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Area Forecast Discussion (AFD)

Issued by San Diego, CA (SGX)

                            
000
FXUS66 KSGX 120519
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
919 PM PST Tue Dec 11 2018

.SYNOPSIS...
High pressure aloft will build into the area through late week
along with offshore flow as surface high pressure builds into the
Great Basin and Rockies. Warming will occur west of the mountains
for Thursday with locally gusty northeast winds near the coastal 
slopes of the mountains and through and below passes. 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...

...Update...

Some fog has already developed with 1/4 mile visibility at Ramona,
but most locales are running 3-6 miles. Believe dense fog will
remain patchy with low clouds though spreading into the inland
valleys. No changes were made to the forecast this evening.

...Previous Discussion (Issued at 143 PM PST Tue Dec 11 2018)...

Today through Thursday... A weak upper level low pressure system 
centered over the California bight this morning continues to move 
toward the southeast. The subtropical moisture being advected 
northward in the form of mid and high clouds has been displaced
eastward this afternoon. A few low clouds linger over the coastal
areas and inland valleys. Patchy low clouds and fog will likely
return to areas west of the mtns and could increase in coverage
late tonight.

High temperatures through Wednesday will vary only slightly from 
those of Monday.

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. The most recent runs of the
deterministic medium-range models continue to disagree
significantly on the potential for precip next Tuesday. The GFS
favors a wet solution and the European model favors a dry
solution.

&&

.AVIATION... 
120440Z...Patchy stratus with bases 1500-2500 ft MSL developing 
along the coast and up to 30 mi inland overnight. Local vis 3-5 SM 
possible in the coastal areas and valleys 06-15Z. Low clouds 
clearing 14-17Z. Low clouds may redevelop Wednesday evening, but 
confidence is low in timing and coverage.

&&

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

&&

.BEACHES...
A west-northwest swell of 7 ft/13-14 sec from 290 degrees will 
continue to bring elevated surf of 3-5 ft with local sets to 6 ft 
and strong rip currents through Wednesday morning. Swell and surf 
will quickly lower through the day.


&&

.SKYWARN... 
Skywarn activation is not needed.


&&

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

$$

PUBLIC...Gregoria (Update)/PG (Prev Discussion)
AVIATION/MARINE...SS