textproduct: Eureka

SYNOPSIS

High risk for sneaker waves Monday through Tuesday. King Tides return on Tuesday and then peak Thursday and Friday. Chances for frost and freezing temperatures increase for areas closer to the coast again starting Tuesday night. Dry weather expected to prevail for this week, followed by a chance for rain late Friday and over the weekend.

DISCUSSION

High pressure is forecast to remain parked over the northeastern Pacific through Friday. Dry weather is highly probable for NW California.

Offshore flow (E-NE winds) has been increasing across the interior ridges overnight, especially in Lake County. Gusts from 25 to 35 mph verified into Monday morning over the exposed ridges in the eastern portion of Lake County. These winds are continuing to diminish throughout the day as the surface pressure gradient relaxes. Satellite imagery depicts only patchy low clouds near the Mendocino coastal areas Mendocino this afternoon while sunshine remains elsewhere.

Another "insider trough" will drive southward across the Great Basin toward southern California Tuesday through Wednesday. This will bring increasing high clouds across the area on Tuesday. Ridging strengthen and upper-level heights rises across the Pacific Northwest in the wake of the "insider trough". Stronger and blustery coastal northerly winds are expected in the wake of this trough by Tuesday afternoon. Gusts around 20-30 mph are forecast. East- northeast winds will also develop Tuesday night into Wednesday for the higher terrain and over Lake County, where gusts from 30-40 mph will be possible over the ridges. Ridge level gusts to 40-45 mph are on the limbs of the distribution (95th percentile and ensemble max) over the high mountain peaks.

Chance for frost around Humboldt Bay area Tuesday morning decreases to around 30% as another shortwave trough generates more cloud cover tonight. Offshore flow resumes Tuesday night into Wednesday morning and the chance for frost increases again to around 40-80% for the Humboldt Bay area. Chance for 32F in the north of Humboldt Bay increase to about 30-50% Wednesday morning. Meaningful chances for early morning frost for the North Coast is expected to continue Thursday morning.

The air mass is not forecast to be exceptionally cold next week. 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 inland areas that have not had a freeze yet. Cold weather advisories for wind chill may also be a factor with winds around around 5-10 mph and minimum temperatures in the lower to mid 30s. Fog and low clouds will form each and every night (100% chance), though the coverage will decrease as the air mass slowly dries out each day this week.

Massive 500mb ridge appears to flatten out Friday and into next weekend. All global ensemble prediction systems continue to indicate increasing chances for 0.10 to 0.25 inches of rain in 24 hours through the weekend. 24 hour chance for > 1 inch is no more than 20%. It is interesting to note that the majority of WPC ensemble clusters are drier than the grand ensemble. The ensemble mean is by no stretch very wet either. It could be wet or it could be dry or both over multiple days. Stay tuned.

AVIATION

VFR conditions are expected through the afternoon into the evening. There is a hint of valley fog forming inland possibly bringing IFR/LIFR conditions to the Russian River Valley (KUKI). However, the North coast looks to have enough of an offshore flow to keep any developing marine stratus trapped in an eddy south of Cape Mendocino. Light variable winds and the passage of high clouds are expected for coastal terminals. /DS

MARINE

Moderate northerly winds have pull away from the coast this afternoon. Steep seas will largely be confined to the outer waters for much of the day. Wind waves are combining with a long period westerly swell which will gradually build to up to 8 ft @ 18 seconds by Tuesday. Combined seas of 8-13 ft are expected. Stronger northerly winds return tomorrow afternoon, with increasing forecast confidence in gale force gusts in the outer waters south of Cape Mendocino and Pt. St. George. Nearshore winds will be lighter, but peak gusts of 15-25 kts are still possible as are propagating steep wind waves making conditions hazardous for Small Crafts. North winds ease slightly and pull offshore by Wednesday. Conditions gradually improve through the end of the week. JB/DS

BEACH HAZARDS

A long period swell, up to 22 seconds, will continue to build in on Monday. This energetic swell is bringing a high risk for sneaker waves, with surf breakers up to 15ft. The threat will last through Tuesday. High astronomical tides will increase the danger, especially over rocks and jetties.

Sneaker waves are a unique hazard, with up to 30 minutes between waves. Large, unexpected waves can sweep across the beach without warning, sweeping people into the sea from rocks, jetties, and beaches. These sneaker waves can also move large objects such as logs, crushing anyone caught underneath. Even ankle to knee deep water can knock you down and drag you out when a sneaker wave hits. Pay attention and stay above the high water line and any wet sand to stay safe. If the ground is wet, waves have surged there recently. Stay safe and never turn your back on the ocean! /JJW

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, a positive tidal anomaly, and a long- period swell will increase the risk of minor coastal flooding around Humboldt Bay, including King Salmon and low-lying roads near Arcata Bottoms. /JJW

EKA WATCHES/WARNINGS/ADVISORIES

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

NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from 4 PM Tuesday to 3 AM PST Wednesday for PZZ450-455.

Small Craft Advisory until 4 PM PST Tuesday for PZZ470-475.

Gale Warning from 4 PM Tuesday to 8 AM PST Wednesday for PZZ470-475.