textproduct: Eureka

KEY MESSAGES

* Near to slightly above average temperatures inland continue through Wednesday with the warmest temperatures in Lake County.

* A passing cold front brings a high chance (70-90%) of light rain to Del Norte and northern Humboldt late Thursday night into Friday, with lower probabilities (under 20%) south into Mendocino County.

* Breezy winds possible late Thursday and into Friday.

* Cooler temperatures will arrive this weekend behind the front, bringing chances for isolated interior frost.

SYNOPSIS

Interior high pressure and a thermal low will maintain warm, dry conditions through Wednesday. An approaching cold front introduces more extensive cloud cover and a chance for measurable rain to Del Norte and northern Humboldt counties late Thursday night into Friday. Colder temperatures will follow through the weekend.

DISCUSSION

The coastal stratus showed some weakness today, allowing for more periods of sunshine. Light coastal drizzle has accumulated up to a few hundredths of precipitation over the past two days, mainly around Humboldt Bay. More drizzle is likely tonight. Temperatures trend warmer Wednesday with a strengthening thermal trough. Low to some mid 90s are forecast for the warmer interior valleys Wednesday before a shortwave trough begins moving in. There will be a compact surface low with the trough that has the potential to bring some stronger southerly winds, especially if the track nudges south at all. NBM has moderate to high chances for gusts over 30 mph for the coastal headlands and interior ridges of northern Humboldt through Del Norte. There looks to also be a period of gusty winds in Lake County Friday.

Chances for rainfall increase late Thursday with the trough and cold front. The bulk of the shortwave energy looks to likely remain north over southern Oregon, with trailing showers and some light rain for mainly northern Humboldt through Del Norte. If the system tracks farther south, than some higher rainfall amounts will be possible, especially with the associated instability. There are currently moderate to high chances for the light rainfall to generally occur.

Cooler temperatures arrive Saturday morning behind the cold front passage. There will be opportunity for isolated interior frost in the colder valleys through the weekend and likely into early next week. Another trough is forest through the weekend however, and the resulting cloudcover may prevent overnight lows from getting too cold. The broader pattern will favor either zonal flow or additional troughs next week, bringing the potential for more at least light rainfall.

AVIATION

Increasing northerly winds helped to mix out some of the stratus, with a mix of IFR to VFR conditions. Lighter nearshore winds are pooling the stratus back to the coast, continuing chances for MVFR to IFR CIGs. Soundings show some morning compression to the CIG heights, brining chances (35 to 45%) for LIFR levels through the morning. There are indications that the stratus may attempt to quickly mix out Wednesday morning with the weakening inversion.

The stratus made a run up to Russian River valley Tuesday morning, but the layer was too shallow to overcome the higher terrain. VFR is forecast to remain through the next 24 hours south for UKI, but ensembles bring a subtle amount of moisture in the valley Wednesday morning. Stratus will pool into the Fort Bragg area through Wednesday morning.

MARINE

A 7 to 9 ft mid period NW swell has built into the waters. The swell is peaking this afternoon, and is combining with short period seas generated from strengthening northerly winds. Northerly winds with gale strength gusts up to near 40kts in the southern waters, around and south of the cape, are combining with the swell to create up to 11 ft seas. The northerlies begin to weaken late Wednesday.

A trough will pass through late Thursday and into Friday. There will be an area of gale strength winds within a core of an area of low pressure. This may impact the northern waters as it passes. The northerlies will quickly restrengthen behind the trough Friday and through the weekend.

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 9 PM PDT Wednesday for PZZ455.

Small Craft Advisory until 9 AM PDT Wednesday for PZZ470.

Small Craft Advisory until 3 PM PDT this afternoon for PZZ475.

Gale Warning until 9 PM PDT this evening for PZZ475.