Marine Weather and Tide Forecast for San Buenaventura (Ventura), CA

.SHORT TERM (TDY-FRI)...23/938 AM.

***UPDATE***

The marine layer has deepened to 4000 feet across LA County this morning based on numerous pilot reports, sloping down to around 2500 ft along the Central Coast. There have been some reports of drizzle or even light rain, especially in southern Santa Barbara County and to around La Conchita in far western Ventura County where amounts of just under a tenth of an inch have been reported.

With this deeper marine layer and an almost 3mb onshore trend it's going to be a very slow clearing day, and would not be surprised if even the LA/Ventura valleys stay socked in well into the afternoon. Most of the high res models are indicating almost full clearing today but given past experience with these patterns this this seems an unlikely outcome. Highs today will mostly be in the low to mid 60s for coast and valleys.

***From Previous Discussion***

A deep marine layer depth is likely to continue to remain in place over the coming days as broad troughing remains anchored along the California coast and strong onshore flow will remain intact. A cooler pattern will linger into late week with temperatures below seasonal normals. Weak dynamics aloft will continue to scrape the area and bring the possibility of night through morning drizzle.

Across the interior portions of the area, stronger onshore flow will bring much breezier to windier conditions during the afternoons and evenings. A wind advisory was added for the western Antelope Valley foothills for this afternoon and this evening where gusts up to 45 mph are possible. Isolated gusts to 55 mph cannot be ruled out near Lake Palmdale. With similar onshore pressure gradients developing over the coming days, additional wind advisory headlines may be needed.

By Friday, an elongating trough in the Gulf of Alaska will enter the region while splitting off from the flow aloft. This cutoff trough will likely deepen the marine layer depth between Friday and Saturday to turn it into a deep moist layer up to around 7000 to 8000 feet deep on Friday night. This will be plenty deep enough to produce night through morning drizzle or light rain across the region. Mountain showers seems to be a high probability given the pattern and favorable flow pattern.

.LONG TERM (SAT-TUE)...23/441 AM.

The cutoff trough will approach the California coastline on Saturday morning as the marine layer mixes out into a deep moist layer. The forecast ensemble members introduce a majority of the perturbations with light rain across the area. EPS members are the wettest relative to the GEFS and CMC ensemble members. Almost all of the EPS ensemble members have precipitation across the region with amounts lessening as one heads south. EPS QPF means suggest a quarter inch or less, with a high chance of values between 0.25 and 0.50 inch for San Luis Obispo County. Meanwhile, GEFS and CMC keep the forecast more inline with night through morning drizzle. Given the cutoff trough, the current forecast generally keeps NBM values for PoPs, while skewing PoPs higher along the coastal slopes of the mountains.

Temperatures will be much cooler than normal on Saturday with most areas being 5-12 degrees below normal. Temperatures in the mid 50s to mid 60s will be common across the coastal and valley areas.
Experimental data analysis on the NBM forecast suggests KLAX and KOXR potentially seeing record low maximum temperatures on Saturday. Local records versus the forecast indicate otherwise, but near record low maximum temperatures will be possible on Saturday.

A warming trend for much of next week is expected as cluster analysis still favors an upper-level ridge of high pressure building into the West Coast. Anomalously high heights seem more plausible across the Pacific Northwest, but the pattern will still likely create above normal temperatures with less marine layer low cloud coverage.

AVIATION
23/1732Z.

At 1646Z at KLAX, the marine layer was 3700 feet deep. The top of the inversion was around 5000 feet with a temperature of 12 C.

Moderate to high confidence in TAFs. Clearing times for KSBP, KSMX, KBUR, and KVNY may be off by +/- 2 hours. MVFR to VFR cigs will linger at coastal sites south of Point Conception today, but there is a 20% chance for any of these sites to briefly scatter out after 20Z. There is a 20-30% chance for IFR cigs at KPRB, KSBP, KSMX, KBUR, and KVNY after 02Z, highest chances for KPRB, KSBP, and KSMX.

KLAX...Moderate confidence in TAF. Flight cat may flip from MVFR and VFR frequently thru this evening as CIGs bounce between 025-040. There is a 20% chance that cigs will scatter out between 20Z and 02Z. There is a 20% chance of an east wind component reaching 8 kt from 11Z-17Z Thu.

KBUR...Moderate confidence in TAF. Cigs may arrive linger until as least as 22Z or clear as early as 20Z. There is a 20% chance for OVC007-010 after 04Z tonight.

MARINE
23/800 AM.

In the Outer Waters, moderate confidence in the forecast. Winds will be close to low-end Small Craft Advisory (SCA) levels at times thru Fri night. SCA conds are likely (60-70% chance) in the northern zone (PZZ670) this afternoon thru late tonight, while there is a 40% chance of SCA level winds elsewhere. There is a 40% chance of low end SCA level winds anywhere across the outer waters Thu afternoon thru Fri night/Sat morning. SCA level conds are likely (70% chance) Sat afternoon thru Sun night.

For the Inner Waters north of Pt. Sal, moderate confidence in the forecast. There is a 40% chance of SCA level winds during the afternoon/eve hours today thru Fri. SCA conds are likely (60% chance) during the afternoon/eve hours Sat and Sun.

For the Inner Waters south of Pt. Conception, moderate confidence in the forecast. There is a 40% chance of SCA level winds during the afternoon/eve hours today thru Fri in western portions of the Santa Barbara Channel, then SCA conds are likely there (60% chance) during the afternoon/eve hours Sat and Sun. Otherwise, SCA conds are not expected thru Sun night.

LOX WATCHES/WARNINGS/ADVISORIES
CA...Wind Advisory in effect until 9 PM PDT this evening for zone 381. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect from 3 PM this afternoon to 3 AM PDT Thursday for zone 670. (See LAXMWWLOX).