19/736 PM.
A weak upper level trough will move over the area this weekend into Monday, cooling temperatures slightly and increasing marine layer stratus. A warming trend will begin Tuesday and peak on Thursday, with highs 5 to 10 degrees above normal.
(Sat-Tue), 19/808 PM.
***UPDATE***
High clouds are just starting to stream into the region thanks to a trough moving over the area. Closer to the surface, marine layer clouds are already starting to spread across the Central Coast, and one little blob extending into a very small section of the Ventura County Coast. Expecting these clouds to extend into the coastal valleys overnight, and may be slow to burn off late morning.
High clouds will continue into tomorrow, and slightly lower temperatures are forecast compared to today, but still in the 70s and 80s. Little moisture is associated with the upper level trough, however there is some instability over the higher elevation mountain areas, mainly for Santa Barbara and Ventura counties. As a result, there is a 5to 10 percent chance of thunderstorms/showers during late Sunday into Monday. Due to the lack of sufficient moisture, little to precip accumulation is expected, and the main risk should a thunderstorm form, would be dry lightning.
No big changes were needed in the evening forecast update.
***From Previous Discussion***
Temperature trends were generally flat today, except for areas above 1200 feet elevation where some places warmed as much as 10 degrees. Expecting a little cooling Sunday as a weak upper low over the eastern Pacific moves closer to the Central California coast and onshore flow increases. Will probably see more in the way of morning low clouds and fog and lingering a little deeper into the morning hours Sunday. And in turn likely a degree or two cooler overall for coast and valleys. Farther inland areas will see little change. There is a little elevated cape tomorrow afternoon but PW's are under .75" and also confined to very high altitudes. Wouldn't be surprised to see some high based clouds over the SB/Ventura mountains but very little chance of any precip reaching the ground.
As the low moves inland Monday heights will lower and temperatures will cool, especially far inland areas where highs will be 4-8 degrees cooler (and 4-8 degrees below normal) with some increasing afternoon sea breezes. Chances for any showers or thunderstorms will be a little higher than Sunday with the low pretty much right overhead. However, moisture remains very limited and chances for any reaching the ground remain below 10% and mostly confined to the mountains. Most likely just some afternoon build ups over the mountain peaks. Otherwise, for coast and valleys just a typical morning marine layer that will clear by late morning with highs 1-3 degrees cooler than Sunday.
A little recovery in high temps Tuesday but most areas (except the immediate coast) remaining 3-6 degrees below normal.
(Wed-Sat), 19/227 PM.
Most of the warming next week is going to be on Wednesday after the low finally exits and higher pressure develops over the Pac NW resulting in a weaker onshore flow and less marine layer influence. The biggest temperature jumps Wednesday will be in the coastal valleys where highs will be in the 90s with around a 20% chance of 100 degrees in the western San Fernando Valley, rising to 50-60 chance of 100 or higher across inland SLO and Santa Barbara Counties. Coastal and intermediate areas will warm up as well with most areas in the high 70s to mid 80s, with a 20-30% chance of 90 degrees in Downtown LA as early as Wednesday or Thursday.
Temperatures will trend cooler later next week across northern areas, as the trough pattern returns over the eastern Pacific. Less confidence in cooling temps in the south due to the uncertainty with the trough position, and it's possible that Wednesday's temps will continue into next weekend.
20/0046z.
At 0015Z at KLAX, the marine layer was 1400 ft deep. The top of the inversion was at 2600 ft with a temperature of 22 C.
High confidence in VFR conds for KPMD & KWJF.
Low to moderate confidence in the remaining sites. The timing of CIG and any VSBY restrictions tonight into Sun morning may be off +/- 2 hrs and flight minimums by one category.
KLAX, Low to moderate confidence in TAF. Flight cat changes may be off by +/- 3 hours, and cigs may scatter and reform due to high clouds after 08Z Sun. Any east wind component is expected remain less than 6kt.
KBUR, Moderate to high confidence in TAF. Flight cat changes may be off by +/- 2 hrs from forecast times.
19/811 PM.
For the outer waters, high confidence in the current forecast. Small Craft Advisory (SCA) level winds are likely across most of the waters through Sunday morning, then for the waters mainly west and northwest of Point Conception Sunday through Sunday or Monday night. The SCA winds will be most persistent around Point Conception. There is a 40%-50% chance of SCA wind gusts west and south of Point Conception Tuesday afternoon and night as well, otherwise conds will be below SCA levels Tuesday through Thursday night. Expect steep, choppy seas with the SCA conditions.
For the inner waters N of Point Sal, moderate to high confidence in the current forecast. SCA wind gusts are likely during the afternoons and evenings through Sunday and again Tuesday. Conds are otherwise expected to be below SCA levels Monday through Thursday.
For the inner waters S of Point Conception, moderate to high confidence in the current forecast. Conds are expected to be below SCA levels for the most part through Thursday night. However, for the western Santa Barbara Channel, there is a 40%-50% chance Monday afternoon/evening and Tuesday afternoon/evening.
Ca, NONE. PZ, Small Craft Advisory in effect until 3 AM PDT Sunday for zones 645-676. (See LAXMWWLOX). Small Craft Advisory in effect from 3 PM Sunday to 3 AM PDT Monday for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Monday for zone 670. (See LAXMWWLOX). Small Craft Advisory in effect until 5 AM PDT Tuesday for zone 673. (See LAXMWWLOX).
