textproduct: Eureka

KEY MESSAGES

- Periods of unsettled weather for Del Norte County and extreme NE Humboldt and Trinity counties is expected over the weekend.

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

- A building Desert Southwest ridge will sharply increase interior temperatures Monday, followed by further warming to above average temperatures into late next week.

SYNOPSIS

A general troughing pattern will keep interior temperatures cooler than average and continue and unsettled pattern over the region bringing a chance for showers or isolated thunderstorms this weekend in Del Norte and extreme NE Humbodlt and Trinity counties. This unsettled pattern could also disrupt diurnal coastal stratus this weekend. Colder morning temperatures could occur for the coldest interior valleys this morning wherever fog does not form. A sharp warmup in temperatures will begin Monday and continue into late next week.

DISCUSSION

An upper level trough will continue to linger over the Pacific Northwest through the weekend. This feature could aid in sporadic coastal stratus development along the coast, light rain showers for Del Norte and extreme NE Humbodlt and Trinity counties, 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 that will dissipate through the morning leading to cooler temperatures through Monday. Low temperatures for interior valleys will be colder than average over the next few days with some of the climatologically colder valleys reaching down in the upper 30s to low 40s. However, a frost advisory has not been issued due to the likelihood of insulating cloud coverage for most 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 very 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. Even the most extreme CAMs show very limited coverage of short lived thunderstorms over the area. Little chances for wetting rain (>0.10") exist for areas away from the high terrain inland for Sunday as well.

A sharp warmup will begin Monday as a strong Desert Southwest ridge develops. Temperatures in the interior valleys may near or reach 100 mid to late next week. There are remaining questions about whether tropical moisture may stream northeast toward the region from decaying tropical systems well off the CA 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.

AVIATION

Calm winds return this evening with around a 40 percent chance of IFR or lower ceilings at ACV through the late evening/early morning. A deep marine layer set up may lead to early dissipation again Sunday morning, and improvements in ceiling heights, but southerly flow from a coastal wind eddy may lock it in longer into the afternoon.

MARINE

A continuously evolving upper level trough over western Oregon is beginning to weaken. As a result, northerly winds are beginning to form. 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 where gusts could reach 20kts or even 25kts. 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 ushering in a long period southerly swell of 3-5 feet at 17 seconds for south facing beaches in Mendocino and Southern Humboldt counties, including the Lost Coast Trail today through into Sunday. Thus, there could be a risk of sneaker waves, especially if the swell comes in slightly larger.

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!

EKA WATCHES/WARNINGS/ADVISORIES

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

NORTHWEST CALIFORNIA COASTAL WATERS... None.