textproduct: Eureka

KEY MESSAGES

* Very large surf tonight and into Saturday with breaking waves over 25 feet is possible. This will increase beach erosion and possibly bring some coastal flooding.

* Another frontal boundary late Saturday through early Sunday, weaker than the one today, but will still bring another round of rain and strong southerly winds.

SYNOPSIS

A strong cold front passage will create gusty winds with moderate to heavy rain starting early Friday morning. Rain showers and thunderstorms are possible Friday afternoon. A brief break in the rain expected Saturday before another system with more rain and winds arrives Saturday night and Sunday morning.

DISCUSSION

A troughing pattern has set up over the Pacific Northwest, persisting through early next week. The first frontal boundary has passed with post frontal showers continuing and diminishing into tonight. The next frontal boundary with the next cutoff low will approach the area late Saturday and bring more southerly winds and moderate rain, but is expected to be weaker than the first.

Showers are forecast to continue into the evening, especially in Humboldt, Del Norte and northern Mendocino counties. Any heavier showers could bring close to an additional inch of rain with them. The threat for isolated thunderstorms continues due to atmospheric instability and colder air aloft. The NBM thunder probabilities continue to be 20 to 25 percent for the coast and 10 to 15 percent for inland areas into this evening. Generally dry weather is expected on Saturday, although there may be some localized lingering showers or drizzle tomorrow morning for mountainous areas.

This calm period will be short-lived, however, as the next weather system moves in Saturday night into Sunday morning. This storm is forecast to be generally weaker than the storm today, yet rainfall amounts of a half inch in southeastern Lake County to nearly two inches in the mountains of Humboldt and Del Norte counties are possible along with gusty southerly winds. Around an inch to 1.5 inches are forecast for the rest of Northwest California. There is over a 70 percent chance for wind gusts greater than 40 mph along coastal headlands and exposed coastal areas of the Del Norte Coast (mostly just Crescent City and north) and southwest Humboldt (around the King Range). Otherwise, there is a high probability (greater than 80%) of wind gusts over 30 mph for the rest of Del Norte and Humboldt. The strongest winds will diminish by sunrise on Sunday with rain lingering through Sunday afternoon/evening.

Drier weather is possible Monday afternoon into Tuesday. Forecast ensembles continue to show a storm arriving mid week likely causing additional strong winds and rain for the area, yet details are limited and uncertain as of now. /JLW

AVIATION...(18Z TAFs)

The front moves out of the area early this afternoon, but rain showers continue through the afternoon and evening. A few stronger showers could result in thunderstorms with small hail, localized downpours, and erratic, gusty winds. Winds may briefly gusts to 30 kts or higher at the coastal terminals. The best thunderstorm chances are early this afternoon along the Humboldt Coast and this evening along the Del Norte and Mendocino Coasts. Ceilings will generally be VFR with occasional MVFR ceilings during heavier showers. Brief visibility reductions down to 3SM are possible, as well. Conditions gradually improve overnight, however a few areas of patchy ground fog is possible given the abundance of moisture. JB

MARINE

Southerly winds have finally eased behind the front, however a gale warning remains in place for the likelihood for numerous showers bringing gale force gusts into the afternoon. Increased instability will allow the strongest of these showers to develop into thunderstorms, which could bring small hail and isolated waterspouts. Seas remain elevated and defined by decaying southerly wind waves and a lingering mid period west swell of 10 to 12 feet. This evening, a very large NW swell of 27 to 30 ft at 18 seconds arrives, bring very hazardous seas. This swell peaks early Saturday and seas remain above 18 ft through Saturday evening.

Saturday night, a second cold front is forecasted to pass over the area once again creating strong gale to near storm force winds for the coastal waters into Sunday morning. Another large swell of 20 to 22 feet at 17 seconds arrives Sunday afternoon, keeping seas above 18 feet through Monday evening. Expect continued storms through next week as the storm track looks to remain fixed over our area through Wednesday at the earliest. JB/DS

BEACH HAZARDS

Just as strong winds and shower activity diminishes Friday afternoon, a very large swell is expected to arrive to the shoreline. Global wave models shows this swell building to around 25-28 feet at 18 seconds. This could lead to breaking wave heights of up to 35ft. A High Surf Warning has been issued north of Cape Mendocino from 1pm Friday (11/13) to 4am Sunday (11/15) and south of Cape Mendocino from 4pm Friday (11/13) to 4am Sunday (11/15).

A second large swell at 19-22 feet at 17 seconds is forecast to arrive late Sunday into Monday. This will likely warrant a high surf advisory with breaking waves of around 25 feet.

High surf in northern California can be very dangerous. It is recommended to stay away from jetties, exposed rocks, steep beaches, and the waterline in general during these events. Large waves can rush up the beach knocking down individuals. Very large logs and tree stumps can also be carried by the waves adding to the hazards on the beach. Low lying parking lots next to beaches could see water inundation and bluffs may be subject to coastal erosion during the peak swell Friday night. Please remain safe and avoid beaches, jetties, and bluffs during periods of high surf.

COASTAL FLOODING

While the water levels inside Humboldt Bay continue to run 1.5 to 2.0 feet over the astronomical tides, the astronomical tides drop enough for coastal flooding to be non- existent or limited this weekend. However, the continued influence of the El Nino's abnormally warm water (Kelvin Wave), the persistent southerly winds and a large westerly ocean swell of over 25 feet will continue this weekend.

EKA WATCHES/WARNINGS/ADVISORIES

CA... High Surf Warning until 4 AM PST Sunday for CAZ101-103.

Coastal Flood Advisory until 3 PM PST this afternoon for CAZ103.

High Surf Warning until 4 AM PST Sunday for CAZ104-109.

NORTHWEST CALIFORNIA COASTAL WATERS... Coastal Flood Advisory until 3 PM PST this afternoon for PZZ415.

Gale Warning until 3 PM PST this afternoon for PZZ450-455- 470-475.

Hazardous Seas Warning until 3 PM PST Saturday for PZZ450- 470.

Hazardous Seas Warning until 9 PM PST Saturday for PZZ455- 475.