Marine Weather and Tide Forecast for Channel Islands Beach, CA

.SHORT TERM (MON-THU)...20/743 PM.

***HIGH WIND WARNINGS ARE IN EFFECT THROUGH EARLY TUESDAY AFTERNOON FOR MOST OF VENTURA COUNTY AND LOS ANGELES COUNTY DUE TO HIGH LIKELIHOOD OF WIDESPREAD DAMAGING WINDS***

***DANGEROUS FIRE WEATHER CONDITIONS EXPECTED FOR MUCH OF VENTURA AND LOS ANGELES COUNTIES THROUGH TUESDAY EVENING WITH A HIGH PROBABILITY OF CONTINUING THROUGH THURSDAY***

Latest Santa Ana wind event increased sharply late this morning and afternoon, with several mountain and foothill observation sites in LA/Ventura counties reporting damaging wind gusts in the 60 to 80 mph range, with Magic Mountain Truck Trail reporting the highest wind gust so far at 88 mph. Upper level low pressure system digging southward across Arizona tonight, giving increased upper level wind support across LA/Ventura counties, with 850 and 700 mb winds peaking at 50-60 knots between 03Z and 09Z. This in combination with strengthening offshore pressure gradients at the surface and strong cold air advection tonight into early Tuesday morning will likely bring stronger and more widespread Santa Ana winds to the typical wind prone areas of LA/Ventura counties. As of 7 pm, the LAX-Daggett pressure gradient is at -4.3 mb, and is expected to peak around -8 to - 9 mb by early Tuesday morning.

Max gusts across many wind prone coasts and valleys will range between 50 and 70 mph through early Tuesday morning (highest winds likely focused near Santa Clarita Valley and Highway 118/126 corridors such as Simi Valley, Moorpark, Porter Ranch, and Santa Paula). In addition, with the strong upper level wind support extending well up to 700 mb level, there is potential for locally strong/damaging mountain wave wind gusts across the foothills of the San Gabriel and San Fernando Valleys, mainly focused near the Highway 210/118 corridors from Porter Ranch to San Fernando, then eastward to La Crescenta/Altadena, extending to Azusa/Glendora. The highest probability of locally stronger mountain wave wind activity would most likely occur this evening through 1 am Tuesday. Max gusts for many mountain/foothill areas will likely range between 60 and 80 mph, with some isolated gusts in the 80 to 100 mph range possible in the most favored mountain locations (most likely in the San Gabriels and Santa Susanas).

While the offshore winds will likely diminish some by Tuesday afternoon, there will likely continue to be a long duration of critical Red Flag fire weather conditions across much of LA/Ventura counties potentially persisting into Thursday due to the long duration of offshore winds combining with widespread single digit humidities. In fact, this will likely be the driest air mass we have seen with all offshore wind events this season, with many areas seeing humidities fall to between 2 and 5 percent Tuesday through Thursday.

***From previous discussion***

Continued offshore flow and low humidities on Wednesday with about 5 mbs of offshore flow predicted both from the N and E. There is negligible upper support, however, and there may only be a need for low end wind advisories in the morning.

On Thursday the offshore push is forecat to increase to around 8 mb. The push from the north is forecast to only a moderate 4 mb offshore. There is an uptick in upper level support with 850 winds increasing to 35 to 40 mph. Its likely that there will be another round of wind warnings/advisories in the typical Santa Ana windy areas. These winds will quickly subside in the afternoon.

Humidities will be very low through the period. The low humidities will combine with the winds to make for dangerous fire weather concerns - please see the discussion below for all the fire weather concerns and details.

Yesterday max temps were so low that the sunny skies and offshore flow have brought 4 to 8 degrees of warming to the csts/vlys this afternoon. As is common with the first day of a Santa Ana the interior has cooled 5 to 10 degrees due to the large amount of cool air coming in from the NE. On Tuesday the area is looking at 3 to 6 degrees of warming to all areas except for the Antelope Vly where continued cool air advection from the interior will cool temps by 1 to 2 degrees. Even more warming on tap for Wednesday as hgts rise and the offshore flow continues. Look for 3 to 6 degrees of warming for almost all of the area. Thursday will be the warmest day of the next 7 with another 2 to 5 degrees of warming on tap. Max temps Thursday should be 8 to 12 degrees above normal with most cst/vlys seeing temps in the 70s and mostly mid to upper 70s.

With clear skies and very low humidity values, it will become very cold in wind sheltered areas tonight and especially Tue night.
Lows will drop to between 10 and 15 degrees in the Antelope Valley, and into the lower to mid 20s in interior portions of the SLO valleys and the Cuyama Valley. Freezing temperatures are possible each night in wind-sheltered portions of coastal SLO and SBA Counties. Freezes are likely in the colder valleys of L.A.
and VTU County, especially Tue night when there is less wind.
Freeze warnings have been issued for many areas tonight with a freeze watch in effect for Tuesday night. Please the product LAXNPWLOX for all areas under the freeze warnings.

