000
FXUS66 KSGX 210941
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
241 AM PDT Sun Oct 21 2018

.SYNOPSIS...
A trough of low pressure will slowly drift across California
through Monday. It will bring cooler weather, higher humidity, and a
return of some night and morning marine clouds along the Coast. An
isolated shower or thunderstorm is not out of the question either
over the mountains and deserts of San Bernardino County, but most
areas will stay dry. High pressure rebuilds off the eastern Pacific
later in the week for a return of very warm days and continued dry
weather.

&&

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

At 2:30 AM PDT...Low, marine clouds were making a comeback just
offshore of southern San Diego County. Thunderstorms had developed
over portions of southern NV and western AZ, but for SoCal, it
was mostly clear. Dewpoints were higher across the entire CWA with
marine air now evident along the Coast. Surface pressure gradients
were trending weakly onshore and winds were light.

A weak upper-level trough will drift across the State through
Monday, maintaining onshore flow and building a shallow marine layer
inland. Areas of low clouds and fog should revisit coastal areas
again nights and mornings through Wednesday. It will be noticeably
cooler as well, especially west of the mountains, over coastal
areas, where temperatures will be some 6 to 12 degrees F lower than
the past couple of days. Small POPS remain in the forecast for
northern areas this evening, but model trends and MOS guidance is
not encouraging for any meaningful precip at this time.

As the trough drifts east later in the week, a ridge will build east
off the Pacific, weakening the onshore flow and setting up SoCal for
another very warm episode with daytime temperatures once again
pushing ten degrees F or more above the late October average. The
high pressure aloft will also keep any chance for precipitation away
through the end of the month.

The dry and warm weather should last through next weekend over
most of the State.

&&

.AVIATION...
210925Z...Coast...Patchy low clouds with bases near 500 ft MSL and
vis 1-3SM developing just off the San Diego County coast this
morning. Low clouds will gradually spread north through the morning,
possibly reaching the beaches and spreading a few miles inland
inland by 14Z. Confidence in clouds/fog reaching any of the coastal
airports this morning is low. Low clouds should become more
widespread late this afternoon and spread 5-10 mi inland overnight.
Bases will be near 500-800 ft MSL with areas of vis 2-4 SM, locally
below 1SM over higher coastal terrain and on the coastal mesas.

There is a slight chance of showers and thunderstorms over the San
Bernardino Mountains and high desert late this morning through this
evening. Otherwise FEW-SCT clouds 7000-1000 ft MSL and unrestricted
vis through Monday morning.

&&

.MARINE...
Isolated patches of dense fog is possible over the coastal waters
through mid-morning. Otherwise, no hazardous marine weather is
expected this afternoon through Thursday.

&&

.SKYWARN...
Skywarn activation is not needed.


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.
&&

$$

PUBLIC...10
AVIATION/MARINE...SS




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