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Area Forecast Discussion (AFD)

Issued by San Diego, CA (SGX)

                            
000
FXUS66 KSGX 190436
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
936 PM PDT Tue Jun 18 2019

.SYNOPSIS... 
It will be a bit warmer through Wednesday, with only minor 
variations near the coast. By Thursday, westerly winds will pick-
up and become quite gusty late in the day over the mountains and 
deserts. The marine layer will deepen and likley begin to leak 
more drizzle Friday, and possibly again Saturday morning with 
minimal daytime clearing. Slightly warmer and drier on Sunday, but
daytime temperatures will continue below normal, and clearing may
still be a struggle along the coast into next week.

&&

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

.UPDATE...
The trough moving to our southeast and the ridge building to our
northwest helped to strengthen offshore flow above 4000 ft this
afternoon, which helped to clear out the marine layer stratus
across our area for the first time in a few days. Other coastal
locations from just north of Orange County to just north of San
Francisco were not as lucky. Low clouds should slowly redevelop
over coastal and valley areas overnight. Lows tonight will be
mostly near normal overnight.

&&

.PREVIOUS DISCUSSION FROM 151 PM THIS AFTERNOON...
A weak trough over SoCal is getting squeezed to the south, as a 
ridge noses in from the NW through Wednesday. The effects of this 
(slight warming and more breaks in the cloud cover) will be 
temporary with a long-wave trough in the westerlies to the north 
on track to deepen over the West later this week. An initial
shortwave is forecast to swing SE over the Great Basin on Friday. 
Ahead of this, sfc pressure falls rev up SW-W winds over the mts/ 
deserts, and deepen up the marine layer through Saturday. Low-level 
atmospheric moisture is rather high, and models show the marine 
layer readily becoming saturated, leading to drizzle or some light 
rainfall over the coastal basin Fri, and possibly again on Sat 
morning. Some measurable rain is possible, although amounts will be 
light. 

The gusty winds over the mts may result in blowing dust and sand in 
the deserts late Thu through Friday and may require a Wind Advisory 
issuance as well. The winds will drop off over the weekend as the 
sfc pressure gradient relaxes, but onshore flow and a deep marine 
layer will prevail under weak troughing aloft. 

By mid next week there are some signs of the subtropical high 
lifting northward from Mexico. At the same time, models continue 
troughing along the West Coast. This sharpens up dry, SW flow aloft 
over SoCal, but also maintains good onshore flow at the sfc and 
significant marine layer presence west of the mts. Bottom line...
the quiet June pattern continues for us well into next week.

&&

.AVIATION...
190258Z...Coast/Valleys...Mostly clear skies in all areas early this 
evening will start to become covered in stratus after 06Z and push 
inland. Bases expected around 1000-1400 feet MSL and extending into 
inland valleys after 05Z. Reduced vis 2-5SM and bases as low as 700 
ft MSL for inland valleys between 11-16Z with some coastal slopes 
obscured in clouds. Scatter out inland after 17Z Wednesday 
advancing to most coastal areas, though some beaches may remain BKN-
OVC for the part of the afternoon.

Mountains/Deserts...Mostly clear with unrestricted vis through 
Wednesday morning. A few cumulus over mountains during afternoons.

&&

.MARINE... 
No hazardous marine conditions are expected through Saturday. 

&&

.SKYWARN... 
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.

&&

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

$$

UPDATE...JJT
PUBLIC...JAD
AVIATION/MARINE...APR