textproduct: Eureka

KEY MESSAGES

* A general troughing pattern will bring additional light rain over the region today and periods of unsettled weather over the weekend.

* Overnight temperatures for the interior will remain chilly, yet fog formation will likely inhibit any frost forming within inland valleys.

SYNOPSIS

A low pressure system over western Oregon will continue to funnel light rain over the region today with another round of unsettled weather expected Sunday. Chilly temperatures are forecasted for the interior each morning this weekend as well.

DISCUSSION

An upper level trough is lingering over western Oregon this Friday. This feature is responsible for a deepened, clearer marine layer, light rain showers for the North Coast, and cooler temperatures inland. Short wave disturbances are anticipated to flow downstream over NW CA through the weekend increasing the chances for light rain showers, especially for Sunday. The interior will likely see morning cloud coverage dissipating to cooler temperatures through Monday. Morning temperatures are beginning to reach Frost Advisory criteria with some inland valleys getting as cold as the mid 30s by early dawn. That said, a frost advisory has not been issued due to the increased, insulating cloud coverage for major valleys.

Sunday, a shortwave disturbance passing over the forecast area is increasing the rainfall chances for the Del Norte and the northern portions of Trinity and Humboldt counties. A slight lightning chance exists for these areas well, yet NW storm motion will likely cause any storms that do form to flow into Siskiyou County quickly. Little chances for wetting rain (>0.10") exist for areas away from the high terrain inland for Sunday as well.

A slight warmup is possible next week as well, yet if it occurs, it should be mild and short lived as ta troughing pattern returns at the end of the coming work week. There are also questions about whether tropical moisture may stream northeast toward the region from decaying tropical systems well off the coast. Model guidance has a large variance in possibilities ranging from completely dry after Sunday to several chances of showers and possibly thunderstorms mid to late week. That said, both the deterministic GFS & ECMWF are showing rain for the North Coast Saturday (+210hr) in both the 9/4/00Z and the 9/4/12Z runs.

AVIATION...18Z UPDATE

MVFR ceilings remain for much of NW CA this morning. Satellite imagery shows clear conditions off the coast which will likely lead to clearing to VFR along the coast through the afternoon. Southerly winds continue through the morning before veering to SW and eventually W through the afternoon as well. This onshore wind could bring haze due to large breaking waves, yet minimal impacts are expected. Models suggest the deep marine layer will persist through the evening leading to MVFR ceilings from 04Z onward before early morning clearing along the coast. Inland terminals in Mendocino and Lake Co. can expect VFR with north winds. Northern inland terminals can expect MVFR with clouds blocking some of the taller mountains in Trinity, Humboldt, and Del Norte Co.

MARINE

A continuously evolving low pressure center over western Oregon is beginning to weaken. As a result, southerly winds are likely to weaken through the evening before turning northerly by early Saturday. Waves during this time are expected to remain below small craft advisory conditions. Northerlies are likely to be between 8-12kts with sporadic gusts up to 15kts with the strongest winds in the far northern waters downwind of Cape Blanco and in the southern waters downwind of Cape Mendocino. The northerlies do not look to fully strengthen again until early next week. Hurricane Marie will deliver a long period southerly swell Saturday. Though small, at around 4 ft at 16 seconds, this swell is a larger than typical swell from this direction at this time of year.

BEACH HAZARDS

Hurricane Marie is expected to send a long period, southerly swell of ~3-4 feet at 16 seconds this weekend. This swell increases the risk of sneaker waves for south facing beaches from Saturday into Sunday. The possibility of increased risk for sneaker waves exists, especially if the swell comes in slightly larger. If so, updates will be posted here.

Sneaker waves are a unique hazard. With up to 30 minutes between waves, large waves can unexpectedly sweep across the beach without warning. These waves are capable of sweeping people into the sea from rocks, jetties, and steep 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 due to sand giving out quickly under ones feet. 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!

EKA WATCHES/WARNINGS/ADVISORIES

CA... Beach Hazards Statement from late tonight through Monday evening for CAZ104-109.

NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 3 PM PDT this afternoon for PZZ450-470.