Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 301050
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
350 AM PDT Sun Apr 30 2017

.SYNOPSIS...
Through Thursday...high temperatures will remain above average for
inland areas. Towards the coast...a shallow marine layer will
return tonight with areas of night and morning coastal low clouds
and fog spreading into the western valleys at times for Tuesday
through Thursday. Onshore flow will bring gusty west winds to the
mountains and deserts each late afternoon through late evening.
For Friday into next weekend...a trough of low pressure will
develop near the West Coast with differences in the details for
next weekend. Onshore flow is expected to strengthen with strong
gusty west winds in the mountains and deserts...deepening of the
marine layer with more clouds...and daytime cooling. There are
small chances for precipitation around next Sunday.


&&

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

Through Thursday...high pressure aloft off the California coast
will strengthen...and move inland on Wednesday and Thursday. This
will bring a warming trend for inland areas. This will take high
temperatures in the lower deserts to around 100...around 10
degrees above average...for Tuesday through Thursday.

Towards the coast...a return of onshore flow and slow deepening of
the marine layer will bring a slow cooling trend. Patchy stratus
may return near the coast late tonight into Monday morning with a
model trend toward lesser coverage. A greater return is expected
for Monday night with night and morning coastal low clouds and fog
extending into portions of the western valleys for Tuesday through
Thursday. The onshore flow will also bring gusty west winds to the
mountains and deserts each late afternoon through late evening.

For Friday through next weekend...the pattern across North America
at the mid latitudes is expected to become highly amplified with
troughs of low pressure over the eastern states and near the West
Coast. The global models are in decent agreement with the details
on Friday as the trough of low pressure develops near and just
off the West Coast. This will bring stronger onshore flow for
Southern California with cooling beginning to spread inland and
with stronger and gusty west winds in the mountains and deserts.

For next weekend...the global models continue to diverge with the
details with the development of a closed upper low somewhere in
the broader area surrounding Southern California. This should
bring additional daytime cooling and more clouds. There are also
small chances for precipitation around next Sunday with
precipitation potential very much dependent on the placement of
the upper low should it develop.

&&

.AVIATION...
300845Z...Clear with unrestricted vis through this evening. A weak
coastal eddy could develop patchy stratus, with bases around 1000 ft
MSL, along the immediate coast tonight, and areas of vis below 5 SM.
Forecaster confidence in coastal aerodromes remaining VFR tonight is
moderate.

&&

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

&&

.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...JJT



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