textproduct: Eureka

SYNOPSIS

A mid period westerly swell will bring a moderate risk for hazardous beach conditions through Saturday afternoon. A much more energetic westerly swell will bring a high risk for sneaker waves Monday through Tuesday. King Tides return on Tuesday, and peak then on Thursday and Friday. Otherwise, dry and seasonably cool weather is forecast through next week.

KEY MESSAGES

* Dry and seasonably cool weather expected through the next 7-days, with a mix of sunshine and clouds.

* Potential for frost and freezing morning temperatures along the coastal areas on Monday.

* High risk of sneaker waves is expected along the Northwest California beaches from Monday morning through Tuesday morning.

* King Tides from December 2nd-7th, and may lead to minor coastal flooding in low-lying areas around Humboldt Bay, Crescent City and Arena Cove.

DISCUSSION

A semi-stationay upper-level ridge over the northeastern Pacific, while a shortwave continue to drop southeast inland into the Great Basin. Abundant high-level clouds continue to stream south-southwest across Northern California overnight, while surface observations reported some coastal low clouds and patchy valley fog. Expect another day with dry and seasonably cool weather, with a mix of sunshine and clouds. Breezy northerly will continues to develop along the coastal headlands and exposed ridges today as the surface pressure gradient tighten. Offshore winds should follow this evening through Monday morning with perhaps gusts to 25-35 mph over the ridges. The strongest winds will most likely occur over the eastern portion of Lake County where gusts from 25 to 35 mph are possible over wind prone ridges by Monday.

Frost and freezing morning temperatures will also be possible for coastal areas if the clouds do not reform and dewpoints dry out near the ocean in response to steady east winds. Granted places where winds stay up all night, temperatures probably will not even fall below 45F. Current guidance indicate morning minimums early Monday above 36F for much of the North Coast. However, NBM probability indicates there is a 15-25 chance for min temperatures below 36F around Humboldt Bay and adjacent areas, with up to 80% chance for McKinleyville. Localized pockets of frost may occur (a 10% chance) along the rest of the NW California Coast.

Another dry shortwave trough will follow a similar track Mon night and Tue. This trough will dig from NE to SW across the area by Tue and then offshore the central and southern Cal coast by mid week. There is an outside chance for a few fleeting light showers or sprinkles for Del Norte and mountains of Trinity Mon night or Tue morning, but it will not be a significant precipitation maker for our forecast area. Once again winds look to be the main impact with these inside slider troughs. Blustery northerly coastal winds are expected with this second trough. ECMWF ensemble mean peak wind gusts are much higher for coastal low lands on Tue. Gusts around 20-30 mph will be possible. E-NE winds will also develop Tue night-Wed for the higher terrain and perhaps Lake County. E-NE wind gusts to 35-45 mph will be possible over the ridges. Gusts to 50-55 mph are on the limbs of the distribution (95th percentile) over the high mountain peaks in the King Range. Now the air mass is not forecast to be exceptionally cold by mid next week either. With dew points in the 20s, calm winds in the valleys and clear skies overnight, frost and freezing temperatures will once again be a forecast challenge for areas that have not had a freeze yet, especially for coastal areas. Cold weather advisories for wind chill may also be a factor with winds around around 5-15 mph and minimum temperatures in the lower to mid 30s.

Massive 500mb ridge appears to flatten out Friday and into next weekend. WPC ensemble clusters do show about an even split (50%) of clusters that are "wetter" (at least for the North Coast) than the grand ensemble mean. The ensemble mean is by no stretch very wet with 0.10 inches of rain in 24 hours ending 4 PM Sat for mostly Del Norte. It could be wet or it could be dry or both. Stay tuned. /ZVS&DUG

AVIATION

Mostly VFR to sporadic MVFR ceilings have arrived along the coast overnight. Model generally suggest similar conditions, with a very slight risk (30% chance) of IFR ceilings early Sunday, but building offshore flow will most likely help clear conditions to VFR even before sunrise. VFR conditions will most likely continue to intensify through the day Sunday as skies clear, with the vast majority of ensembles (90%) pointing to VFR conditions through Sunday night into Monday. /JHW

MARINE

Currently moderate northerly winds in the outer waters will continue to increase through the day Sunday with near gale force gusts up to 30 kts by later int he evening. The inner waters will remain markedly calmer with few gusts over 15 kts near shore. Northerly winds will shunt further offshore by Monday afternoon, but there is good agreement that winds will rapidly return around mid week and push more into the inner waters with high chances (70%) of gale force conditions.

Aside from the winds, a minor mid period westerly around 8 feet is currently impacting the waters and will quickly decay Sunday. Another, much longer period swell will build around Monday into Tuesday up to around 12 feet. Neither swell will be particularly steep but will dominate the inner water sea state where short period seas are calm. /JHW

BEACH HAZARDS

A mid period westerly swell is currently generating a minor sneaker wave risk. This risk will persist into the morning but will quickly decrease through the day. A long period swell (up to 22 seconds) will suddenly build into the waters up to 12 feet midday Monday and continue into Tuesday. With calm winds near shore, this swell will pose a high sneaker wave risk with sudden high surf on beaches in otherwise calm seeming conditions. Take extra care to keep distance from the water. Building short period seas and shortening swell period will decrease the risk by Tuesday afternoon. /JHW

COASTAL FLOODING

King Tides return on Tuesday. High astronomical tides are predicted from Tuesday through Sunday for Northwest California. The combination of a high astronomical tides and steep, short-period northerly waves will increase the risk of minor coastal flooding around Humboldt Bay on Wednesday, including King Salmon and low-lying roads near Arcata Bottoms. Minor flooding potential in low-lying areas around Humboldt Bay, and along much of the coast is then expected through next Sunday. /ZVS

EKA WATCHES/WARNINGS/ADVISORIES

CA... Beach Hazards Statement from Monday morning through Tuesday morning for CAZ101-103-104-109.

Frost Advisory until 9 AM PST Sunday for CAZ113.

NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from 11 AM to 11 PM PST Sunday for PZZ455.

Small Craft Advisory from 11 AM Sunday to 3 PM PST Monday for PZZ470.

Small Craft Advisory until 3 PM PST Monday for PZZ475.