textproduct: Eureka

KEY MESSAGES

- Slight chance of showers or a couple thunderstorms Tuesday over interior Del Norte and Trinity County Sunday.

- 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 slight chance for showers or isolated thunderstorms this Sunday 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

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. Of note, 70s are possible to the coast, with mid 80s to low 90s not too far inland. These values would bring a Moderate HeatRisk to the region, including closer to the coast. NBM has high chances for this occurrence. After the stretch of cooler weather from persistent troughing, the fast warm up will not allow for much acclimation time. Likely aided by offshore winds, Wednesday looks like the warmest day of the stretch.

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 late week or through the weekend. NBM chances for a wetting rain of at least 0.1 inch are only 25% at this time Friday and through next weekend however.

AVIATION

Calm winds continue through Sunday morning. A passing shortwave trough is deepening the marine layer, but a shallow layer has persisted to bring LIFR ceilings. Instability associated with the trough looks to help disrupt the low level inversion Sunday. The only hindrance to faster clearing for the coastal terminals will be weak southerly winds around an expected coastal eddy. Some northwest winds deliver some gusts over the afternoon hours while interior terminals stay VFR.

MARINE

Northerly winds have strengthened, mainly over the southern waters. A mid period NW swell is subsiding. Hurricane Marie has delivered a long period southerly swell up to 5 ft at 17 seconds which will remain in the waters into next week. The northerlies begin to strengthen Sunday afternoon through Monday with winds 20 to 25 kts. Winds will begin to ease late Tuesday as a strong area of high pressure build in from the SE. Wednesday looks to give a break in winds with some offshore flow over the coast. There is some uncertainty in how fast the northerlies restrengthen Thursday or Friday.

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 is an ongoing 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... Small Craft Advisory from 2 PM Sunday to 5 AM PDT Monday for PZZ455.

Small Craft Advisory from 2 PM Sunday to 5 PM PDT Monday for PZZ475.