Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 212113
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
213 PM PDT Mon May 21 2018

.SYNOPSIS...
An upper level low over Southern California will maintain a deep
marine layer, clouds, and spotty light rain and drizzle from the
coast to the mountains with even a slight chance of thunderstorms
from the San Bernardino County mountains to the high desert this
afternoon. The upper low will move east Tuesday through Wednesday,
being replaced by weak upper ridging, before yet another trough
arrives this weekend. Gradual warming will occur away from the
beaches this week, especially across the deserts, but with little
temperature changes near the coast as the marine layer remains in
tact. At the beaches...a south swell will bring elevated surf much
of the week.

&&

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

Upper low centered just north of the service area will move to
Nevada through Tuesday. One shower developed over the eastern San
Bernardinos. SPC mesoanalysis shows MUCAPE of 250 J/KG over this
area. An additional isolated shower, and perhaps a thunderstorm,
is possible through early this evening, including the high deserts
east of I-15.

The marine layer cloudiness remains in tact, but with some breaks
in areas, especially along the immediate coast from Del Mar and
points north to the OC beaches. However, most inland locales
remain locked in cloudiness. More light showers could develop
tonight and affect areas from the coast to the coastal mountain
slopes. Included chances of showers for these areas. Rainfall
amounts are only expected to be a hundredth of an inch or so,
though some isolated coastal mountain slope locales could see
higher amounts to a tenth of an inch or so.

West winds are increasing from the mountain ridge tops to the
deserts and expected to increase further tonight with gusts of
40-50 mph in the wind prone locales. Blowing dust is possible
across the deserts.

The synoptic weather pattern will feature the upper low pulling
east Tuesday, replaced by building heights/weak ridging, followed
by the approach of another trough late in the week with model
consensus showing another closed upper low moving across the state
just to our north this upcoming holiday weekend. So we look to see
gradual, slow warming across inland locales but remaining below
averages for late May. During the upcoming weekend, slight cooling
will occur as the upper low moves inland. For coastal locales,
temperature changes will see little changes due to the marine
layer influence. Cloudiness will dominate along the coast with
perhaps some sunshine occurring during the afternoons with the
best opportunity on Tuesday as the trough axis slides east.
Definitely we are living up to the May Gray theme.

&&

.AVIATION...
212045Z...Coast/Valleys/Coastal Mountain Slopes...Mostly BKN-OVC
clouds will prevail west of the mountains and along some mountain
slopes with bases 2000-3000 ft MSL and tops to 5500 ft MSL. Higher
terrain will be obscured but most vis below the clouds will be 5+
miles. Similar clouds and scattered -DZ or -RA will occur tonight
and early Tue, with BKN-OVC clouds becoming SCT in some locations
after 19Z.

Mountain Crests/Desert Mountain Slopes/Deserts...Occasional high
clouds, at/above 20000 ft MSL with unrestricted vis will prevail
through Tuesday. Areas of west winds 15-25 kt with gusts 25-40 kt
will occur on the desert mountain slopes and through San Gorgonio
Pass, with greatest winds late this afternoon/evening. Isolated
-SHRA will occur with a slight chance of TSRA in the mountains and
deserts of San Bernardino County with bases 8000 ft MSL and tops to
30000 ft MSL this afternoon/early evening.

&&

.MARINE...
A few wind gusts over 20 knots from the WNW will occur through this
evening in the outer coastal waters, beyond 30 nm. Otherwise, no
hazardous marine conditions are expected through Saturday.

&&

.BEACHES...
A long period swell from 200 degrees will arrive late today, and
peak late Tuesday through Wednesday before subsiding slowly Thursday
and Friday. Surf of 4-6 feet with some sets to 7 feet is expected on
south facing beaches late Tuesday through Thursday, mainly in Orange
County, along with strong rip and longshore currents. A beach hazard
statement has been issued Tue-Thu for the elevated surf and rip
currents.

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement from Tuesday morning through Thursday
     afternoon for Orange County Coastal Areas.

PZ...NONE.
&&

$$

PUBLIC...Gregoria
AVIATION/MARINE...Maxwell



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