textproduct: Eureka

SYNOPSIS

Conditions will greatly begin to moisten and cool into the weekend. Widespread wetting rain will cross the area around Sunday into next Monday.

DISCUSSION

Over the past few days, high pressure east of the area has promoted consistent offshore flow, generating clear and unseasonably warm conditions even right along the coast. This pattern will begin to significantly change today.

Broad, weak low pressure will gradually push into California with a broad lobe of high pressure offshore. This will promote moderate onshore flow into Saturday, bringing a resurgence of marine influence, especially to the coast with some weak marine stratus likely by this evening. Marine air pushing inland will greatly cool and moisten conditions each day.

There is high ensemble confidence that a deep trough a strong surface cold front will sweep across the area Sunday into Monday. This front will be focused on the northern half of the area and into Oregon. Widespread wetting rain is expected along the front, though there is still a good amount of uncertainty regarding amounts due to variability in the moisture plume strength and duration, particularly this far south. That said, ensembles consistently place the area in the range for a weak atmospheric river with only very limited high end potential.

Reflecting the moisture plume uncertainty, most likely rainfall amounts vary from about 0.5 to 1.5 inches at low elevations in Humboldt and Del Norte to 1.0 to 2.0 at higher elevations. Rain amounts will be less further south with most likely ranges of 0.1 to 0.5 inches for most of Mendocino and Lake Counties. There is a 15% chance of some wind gusts over 45 mph right along the coast, but any such winds would be very isolated to just the frontal passage itself.

Much colder air will move in behind the front. Snow levels will most likely drop to around 3000 feet by mid next week, but there will most likely be too little moisture at that time to support strong snowfall, with less than an inch or two at any highway passes. Any additional rainfall next week shows very little confidence in specific timing and amount. That said, there is very high ensemble agreement in a generally colder and more moist pattern through at least mid month with additional waves of rain likely over the next couple of weeks. /JHW

AVIATION...(18Z TAFs)

Coastal stratus has returned as high pressure begins to break down. Onshore flow will bring stratus towards the coastal terminals by this evening, bringing LIFR to IFR conditions. The deepening marine layer is likely to lift ceilings some overnight, which could keep visibilities high despite IFR ceilings. Interior river valleys may see fog and stratus again, perhaps with more coverage for the coastal river valleys. UKI has less than a 20% chance to see stratus tonight, and the marine layer currently does not look deep enough to bring stratus from the south or west. JB

MARINE

A long period westerly swell at around 10 to 12 ft at 16 seconds has built into the waters, keeping seas elevated. This will result in hazardous conditions to small craft through early Saturday. Light to gentle winds southerly winds are expected to continue today. Winds are expected to increase to moderate to fresh breezes over the weekend in advance of an approaching front, especially north of Cape Mendocino. NBM shows around a 40 to 50% chance for gale force gusts, but currently these look brief and isolated. Northerlies returns in the wake of the front Sunday night, with generally moderate to fresh breezes. Seas remain elevated as additional west swells build into early next week. /ZVS/JB

BEACH HAZARDS

A Beach Hazard Statement remains in effect through late this evening due to a moderate risk of sneaker waves along areas beaches. A large long period west swell has arrived and has brought heights around 10 to 12 feet at 15 to 16 seconds. These high energy waves will bring a moderate risk of sneaker waves, resulting in the potential deadly waves that unexpectedly surge much farther up the beach than previous waves, overtaking unaware beachgoers. Remember to never turn your back to the ocean, and to avoid steep beaches, jetties, outcroppings, and rocks during these events./ZVS

EKA WATCHES/WARNINGS/ADVISORIES

CA... Beach Hazards Statement until 10 PM PST this evening for CAZ101-103-104-109.

NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 3 AM PST Saturday for PZZ450-455- 475.

Small Craft Advisory until 3 PM PST Sunday for PZZ470.