Marine Weather and Tide Forecast for Los Osos, CA

.SHORT TERM (TDY-MON)...08/337 AM.

Temperatures and wind are the main characters of the weather story for Southwest California in the short term. An upper level ridge of high pressure will continue to build over the area today, and peak in strength on Sunday and Monday before weakening and moving eastward starting Tuesday.

At the surface, offshore flow will mostly persist through Monday, but the north-south gradients will weaken each day, while the east-west gradients strengthen. This means that winds will shift from the north to more northeast this weekend. N-NE wind gusts of 20-30 mph are currently blowing across the typical Santa Ana wind Corridor, while northeast wind gusts of 25-35 mph, locally up to 45 mph, are prevalent over The Santa Lucia Mountains on the Central Coast. These winds are expected to continue through mid- morning and then taper off into the afternoon. Another round of gusty winds will occur across the Santa Ynez and I-5 corridor tonight into the early hours of Sunday, though likely under advisory levels for the Santa Ynez Range especially as the gradients will be 2.5 to 3.5 mb weaker than Friday night into this morning. As for Sunday and Monday, winds will focus over the usual Santa Ana wind areas of Ventura and Los Angeles counties, as well as the Santa Lucia Range. However, the upper level support isn't especially strong, and the LAX-DAG gradients look to reach around -4 to -5 mb, so this event will be on the weak to barely moderate side of things. Current thinking is that maybe 1 or 2 advisories may be needed at most, mainly for the mountain areas.

As for temperatures, the high pressure strengthening (with associated 500mb heights increasing) paired with offshore gradients strengthening will result in warming across the region through Monday. By Monday, high temperatures will be in the mid 80s to lower 90s on the coastal side of the interior mountains, with the coasts spanning the 70s, and the interior areas in the 80s. These temperatures will be around 10-15 degrees above normal for this time of year. Additionally, overnight low temperatures will be elevated, with most foothills and breezy areas only dropping into the 60s to lower 70s. Between the highs and warm overnight lows, heat advisories are not out of the question, but the overnight lows will be the determining factor on if advisories are needed.

Last to be talked about in the short term, are the marine layer clouds. The low clouds are expected to be less expansive as the 500mb heights rise and the offshore gradients strengthen this weekend, but if the offshore winds are slow to kick in tonight, and/or are weaker than expected, clouds will be able to sneak back in the immediate coastal locations tonight, and dense fog will be a possibility. The NBM suggest this outcome, and given how the gradients are slightly weaker than models previously suggested, allowed the official forecast to follow the NBM for tonight into Sunday morning. By Sunday night into Monday morning, however, offshore flow and heat should be established enough to keep marine layer clouds away.

.LONG TERM (TUE-FRI)...08/354 AM.

In the extended period of the forecast, models are in agreement Tuesday, but starting Wednesday things start to differ. What they do agree on, however, is that rain is coming to SoCal sometime during the latter half of the upcoming week.

Tuesday into Wednesday, the upper level ridge will weaken and shift east of the region as a low pressure system approaches from the northwest. This pattern will result in a cooling trend with a return of onshore winds and increasing marine layer clouds and fog.

Thursday and Friday all models are showing a wet and unsettled pattern with an upper level low pressure system affecting the coast. Both the deterministic runs of the EC and GFS now show a low pressure system dropping into SoCal from the north, though the details of placement of the low, the timing, and amounts still differ. While the majority of the models agree that Wednesday will be as previously mentioned, the NBM starts to bring rain in starting early Wednesday morning, while the EC and GFS and their respective ensemble members mainly start the rain late Wednesday night/early Thursday morning. The EC deterministic suggests that rain will have moved through the region by Saturday evening, and another blip of rain will be possible early in the following week.
Meanwhile, the GFS deterministic and ensembles hint at rain being more spread out and carrying on through the weekend. As for amounts, there still is quite a bit of variation as well, as the GFS brings the low more over the ocean, and the EC moving more over land. The ensembles also remain to have widespread outcomes from each member to another. So, current NBM POPs look good (though maybe 12 hours too early), with likely/chance POPs for the entire area. However, amounts through Friday are very much in questions, ranging from minor to significant. Over the coming days, the models should come to a better consensus and details can be greatly fined-tuned. Essentially, be prepared for some rain beginning Thursday.

AVIATION
08/1101Z.

At 0948Z at KLAX, the marine layer was 900 feet deep. The top of the inversion was 1800 feet with a temperature of 23 C.

High confidence in VFR TAFs for desert airfields (KPMD & KWJF).

Low to moderate confidence in remaining TAFs. Timing of CIG/VSBY restrictions may be off +/- 3 hours, with flight minimums off by one category. There is a 15% chance for V/LIFR conditions at KPRB through 16Z Saturday. There is a 30% chance for NE wind gusts up to 20 kts to surface at KSBP through 15Z Saturday.

LLWS and turbulence is possible over & near mountainous terrain through 15Z Saturday. The terminals most likely to be impacted are KSBP and KSMX. Then again after 06Z Sunday but focused across interior LA & Ventura Counties.

KLAX...Moderate confidence in TAF. There is a 30% chance VSBYs of <1SM, 10% chance of 1/2SM, & 10% chance of CIGs persist (or briefly scatter)
from 21Z to 03Z Sunday - Lowest confidence in forecast. There is good confidence that east wind component remains below 7-8 kts.

KBUR...Low confidence in TAF. 20% chance that VV001-OVC002 with vsbys 1/4SM-2SM arrive through 16Z Sat. Otherwise, VFR conditions are expected.

MARINE
08/302 AM.

High confidence in a long period northwest swell continuing to create hazardous seas (10 to 12 feet) through mid-day Saturday across the outer waters, gradually decreasing in height through Sunday. Winds are expected to fall below Small Craft Advisory (SCA) levels by Saturday afternoon, remaining relatively calm into early next week.

SCA conditions may become a concern for portions of our coastal waters after Wednesday. Stay tuned for future updates.

LOX WATCHES/WARNINGS/ADVISORIES
CA...High Surf Advisory in effect until 9 PM PST this evening for zones 340-346. (See LAXCFWLOX).
PZ...Small Craft Advisory in effect until 4 PM PST this afternoon for zones 670-673. (See LAXMWWLOX).
Small Craft Advisory in effect until 9 AM PST this morning for zone 676. (See LAXMWWLOX).