18/944 AM.
Showers and thunderstorms will be possible through Saturday for portions of Los Angeles and Ventura Counties, with the best chance today across the San Gabriel Mountains and Antelope Valley. Night through morning low clouds and fog will continue for most coasts and valleys. Below normal temperatures are expected, with a possible warming trend starting late next week.
(tdy-Sun), 18/940 AM.
***UPDATE***
Monsoon moisture has finally arrived into the southland with PW's up to 1.6" locally and close to 2" to the east and south. The added moisture aloft is also playing games with the marine layer across LA and Ventura Counties, resulting in lots of clear or partly cloudy skies at the coasts this morning.
Shower chances across all of LA County will linger into late morning, with little precipitation if any, and a non-zero chance of isolated lightning strikes. This afternoon into evening, daytime heating will enhance the chance of showers and thunderstorms across higher terrain. Storms are most likely for the eastern San Gabriel Mountains, eastern Antelope Valley, and the Ventura County Mountains, with a slight chance of drifting south into the San Gabriel Valley foothills or Ventura foothills. Hazards with a storm may include; fire starts from dry lighting, damaging winds, and localized flooding, though the greatest flooding potential will be for eastern LA County Mountains/deserts.
***From Previous Discussion***
Temperatures today are expected to be a few degrees cooler than yesterday inland but not much change at the coast where low clouds may linger into the afternoon, especially along the Central Coast where there will be little to no impacts from the monsoon moisture to the south.
Things will start to quiet down Saturday, though still a lingering chance of some thunderstorms across the eastern LA County mountains in the afternoon. Otherwise, similar temperatures as Friday with most areas within a few degrees of normal. Same for Sunday with little or no chance of any storms over the mountains.
(Mon-Thu), 18/246 AM.
Quiet weather is expected next week with few impacts. Below normal temperatures are forecast, though a gradual warming trend possible starting on Thursday. The cooler temperatures will be caused by a period of weak troughing for the region as a low pressure system drifts south from the Pacific Northwest to off the coast of far northern California. Onshore surface pressure gradients will maintain marine layer overnight clouds and fog across the coasts and some valleys, as well on gusty southwest to west winds across interior areas. Winds will be the strongest across the Antelope Valley and adjacent foothills, and the Highway 14 corridor, however all winds are likely to remain below Advisory level.
18/1802z.
At 1712Z, the marine layer depth was around 1200 feet deep at KLAX. The top of the inversion was near 3800 feet with a temperature near 23 degrees Celsius.
Moderate confidence overall in the 18Z TAFs. All coastal airfields should have IFR/MVFR cigs/vsbys mainly tonight into Sat morning, with LIFR conds possible at times at KSMX. Moderate confidence in the timing of the low clouds and changes in flight cats which could be off +/- an hour or two.
Inland airfields are expected to remain VFR thru the fcst period.
KLAX, Moderate confidence overall in the 18Z TAF. The airfield will likely have IFR/MVFR cigs aft about 05Z thru about 20Z Sat. Moderate confidence in the timing of the low clouds and changes in flight cats which could be off +/- an hour or two or more.
KBUR, Generally hi confidence in the 18Z TAF with VFR conds expected thru Sat morning. However, there is a 10%-20% chance that IFR/MVFR cigs could affect the airfield early Sat morning.
18/833 AM.
Moderate to high confidence in the current forecast. Higher confidence exists in the forecast for seas relative to winds.
For the waters southwest through northwest of the Channel Islands and beyond 10 NM of the Central Coast, there is a high-to-likely (50-70 percent) chance of Small Craft Advisory (SCA) level winds developing each afternoon and evening evening through Wednesday evening. Increasing winds and building have a moderate chance of developing late next week.
For the nearshore waters north of Point Sal, winds and seas are expected to remain below SCA levels through this afternoon, then there is a moderate (30-40 percent) chance of SCA level winds this afternoon and evening. The chance for SCA level winds will increase to a moderate-to-high (40-50 percent) chance on Saturday afternoon and evening. For Sunday afternoon through Wednesday evening, there is a moderate (30-40 percent) chance of SCA level winds during the afternoon and evening hours.
Inside the southern California bight, there is a low-to-moderate (20-30 percent) chance of SCA level winds through Wednesday evening, except for a moderate (30-40 percent) chance of SCA level winds across the western half of the Santa Barbara Channel on Saturday evening.
There will be a slight chance of thunderstorms this morning for the coastal waters south of the Channel Islands. Main threats with any storms will be gusty outflow winds, locally rough seas and dangerous cloud-to-surface lightning.
Ca, NONE. PZ, Small Craft Advisory in effect from 9 PM this evening to 3 AM PDT Sunday for zone 670. (See LAXMWWLOX). Small Craft Advisory in effect from 3 PM this afternoon to 3 AM PDT Sunday for zones 673-676. (See LAXMWWLOX).
