Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 231537 AAA
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
830 AM PDT Mon Apr 23 2018

.Morning Update...

Areas of fog and coastal stratus continue this morning and will be
slow to burn off this morning. 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. No significant changes were needed to the forecast this
morning.

&&

.SYNOPSIS...
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 slight cooling.

&&

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

(Previous discussion)

Coastal low clouds are gaining traction this morning, with an assist
from a weak coastal eddy circulation over the coastal waters.
Visibilities are and will be rather low along the inland extent of
these clouds this morning: on mesas and into coastal hills and
valleys. Widespread dense fog is not expected, but patchy dense fog
is. Be aware of this on the morning commute, particularly if you`re
traveling on I-5 in southern OC and on I-15 or east I-8 in San Diego
County. Weak high pressure aloft will continue to bring us fair and
seasonal weather the next few days, with daytime temperatures a
little above average for late April. In fact, there are almost no
sensible changes or trends Tuesday probably through Thursday. So
expect similar cloud cover over coastal areas and western valleys
each night and morning, along with occasional high clouds over all
areas, especially Tuesday. There will also be areas of brisk winds
through mountain passes and into adjacent deserts each evening, but
with gusts mainly below 35 mph. 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.

&&

.AVIATION...
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.

&&

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

&&

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

&&

$$

PUBLIC...MM/JMB
AVIATION/MARINE...PG



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