Ion Discussion,
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.
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.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
.Updated Aviation Discussion,
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.
270300z, Coast/Valleys, Mostly SKC this evening, even off the coast. Model guidance is suggesting very patchy cloud development near the coast through around 05z beforfor the 06z TAF Packagee coverage slowly starts increasing and spreading inland (including the Inland Empire) up to the foothills through 09z. Bases 1800-2500 ft MSL. Even at maximum coverage (around 10z), ceilings will be patchy, especially in SD County. Patchy vis reductions (3-6SM) for highest inland valleys (Hemet, Ramona, ) and foothills with cigs. Clouds scatter back toward the coastline 14-18z Sat. Low clouds begin redeveloping along the SD County coast after 01z Sun with similar bases.
Mountains/Deserts, Mostly clear and VFR conditions expected through Saturday evening. 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. MOD up/downdrafts in lee of mountains. Winds slowly weaken 06-12z Sat, remaining locally strong (25-40 kts) along desert slopes and through passes. West winds increase once again - even stronger than this evening - after 21z Sat. Top gusts peak Saturday evening, reaching 35-55 kts along desert slopes and up to 65 kts through the Banning Pass.
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.
While the long-period south swell has mostly diminished, a brief uptick in period (15-17 seconds) this evening will create locally elevated surf up to 5 feet and higher rip current risk along south facing beaches.
Ca, Wind Advisory until 5 AM PDT Sunday for Apple and Lucerne Valleys.
Wind Advisory until 11 AM PDT Sunday for San Diego County Deserts.
Wind Advisory until 5 PM PDT Sunday for San Gorgonio Pass near Banning.
PZ, None.