.LONG TERM (FRI-MON)...20/105 PM.

The upper high will will be pushed to the south and west by a large trof moving out of the PAC NW. Hgts will fall through the day and will end up near 570 dam over LA county and 568 dam over SLO county. More importantly the offshore flow will only about half as strong as it was Thurday in the morning and will turn onshore in the afternoon. There will be enough offshore flow in the morning to prevent the low clouds from forming, but the switch to onshore in the afternoon will bring a big 4 to 8 degree cool down across the csts/vlys. The falling hgts will also cool the interior of SLO and SBA counties as well as the western portion of the Ventura County interior. The switch to onshore flow will produce some downsloping warming across the Antelope Vly.

There is better but still not great agreement with the mdls and ensembles about the weekend forecast. Both now agree that the main weather player will be the cold long wave pos tilt trof that will sweep through the state over the two day period. A cut off low will likely form at the base of the trof. The GFS is colder drier and further to the west than the EC. All the ensembles are pretty spread out but mostly favor their parent model.

There is a even considering the wetter EC (PWs near .65 as opposed to the GFS .28) this a drier solution than ydy's likely because the compact upper low off in the east Pacific is no longer forecast to phase into the bigger upper and provide additional moisture. Still think there is a 70 to 80 percent chc of rain over the area over the two day period with very low confidence on any given 6 hour period. Rainfall amounts should come in anywhere from .15 to .35 inches with up to a half in across portions of eastern LA county.

Snow levels will be quite low with this system between 4000 and 5000 ft on Saturday and under 4000 ft on Sunday. Given the low amount of available moisture it does not look like there will be any significant accumulations below 6000 ft.

The cold core of the low will be over the forecast area. This will bring a 15 to 20 percent chc of a thunderstorm. This is less of a chc than ydy since the upper diffluence is now missing.

Warm it will not be. With good onshore flow and rapidly falling hgts as the cold air from the interior moves in, max temps will plummet 12 to 18 degrees on Saturday and chance little on Sunday.
Max temps will almost all be in the mid to upper 50s or about 10 degrees under normals.

The upper low should slowly depart on Monday. Look for decreasing clouds, a decreasing chc of rain and a slight warm up.

AVIATION
21/0559Z.

At 06Z at KLAX, There was no marine layer or inversion.

Overall, moderate confidence in 06Z TAF Package. Timing of arrival and departure of possible V/LIFR conds at KPRB may be off +/- 2 hours. Otherwise, high confidence in VFR conds at remaining airfields.

Strong, gusty NE to E winds for VTA/LA county terminals to continue, especially thru first half of fcst pd. Moderate to locally severe LLWS, turbulence, and UDDF is possible to likely especially near mtns and foothills. Maximum wind gusts could vary +/- 10 kts.

KLAX...Moderate confidence in 06Z TAF. High confidence in VFR conds through the period, but moderate confidence in winds.
Moderate LLWS and turbulence is possible around airfield, especially through first half of fcst pd. Moderate chance of east wind component of 6-8kt thru 18Z Tue, with low to mdt chances again 06Z to 12Z Wed.

KBUR...Moderate confidence in 06Z TAF. NE to E winds will impact the terminal through first half of fcst pd, with strongest winds through 12Z. Moderate to severe LLWS, turbulence, and UDDF is likely. LLWS, turb, and UDDF may be locally severe, especially over nearby mountains. Maximum wind gusts may be off +/- 10 kts.

MARINE
20/1004 PM.

For the Outer Waters, Gale Force winds from the northeast to east continue to be possible through at least Tuesday morning, focused on the waters around and south of the Channel Islands. Current Gale Warnings look on track. Small Craft Advisory (SCA) level winds are then likely through Tuesday evening (60% chance) and could then linger through Wednesday morning (30% chance) around the Channel Islands. Late Wednesday into Thursday afternoon, SCA winds are highly likely for similar areas (80-90% chance), and there is a 50-60% chance for Gales. In the northern Outer Waters, sub- advisory conditions are likely, except for a 30% chance for SCA level winds Tuesday afternoon through Wednesday morning.

For the Inner Waters North of Pt Sal (PZZ645), there is a good chance for localized areas of Small Craft Advisory (SCA) level wind gusts, north of Morro Bay. Then there is a 40-50% chance for SCA level NE winds Tuesday afternoon through Wednesday evening.
Then, sub-advisory conds are expected Thursday.

