Blowing Dust Advisory 1, NWS San Diego, CA

Area Forecast Discussion
National Weather Service San Diego CA
117 PM PDT Wed Apr 21 2021

.SYNOPSIS...
A weak low pressure system will move through Southern California
through Thursday with gusty mountain and desert winds, more clouds,
and periods of light rain or drizzle along west of the mountains.
There is also a small chance of isolated, heavier showers over the
higher mountains on Thursday afternoon. It will be much cooler
through Thursday, then warmer into the weekend as a weak ridge
develops aloft. A stronger Pacific storm system will arrive early
next week with a chance for more widespread and heavier rain and
mountain snow.

&&

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

Clouds prevailed west of the mountains at midday, although there
were plenty of breaks providing some sun. Little if any rain shower
activity was observed at the noon hour. Most reporting sites were
considerably cooler than midday yesterday. Moderate to strong
onshore sfc pressure gradients across the region were supporting
stronger winds through the passes. Peak gusts were over 60 MPH
there, but peak gusts to around 40 were more broadly prevalent in
the desert.

Low pressure is centered over SW NV at midday. It will be trailed by
a weak trough aloft through Thursday. Scattered, light showers will
likely redevelop and continue along and west of the mountains ahead
of the trough tonight, shifting toward the mountains on Thursday.
Instability and moisture will still be sufficient for isolated,
heavier showers to develop over the mountains on Thursday afternoon.
Aside from that, rainfall totals through Thursday night are expected
to remain below one-quarter inch, except near the coastal mtn slopes
where isolated heavier amounts are possible. A few light showers may
redevelop Thursday night west of the mountains, but after early Fri
morning, fair and dry weather is expected through the weekend.

A weak ridge will drift over SoCal this weekend, suppressing the
marine layer and weakening the onshore flow. This will set up SoCal
for modest warming under fair skies as temperatures return to
about average levels.

An anomalous, late season Spring storm still has it's sights set on
SoCal for Monday. Precipitation will spread south through the
northern half of the State on Sunday, reaching the south by Monday
morning, based on current trends. All of the ensemble members of the
ECMWF are wet, while about one-third of the GFS members remain dry.
Most of the Canadian members are wet too, so pretty good odds for
precipitation. It could be substantial as well, with the models
showing a decent tap on some Pacific moisture. And given the depth
of the saturated layer, some of this should make it into the
deserts. Depending on the speed of the system, some precipitation
could continue into Tuesday.

For the latter half of next week, many of the ensemble members of
the various global models show warming, but it doesn't last, as
heights begin to fall along the West Coast again. The trend is for
cooling the following week to end the month.

&&

.AVIATION...
212000Z...BKN-OVC low clouds with bases 3500-4500 feet continuing
through this evening. Coastal mtn slopes below 5000 feet remaining
obscured in low clouds/fog through Thursday morning. Clouds lowering
to 1800-2500 feet after 03Z Thursday. Areas of -DZ/-SHRA possible
again tonight through Thursday morning over and west of the
mountains, with vis reduced down to 2-5 miles.

Southwest to west winds with surface gusts 30-40 kt will continue
through this evening along the ridges/desert slopes and east of San
Gorgonio Pass, weakening tonight into Thursday morning. Moderate
up/downdrafts and areas of LLWS will be possible over/east of the
mountains.

&&

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

&&

.BEACHES...
A south swell from 180-190 degrees of 3-4 ft with a period of 16-20
seconds will reach the beaches of Southern California Friday through
Sunday. This swell could bring elevated to possibly high surf,
especially to the south-facing beaches of Orange County, as well as
strong and dangerous rip and longshore currents at all beaches.
Occasional sets of 6-7 feet will be possible at south facing beaches
of Orange and far northern San Diego Counties, with surf of mostly 3-
5 ft elsewhere. &&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory until 10 PM PDT this evening for San Diego County
     Deserts-San Gorgonio Pass Near Banning.

PZ...NONE.

&&

PUBLIC...10
AVIATION/MARINE...Connolly