Dense Fog in California, May 30, 2018

Area Forecast Discussion
National Weather Service San Diego CA
322 AM PDT Wed May 30 2018

.SYNOPSIS...
A deep marine layer combined with a coastal eddy will bring
widespread low clouds west of the mountains through Thursday with
drizzle possible during the late nights and early mornings.
Otherwise, a trough of low pressure will bring a cooling trend with
breezy conditions in the mountains and deserts. After the trough
moves east, it will be warmer with low clouds restricted to near the
coast for the weekend, followed by a cooling trend early next
week.

&&

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

.SHORT TERM (Today through Friday)...
A trough of low pressure off the West Coast will move slowly
inland through Friday. This will strengthen the onshore flow
through Thursday spreading cooling inland with a warming trend
beginning on Friday.

The marine layer has deepened to around 3000 feet with widespread
coastal stratus extending inland across all of the valleys.
Drizzle reports so far have been limited with the greatest
concenration of light measurable amounts across the Orange County
coastal plain. Given the depth of the saturated layer...from
around 1200 feet to 3500 feet...patchy drizzle is quite possible
for coastal areas into portions of the valleys this morning.
Additional deepening of the marine layer is expected for tonight
into Thursday morning with coastal low clouds extending inland
onto the lower coastal mountain slopes. Patchy drizzle is once
again possible for tonight into Thursday morning with light rain
possible in some locations. Low clouds will extend into the far
inland valleys or possibly the lower coastal slopes for Thursday
night into Friday morning...but with faster and greater clearing
for Friday afternoon.

The stronger onshore flow will also bring periods of stronger and
gusty southwest to west winds in the mountains and deserts with
the stronger gusts mostly 45 mph or less.

&&

.LONG TERM (Saturday through Tuesday)...
A much weaker low pressure system will linger across the area on
Saturday...weakening and moving inland on Saturday night and
Sunday. High temperatures will warm for Saturday and Sunday with
inland high temperatures on Sunday around 10 degrees above
average. This would push high temperatures in the lower deserts to
near 110...near the lower end of excessive heat warning criteria
for early June.

Another weaker trough of low pressure is expected to move inland
along the West Coast early next week with some continuing timing
and amplitude differences among the global models. This is
expected to bring a cooling trend for the early to middle part of
next week. Areas of night and morning coastal low clouds and fog
will begin to spread farther into the valleys for the early to
middle part of next week.

&&

.AVIATION...
300900Z...Coast/Valleys...Low clouds with bases around 1000-1500
feet msl and tops to 3200 feet fill the coastal basin this morning.
Vis locally reduced to 3-5 SM in BR and -DZ, and areas of obscured
terrain between those elevations. Scatter out from inland to near
the coast 16-19Z, but not at the coast. Low clouds will spread
inland after 00Z with bases/tops a little higher, but with
occasional lower cigs and vis in -DZ overnight.

Mountains/Deserts...Mostly clear and VFR conditions today and
tonight. Surface winds 25-35 kt through a few mountain passes and
into adjacent desert after 23Z.

&&

.MARINE...
No hazardous marine weather is forecast through Sunday, although a
few wind gusts exceeding 20 kt are expected in the outer coastal
waters Thursday afternoon and evening.

&&

.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...17
AVIATION/MARINE...MM