textproduct: San Diego

SYNOPSIS

Windy on the desert mountain slopes and into the deserts, well below average temperatures across Southern California, and a deeper marine layer this weekend. Areas of drizzle are possible Saturday and Sunday mornings. Conditions will gradually warm into next week.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES...

A unseasonable trough of low pressure is still on track to dig into the Great Basin late this weekend. This will increase the onshore pressure gradient, resulting in stronger westerly winds on the desert mountain slopes into the deserts, well below average temperatures, and a deep marine layer. By Sunday, highs are expected to be 7 to 9 degrees below average at the coast and low deserts and 15 to 20 degrees below average in the valleys, mountains, and High Desert. There is also a potential for patchy drizzle west of the mountains both Saturday and Sunday morning.

Peak wind gusts today of 35 to 55 mph, combined with relative humidity 7 to 15 percent in the deserts will create periods of near critical to locally critical fire weather conditions in the deserts and on the desert slopes of the mountains. For more information on fire weather concerns, see the Fire Weather section below. Winds are expected to become more widespread and peak in strength on Saturday afternoon and evening, with peak gusts 50 to 65 mph with locally higher gusts possible below the San Gorgonio Pass. Winds will decrease Sunday into next week.

Global ensembles are indicating broad scale weaker troughing may linger into the end of next week. Even with the lingering troughing, heights will rise leading to a gradual warming. About 27 percent of ensemble guidance is indicating a ridge may begin to build back near the Four Corners region by next weekend, all other solutions maintain some degrees of troughing over the Western United States. By next Friday, highs are still forecast to be 3 to 7 degrees below average. The weak troughing will maintain a deeper marine layer into at least the middle of next week, decreasing in depth for the end of the week.

AVIATION

261800Z...Coast/Valleys...SKC through this afternoon. Patchy low clouds based 1800-2500 ft MSL will push back into coastal areas 00- 03z Sat. Clouds quickly push inland late Friday evening and overnight, filling the coastal basin by 09-10z Sat. Clouds scatter back toward the coastline 14-18z Sat.

Mountains/Deserts...Mostly clear and VFR conditions expected through Saturday morning. West-wouthwest winds strengthen after 21z this afternoon. Gusts 25-40 kts to occur this evening for deserts and desert slopes with gusts locally to 55 kts through wind-prone slopes and passes. There is a 25% chance for gusts exceeding 35 kts this evening at KPSP and higher chances in the vcnty, north and east of KPSP. MOD up/downdrafts in lee of mountains. Winds slowly weaken 06- 12z Sat, but gusts 25-40 kts will continue along desert slopes and through passes.

MARINE

Breezy NW winds gusting over 20 kts Saturday afternoon and evening near San Clemente Island may create hazardous conditions to small craft. Otherwise, no additional hazardous marine conditions are expected through Wednesday.

BEACHES

While the long-period south swell has mostly diminished, a brief uptick in period (15-17 seconds) this afternoon and evening will create locally elevated surf up to 5 feet and higher rip current risk along south facing beaches.

FIRE WEATHER

Southwest to west winds for the mountains and deserts will gust to 35 to 55 mph this afternoon. Lowest humidity for this afternoon and early evening for the Apple and Lucerne Valleys will fall to 10 to 15 percent and for the lower deserts to 6-10 percent. This will result in near critical to locally critical fire weather conditions for this afternoon and early evening for the deserts onto the desert slopes of the mountains. Stronger winds will continue for Saturday afternoon and evening for the mountains and deserts, but with lowest humidity for the deserts on Saturday recovering to 15 to 25 percent.

SKYWARN

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

SGX WATCHES/WARNINGS/ADVISORIES

CA...Wind Advisory until 5 AM PDT Sunday for Apple and Lucerne Valleys.

Wind Advisory from 5 PM this afternoon to 11 AM PDT Sunday for San Diego County Deserts.

Wind Advisory until 5 PM PDT Sunday for San Gorgonio Pass near Banning.

PZ...None.