For the Inner Waters South of Point Conception, from Ventura Harbor to Malibu and out past the Channel Islands, there is a 80-90% chance of GALE FORCE E/NE wind gusts through early Tuesday afternoon. There is also a 50% chance of localized STORM FORCE wind gusts (48-55 kts) midnight tonight into early Tuesday morning. Strong winds are also expected from the Orange County shores through the San Pedro Channel, and there is a 60-80% chance of GALE FORCE wind gusts through Tuesday late morning, likely impacting Avalon Harbor. Steep, choppy seas of 4 to 8 feet will be possible during this time frame. From Ventura to Malibu and out to the Channel Islands, SCA level winds are likely to continue from Tuesday afternoon through late night (60-70% chance), and a 40-50% chance continuing all the way through Wednesday afternoon. Another round of Santa Ana Winds are on tap for late Wednesday into Thursday, with an 80-90% chance for SCA winds in similar areas, and a 50-60% chance a Gale Warning will be needed.

FIRE WEATHER
20/758 PM.

Another active fire weather period this week with at least two distinct periods of moderate to strong Santa Ana winds, mainly over LA/Ventura Counties. This first is peaking tonight into Tuesday morning with 60 to 80 mph wind gusts in the mountains and possibly as high as 100 mph in very isolated mountain locations. For coast and valleys gusts of 50 to 70 mph likely through Tuesday morning. With the strong and damaging winds and humidities lowering to the single digits, a Particularly Dangerous Situation (PDS) Red Flag Warning is in effect for much of Ventura and Los Angeles Counties until 10am Tuesday.

In additional to the traditional areas of Santa Ana winds, the strong and gusty winds and dry air mass are expected to spread to the Palos Verdes Hills and off the coast to the Channel Islands and Catalina Island, and a Red Flag Warning is in effect for these areas as well.

Santa Ana winds will weaken and decrease in areal coverage Tuesday afternoon with even a light sea breeze expected at some coastal areas along with rising humidities. However, a core of gusty winds up to 45 mph are possible through the day and even into Wednesday morning, particularly over the Santa Susana and western Santa Monica Mountains.

The next widespread increase in Santa Ana winds is expected to be Wednesday night into Thursday. Winds are not expected to be as strong as the winds tonight into Tuesday morning, however, daytime humidities will still be under 10 percent and with wind gusts to 50 mph for coast/valleys and up to 60 mph in the mountains. A fire weather watch covers the period from Tuesday night through Thursday evening. This almost certainly will be converted to a red flag warning on Tuesday, though the start time for some areas particularly near the coast, may need some adjustment depending on how long the decrease in winds lasts.

Across the Santa Lucia and interior Santa Barbara County mountains, gusty east winds up to 35 mph are expected at times, strongest during the overnight and morning hours. This may cause brief periods of elevated or locally critical fire weather conditions.

Friday will be quickly transitioning to onshore flow with rising humidities. Over the weekend a low pressure system will create a chance of showers across the area. Preliminary rain amounts are a quarter inch or less most areas with peak totals around a half inch. Rain rates are mostly expected to be a tenth of an inch per hour or less. However, there is a 5-10% chance of a thunderstorm with briefly higher rates that could generate a debris flow if it falls over a recently burned area.

LOX WATCHES/WARNINGS/ADVISORIES
CA...Wind Advisory remains in effect until 2 PM PST Tuesday for zones 87-367-370-381>383-548. (See LAXNPWLOX).
High Surf Warning in effect until 2 PM PST Tuesday for zone 87. (See LAXCFWLOX).
Coastal Flood Advisory in effect until 2 PM PST Tuesday for zone 87. (See LAXCFWLOX).
High Wind Warning remains in effect until 2 PM PST Tuesday for zones 88-354-355-358-362-369-371>380-549-550. (See LAXNPWLOX).
Freeze Warning in effect until 9 AM PST Tuesday for zones 346-347-356-357-383. (See LAXNPWLOX).
Freeze Watch in effect from Tuesday evening through Wednesday morning for zone 383. (See LAXNPWLOX).
Red Flag Warning in effect until 10 PM PST Tuesday for zones 288-354-355-358-362-369-371>380-548. (See LAXRFWLOX).
Fire Weather Watch in effect from Tuesday evening through Thursday evening for zones 288-354-355-358-362-369>380. (See LAXRFWLOX).
Red Flag Warning in effect until 2 PM PST Tuesday for zones 367-370-381-382. (See LAXRFWLOX).
PZ...Gale Warning in effect until 2 PM PST Tuesday for zones 650-655-676. (See LAXMWWLOX).
Gale Warning in effect until 9 AM PST Tuesday for zone 673. (See LAXMWWLOX).