Area Forecast Discussion
Issued by NWS San Diego, CA

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511
FXUS66 KSGX 142052
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
152 PM PDT Tue Aug 14 2018

.SYNOPSIS...
Monsoonal flow will return on Wednesday and Thursday bringing back
higher humidities and a chance for afternoon thunderstorms to the
mountains and deserts. From Friday through Monday, high pressure to
the east will expand westward across Southern California bringing
drying and inland warming.

&&

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

Overall it was a seasonal summer day in Southern California with
generally sunny skies and scattered afternoon cumulus over the
mountains and high deserts. Marine layer clouds over the coastal
areas dissipated by mid-morning, but will return to the coastal
zones and some of the inland valleys the next few nights.

Early afternoon dewpoints ranged from 60-65 in the coastal areas and
were in the 40s and 50s in the inland valleys. These values are
lower than they have been since early August, and it feels a little
more comfortable outside. That will change over the next couple of
days as moisture streams back into SoCal.

Moisture will start moving back into the region Wednesday as mid
level southeast flow raises the precipitable water back over 1 inch
in the mountains and to nearly 2 inches in the lower deserts. A low
level gulf surge will raise dewpoints back into the 70s in the lower
deserts Wednesday and Thursday. Forecast soundings over the
mountains have CAPE potential of 1000 J/kg, and it appears that any
thunderstorms that form will initiate along the surface wind
convergence zone over the mountains the next two days. Some storms
may drift into the high deserts.

This brief moisture surge will start to fade on Friday as high
pressure aloft becomes more centered over Southern California. This
will shut down the southeast flow this weekend, and drier northwest
flow will bring lower humidities Saturday and Sunday. This dry, warm
airmass will remain in place through next Tuesday, then shift a
little farther east Wednesday and Thursday when small influxes of
monsoonal moisture will return to SoCal.

The high temperature at the San Diego Airport has been 80 degrees or
higher for 17 days in a row, which ranks 3rd longest. Forecast highs
will be near 80 for the next several days, so the record could be
extended. The record for consecutive days with a high of 80 or more
is 30 days set back in 1983.  The second longest streak is 19 days
set in 1984.

&&

.AVIATION...
142020Z...Coasts/Valleys...Mostly clear early, then patchy
low clouds based 1600-2000 ft MSL with tops near 2500 feet
MSL extending up to 20 miles inland. The risk of somewhat
patchy/erratic low clouds again tonight at KSAN is high,
but the confidence in both the timing and coverage of
the low clouds at KSAN in the TAF is low.

Mountains/Deserts...SCT clouds at or above 10 kft MSL with
unrestricted visibility through Wed morning. There is
a small chance of -SHRA this afternoon, mainly over the
San Diego County mountains, with an increase in activity
expected Wednesday afternoon. CB bases will be near 9000 ft
MSL and tops to 35000 ft MSL.

&&

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

&&

.BEACHES...
A south swell of 3-4 FT/16-18 second period from 180 degrees
arriving late Wednesday will bring a period of elevated
surf and strong rip currents Thursday into the weekend.
This could produce surf of 4-7 feet on south and southwest
facing beaches in Orange County and northern San Diego County
through at least Friday.

&&

.SKYWARN...
Skywarn activation may be requested Wednesday afternoon.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement from Wednesday evening through Friday
     evening for Orange County Coastal Areas-San Diego County
     Coastal Areas.

PZ...NONE.

&&

$$

PUBLIC...Moede
AVIATION/MARINE/BEACHES...Small



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