26/132 PM.
Cooler temperatures are expected this weekend as high pressure aloft weakens. High temperatures will drop to 4 to 8 degrees below normal across the region with an increase in morning low clouds and fog for coasts and some valleys. Locally gusty winds are expected during the afternoon and evening for the Santa Barbara southwestern coast and the Antelope Valley. Starting Monday, temperatures will gradually trend warmer each day.
(Fri-Mon), 26/712 PM.
***UPDATE***
Fairly quiet weather day today. Onshore trends and lower hgts brought 3 to 6 degrees of cooling to the entire area. Despite the cooling, most max temps remained 2 to 4 degrees above normal today with the only exception being the Central Coast where max temps ended up 2 to 4 degrees blo normal. Some CU did develop over the mtns but there little in the way instability and none of the clouds showed any vertical development.
The more difficult forecast is the marine layer stratus pattern. Low clouds are hugging the beaches of the Central Coast but there are just a few patches of low clouds milling about south of Pt Conception. Super low confidence in exact timing of the arrival of the low clouds, but quite good confidence that by dawn most of the coasts and portions of the lower vlys will be covered with stratus.
The cooling forecast for tomorrow remains on track. Look for still lower hgts and even stronger onshore flow to combine to bring 4 to 8 degrees of cooling to most areas.
Forecast is in good shape and no updates are planned.
***From Previous Discussion***
A relatively quiet and much cooler period of weather is expected across the southland through the weekend. Highs actually expected to be BELOW normal for the first time in several weeks, by as much as 10 degrees in some areas but on average 3-7 degrees cooler than normal. This is all due to a low pressure system that will move into northern California Saturday, followed by lingering troughiness into Sunday. This will deepen the marine layer over the weekend, possibly reaching the coastal valleys. Skies will clear in the afternoon in most areas except some beaches may stay cloudy well into the afternoon. Southwest flow aloft will keep the area free of any convection, though a few cumulus clouds are possible near the higher peaks in the afternoon.
High pressure will build up from the south starting Monday, which will be the beginning of the next warming trend that will last through next week.
(Tue-Fri), 26/212 PM.
High pressure will continue to build up from the desert southwest through California next week with the center of the high around the 4 corners region. Ensembles show very strong consistency in this feature so there is high confidence in the warming trend. However, it will a slow climb and most areas won't even be back to normal high temperatures until at least Wednesday. After mid week temperatures will continue to climb, rising 2-3 degrees each day through next Saturday. Highs across the Antelope Valley will be approaching 110 degrees as early as next Friday, while the warmer coastal valleys will be approaching 105. The probabilities for those sites to reach 110 by Saturday are about 30% and 10% respectively.
With the high pressure system settling in near the 4 corners that definitely raises the potential for monsoon moisture moving into the area from the southeast. The deterministic 12z GFS actually shows quite a favorable upper air pattern by next Fri with an inverted trough across southern California and quite a bit of PVA and instability. And to go along with that, ensembles are indicating a rapid increase in PW's late next week and next weekend to over 1 inch across the area. Expect there will be at least isolated thunderstorms across the eastern part of LA County (mountains and Antelope Valley) during this period, possibly expanding west into the Ventura mountains. And if that GFS upper air solution comes to fruition that certainly increases the chances for showers and storms closer to the coast as well.
26/2352z.
At 2215Z at KLAX, the marine layer was 800 feet deep. The top of the inversion was around 2400 ft with a temp of 28 C.
High confidence in valley/desert TAFs, but low to moderate confidence in coastal TAFs. There is a 25 percent chc of no cigs for coastal TAFs KSBA and south. If cigs do arrive timing could be off by as much as 2 hours. VFR transition may occur 1 hour earlier than fcst.
KLAX, Moderate confidence in TAF. There is a 25 percent chc of no cigs. If cigs do form they could arrive as early as 06Z or as late as 10Z. There is a 30 percent chc of VFR conds arriving at 17Z. No significant easterly wind component is expected.
KBUR, High confidence in CAVU TAF.
26/935 PM.
For the Outer Waters, moderate to high confidence in current forecast. For PZZ673/676, high confidence in Small Craft Advisory (SCA) level winds continuing through Sunday night. For Monday through Wednesday, there is a 60-80% chance of the SCA level winds continuing. For PZZ670, there is a 60-80% chance of SCA level winds through Saturday night. For Sunday through Tuesday, there is a 40% chance of SCA level winds, then a 60% chance of SCA level winds on Wednesday.
For the Inner Waters north of Point Sal, moderate to high confidence in current forecast. Today through Saturday, there is a 60-70% chance of SCA level winds in the afternoon and evening hours. For Sunday through Wednesday, there is a 50-60% chance of SCA level winds, mainly in the afternoon and evening hours.
For the Inner Waters south of Point Conception, moderate to high confidence in current forecast. For the western half of the Santa Barbara Channel, there is a 60-70% chance of SCA level winds tonight and Saturday, mainly in the late afternoon and evening hours. Otherwise for the southern Inner Waters, high confidence in winds and seas remaining below SCA levels today through Wednesday.
Ca, Wind Advisory remains in effect until 6 AM PDT Saturday for zones 349-351. (See LAXNPWLOX). PZ, Small Craft Advisory in effect from noon to 9 PM PDT Saturday for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Saturday for zone 650. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Sunday for zone 670. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Monday for zones 673-676. (See LAXMWWLOX).
