Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 202021

Area Forecast Discussion
National Weather Service San Diego CA
121 PM PDT Mon Aug 20 2018

Southwestern California will be on the western fringe of
monsoonal moisture, which will bring a slight chance of
thunderstorms today and Tuesday in the mountains and deserts.
Dry and fair weather will follow for the rest of the week, with
coastal clouds nights and mornings.



High clouds from Mexico have migrated north today and so far only
some fair weather cumulus have developed over the mountains. An
increase in monsoonal moisture and instablity have created a small
chance of thunderstorms in the mountains and deserts this
afternoon, but right now those cumulus clouds don`t look too
interested. A thunderstorm complex in Sonora tonight will turn
into an easterly wave that moves northward into Arizona Tuesday.
Most of the thunderstorm action will stay in Imperial Valley or
Arizona, but we`re close enough on its western fringes to mention
a small chance of thunderstorms over our lower desert and eastern
slopes of the mountains. Not a whole lot of change occurs this
week in the overall pattern, which features a weak low-pressure
trough over the Pacific Northwest along with a high- pressure
ridge over New Mexico and Texas. This set up effectively cuts off
the monsoon flow which will keep our forecast dry Wednesday and
beyond. The rather stagnant holding pattern will mean no
discernible temperature trends or changes in the marine layer this
week. Westerly winds aloft increase later this week, which will
increase mountain/desert winds during afternoons/evenings. Coastal
clouds will continue pretty much as is each night and morning
covering coastal and western valley areas, playing peek-a-boo with
the Inland Empire. Next week that Pac NW trough appears to deepen
a little further, which would bring cooler weather, stronger
mountain/desert breezes and a more extensive coverage of coastal
clouds if it pans out as currently depicted.


202020Z...Coasts/Valleys...SCT012 near the coast this evening
becoming BKN-OVC012-015 tops 022 after 03Z and spreading 25 miles
inland through 14Z Tuesday. A brief period of 4SM BR BKN010 at KONT
between 12Z-16Z Tuesday.

Above the marine layer...BKN200 through Tuesday morning.

Mountains/Deserts...SCT100 BKN200 through Tuesday morning. Small
chance for an thunderstorm Tuesday afternoon CB bases 10000 ft MSL
and tops to 40000 ft MSL.


No hazardous marine weather is expected through Friday.


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





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