Marine Weather and Tide Forecast for Signal Hill, CA

.SHORT TERM (TDY-MON)...07/951 AM.

***UPDATE***

Offshore pressure gradients continue today, though not as strong as yesterday as surface pressures fall over the Great Basin in response to a cold front moving into the Pac NW. Highs will still be 10-15 degrees above normal in most areas, though an earlier sea breeze at coastal locations will cut off the heating earlier than yesterday.

Overnight tonight, mostly after midnight, gradients will be rapidly trending onshore leading to a quick expansion of stratus near the coast and quite likely some very dense fog. This could lead to some delays at coastal airports, including LAX and LGB.

***From Previous Discussion***

Sunday night and Monday the state will be in between a ridge to the west and a trof to the east. NW flow will set up over the area. There will only be weak offshore flow and some low clouds may form across the LA/VTA coasts. Other than the low clouds Monday will be sunny. Monday will be an unusual day as a strong Great Basin sfc high will develop and will accelerate the offshore flow during the day even against the typical diurnal onshore trends. The trof passing over NV will also usher in some cold air thermal support for offshore winds. Gusty offshore winds will likely develop in the afternoon rather than the typical early morning time frame. Advisory level gusts are possible later in the afternoon across the Santa Clarita Vly and Santa Susana Mtns. Max temps not change much for most of the area but the incoming cool air from the interior will lower temps across the Antelope Vly by 4 or 5 degrees.

.LONG TERM (TUE-FRI)...07/320 AM.

All eyes on Monday night and Tuesday as another strong Santa Ana wind event looks likely. The E/W gradients will continue to accelerate in the offshore direction and will likely end up in the 7 to 8 mb range with a 25 percent chc of it hitting 9 mb. Almost as important as the actually gradient is the rapidness of the 24 hour gradient change which will be near a very impressive 12 mb.
Add in some good upper level and thermal support and you have the makings of an impressive wind event. Advisory level gusts are almost a guarantee and widespread warnings are looking more and more likely. Since this there is not much of a northerly component to this event the winds will be more easterly than normal and this will increase the danger to Avalon Harbor. Fire weather concerns will be greatly heightened with these strong winds please see the fire weather discussion below for details. SLO and SBA counties, will also see some northeasterly winds, but the speeds will be noticeably weaker than the VTA/LA winds. Stay tuned for further updates and refinements of this potentially dangerous wind event.

Wednesday will also be windy but with onshore trends the winds will be not be nearly as strong as on Tuesday.

The deterministic mdls diverge starting Thursday and the ensemble members begin to exhibit noticeable spread so not the best confidence in the fcst from Thursday on. Thursday will be dry with max temps remaining 3 to 6 locally 8 degrees above normal.

On Friday and into Saturday there will be an increasing chance of some light rain. The latest mdl runs are now thinking that the rain is more likely Friday night and Saturday which is later than what last night's runs were saying. Cooling does seem like pretty safe bet with max temps falling to near normal by Friday.

AVIATION
07/1907Z.

Around 19Z, there was no marine layer or inversion at KLAX.

Low confidence in coastal TAFs between 06Z-18Z with a 20-40 percent chance (except 50 percent at KLGB) of at least brief VLIFR/LIFR cigs/vsbys.

Otherwise high confidence in light winds and VFR conds elsewhere and otherwise.

KLAX...There is a 20-30 percent chance of VLIFR conditions between 10Z and 17Z. Any east winds will likely be less than 7 knots.

KBUR...VFR conditions are expected through the period.

MARINE
07/906 AM.

Moderate confidence in the current forecast. Slightly higher confidence in seas relative to winds.

For the waters southwest through northwest of the Channel Islands and along the Central Coast, there is a low chance (10 to 30 percent) chance of Small Craft Advisory (SCA) level northwest winds through this afternoon, increasing to a moderate- to-likely (30 to 60 percent) chance of SCA level winds this evening through early Monday morning. The highest chance for SCA level winds will be for the waters beyond 30 NM offshore of the Central Coast extending south to northwest of San Nicolas Island, while the lowest chance will be for the waters nearshore along the Central Coast. There is a moderate-to-high (30-50 percent) chance of widespread SCA conditions between Sunday night and Monday across this region. After Monday morning, winds and seas will likely drop below SCA levels through Wednesday.

Inside the southern California bight, there is a 20-30 percent chance of SCA level northeast winds nearshore between Rincon Point and Pacific Palisades this morning. SCA level winds are likely (80 percent chance) late Monday to early Wednesday with a 30-50 percent chance of peaking at GALE strength Tuesday morning to early afternoon. There is a moderate- to- high chance of east facing harbors seeing significant impacts. Theses harbors would include Avalon and Two Harbors on Catalina Island, and Smugglers Cove on Santa Cruz Island.

BEACHES
07/250 AM.

High astronomical tides approaching 7 feet during the early morning hours will bring a chance of moderate coastal flooding to southwest California shores late next week and next weekend.
Normally dry beach walkways and parking lots may see tidal overflows and minor coastal flooding. There is a chance that beach erosion may occur. Rip current activity may increase during the run up to high tide.

LOX WATCHES/WARNINGS/ADVISORIES
CA...Fire Weather Watch in effect from Monday morning through Wednesday afternoon for zones 288-354-355-358-362-369>380-548. (See LAXRFWLOX).
PZ...Small Craft Advisory in effect from 4 PM this afternoon to 4 AM PST Monday for zone 670. (See LAXMWWLOX).
Small Craft Advisory in effect from 9 PM this evening to 9 AM PST Sunday for zone 673. (See LAXMWWLOX).