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Area Forecast Discussion (AFD)

Issued by San Diego, CA (SGX)

                            
000
FXUS66 KSGX 111731
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
931 AM PST Tue Dec 11 2018

.SYNOPSIS...
Mid and high clouds over the region this morning will move to the
east this afternoon. Decreasing clouds with weak offshore flow
developing on Wednesday, however daytime temperatures west of the
mountains will remain in the sixties to low seventies. High 
pressure aloft and weak offshore flow will bring warming west of 
the mountains for Thursday with locally gusty northeast winds near
the coastal slopes of the mountains. A little cooler for Friday 
as onshore flow returns, then a little warmer for next weekend 
under weak high pressure aloft.

&&

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

Today through Thursday... A weak upper level low pressure system 
centered over the California bight this morning will continue to 
move toward the southeast. The subtropical moisture that it is 
drawing northward into portions of southern California in the form
of mid and high clouds will be pushed off to the east this 
afternoon. Some mid-level instability has resulted in enhanced
altocumulus with virga, and there have been no reports of precip
reaching the ground. Patchy low clouds and fog had developed near
the coast early this morning but they are being mixed out easily
due to an absence of a marine layer inversion.

High temperatures will vary only slightly from those of Monday 
for today and Wednesday with more patchy coastal low clouds and 
fog tonight into Wednesday morning.

For Thursday, building high pressure aloft along the West Coast 
and surface high pressure over the Great Basin and central Rockies
will bring warming west of the mountains and gusty east to 
northeast winds near the coastal slopes of the mountains and below
passes and canyons.

Friday through Monday... A trough of low pressure moving inland 
along the West Coast on Friday will bring a return of onshore flow
with cooling for coastal and valley areas. The return of onshore 
flow will also bring a return of patchy coastal low clouds and fog
for Friday night into Saturday morning. High temperatures will 
increase by a few degrees for Saturday and Sunday with weaker 
onshore flow and with weak high pressure aloft moving inland 
through the western states.

For Sunday night into Monday, a weak low pressure system in the
southern stream of the westerlies may amplify somewhere in the
vicinity of the southwest states. If it amplifies a little to the
west of southern California, it could bring some light
precipitation to portions of southern California. It it amplifies
to the east, the passage through southern California would be
mostly dry. This brackets the range of global model solutions for
early next week in the vicinity of the southwest states with no
clear model preference yet to emerge.

&&

.AVIATION... 
111625Z...Decreasing clouds during the day today but then areas of 
coastal low cloud redeveloping after about 12/06z tonight. Bases 
should be closer to 1500 feet MSL with tops to around 2000 feet MSL 
tonight, and visibilities locally near 3SM in haze.

&&

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

&&

.BEACHES...
Surf will create a high rip current risk today. Surf up to 6 feet is 
forecast, mainly in southern San Diego County, before subsiding 
tonight and Wednesday.

&&

.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...PG
AVIATION/MARINE/BEACHES...Small