Marine Weather and Tide Forecast for Atascadero, CA

.SHORT TERM (TDY-SAT)...05/200 AM.

The north wind event is upon us. At the upper levels, the axis of the trough has situated itself over the great basin, and the upstream side of the trough has lined up perfectly with California from north to south. Subsidence will help enhance the surface gradients, thus wind speeds of 35-50 mph with higher elevation gusts of 55-65 mph will be common through this morning.

All Warnings and Advisories remain unchanged, except for the extension of the High Wind Warning (HWW) through 9 am this morning. Winds will diminish some later this morning, but some of the HWWs may need to be converted to Wind Advisories on the heels of the expiry times. North winds will likely pulse up again in the evening, but winds are expected to be quite weaker than this morning. There still remains a low chance for additional Wind Advisories to be issued in similar areas.

The secondary upper low will move into Southern California on Friday, and surface pressure gradients will become more favorable for offshore east to west flow. The upper level support will be somewhat muted Friday, but the upper low will cut off and orient itself such that northeast winds aloft will be almost in parallel with surface winds. Subsidence will help strengthen the surface winds, making Saturday the most potent day in terms of wind speeds for this Santa Ana Wind event. Sunday will start off quite windy as well, but a skosh weaker than Saturday due to weakening upper level support.

This Santa Ana Wind event does appear to be a bit stronger than the current northerly wind event we are in the middle of. The most likely outcome in terms of wind speeds are expected to be 20-30 mph with gusts to 35-55 mph. Isolated gusts to 55-65 mph are likely, especially across higher terrain. One of the limiting/driving factors in the peak wind speeds is the positioning of the cutoff low. If the upper level wind support is favorable (magnitude and direction), there is a potential for strong and damaging winds of 25-40 mph with gusts of 60-75 mph, with highest chances across the mountains. The speed of the southwest transit of the upper low will also impact the timing of the peak winds. Over the last few days, things have been trending slightly later, so stay tuned for better info on the timing as we get closer to the weekend. With these conditions expected, a slew of Wind Advisories and HWW’s are likely Friday-Sunday.

IMPACTS: Through tonight, but peaking through this morning, northerly winds across most of western LA County will create potentially hazardous travel conditions across major freeways such as the I-5, the I-405, and even travel delays due to crosswinds at LAX. Downed trees and power lines resulting in power outages are also possible. For Friday-Sunday’s Santa Ana event, there again is a risk for downed trees and power lines (and power outages), as well as hazardous travel conditions across the typical Santa Ana wind corridor of LA and Ventura Counties.
Blowing debris may also create further hazards on the roads from this morning through the weekend.

A mixed bag of temperature trends today as interior areas cool significantly while coastal areas will warm significantly. The cooler air will move over the region, but the downsloping northerly winds will warm the lower elevation areas. Much of the region will warm Friday, then Saturday and Sunday will warm up steadily. By Sunday, most of LA and Ventura Counties will reach the low to mid 80s, while Santa Barbara and San Luis Obispo Counties will be solidly in the mid to high 70s.

.LONG TERM (SUN-WED)...05/200 AM.

As the timing of the movement of the upper low has slowed some, so has the expected timing for this pesky low to exit the region.
Monday will be somewhat of a transition day. The Pacific Ridge will begin nudging the low eastbound and surface gradients are expected to rapidly shift from offshore towards neutral, likely becoming onshore to the north and east by the afternoon. Coastal areas will likely cool under the marine influence, but coastal valleys and interior areas are a bit trickier depending on the timing and strength of the winds. Quicker timing and stronger onshore flow will favor cooling of coastal valleys and warming of the interior (due to downsloping winds). Widespread cooling is expected Tuesday and temps will dip into the 60s and 70s everywhere. The increasing strength of the ridge will allow for some dramatic warming Wednesday.

AVIATION
05/0547Z.

At 0453Z, the marine layer was around 1100 ft deep at KLAX. The top of the inversion was at 1900 feet with a temperature of 15 degrees Celsius.

High confidence in VFR conds for most TAF sites, except moderate confidence in the Ventura and LA County coastal sites where the flight categories could be off by 1, and the timing could be off by +/- 2 hours. Chance for no cigs at KOXR (30%) and KCMA (40%).

Lower confidence in the wind forecast as timing of wind group changes may be off +/- 3 hours. Mdt LLWS due to increasing winds with height possible at all sites except KPRB and KSBP. Highest confidence for KSBA, KLAX, KSMO, KBUR focused 06Z-18Z. Mdt turbulence also likely, especially over terrain.

KLAX...Low to moderate confidence in TAF. North winds will rapidly increase sometime between 08Z and 12Z. Lower confidence in peak wind gusts, but higher confidence in timing being between 10Z and 18Z, then again 06/00Z-08Z. LLWS likely due to wind speeds rapidly increasing with height 10Z-18Z (+/- 3 hours).

KBUR...Moderate confidence in TAF. North winds will rapidly increase over the next few hours. LLWS possible due to wind speeds rapidly increasing with height 08Z-18Z (+/- 3 hours), however.

MARINE
04/703 PM.

***UPDATE***

Have pushed back the starting time of GALE WARNING for the waters adjacent to Los Angeles and Orange County (PZZ655) to 1 AM.

Small Craft Advisory level N winds will develop during the late evening hours nearshore from Malibu to Palo Verdes. These winds will spread southward and increase to GALE Force after midnight.

***MAIN DISCUSSION***

Moderate to high confidence in the current forecast. Higher confidence exists in the forecast for winds. Less confidence in the forecast for seas. Seas could be up to 1-3 feet higher than forecast, especially today through Saturday.

Marine weather conditions will deteriorate through tonight with widespread strong Small Craft Advisory (SCA) and GALE conditions expected through at least Thursday night. GALE WARNINGS remain in effect through Friday morning for some waters.

Another period of strong winds will develop across the region as an offshore flow pattern will set up Friday through Sunday. There is a high to likely (40 to 60 percent) chance of SCA level winds between Friday night and Sunday. There is a moderate (30-40 percent) chance of GALE FORCE wind gusts inside the southern California bight, and high (40-50 percent) chance of SCA level winds along the nearshore waters of the Central Coast.

LOX WATCHES/WARNINGS/ADVISORIES
CA...Wind Advisory remains in effect until 9 AM PST this morning for zones 87-88-349>352-356-357-366-367-371>375-381>383. (See LAXNPWLOX).
Wind Advisory in effect until 9 AM PST this morning for zones 349-351-352. (See LAXNPWLOX).
High Wind Warning now in effect until 9 AM PST this morning for zones 353-376>378. (See LAXNPWLOX).
High Wind Warning remains in effect until 9 AM PST this morning for zones 362-369-370-379-380. (See LAXNPWLOX).
PZ...Gale Warning in effect until 9 AM PST this morning for zones 645-650. (See LAXMWWLOX).
Gale Warning in effect until 10 AM PST this morning for zone 655. (See LAXMWWLOX).
Gale Warning in effect until 3 AM PST Friday for zones 670-673-676. (See LAXMWWLOX).