and afternoon today. Isolated
SHRA/TSRA over the mountains and deserts starting around 20Z this
afternoon into the evening, including a slight chance VCTY
KPSP/KTRM. CB bases near 10,000 feet MSL and tops to 25,000 feet
MSL. Gusty outflow winds and reduced vis in RA possible in/near
storms.

&&

.MARINE...
Wind gusts approaching 20 knots are possible in the outer waters
each afternoon through Monday. Otherwise, no hazardous marine
conditions are expected through Tuesday.

&&

.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...17
AVIATION/MARINE...APR


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