textproduct: Eureka

KEY MESSAGES

* Dry and unseasonably warm weather expected Thursday.

* Moderate to heavy rain and gusty south winds across much of the area through 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 winds are possible over the weekend and into early next week.

SYNOPSIS

Unseasonably warm and dry weather is expected today. Early Friday, a strong cold front is expected to create gusty winds, moderate to locally heavy rain, and dangerously large surf for NW CA. A brief break in the rain forecasted for Saturday before another system brings more rain and wind Saturday night and Sunday.

DISCUSSION

A brief period of high pressure will continue for Northwest California through mid Thursday. Dry air and warmer than average conditions will continue as a result. There is over an 80% chance of high temperatures over 65 degrees along the Mendocino Coast again Thursday with over a 70% chance of high temperatures over 65 degrees along the Humboldt and Del Norte Coast. Offshore flow has aided in increasing high temperatures along the coast today. Interior valley temperatures will range from the low 70s to high 70s. Also, early morning low clouds/fog can be anticipated through this time period for moist interior valleys, as well as a general marine layer along the coast overnight/early morning that will clear and scatter by the afternoon. Tonight and into Thursday morning, a weak front is anticipated to approach the area. Some models show this front bringing isolated light showers or sprinkles to coastal areas.

By late Thursday, a cutoff low pressure system will approach the Pacific Northwest. Models also depict a troughing pattern lasting through early next week with a potential for multiple rounds of rainfall and strong southerly winds. Widespread rainfall and gusty winds are expected for Northwest California, as a result.

With the first front, southerly winds are anticipated to ramp up by Thursday evening with models indicating rain beginning very late Thursday night or very early Friday morning. The winds will likely be strongest just ahead of the heavier rain. The strongest winds are forecast for Del Norte County along with the King Range in Humboldt County. The GFS and the RRFS both show 55 to 65 kt at 925 and 850 MB as the front moves into Humboldt and Del Norte counties. Lower levels could be unstable enough to enable the higher winds to mix down to the lower elevations, especially along the coast. NBM also indicates at least a 75 to 80% chance of 24-hour max wind gusts of 45 mph or greater for Coastal Del Norte, along with coastal headlands and higher terrain areas of Humboldt and Del Norte counties and higher elevations in extreme northeast Lake County on Friday. A Wind Advisory has been issued for Del Norte County and the higher terrain areas of Humboldt County. This may need to be expanded or upgraded. As of this afternoon, a High Wind Watch may be issued for coastal headlands and higher terrain areas of Del Norte County for Friday morning. Otherwise, also on Friday, there is a 65 to 70% chance of 24-hour max wind gusts of 35 mph of greater for more populated areas of coastal Humboldt along with higher terrain areas of Trinity, Mendocino and Lake counties.

Moderate to heavy precipitation is expected through the day Friday, with showers likely through Saturday and the potential for another bought of moderate rainfall on Sunday. Light rain will most likely start very late Thursday evening on the upslope areas, such as the south slopes of the King Range. The heavier rain is expected to begin a few hours before sunrise on Friday morning. The National Blend of Models (NBM) indicates over a 80% chance of 24-hour rainfall totals of 2 inches or more for Del Norte, Humboldt, northern and western Trinity, and northern Mendocino from 4am Friday (11/13) to 4am Saturday (11/14). A 65 to 85 percent chance for 1.5 inches or greater is expected during the same time period for eastern central Trinity, southern Mendocino, and Lake counties. The Humboldt Bay region could see slightly less total precipitation due to a rain shadow effect.

Showers are anticipated behind the front, especially in Humboldt, Del Norte and northern Mendocino counties. The heavier showers may bring close to an additional inch of rain with them. There is a potential for some thunder with these showers, as well. The NBM thunder probabilities have come down slightly, but are still around 15 to 20 percent.

Generally dry weather is expected on Saturday, although there may be some lingering showers. This will be short-lived, however, with the next weather system moving in Saturday night or Sunday. This one is expected to have lighter winds and rain, but still could see a half inch in Lake county to nearly two inches in the mountains of Humboldt and Del Norte counties. Drier weather is possible Monday and part of Tuesday with another system possible later on Tuesday. /JLW

AVIATION...06Z UPDATE

Satellite imagery and live cameras show a bank of coastal cumulus clouds covering the North Coast causing MVFR OVC conditions. These clouds are expected remain through the night before dissipating in the early morning as offshore then southerly winds increase. Ceilings are likely to reform around 3000 ft AGL as southerlies increase up to 20-30kts through the afternoon. Inland terminals will see continued VFR conditions with gusty southerly winds developing through the day. Expect localized LLT near all terminals and gusty winds near terrain midday Thursday through Friday. Rain arrives early Friday morning likely causing for LIFR conditions followed by VCTS Friday afternoon. DS

MARINE

Southerly winds continue across the waters overnight remaining round 10 to 20 kt. A northwest swell of 8-11ft@13sec continues to move through as well. The southerly winds are expected to increase to 20-25kt through Thursday as a weak front approaches the area. A new northwest swell is expected to move in building waves slightly to 13 to 14 feet at 15 seconds. This front is forecasted to cross over the area early Friday morning with widespread gale to strong gale force winds beginning around 1 AM in the northern waters and 4 AM in the southern waters lasting through around noon. Gale warnings have been issued for these areas through the timing will need to be watched. Heavy rain and steep short period seas are also to be expected during this timeframe.

After the frontal passage, a very large NW swell of 26-29ft@18sec is forecasted to enter the coastal waters. In addition, water spouts are possible as thunderstorms linger in the wake of the front. Expect hazardous conditions to continue through the weekend with the increased potential for a hazardous seas warning to follow the gale warnings. 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 these strong winds are diminishing on 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 breakers around 30-35ft. 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 is forecasted to arrive late Sunday into Monday. As of right now, it is possible that this swell will warrant a high surf advisory. Stay tuned for details and updates.

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. Please remain safe if at the beach during this time.

COASTAL FLOODING

Water levels inside Humboldt Bay continue to run 1.5 to 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 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. The water levels are expected to be slightly below 8.8 feet the next couple of days around high tide (11/12 @12:527pm, 11/13 @1:04pm, 11/14 @1:45pm).

EKA WATCHES/WARNINGS/ADVISORIES

CA... Wind Advisory from midnight Thursday night to 1 PM PST Friday for CAZ101>106.

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

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

NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until midnight PST Thursday night for PZZ450.

Gale Warning from midnight Thursday night to 3 PM PST Friday for PZZ450.

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

Gale Warning from 1 AM to 3 PM PST Friday for PZZ455-475.

Small Craft Advisory until 10 PM PST Thursday for PZZ470.

Gale Warning from 10 PM Thursday to 1 PM PST Friday for PZZ470.