Area Forecast Discussion
Issued by NWS San Diego, CA

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580
FXUS66 KSGX 261609
AFDSGX

AREA FORECAST DISCUSSION
National Weather Service San Diego CA
909 AM PDT TUE JUL 26 2016

.SYNOPSIS...
Continued warm inland today with a slight chance of afternoon showers
and thunderstorms over the mountains and desert slopes, but less
humid west of the mountains. Gradually warmer through Thursday or
Friday, then minor cooling into early next week. A greater influx
of monsoonal moisture will bring a slight chance of afternoon and
early evening thunderstorms in the mountains and deserts for
Friday through early next week.

&&

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

The marine layer is about 900 ft deep this morning, with patches
of low clouds over the immediate coast. Above the marine layer,
southeast flow in the mid levels will continue to provide moisture
and some instability so that thermally driven showers and tstms
will be possible over the mountains and desert slopes this
afternoon/evening. Of some concern is a collapsing mesoscale
convective system over the Sonora desert. This could provide
additional low-level moisture, thereby enhancing the potential
for deep convection this afternoon/evening. However, the short-
range high resolution models indicate that the bulk of this
moisture will be farther south so that the best chances for deep
convection this afternoon/evening will be over the Baja mtns.

Gradually warmer through Fri as the upper-level pattern shifts,
with a trough deepening over the eastern U.S. and the ridge
amplifying over the western U.S. This will bring less monsoonal
moisture with a more stable atmosphere through Thu, reducing the
chances for afternoon/evening showers and tstms. The marine layer
will remain very shallow with night and morning low clouds limited to
the immediate coast.

For the weekend into early next week...a trough of low pressure
will deepen over the west coast, weakening the upper ridge and
bringing generally lower temperatures and a little deeper marine
layer. As the upper high repositions itself, monsoonal flow will
once again bring more moisture into the region, resulting in
chances for afternoon/evening showers and tstms over the mtns and
deserts.

&&

.AVIATION...
261530Z...Coast/Valleys...Low clouds, with bases 900-1100 ft MSL and
tops around 1200 ft MSL, will clear along the San Diego County coast
by 16Z this morning. Reduced vis of 4-6 SM HZ will improve to P6SM
by 17Z. VFR conditions this afternoon, then BKN/OVC stratus will
redevelop along portions of the coast late tonight with bases
700-1000 ft MSL and tops 1300 ft MSL.

Mtns/Deserts...Isolated TSRA are possible over the mountains this
afternoon with bases 9K ft MSL and tops to 35K ft MSL, along with
local surface gusts to 40 knots and LLWS. Otherwise, occasional SCT-
BKN clouds at/above 15K ft MSL and unrestricted vis through Wed
morning.

&&

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

&&

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



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