textproduct: Eureka

KEY MESSAGES

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

* Coastal stratus likely to continue to form each night

* Hot temperatures return late week and into the weekend.

* Elevated fire danger returns late in the week and at least into next week with increased wind and increasingly hot, dry conditions.

SYNOPSIS

Near to slightly below normal temperatures forecast to continue for interior areas into tomorrow, while near to above normal coastal temperatures are likely to end today. Breezy afternoon winds elevate fire danger in eastern Trinity, eastern Mendocino, and Lake counties. Hot interior temperatures return later this week, further increasing fire weather risk.

DISCUSSION

An upper level trough over the Gulf of Alaska will continue to affect weather patterns over Northwest California today and tomorrow. Zonal flow continues to aid in reinforcing a stubborn stratus layer over the North Coast through the afternoon. Stratus is then expected to deepen and expand over the coast and down coastal river valleys again overnight tonight. Cooler than average temperatures will continue today and tomorrow for the interior as the upper low affects the area. The rest of this week and into the weekend, northerlies will continue to strengthen over the ocean restarting upwelling and leading to the usual cooler near shore ocean temperatures. This will cause cool air advection into coastal areas which will help trend coastal temperatures back towards normal. A pronounced shortwave perturbation will advance over N CA Thursday. Moisture and instability will be very limited, so only mid to high level clouds should result.

A Four Corners/Desert Southwest dome of high pressure will then begin to strengthen Thursday. The 500mb ridge will continue to strengthen, reaching 597 to up to 600dm by Friday. This will translate to hot interior temperatures. Probabilities for interior temperatures over 100 increase going into next week, with high chances (60 to 80%) for temperatures over 100 by Monday, and moderate chances (40%) for temperatures over 104 Tuesday and Wednesday of next week.

Fire weather concerns will become elevated again with the duration of the building heat along will periods of breezy conditions. See the Fire Weather section below. /JJW /JLW

AVIATION

An upper level trough along with a passing weak front continues to reinforce coastal stratus into the afternoon, especially along the Humboldt and Del Norte coasts north of Cape Mendocino. Some clearing and lifting is possible later this afternoon and early evening for some coastal terminals (more likely for KACV). But, most coastal terminals of Humboldt and Del Norte counties will maintain at least a MVFR ceiling throughout the day. Another deep marine layer is anticipated to form late this evening and overnight, enveloping the coast and stretching down river valleys. LIFR/IFR conditions are anticipated for KCEC and KACV tonight. Gusty northwest winds are possible this afternoon, gusting from 15 to 20 knots, at most terminals. /JLW

MARINE

Northerly winds have trended higher over all zones. Winds north of Cape Mendocino look to generally remain below 20 kts through Friday. The focus of stronger northerlies will remain around and south of Cape Mendocino. Northerlies of 20-25 kts in these southern zones, locally with gale conditions up to 30 kts around the cape, can continue to be expected. Short period northerly seas will increase over the waters, along with a small long period southerly swell. A ridge of high pressure will strengthen through the weekend, bringing increased chances for gale strength northerlies over much of the waters. /JJW

FIRE WEATHER

Afternoon westerly breezes will likely bring isolated areas of enhanced fire weather danger and perhaps brief critical conditions locally. Overnight recoveries are expected to be moderate to 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 low 20s in interior Humboldt, Del Norte, and western Mendocino Counties Wednesday.

Ridging rebuilds back in starting Thursday, bringing much warmer high temperatures to the interior. Most valleys are forecast to reach the high 90s and triple digits, with highest chances for temperatures over 100 early next week. Afternoon RHs will again be in the teens and 20s for the eastern interior. Troughing to the north will likely enhance winds over the weekend and possibly Monday, increasing the fire weather threat, especially when coinciding with the building heat and low RH. /JJW

BEACH HAZARDS

A long period southerly swell, with periods up to 18 seconds, remains from tropical systems in the Eastern Pacific through this evening, with easing of size and energy thereafter. This energetic swell will continue to bring a low to moderate risk of sneaker waves into this evening. With this sneaker wave event the most hazardous areas are steep, south and southwest facing beaches along the Lost Coast and Mendocino Coast through Wednesday.

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 until 6 PM PDT this evening for CAZ104-109.

NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 2 PM PDT Friday for PZZ455-475.