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

Evening Update
Low clouds continue to move over the coastline this evening with cloudy skies taking form over much of San Diego. Forecast remains on track with latest model guidance in bringing in low clouds for most western valleys through the early morning hours, with a small chance of low clouds reaching the Inland Empire. Onshore flow will decrease this evening and lightly continue with the troughing pattern into Thursday, with desert areas becoming near 5 degrees cooler than they saw today. Minimal changes will occur through the weekend. Probabilities still look low in seeing any precip with this troughing pattern, but are non-zero. A better chance exists by early next week, as a colder closed low moves near the area.

From previous discussion...
This afternoon...Low clouds persist over the coastal waters and at a few beach locations but will likely return to the coastal areas and spread inland to the foothills overnight. Temperatures are generally lower than at this time yesterday, with some inland locations as much as 15 to 18 degrees cooler.

Through Friday...The relative humidity for the deserts onto the desert slopes of the mountains will fall to 5 to 10 percent this afternoon. This very low humidity combined with southwest to west winds gusting 30 to 40 mph will create critical fire weather conditions for the deserts on the lower desert slopes of the mountains this afternoon and early evening. West of the mountains, additional cooling and deepening of the marine layer will bring a greater recovery in humidity for Thursday and Friday, with weakening winds.

Cooling will continue today with high temperatures an additional 5 degrees cooler than Tuesday to as much as 10 to 15 degrees cooler for the valleys and inland Orange County. High temperatures for the inland valleys will be mostly in the 80s, with high temperatures for the coast and valleys 5 to locally 10 degrees below average. High temperatures on Friday will change little near the coast with the deserts becoming another 5 degrees cooler.

The marine layer will continue to deepen into Friday with the coastal low clouds spreading farther into the valleys each night.

The smoke from the Bridge, Line and Airport fires will continue to spread off toward the east and northeast and across the deserts with flow aloft from the southwest to west.

Saturday through Tuesday...Numerical models are beginning to converge on a solution, with some narrowing of the ensemble spread with respect to timing and trajectory. The next low pressure system will likely move inland along the West Coast some time around late Sunday into Monday. After cooling for today into Thursday, there will be only minor day to day differences in high temperatures for Friday through the weekend. Additional cooling is expected for next Monday and Tuesday, with high temperatures in the mountains and inland valleys falling to 15 to 20 degrees below average with high temperatures for the inland valleys mostly in the 70s and high temperatures for the lower deserts in the 80s and lower 90s.

Night and morning coastal low clouds will continue to spread into portions of the inland valleys over the weekend and spread onto the lower coastal slopes of the mountains early next week. It's possible there could be some light precipitation from the marine layer around Monday with NBM chances of measurable precipitation from the coast to the mountains of 15 to 20 percent.

After the stronger onshore winds this afternoon and evening, most model ensemble members show weaker winds through the weekend then another round of similarly strong winds next Monday with the inland movement of the next low pressure system.



AVIATION
120300Z...Areas of near-surface smoke and smoke layers aloft from ongoing fires near Santiago Peak (Airport Fire), Wrightwood (Bridge Fire) and Running Springs (Line Fire) will continue through Thu evening. Local VIS will be below 3 miles in smoke, with local BKN CIGs 5000-10000 ft MSL.

Low clouds will gradually develop and expand along the San Diego County coast 03Z-07Z Thu and along the Orange County coast 04Z-10Z Thu, extending 20-35 miles inland by 13Z Thu, including far W and S parts of the Inland Empire. There is a 15% chance for CIGs around 1000 ft MSL and reduced VIS 3-5 miles at KONT 11Z-16Z. Bases will generally be 1500-2200 ft MSL with tops to 2500 ft MSL. Most areas will clear 15Z-18Z Thu, except parts of the southern San Diego County coast will have CIGs through 21Z Thu. Stratus will develop earlier Thu evening along the coast.

Areas of west-southwest winds 25-40 kt over the desert slopes and into the deserts, will gradually weaken 05Z-08Z Thu, with MOD UDDFS over and east of the mountains. Some increase in wind will occur again Thu after 22Z with gusts mostly 20-35 kt.

MARINE
No hazardous marine conditions are expected through Monday.



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



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