27/407 AM.
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.
(tdy-Mon), 27/410 AM.
This weekend will feature a cooling trend, with temperatures below normal across the region. 500 mb heights will hold consistent and on the low side, kept at bay by a trough moving across the northern part of California. Today temperatures will drop dramatically to around 3 to 7 degrees below normal (near normal for DTLA), followed by another couple of degrees of cooling likely for Sunday. Expect highs this weekend to be in the upper 60s to around 80 for the beaches and coastal plains, in the 80s to low 90s for the valleys and foothills, and mid 90s for the deserts. Monday, as a broad high pressure system starts to develop over the central southern United States, 500 mb heights for SoCal will creep up slightly. Temperatures are likely to increase by a couple degrees Monday, especially across inland areas, however will still be several degrees below normal.
Strong onshore and north-to-south pressure gradients will drive gusty winds for wind prone areas, especially today and tonight. Across the Antelope Valley and adjacent foothills, southwest wind gusts of 20 to 40 mph will be common this afternoon and evening. Sundowner winds are expected to continue this afternoon through tonight across the Santa Barbara Southwestern Coast, with northwest wind gusts of 25 to 40 mph. Both the Sundowner and the Antelope Valley winds may repeat on Sunday and Monday, but pressure gradient trends indicate that they are likely to be slightly weaker. At this time, no wind advisories are anticipated to be needed.
The atmosphere will continue to dry over next few days, with no significant source of moisture for inland ares. Despite much cooler temperatures this weekend, low humidities and the previously mentioned gusty winds will drive fire weather concerns. Fire weather risk will correspond with the strongest wind, thus is highest across the Antelope Valley and adjacent foothills, and the Santa Barbara Southwestern Coast. Members of the public are encouraged to remain cautious with any sources of fire starts and residents are urged to stay on alert this weekend.
(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 early this morning for zones 349-351. (See LAXNPWLOX). PZ, Small Craft Advisory in effect from noon today to 9 PM PDT this evening for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect from 3 PM this afternoon to 3 AM PDT Sunday 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).
