Area Forecast Discussion
Issued by NWS San Diego, CA

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484
FXUS66 KSGX 220437
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
935 PM PDT Fri Jul 21 2017

.SYNOPSIS...
High pressure aloft will bring seasonally hot weather through the
weekend. Marine layer clouds will spread several miles inland each
night before retreating to the beaches each morning. A surge of
monsoonal moisture will bring higher humidity Monday and Tuesday
along with a chance of showers and thunderstorms. Dry and warmer
again for the latter half of next week.

&&

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

The broad upper ridge over the Southwestern U.S. will be the
dominate player this weekend bringing warm/hot days and mild nights.
The marine layer depth was around 1500 feet this evening and will
remain relatively unchanged through Sunday with night and morning
low clouds spreading about 20 miles inland before retreating back to
the coast.

On Sunday afternoon the flow aloft turns southeasterly and the first
signs of monsoon moisture will arrive in the mountains and deserts
for possible isolated convection. Better chances for more widespread
showers and thunderstorms arrive Monday into Tuesday when a deeper
moist layer moves into SoCal. It will turn noticeably more humid
with dewpoints climbing into the mid to upper 60s west of the
mountains and in the low to mid 70s in the lower deserts. A deep 850-
300 mb moist layer may result in a mid and high level cloud deck,
but instability associated with an easterly wave may trigger
elevated convection anywhere from the coastal waters to the deserts.
Due to the increased cloud cover expected, deep thermally driven
convection is less likely on Mon.

By Tuesday, the upper-levels dry, and mid-level winds weaken
slightly and turn SW. With more sun, thermally driven convection on
the mts is again possible, with a drift off into the deserts, so
POPS are greater again over eastern portions of the CWA.

Wednesday and Thursday: Dry with lower humidities midweek as the
southeasterly flow aloft shifts southwesterly ahead of a weak trough
along the West Coast.

&&

.AVIATION...
220400Z...Coast/Valleys...Areas of BKN-OVC stratus will continue to
develop along the coast through 08Z and spread up to 25 miles inland
by 12Z. Bases will be 1000-1400 ft MSL with tops to 1600 ft MSL.
Local vis below 3 miles will occur in the valleys 09Z-15Z, including
VCNTY KRNM. Most areas will clear 15Z-17Z Sat. Stratus will develop
again Sat evening.

Mountains/Deserts...Mostly clear skies with unrestricted vis will
continue through Sat evening.

&&

.MARINE...
There is a slight chance of thunderstorms over the coastal waters
Sunday night and Monday as an upper level disturbance moves through
the region. Otherwise, no hazardous marine weather is expected
through Wednesday.

&&

.BEACHES...
Highest tides will reach near or above 7 feet during the mid-to-late
evenings tonight through Sunday. This could result in minor tidal
overflow at low-lying beach areas during times of highest tide. A
Beach Hazards Statement is in effect.

Also, an upper level disturbance moving through the region may bring
some thunderstorms to the coast Sunday night and Monday, potentially
resulting in a lightning threat at the beaches.

&&

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

&&

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

PZ...NONE.

&&

$$

PUBLIC...Moede
AVIATION/MARINE...Maxwell



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