The marine layer will gradually deepen to around 5000 feet by early Wednesday, with night and morning coastal low clouds extending inland and onto the coastal slopes of the mountains. High temperatures will lower by several degrees for Tuesday and Wednesday reaching as much as 15 to 20 degrees below average in the mountains on Wednesday. Southwest to west winds in the mountains and deserts will strengthen for Tuesday afternoon through Wednesday night, with gusts of 35 to 45 mph with isolated gusts to 65 mph through the passes. There could be patchy drizzle or light rain from the coast to the mountains during the nights and mornings from late tonight into Thursday morning. There will be warming for Friday through next weekend, with high temperatures a few to around 5 degrees above average for next Sunday.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
New Aviation and Marine Discussion,
The marine layer is currently about 3500-4000 ft deep with an inversion noticeably weaker than yesterday. This morning, the low clouds had extended inland to the coastal mtn slopes but now most areas are clearing except for the coastal areas of San Diego County. The clearing is likely to continue for a few more hours and the beaches of southern San Diego County could still see some sunshine.
Weak, large-scale troughing over SoCal will be reinforced with colder air as a low pressure system moves in from the northwest. It will bring a cooling trend through Thursday. Wed and Thu are likely to be the coolest days with daytime high temperatures 10-15 degrees below average in the inland valleys and deserts while the mountains could be as much as 20 degrees below average. The coastal areas will be near or a few degrees below average. This system will also bring stronger onshore flow and a deepening marine layer. Southwest to west winds will strengthen for Tue into Thu with wind gusts of 35 to 45 mph in the mountains and deserts, locally gusting to 65 mph in the favored locations. The marine layer could deepen to about 5000 ft by Wed, and could produce patchy drizzle or light rain west of the mtns each night and morning into Thursday morning.
Toward the end of the week, temperatures rise as the low pressure system moves east into the Rockies. Next Sun and Mon will likely be the warmest days with temperatures generally a few degrees to about 8 degrees above average. High temperatures for next Mon will likely range from 70-75 near the coast to the low 90s for the Inland Empire, with the lower deserts around 105. The marine layer will also be shallower with night and morning low clouds not spreading as far inland.
260430z, Coast/Valleys/Foothills, Low clouds with bases 2500- 3000ft MSL have filled in from the coast to the foothills of the San Diego County mountains. Low clouds are beginning to develop in Orange County and along the edges of the Inland Empire, and will continue to increase and spread throughout the coastal basin over the next few hours. Patchy drizzle will be possible around 13-18Z as the marine layer deepens. Highest chances will be in areas near the coast. Cloud bases will likely lift slightly after 17-19Z to 3000- 3500ft MSL and scatter in the Inland Empire. Higher Mountains/Deserts, Mostly clear skies and VFR conditions expected through the TAF period. West to southwest winds have developed, creating stronger winds in the mountain passes and desert slopes. These winds will increase after 18-19Z with gusts up to 35 to 45 mph with isolated gusts to 65 mph through the passes.
Winds and seas increase Tuesday afternoon and into early Wednesday, generating hazardous conditions for small craft in the outer waters. For more details, read the Small Craft Advisory. Otherwise, no hazardous marine conditions are expected through Saturday.
Ca, Wind Advisory from 3 PM Tuesday to 5 AM PDT Thursday for Riverside County Mountains-San Diego County Deserts-San Diego County Mountains-San Gorgonio Pass near Banning.
Wind Advisory from 3 PM Tuesday to midnight PDT Tuesday night for Apple and Lucerne Valleys.
PZ, Small Craft Advisory from 1 PM Tuesday to 1 PM PDT Wednesday for Waters from San Mateo Point to the Mexican Border Extending 10 to 60 nm out including San Clemente Island.
