textproduct: Eureka

KEY MESSAGES

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

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

* Near to slightly below normal interior temperatures expected through the middle of next week.

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

* Hot interior temperatures likely to return late next week.

SYNOPSIS

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

DISCUSSION

Depending on the persistence of stratus into the afternoons and how early the northwesterly winds start, warmer coastal temperatures may continue into mid next week. A weak marine inversion will allow for at least partial, if not full, clearing in the afternoons. The Mendocino Coast will see breezier afternoon winds which will support closer to normal temperatures.

The troughing pattern has also brought breezy afternoon winds of 20 to 30 mph in the interior areas, 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 late next week and next weekend. NBM is showing moderate to high probabilities for high temperatures in the triple digits for most interior valleys. Hot temperatures may continue into much of the following week with over half of ensemble members showing near- persistent ridging. /JB/JJW

AVIATION

06Z TAFs.

Key Message:

-IFR to LIFR conditions with a 30% chance for a period of fog visibilities (highest chances north through CEC) possible at the coastal terminals, but confidence is overall low (see below). There is a small (15%) chance of stratus impacting KUKI from the west. Northwesterly winds will be breezy in Mendocino and Lake Counties this afternoon and evening. Improvement to VFR is anticipated through Monday afternoon, but additional stratus will advect down the coast from the north.

Discussion and Forecast Reasoning:

Ceiling heights began at MVFR levels, modeled to generally lower. One complication to the ceiling heights and clearing window Monday is a weak shortwave disturbance progged to advance through in the 13Z to 17Z Monday time span.

Associated mid-level subsidence on the northern periphery of this feature would quickly compress the marine layer boundary and lead to more persistent LIFR CIG heights. A slight nudge north of the shortwave (PVA sector) would allow for some deepening and more dominant IFR levels. RAP guidance has been shifting north and MOS guidance has trailed with a trend away from fog greater chances

The shallower levels would give higher confidence for solar heating to somewhat cleanly break the inversion from north to south, scattering out KCEC after 18Z and ACV soon after, or as late as 21Z. A light onshore NW breeze may briefly slosh or advect remnants of the marine deck back towards the immediate North Coast through the afternoon. Guidance also drives a more atypical northerly stratus surge sometime through the afternoon or evening, with currently a high degree of uncertainty in timing.

The deepened southern portion of the marine layer does bring a small (15%) chance of stratus impacting KUKI from the west, but sounding imply the depth will be just short of overcoming the western high terrain. Northwesterly winds are likely to be breezy in Mendocino and Lake Counties this afternoon and evening. /JJW

MARINE

The sea state is dominated by a small 3 to 5 foot long period southerly swell and some small mid period westerly and northerly swells. A second reinforcing long period southerly swell will arrive Tuesday. Winds will remain very light, only up to 4 to 8 kts Monday north of Cape Mendocino. Northerly winds strengthen 15 to 20 kts, locally up to 25 kts around the cape by Monday afternoon. Northerlies trend higher in all waters starting Tuesday. Localized areas of gale conditions will develop in the expansion fan around Cape Mendocino. /JJW

FIRE WEATHER

Breezy westerly winds will continue in the afternoons 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 very low afternoon RHs in the single digits and teens. Overnight recoveries are expected to be good aside from the higher elevations of Lake and eastern Trinity County.

Localized critical conditions are possible each afternoon, with the potential for slightly stronger and more persistent winds Monday afternoon and evening. This will likely raise RH at least into the teens or 20s, but so far the marine influence has not had a significant impact in eastern Lake, eastern Mendocino, and eastern Trinity Counties. This will need to be watched for the potential of a Red Flag Warning, should relative humidities remain low into the evening on Monday while winds remain persistent in the afternoon and evening.

Closer to the coast, a deep marine layer will bring high RH and perhaps stratus and/or fog into the river valleys. Afternoon RH ranges from 70s to 80s at the immediate coast to 20s and 40s in interior Humboldt, Del Norte, and western Mendocino Counties. /JB

BEACH HAZARDS

A long period southerly swell with periods up to 20 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 from 4 AM early this morning to 1 PM PDT Tuesday for PZZ455-475.