Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 231921

Area Forecast Discussion
National Weather Service San Diego CA
1221 PM PDT Mon Apr 23 2018

Weak onshore flow will result in more widespread low clouds and fog
nights and mornings, otherwise fair and mild weather will continue
this week under weak high pressure aloft. Low pressure will move
toward the north coast of California late in the week, strengthening
the onshore flow, and deepening the marine layer. Areas of night
and morning coastal low clouds and fog will expand into the
valleys, along with cooling.



Areas of fog and coastal stratus have burned off this morning
revealing mild and moistly sunny conditions except for a few
clouds lingering at some of the beaches. Expect a renewal of
coastal fog and low clouds this evening through Tuesday morning.
Areas of fog will again affect coastal areas and along the mesas
with visibilities as low as 1 SM.

Weak high pressure aloft and otherwise benign synoptic pattern
will continue a deep marine layer contributing to night and
morning low clouds and fog each day through the end of the week,
with warm and sunny afternoons each day. Patchy dense fog could
bring some impacts near the coast and along the mesas each
morning. There will also be areas of brisk winds through mountain
passes and into adjacent deserts each evening, but with gusts
mainly 35 mph or less.

A low pressure trough will develop off the coast of Northern
California during the latter part of the week. Some model
solutions have it going northward this weekend, and others have it
digging southward, moving into Southern California around Sunday.
These solutions are bouncing around regarding the intensity of
this trough, but especially the timing of it. It could bring rain,
or nothing. We`ll need much more confidence before adding chances
of rain to the forecast. For now, the most responsible forecast
is for cooler weather with an expanded marine layer and more
extensive coastal clouds. Daytime temperatures look to sink below
average by the weekend.


231530Z...Coast...Low clouds and fog cover the the coastal areas
this morning, extending 5 to 10 miles inland. OVC cigs with bases
600-800 ft MSL will persist at coastal TAF locations until about
17Z, along with areas of fog reducing vis to 3-5 miles and locally 1
mile or less on higher coastal terrain. Partial clearing to the
beaches is likely between 17Z and 19Z with patches of low clouds/fog
lingering at the beaches into the afternoon. More low clouds/fog
should develop this evening, again spreading into the coastal areas
after 02Z Tuesday with similar bases/tops.

Valleys/Mountains/Deserts...FEW-SCT clouds at/above 25000 ft MSL
with unrestricted vis through Tuesday morning.


Patchy fog will occur over the coastal waters each night through
Wednesday, but visibility should remain above 1 NM. Otherwise 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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