01/750 PM.
Stagnant pattern through Friday, with below normal temperatures, patchy marine layer clouds, and moderate Sundowner winds. Several potential scenarios for the Labor Day weekend, with anything from benign conditions, tropical rain, or even hot offshore winds.
(Tue-Fri), 01/818 PM.
***UPDATE***
Today made out to be a sunny day once the morning patchy marine layer clouds burned off. High temperatures were mainly in the 70s and 80s across the region, with 60s the Central Coast. Typical sub-advisory gusty late afternoon/evening onshore winds have been affecting the Antelope Valley. Meanwhile, Sundowner winds have started to pick up this evening across the Santa Barbara Southwest Coast, where a Wind Advisory is in effect until 6am PDT Wednesday morning.
Current satellite imagery shows patchy marine layer clouds forming along the Central Coast, but not much else at this time. Expecting clouds to spread throughout the Central Coast overnight, with less confidence for south of Point Conception. Onshore surface pressure gradients are a little bit weaker tonight compared to yesterday and no clouds are currently in sight, so if clouds do form, it would either be randomly on sight, or pushed in much later tonight, and for a few hours into the morning.
Similar conditions are expected tomorrow with little change in the upper level pattern and a slight decrease in onshore winds from the N/S gradient.
***From Previous Discussion***
Overall, 12Z models in good synoptic agreement through the short term period. At upper levels, a trough will remain over the West Coast, varying in strength from day-to-day. At the surface, moderate onshore flow will continue to the east with some offshore flow from the north.
With this pattern, relatively benign weather is expected for the area. Main concern will be winds, specifically Sundowner winds, across southern Santa Barbara county. High resolution models indicate stronger SBA-SMX gradients tonight which will produce stronger winds across the western Santa Ynez Range and will likely hit advisory-levels overnight. So, have issued a WIND ADVISORY for the western Santa Ynez Range and adjacent coastal strip through 600 AM Wednesday morning. Based on SBA-BFL gradient, there may be some gusty winds across the eastern Santa Ynez Range (Montecito area), but advisory-level winds are expected at this time. For Wednesday night, models indicate even a bit strong northerly flow, so advisory-level winds will likely continue across southern Santa Barbara county.
As for clouds, there will be some marine layer stratus/fog each night and morning across the coastal plain and some coastal valleys, due to the onshore flow and potential eddy circulations. However, confidence in areal coverage each night remains low. Other than any stratus/fog, skies should remain mostly clear through Friday.
Finally for temperatures, there will only be minor day-to-day changes, based on the whims of the marine influence and changes in H5 heights. For most areas, high temperatures will remain about 2-6 degrees below seasonal normals.
(Sat-Tue), 01/932 PM.
For the long term period, an upper low is forecast to wobble over and around the Pacific Northwest through the Labor Day weekend. Models vary on the exact path of the wobble, but cyclonic flow aloft will remain over the area through early next week. At the surface, focus remains on current Tropical Storm Marie. While some more models/ensemble members are starting to come into agreement with a more northwestward track away from SW California, still quite a bit of uncertainty in exact details for impacts across the region this weekend.
Currently, Marie is located between 15N and 20 N, and around 110W. The latest forecast from the National Hurricane Center has Marie intensifying to hurricane strength early this morning, following a track to the northwest through the Labor Day weekend. The chances of Marie directly hitting Southern California as a hurricane or tropical storm remain VERY LOW (with only a few ensemble members from the models indicate any track close to Southern California).
However, despite the HIGH likelihood of Marie maintaining a west to northwest track away from the West Coast, there still be some noticeable impacts for the area from this storm. With the upper level pattern, moisture from Marie will be advected over the area during the Labor Day weekend, but the amount of moisture will be greatly impacted by the exact track of the hurricane. At this time, there is a 50-60% chance of widespread light rainfall (amounts 0.10-0.50 inches) Sunday through Tuesday and about a 10-15% chance of heavy rainfall and thunderstorms. As for winds, there will be about a 10-15% chance of moderate to strong easterly winds ahead of any rainfall, which could produce some fire weather concerns. Finally, there is high confidence in significant coastal risks which are detailed in the Marine and Beaches segments of this discussion.
Needless to say, the weather for the upcoming Labor Day weekend may by highly dynamic. A minor change in the track of Marie could result in significant changes to the current forecast. So, given the uncertainty with this pattern, stay tuned and monitor the latest forecasts.
02/0519z.
At 0439Z at KLAX, the marine layer was 1100 feet deep with an inversion at 2500 feet and 21 degrees C.
High confidence on VFR TAFs at KPRB, KSBA, KOXR, KCMA, KBUR, KVNY KWJF, and KPMD. 10% chance for very brief MVFR cigs at coastal sites sometime between 12Z-17Z.
Low to moderate confidence in SCT to BKN MVFR conds for remaining sites, with best chance of cigs at KSMX/KSBP. Small chance for IFR conds at those sites. 50% chance for VFR conds to prevail at KLGB, and 30% chance for very brief MVFR cigs at coastal sites sometime between 12Z-17Z at KLAX/KSMO.
KLAX, Moderate confidence in TAF. There is a 30% chance for brief BKN012-015 cigs developing sometime from 12Z-17Z. No significant east wind component expected.
KBUR, High confidence in TAF otherwise, with a 10% chance for brief BKN0010-15 cigs from 12-16Z.
01/900 PM.
Moderate to high confidence for Small Craft Advisory (SCA) level winds and short-period seas across the southern Outer Waters today through Friday, with a 20-40% chance of SCA level winds extending to the inner and outer waters north of Point Sal (greatest chance in the afternoon/evenings). For Saturday, there is a 30-40% chance of SCA level wind across all of the Outer Waters.
SCA level winds appear likely across the Santa Barbara Channel for Wednesday evening, with local SCA gusts possible for the inner water south of Point Sal. For Thursday evening, there is a 60-80% chance for SCA winds for the Santa Barbara Channel and a 30% chance of local SCA winds for the inner waters off the coast of LA and Orange Counties.
Expecting increasing southerly swell this weekend due to tropical activity to the south. The details and timing are very much dependent on the track of the tropical storm, but confidence is moderate to high that the coastal waters will see a larger than normal in southerly swell over Labor Day Weekend.
01/300 PM.
While there remains a range of outcomes in terms of the track of Tropical Cyclone Marie, SoCal is likely to see an increasing southerly-southeasterly swell this weekend into Tuesday (which may combine with the swells from the current Hurricane Karina). This most likely scenario would result in high surf advisories for south facing beaches (Avalon, Long Beach Peninsula, Malibu, Point Mugu) during a busy holiday weekend (especially Sunday into Monday night), with very strong rip currents.
Additionally, evening high tides are expected to be around 7 feet during portions of the event. As a result, there is an increasing chance of moderate coastal flooding of low- lying areas and significant beach erosion. There is a chance that coastal flood advisories will be issued.
Ca, Wind Advisory in effect until 6 AM PDT Wednesday for zones 349-351. (See LAXNPWLOX). PZ, Small Craft Advisory in effect until 3 AM PDT Wednesday for zone 650. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Thursday for zones 673-676. (See LAXMWWLOX).
