Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 231628
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
928 AM PDT Wed Aug 23 2017

.SYNOPSIS...
Below normal high temperatures and a deep marine layer will
continue through Thursday. Patchy drizzle is expected again over
portions of the coast and valleys Thursday morning. High pressure
building near the region will create above normal high
temperatures this weekend into early next week, with temperatures
peaking Monday.

&&

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

At 9 am PDT, water vapor satellite imagery displayed an upper-
level low just off the coast of Point Conception, and an upper-
level ridge over New Mexico. Visible satellite showed a deep
marine layer, with low clouds extending into parts of the Inland
Empire. The 23/1200Z Miramar sounding displayed a 9 deg C marine
layer inversion, and calculated a precipitable water of 1.17
inches, and most unstable CAPE of 800 J/Kg. An inversion in the
mid-levels will likely limit convection across our area today.
However, portions of San Bernardino County deserts just outside of
our CWA may see some development this afternoon. Low clouds may
linger along portions of the beaches this afternoon. Low
pressure aloft will maintain a deep marine layer west of the
mountains through Thursday, with below normal high temperatures
continuing through the period and patchy drizzle possible again
Thursday morning.

The aforementioned ridge will build northwest by the end of the
weekend, and hover over Nevada through early next week. This will
transition us from the extended below normal high temperatures to
above normal high temperatures by the weekend. H850 temperatures
increasing to around 31 C will yield highs 5 to 10 F above normal
by Monday. Heat Advisories or Heat Warnings may be needed. Highs
will range from 100-110 F in the Inland Empire and the High
Deserts, and from 110-115 F in the Lower Deserts. Afternoon inland
thunderstorms may return to the forecast by mid week next week as
the upper-level high transitions back towards the southeast.

&&

.AVIATION...
231500...Coast/Valleys...Low clouds with bases 1000-1700 ft MSL
continuing along the coast and up to 25 SM inland, including KONT.
VSBY restrictions 2-4 SM at times where clouds near higher terrain
in the valleys. Low clouds slowly clearing inland 16-18Z, with only
partial clearing along the coast 18-21Z. Low clouds beginning to
move back inland around 25/00Z and spreading into the valleys
overnight. Bases will be near 1500-2000 ft MSL, and continue through
Thursday morning.

Mountains/Deserts...FEW afternoon cumulus over the ridges and
unrestricted visibility through Thursday. Gusty diurnal winds each
afternoon and evening over the mountains and desert slopes with
gusts to 35 knots at times.

&&

.MARINE...
Wind gusts around 20 knots this afternoon and evening on the outer
waters. Otherwise no hazardous marine weather is expected through
Sunday.

&&

.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...JJT
AVIATION/MARINE...Brotherton



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