25/117 AM.
May Gray low clouds and fog will be widespread across the coasts and valleys each night through morning period through at least Tuesday. Some cooling is expected over the next couple days, with well below normal temperatures Tuesday through Thursday. Additionally, areas of gusty afternoon and evening winds are expected, strongest on Tuesday or Wednesday.
(tdy-Wed), 25/126 AM.
Today will be the last day with near normal temperatures until late in the week. Although low clouds have been slow to form, a weak to moderate eddy will likely support low clouds into at least coastal sections of LA County with broad northwest onshore flow also favoring the Central Coast and adjacent valleys. Low clouds that are established by morning will likely burn off a bit faster than previous days.
Below normal forecast confidence for the Wednesday into Thursday timeframe related to uncertainty in the track and resulting impacts associated with notoriously difficult to forecast cut-off low pressure systems.
A potent (for late May) cold cut- off low pressure system has trended further south and west and closer to Southwest California for the Wednesday and Thursday time frame in particular. This places increased confidence toward enhanced southwest to northwest winds across the region by Tuesday with the potential for additional wind advisories especially for San Luis Obispo and Santa Barbara Counties. A deepening marine layer will likely bring drizzle at times especially Tuesday and Wednesday mornings just about anywhere low to mid level clouds occur. By Wednesday we'll likely have a deep moist layer with sufficient dynamics and shallow instability for a 10-30 percent chance of generally light showers or drizzle, highest across the interior mountains. Snow levels may dip to 6000-8000 feet, lowest at night, potentially supported a rain/snow mix at times for high elevations. The closer proximity of the system also brings with it sufficient instability to warrant a small (5-10 percent chance) of a thunderstorm focused across interior mountains and valleys of San Luis Obispo, Santa Barbara, and Ventura Counties mid afternoon Wednesday to the evening hours. Gusty winds, brief heavy rain and cloud-to-ground lightning look to be the main threats should a thunderstorm occur.
(Thu-Sun), 25/115 AM.
The low pressure system may remain parked in the region into Thursday with additional rotating spokes of moisture and energy around the weakening system retaining at least a small chance of showers across the region, perhaps focused across San Luis Obispo and Santa Barbara Counties.
Friday through Sunday temperatures will trend upwards as the low travels to the east, becoming within a few degrees of normal over the weekend (highs in the low 70s to low 80s for coast and valleys). Moderate strength onshore surface pressure gradients will continue, thus some coverage of marine layer stratus is likely each night and morning, and breezy onshore afternoon to evening winds will continue for the Antelope Valley and likely return in the form of Sundowner winds for southwest Santa Barbara County.
25/1156z.
At 0800Z at KLAX, a weak marine layer was 1500 feet deep. The top of the inversion was at 5000 feet with a temperature of 16 degrees Celsius.
High confidence in KWJF and KPMD. For all other sites, low confidence in forecast with a 20-40 percent chance of MVFR cigs/vsbys occuring where not forecast and 20-40 percent chance of not occuring where forecast.
KLAX, Low confidence in TAF. There is a 30 percent chance of MVFR/IFR cigs 13Z to 18Z. No significant easterly wind component is expected.
KBUR, Low confidence in TAF. There is a 10 percent chance of at least brief MVFR/IFR cigs/vsbys 13Z-17Z.
25/206 AM.
For the Outer Waters, moderate to high confidence in current forecast. Through Monday morning, high confidence in winds and seas remaining below Small Craft Advisory (SCA) levels. Winds will increase to SCA levels Monday afternoon for the waters south of Point Sal to San Nicholas Island, then after a brief lull Tuesday morning, high confidence in both winds and seas increasing to SCA levels Tuesday afternoon through at least Wednesday night for all the outer waters. Additionally, there is a 40-60% chance of Gale force winds Tuesday late afternoon through Tuesday night across all of the outer waters, then followed by SCA winds Wednesday into early Thursday. For Thursday afternoon and Thursday night, conds are likely to drop below SCA levels across the waters.
For the Inner Waters north of Point Sal, moderate confidence in current forecast. Through Monday afternoon, high confidence in winds and seas remaining below SCA levels. There is a 30% chance of SCA level winds Monday afternoon and evening. For Tuesday through early Wednesday, high confidence in a combination of SCA level winds (strongest in the afternoon and evening hours) and seas. There is a 40% chance of SCA winds and seas Wednesday afternoon through evening. Additionally, there is a 40-60% chance of Gale force wind gusts Tuesday afternoon and especially Tuesday night. From late Wednesday night through Thursday night, conds should drop below SCA levels.
For the Inner Waters south of Point Conception, moderate confidence in current forecast. This afternoon through night, there is a 50-60% chance of SCA level NW to W winds across the Santa Barbara Channel, around the Channel Islands, and into the Santa Monica Channel. On Tuesday and Tuesday night, there is a 80% chance of SCA level winds across the Santa Barbara Channel with a 40-50% chance of Gale fore winds, and a 30-50% chance of SCA winds over PZZ655 late Tuesday. Otherwise, moderate to high confidence in winds and seas remaining below SCA levels.
Ca, Wind Advisory remains in effect from 2 PM to 10 PM PDT Tuesday for zones 340-341. (See LAXNPWLOX). High Surf Advisory in effect from 5 PM Tuesday to 5 PM PDT Wednesday for zones 340-346. (See LAXCFWLOX). Wind Advisory remains in effect from 6 PM Tuesday to 6 AM PDT Wednesday for zones 349-351. (See LAXNPWLOX). Wind Advisory remains in effect from 11 AM Tuesday to midnight PDT Tuesday night for zones 381-383. (See LAXNPWLOX). PZ, Small Craft Advisory in effect from 8 AM to 4 PM PDT Tuesday for zones 645-670-673. (See LAXMWWLOX). Gale Watch in effect from Tuesday afternoon through late Tuesday night for zones 645-650-670-673-676. (See LAXMWWLOX). Small Craft Advisory in effect from 2 PM this afternoon to 1 AM PDT Tuesday for zones 650-655-673-676. (See LAXMWWLOX). Small Craft Advisory in effect from 10 AM to 4 PM PDT Tuesday for zone 676. (See LAXMWWLOX).
