03/846 PM.
Below normal temperatures, patchy marine layer clouds, and breezy onshore winds will continue through Friday. Tropical Cyclone Marie, which will remain well offshore of SoCal, will bring impacts to the region over the weekend into early next week. Light rain is favored for Sunday focused over Los Angeles County. Increasing southerly swell will create hazardous surf conditions at the coasts.
(Thu-Sun), 03/910 PM.
***UPDATE***
Once again another sunny day for SoCal. High temperatures were in the 70s and mid-80s. Away from the coast, these temperatures were 5 to 12 degrees below normal for this time of a year (a big change from all our heatwaves this summer). Gusty, sub-advisory level, afternoon winds were common across the region, with the strongest winds along the Antelope Valley Foothills/I-14 corridor. As for the Santa Barbara Southwestern Coast, yet another round of Advisory level N-NW Sundowner winds are occuring, and a Wind Advisory is in effect through 6am Friday. Patchy marine layer clouds are on tap once again, with a few hours of formation possible for LA County Coastal locations late night into morning. The highest chances for marine layer clouds to form will once again be the Central Coast. Additionally, there is a small chance of light rain across the Central Coast tonight and tomorrow morning as a broad trough digs into Oregon and northern California.
Similar conditions are expected across Southwest California tomorrow. However, sundowner winds are expected to be a touch weaker, and a wind advisory will likely not be needed Friday evening/overnight.
No major updates were needed to the forecast for the evening update.
***From Previous Discussion***
Marine layer clouds are expected each night into morning, but coverage will be patchy.
Hurricane Marie is likely to follow a west-northwest trajectory, keeping the storm well south of the California Coast. Impacts will be possible for the region over land starting Saturday, when a small increase in temperatures and humidity is expected. Temperatures will still be near normal, but the humidity may contribute to some additional heat discomfort. By Saturday night, there will be a slight chance of showers focused over Los Angeles County. PWATs will shoot up on Sunday as Marie gets close enough for moisture to stream in to the region from the southwest along the bottom edge of the trough. The greatest chance for any rain will be on Sunday. Chances for rain for each county will be as follows: Los Angeles County (40-50% chance), Ventura County (25-50% chance), Santa Barbara County (10-30% chance) and San Luis Obispo County (10-20% chance). There will also be a 5-15 percent chance of thunderstorms focused over Los Angeles County Sunday afternoon. Rain totals are expected to be light, generally between a trace to around 0.25 inches. Local areas up to 0.5 inches will be possible, but not common. The greatest impacts from Marie will be at the coasts, see the Beaches Discussion below for surf, rip current, and coastal flooding details.
(Mon-Thu), 03/232 PM.
Marie is favored to linger well off the coast to the southwest of the region into mid next week. Thus Monday through Thursday, moisture may be transported into region as Marie breaks down. Sporadic slight chances of showers will continue each day, and humidity is likely to remain elevated. However it should be noted that Tuesday onward, there is a lot of uncertainty in the upper level pattern. The GFS and EC break from each other significantly. The GFS favors a trough dipping down in Central California, which would bring cooler temperatures and likely some fairly breezy southwest onshore flow. The EC shows the 4-Corners high pressure extending out to include SoCal, which would bring warmer temperatures and even the chance for monsoonal mositure out of the southeast.
03/2332z.
At 2239Z at KLAX, the marine layer was 1300 ft deep with a weak inversion up to 2700 ft with a maximum temperature of 19 C.
High confidence in VFR TAFs for desert airfields (KPMD & KWJF).
Expecting another night through morning period of patchy marine layer clouds. Low confidence in timing (+/- 3 hours) and moderate confidence in CIG height forecasts (+/- 200 ft). There is a 15% chance of patchy MVFR CIGs at KSBA, KOXR, & KCMA. 20% chance VFR conditions prevail at KBUR/KVNY thru fcst period.
KLAX, Moderate confidence in TAF. Arrival and clearing times of MVFR CIGs 015-025 may be off +/- 2 hours of current forecast. Good confidence that any east wind component remains below 8 kts.
KBUR, Moderate confidence in TAF. Timing of MVFR CIGs around 013 (+/- 300 ft) may be off +/- 2 hours of current forecast. No wind issues expected.
03/809 PM.
Small Craft Advisory (SCA) winds will be common each afternoon and night for the offshore waters of the Central Coast for the foreseeable future. Compared to the next 4 days, winds should be strongest through tonight (Thursday), with also the highest chances for SCA conditions nearshore.
For the western portion of Santa Barbara Channel, SCA conditions are likely this evening (Thursday), but the chances decrease through the weekend. All of other waters should stay below SCA.
Tropical moisture will approach the area Sunday through at least Tuesday. While unlikely at this point, there is a 5 to 10 percent chance of a thunderstorm over the coastal waters, highest south of Point Conception. A large south swell will also impact the area, causing increased currents and surges in the vulnerable harbors.
03/246 PM.
The range of swell and surf outcomes have tightened, with peak south swell associated with Hurricane Marie likely in that 5 to 8 foot range. With moderate periods of 12 to 14 seconds, surf heights on exposed south-facing shores should be of similar height (5-8 feet). Some spots might see larger waves (like Malibu). The Santa Barbara South Coast will be largely protected from this swell, but there are some small windows of southeastly and southwesterly energy that could cause boosts in the waves. High Surf Advisories are now in place for Los Angeles and Ventura Counties, with Beach Hazards statements (a step below high surf advisories) in effect for Santa Barbara and San Luis Obispo Counties. With huge crowds expected at the beaches for the Labor Day holiday, the emphasis for these statements is to alert the public to be extra careful in and near the ocean.
High tides will also be increasing through early next week. Due to a variey of reasons, the actual observed tides have been running 6 inches above predictions for sometime now. The south swell will likely enhance that enhancement. As a result, high tides should exceed 7 feet by Monday. Adding large tides like that with the south swell will result in a moderate risk for coastal flooding over the vulnerable south-facing shores. Areas of most concern include Avalon, Long Beach (Alamitos Peninsula), Malibu, and Point Mugu. Coastal Flood Advisories have been issued as well for Los Angeles and Ventura Counties where the best combination of tides and waves will occur, but Santa Barbara and San Luis Obispo Counties could also see some isolated issues.
Ca, Coastal Flood Advisory in effect from 6 AM Saturday to 11 PM PDT Tuesday for zones 87-354-362-366. (See LAXCFWLOX). High Surf Advisory in effect from 6 AM Saturday to 11 PM PDT Tuesday for zones 87-354-362-366. (See LAXCFWLOX). Beach Hazards Statement in effect from Saturday morning through Tuesday evening for zones 340-346-349-350. (See LAXCFWLOX). Wind Advisory in effect until 6 AM PDT Friday for zones 349-351. (See LAXNPWLOX). PZ, Small Craft Advisory in effect until 3 AM PDT Friday for zones 650-673. (See LAXMWWLOX). Small Craft Advisory in effect until 6 AM PDT Friday for zone 676. (See LAXMWWLOX).
