textproduct: Eureka

KEY MESSAGES

* Moderate to heavy rain and strong gusty south winds across much of the area throughout Friday.

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

* Additional rain and wind possible over the weekend and into early next week.

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. Two cutoff low pressure systems are projected to affect Northwest California as this pattern takes hold. The frontal boundary associated with the first cutoff low will begin to impact the region by late tonight causing strong southerly winds through mid-morning Friday along with widespread moderate to heavy rain tomorrow morning. 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 anticipated to be weaker than the first.

With this first front, southerly winds have already been recorded with gusts between 30-50mph as of 12:30am. These winds are expected to increase, starting first at coastal headlands and higher elevations near the coast of Del Norte and Humboldt counties. Several high-resolution models show 55-65 kt winds aloft (at 925mb and 850mb) as the front moves into Humboldt and Del Norte counties. Lower levels of the atmosphere could be unstable enough this morning allowing these stronger winds to mix down to the lower elevations, especially along the coast where topographic friction is limited. The strongest winds are forecast for Del Norte County along with the King Range in Humboldt County. As this frontal boundary moves eastward, the higher elevations of Mendocino and Lake county are expected to have wind speeds between 40-50mph through the morning as well. Multiple warning and advisories have been issued for the CWA through this morning.

In addition to the wind hazards, moderate to locally heavy precipitation is expected through the morning Friday. Friday afternoon after the initial frontal boundary passage, showers and even a few localized thunderstorms are expected into Saturday morning. and the potential for another bought of moderate rainfall on Sunday. Light rain has already begun in the King Range. The heavier, main band of rain is forecast 2 to 3 hours before sunrise or around ~4-5am this morning. The National Blend of Models (NBM)indicates over an 85% chance of total rainfall amounts of 2 inches or more for Del Norte, most of Humboldt, northern and western Trinity, and northern Mendocino and over a 75 percent chance for 1.5 inches or greater during the same time period for central eastern Trinity, southern Mendocino, northwestern Lake counties with southeastern Lake most likely seeing close to an inch. The Humboldt Bay region has about a 65 to 75 percent chance of rainfall totals of 2 inches due to a rain shadow effect caused by southerly winds interacting with the King Range.

Behind the initial band of heavy rain, showers are expected, especially in Humboldt, Del Norte and northern Mendocino counties. The more heavy showers may bring close to an additional inch of rain with them. There is even the potential for some thunder with these showers as well due to increase atmospheric instability and colder air aloft entering the area. The NBM thunder probabilities have come down slightly, but are still around 15 to 20 percent for the coast and 10-15% for inland areas.

Generally dry weather is expected on Saturday, although there may be some localized lingering showers or drizzle in the 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 expected to have lighter winds and rain, yet rainfall amounts of a half inch in Lake county to nearly two inches in the mountains of Humboldt and Del Norte counties is possible. 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. DS

AVIATION...(09Z UPDATE)

A strong cold front moves through the area overnight bringing widespread moderate to heavy rain. IFR to MVFR ceilings and visibility reductions are expected as the front moves over terminals. Gusty south winds continue to build with gusts likely exceeding 40 kts at CEC and 35 kts at ACV. LLWS is likely as winds 2000-2500 ft AGL remain much stronger at 50-60 kts, expect LLT in and around the aerodrome through the morning. Steady rain turns showery by late Friday morning. Thunderstorms are possible within the strongest showers, especially along the coast. Storms are likely to cause brief periods of erratic, gusty winds with the potential for small hail. Rain showers continue through Friday evening, bringing occasional MVFR to IFR ceilings and visibilities. DS

MARINE

South winds have built into the coastal waters with buoys recording gale force gusts as of 12:30am. Gale to storm force gusts are likely to continue through the morning, with the strongest winds in the northern waters. Atmospheric instability with this front could allow some the stronger elevated winds at ~2000ft to mix down creating isolated wind gusts of 60kts as the front passes overhead this morning. Meanwhile, seas will be elevated due to a 11 to 13 foot mid period westerly swell. This swell will combine with southerly wind waves of 8 to 14 ft, with the highest seas in the northern waters, creating a very confused and hazardous sea state. By 10 AM Friday, the front will have moved through and winds shift more westerly into the afternoon. Steady, heavy rain in the morning, will transition to rain showers and potential thunderstorms with the slight chance for water spouts through the afternoon.

After the initial frontal passage, a very large NW swell of 26-29ft@18sec is forecasted to arrive Friday evening lasting through Saturday. Expect hazardous conditions to continue through the weekend as the forecast shows the increased potential for a hazardous seas warning to follow the gale and storm warnings later this morning.

Saturday night, a second cold front is forecasted to pass over the area once again creating strong, likely gale force winds for the coastal waters into Sunday morning. Another large swell of 21- 23ft@18sec is also expected to arrive Sunday afternoon lasting into Monday. Expect continued storms through next week as the storm track looks to remain fixed over our area through Wednesday at the earliest. 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

Water levels inside Humboldt Bay continue to run 1.5 to 2.2 feet over the astronomical tides. The max high tide is expected to drop each day through the end of the week and into the weekend, yet the continued influence of the El Nino's abnormally warm water (Kelvin Wave) in addition with stronger southerly winds and a large westerly ocean swell of over 25 feet on Friday will likely offset at least some of this decrease in max tide height. A Coastal Flood Advisory has been issued for areas around Humboldt Bay from 11am to 3pm Friday. The water levels are expected to be slightly below 8.8 feet the next couple of days around high tide (11/13 @1:04pm, 11/14 @1:45pm).

EKA WATCHES/WARNINGS/ADVISORIES

CA... High Wind Warning until 1 PM PST Friday for CAZ101.

High Surf Warning from 1 PM Friday to 4 AM PST Sunday for CAZ101-103.

Wind Advisory until 1 PM PST Friday for CAZ102>106.

Coastal Flood Advisory from 11 AM to 3 PM PST Friday for CAZ103.

High Surf Warning from 4 PM Friday to 4 AM PST Sunday for CAZ104-109.

Wind Advisory from 4 AM to 11 AM PST Friday for CAZ109>111.

Wind Advisory from 7 AM to 2 PM PST Friday for CAZ119-120.

NORTHWEST CALIFORNIA COASTAL WATERS... Coastal Flood Advisory from 11 AM to 3 PM PST Friday for PZZ415.

Storm Warning until 6 AM PST Friday for PZZ450-470.

Gale Warning from 6 AM to 4 PM PST Friday for PZZ450-470.

Small Craft Advisory until 1 AM PST Friday for PZZ455-475.

Gale Warning from 1 AM to 4 PM PST Friday for PZZ455-475.