944
FXUS66 KSGX 201632
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
932 AM PDT Mon May 20 2024

.SYNOPSIS...
A large-scale trough over western North America will persist
through this week. Temperatures will remain below seasonal
averages with gusty winds across the mountains and deserts. An
upper level disturbance moving across the region today will bring
the coolest and windiest conditions overall. Low clouds will
continue nights and mornings, retreating back to the coast each
afternoon.

&&

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

This morning, the sounding and aircraft reports show the marine
layer almost 5000 ft deep, with low clouds covering most of the
areas west of the mtns and extending to the top of the Cajon Pass
in the San Bernardino mtns. A few locations also reported drizzle
earlier. There are also mid and high clouds streaming across San
Diego, Riverside and portions of eastern San Bernardino Counties
as the upper low that was to our southwest is being drawn into the
mean flow and becoming an open wave. These higher clouds and
associated mixing may be affecting the low clouds which are
breaking up in San Diego county at this hour. It`s likely that
we`ll see clearing similar to the last 2 days but it may be a
little slower due to a slightly stronger inversion. Sfc pressure
gradients remain strongly onshore with 8.1 mb SAN-TPH and 6.8 mb
SAN-IPL. At this hour, winds are gusting between 30 and 60 mph in
the wind-prone locations of the mtns and desert slopes. The winds
may strengthen further this afternoon before weakening overnight
as the upper level trough axis moves to the east. Isolated top
gusts through San Gorgonio Pass exceeding 50 mph will continue
through this evening, but more widespread gusts of 35-45 mph.

As the trough axis moves east, the trend will be toward a
shallower marine layer and weaker winds. That should bring more
sunshine west of the mountains and weaker winds in the mountains
and deserts for Tuesday and Wednesday. High temperatures in the
60s to low 70s west of the mountains today represent up to 10
degrees below normal in the valleys. Tuesday and Wednesday will be
a few degrees higher, approaching but still not achieving normal.
A very weak trough rotates through California again Thursday into
Saturday. This should deepen the marine layer again and extend
low clouds into foothills each night and morning, and make it
harder for coastal areas to get sunshine in the afternoons. This
will also boost those seasonal winds in the mountains and deserts.
The cooler weather starts Thursday, and right now, Saturday
appears to be the coolest day, when temps will be more than 10
degrees below normal in the valleys. Next week the mean trough
over the West appears to weaken, maybe making way for an actual
ridge of high pressure. While ensembles paint a wide range of
outcomes, most solutions indicate at least weaker low pressure and
warmer weather next week.

&&

.AVIATION...
201530Z...Coast/Valleys...Widespread low clouds with ceilings 1200
to 3000 AGL and the marine layer top is around 4000 feet MSL. Clouds
are extending into the mountain passes and also getting disrupted
due to the weather disturbance arriving from the south. There
should be rather rapid clearing from south to north through 18z.
The return of clouds will be patchy and slow after 02z and may not
be widespread tonight as the marine layer settles in after the
disturbance today.


Mountains/Deserts...Clear skies with unrestricted VIS will continue
through this evening. West winds near 15-25 kts this morning will
strenghten and expand across most locations by the afternoon hours,
where wind gusts will range from 20-30 kts, locally near 45 kts in
San Gorgonio mountain pass.  There is around a 50 percent chance of
a 30 kt gust at KPSP from 22Z Mon to 04Z Tue. Blowing dust could
locally reduce VIS to 3-5 miles at times. Winds decreasing after
06z.

&&

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

&&

.BEACHES...
A series of southwest swells of 2-3 ft at 16-18 seconds from 200-220
degrees will produce elevated surf of 3-5 ft with locally higher
sets on exposed SW facing beaches, as well as a high risk of rip
currents at all beaches. A Beach Hazards Statement is in effect
through this evening. Swell and surf will slowly lower Tuesday
through Thursday.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement through this evening for Orange County
     Coastal Areas-San Diego County Coastal Areas.

PZ...None.

&&

$$

PUBLIC...PG
AVIATION/MARINE/BEACHES...Tardy