textproduct: Eureka

KEY MESSAGES

* Moderate risk for sneaker waves along the Lost Coast and Mendocino Coast through Wednesday.

* Elevated fire danger Tuesday for interior areas due to breezy afternoon winds.

* Hot temperatures return late week into the weekend.

* Coastal stratus likely to form each night and clear each afternoon through at least the middle of the week.

SYNOPSIS

Near to slightly below normal temperatures are likely for the interior areas, while near to slightly above normal coastal temperatures are likely continue through Wednesday. Breezy afternoon winds elevate fire danger in eastern Trinity, eastern Mendocino, and Lake counties. Hot interior temperatures return late this week.

DISCUSSION

The extended period of lighter northerly winds has shut down much of the coastal upwelling. This created warmer than average coastal water temperatures, into the low 60s, and a weaker low level inversion. The lack of cool air advection from the coastal waters and quickly dispersing daytime stratus will once again lead to some warmer coastal temperatures Tuesday. The northerlies will be trending higher this week, allowing for more typical seabreeze temperature moderation.

A continued troughing pattern will once again bring breezy afternoon wind gusts of 20 to 30 mph in the interior areas Tuesday afternoon, mainly in the higher elevations and channeled terrain (such as Clear Lake and the Trinity River valley). Low afternoon relative humidities in Trinity, eastern Mendocino, and Lake Counties along with these winds brings an elevated fire weather threat.

There is high confidence in high pressure rebuilding over the area later this week. NBM is showing moderate to high probabilities for high temperatures in the triple digits for most interior valleys starting Friday and continuing into next week. Currently, minor to moderate HeatRisk is expected. /JB/JJW

AVIATION

06Z TAFs.Stratus reformed Monday evening after periods of full clearing and VFR conditions. The marine layer has been deepened by a passing weak shortwave, and a second one is forecast to pass through Tuesday. This should maintain mostly MVFR to IFR ceilings Tuesday. Coastal seas surface temperatures have been warmer than average, in the low 60s, and this has contributed to a largely weakened low level inversion. Aside for the potential for some lingering stratus to get driven back to the coast with the afternoon seabreeze, effective afternoon clearing is expected with the weak inversion. VFR conditions will prevail for the interior. Northerly winds will increase through the afternoon hours, with some gusts near 20 kts expected at CEC, ACV and UKI. Stratus will begin expanding back over the coast Tuesday evening, but should not be initially too shallow. /JJW

MARINE

Northerly winds will begin trending higher over all zones starting Tuesday. Winds north of Cape Mendocino look to generally remain below 20 kts through the week. The focus of stronger northerlies will remain around and south of Cape Mendocino. Northerlies will strengthen to 20-25 kts in these southern zones, locally with gale conditions up to 30 kts around the cape. Short period northerly seas will increase over the waters while a persistent small long period southerly swell is reinforced by a second Tuesday. A ridge of high pressure will strengthen through the weekend, bringing increased chances for gale strength northerlies. /JJW

FIRE WEATHER

Breezy westerly winds will continue in the afternoons Tuesday for interior areas and may be particularly breezy with gusts of 20 to 30 mph over the ridges and channeled terrain in eastern Trinity, northeast Mendocino, and Lake Counties. These areas are forecast to have low afternoon RHs in the teens and 20s. Localized and brief critical conditions are possible with these low RHs and winds. Overnight recoveries are expected to be good aside from the higher elevations of Lake and eastern Trinity County.

Closer to the coast, a deep marine layer brings high RH and perhaps stratus and/or fog into the river valleys overnight. Afternoon RH ranges from 60s to 80s near the immediate coast to 20s to 40s in interior Humboldt, Del Norte, and western Mendocino Counties.

Ridging rebuilds later this week into the weekend bringing much warmer high temperatures to the interior with most valleys forecast to reach the high 90s and triple digits. Afternoon RHs will again be in the teens and 20s for the eastern interior. Weak shortwaves arrive over this same period which may support some breezier afternoons along with this heat and low afternoon RH. Confidence is low at this time, but elevated fire weather conditions are again possible. /JB

BEACH HAZARDS

A long period southerly swell with periods up to 19 seconds remains in from tropical systems in the Eastern Pacific. A second reinforcing long period southerly swell will arrive Tuesday. These energetic swells will bring a low to moderate risk of sneaker waves that would be most hazardous on steep, south and southwest facing beaches along the Lost Coast and Mendocino Coast.

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

EKA WATCHES/WARNINGS/ADVISORIES

CA... Beach Hazards Statement through Wednesday afternoon for CAZ104-109.

NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 9 PM PDT Wednesday for PZZ455- 475.