Marine Weather and Tide Forecast for Rossmoor, CA

.SHORT TERM (MON-THU)...28/817 PM.

Satellite imagery showing mostly clear skies this evening, except patchy low clouds and fog across the Central Coat. Weak high pressure aloft will build through Tuesday and continue a warming trend. Night through morning low clouds and fog will remain in the forecast for tonight and into Tuesday morning, but the clouds will be less extensive and mainly confined to the Central Coast and into southern Los Angeles County. With high pressure aloft building in, there is a moderate chance that the marine layer depth could thin enough for the northern areas to bring dense fog to the Central Coast and Santa Ynez Valley. A wind advisory is in effect until 3 am tonight for southwest Santa Barbara county.
Already seeing some wind gusts in the 35 to 40 mph range as of 8 pm across Refugio and Gaviota, and winds are expected to trend up slightly this evening.

*** From previous discussion ***

A weak trough in the Gulf of Alaska this afternoon will move over the top of the ridge, dig into southern California by Wednesday, and cutoff from the flow. This trough of low pressure will bring cooler temperatures for Wednesday and Thursday. The marine layer depth should deepen as onshore flow strengthens with the cutoff low lingering over the region. Night through morning low clouds and fog should be expected, but night through morning drizzle seems to be the most plausible scenario developing. Clouds may struggle to clear from the land mass each afternoon, staying perfectly on track for the arrival of May. A lower confidence scenario could be isolated showers and thunderstorms developing over the mountains, but currently, the system looks too warm aloft to support the steeper lapse rates necessary for convective development.

.LONG TERM (FRI-MON)...28/253 PM.

Weak ridging aloft should build in for Friday. While a brief warm-up will likely occur on Friday, onshore flow will remain in place and keep night through morning low clouds and fog in the forecast.

A much stronger trough will move into the region over the weekend. Surprisingly for its cutoff nature, a majority of the ensemble member solutions agree that this system will have the potential to have a number of high impact scenario. Cluster analysis leans toward the stronger solutions with a deeper trough moving over the region. Moisture parameters in the ensembles provide ample moisture for precipitation. EPS precipitable water means sit near 0.85-0.90 inch, more than ample for precipitation.
The forecast goes higher than NBM values for PoPs and the forecast now mentions showers. This system will likely have more moisture than the system that moved over the region this past weekend. In fact, 40 percent of the EPS solutions suggest precipitable water values 1+ inch at KLAX. This could introduce the possibility of brief heavy downpours and minor flooding.

With the cold air mass aloft, thunderstorms cannot be ruled out.
GFS and ECMWF solutions suggest a 500 mb cold pocket near -26 degrees Celsius moving over the region through the weekend.
Currently, the forecast introduces a 5-10 percent chance of thunderstorms. EPS ensemble members and ECMWF EFI values suggest a high potential for gusty winds with this system. EPS wind gust means advertise advisory level winds across many coastal locales with the strongest winds across the southern California bight. As this is a late season storm system, there could be a few more surprises such as lower snow levels or small hail. Stay tuned and this system could be rather significant for this time of year.

AVIATION
28/2353Z.

At 00Z at KLAX, there was a weak marine layer at 3700 feet. The top of the inversion was 5000 feet with a temperature of 13 C.

High confidence in TAFs for KPMD and KWJF.

Low confidence elsewhere, focused after 08Z with a 50-60 percent chance of MVFR to IFR conds for KLAX, KLGB, KSMO and KSMX between 08-18Z with a 20 percent chance of LIFR conds for KSMX. There is a 30-50 percent chance of MVFR BR elsewhere during this timeframe.

KLAX...Low confidence in 00Z TAF. There is a 60 percent chance of MVFR cigs/vsbys between 08-18Z with a 20 percent chance of IFR cigs. No significant east wind component expected.

KBUR...Good confidence in 00Z TAF. There is a 10 percent chance of IFR cigs/vsbys 10-17Z.

MARINE
28/821 PM.

High confidence in Small Craft Advisory (SCA) conditions for the northern and outer waters through this evening, with moderate confidence in marginal SCA conditions for the same areas Tuesday afternoon and evening.

Moderate confidence that winds and seas will remain below SCA levels for most of the waters Wednesday and Thursday. However there is a 40-50% chance of SCA conds over the northern outer waters through Wednesday morning.

A late season storm will very likely bring SCA to Gale conditions to most, if not all coastal waters by this weekend.

LOX WATCHES/WARNINGS/ADVISORIES
CA...Wind Advisory remains in effect until 3 AM PDT Tuesday for zones 349-351. (See LAXNPWLOX).
Beach Hazards Statement in effect through Wednesday evening for zones 362-366. (See LAXCFWLOX).
PZ...Small Craft Advisory in effect until 4 AM PDT Tuesday for zone 645. (See LAXMWWLOX).
Small Craft Advisory in effect until 9 PM PDT Tuesday for zones 670-673-676. (See LAXMWWLOX).