876
FXUS66 KSGX 202034
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
134 PM 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 afternoon, low clouds have mostly cleared except from parts
of Orange County, the Inland Empire and San Diego County coastal
areas. The high clouds from this morning have moved east with the
upper level trough axis. The low clouds will continue to clear for
one or two more hours before beginning to fill in the areas west
of the mtns. The marine layer may be marginally shallower tonight
but low clouds are expected to cover the areas from the coast
inland to the coastal mtn slopes by early tomorrow morning. Sfc
pressure gradients are still onshore with 4.2 mb SAN-DAG and 6.2
mb SAN-IPL. This continues to support westerly winds gusting 30-50
mph in the wind-prone passes and canyons. The winds will steadily
weaken overnight.

From previous discussion... 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...
202000Z...Coast/Valleys...Clearing has occurred in San Diego county
and most of western Riverside County with residual stratocu cloud
layer 2,500 to 3,500 ft AGL. Clearing is only partial in Orange
County affecting SNA. The return of clouds will be patchy and slow
after 02z and may not be widespread tonight as the marine layer
settles (lowers) in after the disturbance today. There is slight
offshore flow that accelerates clearing for ONT, SNA and SBD during
early Tuesday morning.

Mountains/Deserts...Clear skies with unrestricted VIS will continue
through this evening. West to northwest winds near 15-25 kts will
continue strenghten and expand across most desert locations. Wind
gusts will range from 25-33 kts at PSP and TRM, locally near 45 kts
in San Gorgonio mountain pass.  There is around a 30 percent chance
of a 35 kt gust at KPSP from 22Z Mon to 04Z Tue. Blowing dust could
locally reduce VIS to 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 Wednesday and
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 until 11 PM PDT this evening for Orange
     County Coastal Areas-San Diego County Coastal Areas.

PZ...None.

&&

$$

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