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Area Forecast Discussion (AFD)

Issued by San Diego, CA (SGX)

                            
000
FXUS66 KSGX 171018
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
318 AM PDT Wed Oct 17 2018

.SYNOPSIS...
Weaker offshore flow will prevail into the weekend with locally
gusty northeast winds near the coastal foothills at times and a
slow warming trend for inland areas. For Sunday into early next
week, offshore lower level flow will weaken further if not turn
weakly onshore. Cooling is expected to develop near the coast and
spread into the valleys. Patchy night and morning coastal low 
clouds may return as early as late Saturday night into Sunday 
morning.

&&

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

.SHORT TERM (Today through Friday)...
Closed upper level low pressure is centered over northern Arizona
early this morning. It will weaken and move to the north and east
through Friday with another weaker upper low forming over the
southern California coastal waters on Friday as part of a 
blocking pattern along the West Coast. A few high clouds will move
southward across southwestern California this morning in the 
circulation around the upper low centered over northern Arizona.

Weak offshore flow will prevail through Friday with periods of
weaker northeast winds near the coastal foothills at times with
gusts mostly 35 mph or less. High temperatures will cool towards 
the coast in Orange County today with the weaker offshore flow 
while most other areas will warm slightly today and Thursday with
a little more warming on Friday. The weak offshore flow may 
strengthen slightly on Friday which would bring a little more of 
the warming towards the coast. 

&&

.LONG TERM (Saturday through Tuesday)...
The model trend in the past 24 hours for the extended portion of
the forecast is for the weak upper low off the southern California
to move slowly northward for Saturday into Sunday before weakening
and moving inland the Sunday and Monday. The main impact to
southwestern California of the northward shift of this weak upper
low is to shift to the north and east the axis of moisture 
feeding into the upper low from the southeast and east. This 
should reduce chances for any precipitation across southwestern 
California though a slight chance is still retained for areas 
around the San Bernardino Mountains for Sunday afternoon and 
evening.

High temperatures will continue to warm a few more degrees on
Saturday for inland areas with not much change near the coast.
A weak upper trough of low pressure along the Baja and southern 
California coast on Sunday will weaken and move inland early next 
week. This should further weaken the offshore lower level flow if
not turn the lower level flow weakly onshore. Some patchy stratus
may return near the coast as early as late Saturday night into 
Sunday morning. Cooling will develop near the coast on Sunday and 
spread into the valleys early next week.

&&

.AVIATION... 
170900z...Mostly clear today and tonight, except for variable high 
clouds across the interior this morning. Offshore winds mainly in 
the foothills 15-25 KT with gusts 25-35 KT between 14-23Z today, 
with isolated pockets of LLWS and moderate up/down drafts in lee of 
mountain crests.

&&

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

&&

.FIRE WEATHER...
Weaker offshore flow will prevail into the weekend with periods of
northeast winds near the coastal foothills at times with gusts
mostly 35 mph or less. Humidity for inland areas will slowly
recover through Thursday. Offshore flow might strengthen slightly
for Friday which would bring slightly stronger northeast winds
near the coastal foothills in Orange and San Bernardino Counties
with slight drying. However critical fire weather conditions are
not expected on Friday, even with slightly stronger winds and some
drying. Offshore lower level flow will weaken from the weekend 
into early next week if not turn weakly onshore at times. This 
will bring a greater recovery in humidity with some cooling 
spreading inland from the coast into the valleys for Sunday into 
early next week.

&&

.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/FIRE WEATHER...17
AVIATION/MARINE...MM