Cooler for this weekend, especially for inland areas with stronger onshore flow. The marine layer will deepen during the weekend with night and morning coastal low clouds extending well inland and onto the coastal slopes of the mountains. For Saturday afternoon into Sunday evening, southwest to west winds for the mountains and deserts will gust to 40 to 50 mph, with isolated gusts to 65 mph. The coast and valleys will warm on Monday with the greater warming for inland areas for Tuesday through Wednesday, followed by a slight cooldown from Thursday into Friday.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Today through tomorrow night,
An "inside slider" type major shortwave trough is going to deepen and propagate over the desert southwest, which will result in a tightening of the surface gradient and allow for winds to become rather strong and gusty over the higher terrain, and through the mountain canyons, where winds will be sustained up around 40 to 50 mph by later this afternoon for wind-proned areas. There could also be some isolated gusts approaching 65 to 70 mph for the windiest areas. There could be some areas of blowing dust, and especially within the Coachella Valley. For the high deserts, as min RH values drop into the low teens by later this afternoon, with strong and gusty winds, conditions will be favorable for fire growth and spread, although fuels are not yet critical for these areas. Onshore flow will also become more enhanced, leading to a more persistent marine layer, which will likely remain rather prevalent for the coastal areas. Temperatures will also be on the cooler side with some reinforcement of colder air behind this trough as it passes over the region, with highs being slightly below the seasonal average for this time of year, especially for the inland valleys, where highs will be as much as 10 degrees below average for some locations. Given the track of this system, it should remain dry, only perhaps a few areas of drizzle will be possible against the coastal slopes, otherwise just cooler and more breezy throughout the weekend.
Monday through Friday,
After passage of the trough moving through this weekend, high pressure is going to build back in behind it, with diminishing winds switching to a weak offshore flow aloft returning through the early part of the week. This will result in gradual warming through Wednesday before the longwave pattern becomes more zonal with only weak ridging aloft going into the latter half of the week. This will give way to the appearance of the more common "May Grey" diurnal pattern, with better coverage at the coast throughout the day, and temperatures slowly cooling off from Thursday into Friday. Dry conditions look to also persist through next week.
161800z, Coast/Valleys, Low clouds are beginning to break up along the coast though southern San Diego County looks to remain under low cloud cover for most of the period. Low cloud bases are expected to remain between 2000-4000ft MSL with a few clouds moving in and out AOA 1500ft MSL. Low clouds will increase in coverage after 23Z beginning in SD County, stretching north and filling inland valleys after 00Z. Low clouds are expected to reach coastal OC after 06-08Z. Minor VIS reductions (3-5SM) expected for some elevated inland valleys, with lower VIS where clouds intersect terrain.
Mountains/Deserts, Winds have been gusty out of the north to northwest and will continue through this evening. Gusts have already reached 25-35 knots in desert slopes and mountain passes, locally up to 50 knots. MOD up/downdrafts and local LLWS in lee of mountains. Winds will continue to strengthen into the afternoon with widespread gusts 35-45 knots, locally to 60 kts in wind prone locations. Winds will remain gusty through Sunday. Strong up/downdrafts in lee of mtns with BLDU and reduced VIS expected. Otherwise, SKC and VFR expected through the period.
Gusty westerly winds with gusts 20-30 kt will develop in the outer coastal waters late this afternoon. The strongest gusts will occur near San Clemente Island. Seas of 7-10 feet with a 9-12 second period will generate choppy seas. Winds and seas will slowly diminish through the day Sunday. A Small Craft Advisory is in effect and contains more information.
A westerly swell from 290 degrees with a 9 to 10 second period will bring elevated surf of 4 to 6 feet, sets to 7 feet this afternoon through Monday morning. Highest surf at west to northwest facing beaches. The combination of elevated surf and high tides of 6.5 to 7 feet will result in minor tidal overflow, especially for beach parking lots and boardwalks. Surf will start to decrease Monday afternoon. A Beach Hazards Statement is in effect and contains more information.
Ca, Beach Hazards Statement from 6 PM PDT this evening through Monday morning for Orange County Coastal Areas-San Diego County Coastal Areas.
Wind Advisory until 11 PM PDT Sunday for Apple and Lucerne Valleys-San Bernardino County Mountains-San Gorgonio Pass near Banning.
Wind Advisory until 11 PM PDT Sunday for Riverside County Mountains-San Diego County Deserts-San Diego County Mountains.
PZ, Small Craft Advisory from 3 PM this afternoon to 7 AM PDT Sunday for Waters from San Mateo Point to the Mexican Border Extending 10 to 60 nm out including San Clemente Island.
