Areal Flood Advisory 21, NWS San Diego, CA

AREA FORECAST DISCUSSION
National Weather Service San Diego CA
111 PM PDT SUN AUG 21 2016

.SYNOPSIS...
Residual monsoonal moisture will continue a slight chance of
thunderstorms in the mountains and deserts through early evening.
Otherwise...high temperatures will remain near to slightly below
average into next weekend. The marine layer and onshore flow will
bring areas of night and morning coastal low clouds and patchy fog
extending locally inland. There will be locally gusty southwest
to west winds in the mountains and deserts each afternoon and
evening.

&&

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

This afternoon...A weak upper level circulation over the lower
Colorado River valley is bringing mid and high clouds into extreme
southeastern California, and a few sprinkles have been reported
at higher elevations of the San Bernardino and Riverside County
mtns. So far, no lightning has been detected and no precip
accumulations have been measured. However, the potential exists
for the development of showers/tstms this afternoon/evening. If
any deep convection develops, it will likely produce occasional
lightning strikes and locally gusty winds, but little in the way
of precipitation. The marine layer low clouds have cleared, but
will likely return to the coastal areas in similar fashion to last
night.

The weak low pressure system off the Southern California coast
will begin to move inland on Monday. This will establish dry
northwest flow aloft, displacing the moisture to the east and
south. The absence of low and mid level moisture will effectively
end the chances for convection in southwestern California.

High temperatures into next weekend will be mostly near to
slightly below seasonal averages, with the possible exception of
Wed which looks to be the warmest day with weak high pressure
ridging from the southwest. After Wed, another low pressure trough
extends into socal from the north, lowering temps a little and
increasing the onshore flow.

Onshore flow and the marine layer will continue to bring areas of
night and morning low clouds and patchy fog...extending locally
into the western valleys at times. The onshore flow will also
bring gusty southwest to west winds to the mountains and deserts
each afternoon and evening.

&&

.AVIATION...
211959Z...Coast/Valleys...Through 22/0300 UTC, mostly unrestricted
vis with SCT-BKN clouds AOA 10000 ft msl. Isol -DZ in the Inland
Empire. 22/0300-1500 UTC, patchy stratus will gradually develop 15-
20 sm inland again, with bases 1100-1400 ft msl, tops 1500-1700 ft
msl, areas of 3-5 sm vis and local vis AOB 1 sm along higher coastal
terrain/inland mesas. Confidence moderate-to-high for stratus
occurrence and CIG heights/VIS forecast at KSAN and KCRQ, with low
confidence for KSNA. Confidence on timing is low-to-moderate.
Forecast marine layer inversion strength of around 6 deg C. Clearing
of stratus 22/1500-1700 UTC.

Mountains/Deserts...Slight chance of showers and thunderstorms over
the mountain ridges and deserts through 22/0300 UTC with CB tops to
30000 ft msl. Otherwise, primarily unrestricted vis through Monday
morning. BKN-SCT clouds in the 10000-20000 ft msl layer will likely
continue over much of the area through this afternoon before
decreasing tonight.

&&

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

&&

.BEACHES...
At 12 PM, nearshore buoys show the south swell at around 3 feet/14
seconds out of the 200 degree direction. With the swell a little
lower today, Surfline and lifeguards are reporting slightly smaller
surf today in the 3-5 ft range (and local 6 ft) in Orange County,
and mainly 3-4 ft in San Diego county. This surf is still above
normal however, and it will help create strong rip and longshore
currents, resulting in dangerous swimming conditions. A Beach
Hazards Statement remains in effect through early this evening.

The swell and surf will continue to lower tonight into Monday,
resulting in improving surf zone conditions.

&&

.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.

&&

.SGX Watches/Warnings/Advisories...
CA...Beach Hazards Statement until 8 PM PDT this evening for Orange
     County Coastal Areas-San Diego County Coastal Areas.

PZ...None.

&&

PUBLIC...PG
AVIATION/MARINE/BEACHES...Harrison