Cooler weather persists through the weekend, with a deeper, more persistent marine layer and night and morning coastal low clouds extending well inland and onto the coastal slopes of the mountains. Southwest to west winds for the mountains and deserts will gust to 40 to 50 mph through Sunday, with isolated gusts to 65 mph. Gradually warmer, dry weather with generally weak winds will follow Monday through Thursday, 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 Monday 5/18, A broad trough over thewestern U.S. centered over the Great Basin is leading to our current cool, breezy weather. Current westerly gusts over the mountain desert slopes into the deserts are 30-50 mph, with gusts to 65 mph through the Banning/San Gorgonio passes. Peak gusts to 40-50 mph with isolated 65-70 mph through passes are expected through Sunday. Winds weaken slightly late tonight through Sunday morning, before strengthening again to similar levels Sunday afternoon and evening. This will lead to areas of blowing dust which could result in locally lowered visibility. Elsewhere, winds are more moderate with peak gusts generally 15-25 mph for the coasts and valleys.
Cool air brought by the trough in combination with more persistent marine layer cloud cover today are contributing to temperatures on the cooler end this afternoon, with highs near average to about 6 degrees below average widespread through the region. Sunday will be cooler than today, with high temperatures a few up to 10 degrees cooler than average. This will amount to high 60s to low 70s for the coasts and valleys, high 70s for the high desert, and 80-92 degrees for the San Diego desert and Coachella Valley. Cloud cover will continue to persist today, becoming more widespread this evening and moving to cover the entire coastal basin again overnight. Patchy areas of drizzle are possible tonight, most likely along the mountain foothills and for San Diego County. More clearing is expected Sunday, but patchy cloud cover will linger, especially towards the coast/western valleys.
As the axis of the trough continues to move to the east into the Intermountain West late Sunday into Monday, winds will turn offshore (north to northeast) in the deserts as they gradually weaken. Temperatures will start to warm for coastal and valley regions while the mountains and deserts continue to cool a few degrees.
..Tuesday 5/19 through Saturday 5/23, While broadtroughing lingers over the western U.S., mid-level heights will build over the region, resulting in gradual warming Monday through Thursday, to a few to 10 degrees above average by Wed/Thu. Winds will return to average next week, with daily afternoon sea breezes mountains westward and periodic, weak offshore winds in the deserts. The return of deeper low pressure aloft Thursday into the weekend will lead to slightly lowered temperatures and the return of the more typical "May Grey" cloudy weather with possible patchy drizzle.
170600z, Coast/Valleys, SCT-BKN deck of clouds around 3000-4000ft has been retreating to the inland valleys and coastal slopes over the last few hours, with the lower deck of clouds near 1800-2400ft MSL also becoming more sparse and limited to inland valleys. As a coastal eddy is expected to strengthen overnight, expecting MVFR CIGs near 2500ft to gradually fill in along the coasts again from south to north between 08-12z Sunday. Localized VIS reductions to 3- 5SM in BR expected for some elevated inland valleys, with obscurations where clouds intersect terrain. Elevated south- southwest winds expected to pick up as the coastal eddy strengthens overnight, with gusts 15-20 knots picking up after 16z Sunday. Most cloud cover expected to clear out by 18z with VFR prevailing thereafter.
Mountains/Deserts, Gusty north to northwest winds of persisting this evening. Widespread 25-35 knot gusts expected in the deserts, locally up to 55-60 knots in vulnerable mountain passes such as the Banning Pass. Gusts gradually relaxing between 09-15z Sunday, with elevated gusts 25-30 kts lingering for mountain passes. Similar, but slightly stronger, gusts will pick back up after 18z. MOD up/downdrafts and local LLWS in lee of mountains as well as localized VIS reductions to 4-6 SM in BLDU expected, especially during periods of strong gusts.
West-northwest gusts up to 20-25 knots remain possible for the outer coastal waters near San Clemente Island through about 5 AM Sunday. In addition to the winds, 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 remains in effect until 7 AM Sunday and contains more details.
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 through Monday morning. Highest surf on 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 remains in effect until 9 AM Monday and contains more details.
Ca, Beach Hazards Statement 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-Riverside County Mountains-San Bernardino County Mountains-San Diego County Deserts-San Diego County Mountains-San Gorgonio Pass near Banning.
PZ, Small Craft Advisory until 7 AM PDT Sunday for Waters from San Mateo Point to the Mexican Border Extending 10 to 60 nm out including San Clemente Island.
