Area Forecast Discussion
Issued by NWS San Diego, CA

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581
FXUS66 KSGX 222035
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
135 PM PDT Tue Aug 22 2017

.SYNOPSIS...
High temperatures will be slightly cooler for Wednesday and
Thursday. Areas of night and morning coastal low clouds and patchy
fog will extending locally into the western valleys with some
afternoon clouds over the mountains. A warming trend begins on
Friday, with temperatures returning to seasonal averages.
Temperatures increase to 5 to locally 10 degrees above average for
Saturday through Monday.

&&

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

Modest amounts of moisture in a relatively stable atmosphere has
resulted in the development of small elements of cumulus clouds
over the mtns this afternoon. The marine layer low clouds have all
but burned off, except at some San Diego County beaches. The
position of the weak upper low over the central California coast
is keeping most of the monsoonal moisture east of the lower
Colorado River valley.

For Wednesday and Thursday...the weak low pressure system off the
central California coast will weaken as it moves inland through
Southern California. This will bring slight cooling with high
temperatures for inland areas a few degrees below average. Areas
of night and morning coastal low clouds and fog will extend into
the western valleys. Some of the higher resolution models show an
area of elevated instability moving across portions of
southwestern California from the south late tonight and early
Wednesday...however moisture aloft remains quite limited. This may
bring some mid level clouds into our area...but any chances for
precipitation are quite limited. Otherwise...there may continue to
be some afternoon clouds near the mountains into the upper
deserts the next few days.

Friday through Monday... High pressure aloft over northwest
Mexico on Friday...will expand into the southwest states and Great
Basin for Sunday and Monday. High temperatures for inland areas
will warm to near average on Friday...then warm to 5 to locally 10
degrees above average. The marine layer will become shallower
with areas of night and morning coastal low clouds and patchy fog
not extending inland much past the coastal areas. Mid level
moisture may increase somewhat during the weekend into early next
week with more afternoon clouds for the mountains, however the
global models are keeping precipitation mostly to the east.

Some medium-range deterministic models are indicating the
possibility of more substantial monsoonal moisture returning to
the region by next Tue, but that`s mostly speculative at this
time.

&&

.AVIATION...
222000...Coast/Valleys...Patchy stratus along the San Diego County
beaches this afternoon, otherwise VFR conditions expected through
this evening. Low clouds, with bases 1500-1800 ft MSL and tops near
2000 ft MSL, will develop along the coast tonight, and push around
20 SM inland by early Wednesday morning. VIS of 1-3 SM BR is
expected where low clouds near higher terrain. Stratus will clear
towards the coast by late Wednesday morning.

Mountains/Deserts...FEW afternoon cumulus and unrestricted
visibility through Wednesday afternoon.

&&

.MARINE...
No hazardous marine weather is expected through Saturday.

&&

.SKYWARN...
Skywarn activation will not be needed today.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

$$

PUBLIC...PG
AVIATION/MARINE...JJT



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