textproduct: Eureka

KEY MESSAGES

* Thick smoke remains stuck around the Hoopa Valley with weak mixing keeping smoke stuck in terrain into the weekend.

* Very slight chance for isolated dry storms in the interior during the day Friday.

* High level clouds will help create near to slightly below normal temperatures Friday and into the weekend.

SYNOPSIS

Warm temperatures will ease through the week thanks to increasing marine influence. Marine clouds will persistent along shore with some slightly drizzle and the clearing potential Friday. Warmed conditions return later in the weekend.

DISCUSSION

High pressure finally began to weaken today with the hottest interior valleys closer to 90 than 100 and deeper, though still persistent, marine layer along the shore. An elongated trough approaching shore tonight and through the day Friday will continuing the drive a shift in the weather.

Along shore, the trough will keep the marine layer strong but also help lift marine influence, likely driving some very light drizzle along shore and encouraging less dense fog and better afternoon scattering. For the interior, a band of high clouds streaking across the area from the south will most likely help support much cooler temperatures. Mid level moisture and and jet streak aloft will provide some potential for isolated showers and thunderstorms, but almost no models show instability which will keep chances very low (less than 5% across the interior). Despite the trough, cooler temperatures and still weak wind will most likely keep smoke stuck around Hoopa Valley, at least as long as fire activity continues to support new smoke production.

For the extended forecast, cooler temperatures will remain through the day Saturday, but high pressure will briefly rebuild Sunday and into early next week. This will return clear, warm, and calm conditions. Conditions will be near normal temperatures, which is slightly cooler than this past week. Offshore flow on the lee side of through may allow for one day of coastal sun around Monday, but otherwise, interior heat will help keep a consistent marine layer with stratus and mist. /JHW

MARINE

North winds have rapidly fallen off today in the outer waters with gusts below 15 kts. Short period seas have fallen below 5 feet with very minor mid period westerly and southerly swells the only other waves of note. Unusually calm conditions will dominate Friday with winds almost below 5 kts in all waters. Winds will be weak and southerly north of Cape Mendocino and Northerly south of the Cape. Broader northerly winds and short period waves will begin to rebuild late Saturday and into Sunday particularly south of Cape Mendocino. /JHW

FIRE WEATHER

Hot and dry weather conditions ever so slightly began to ease today. Conditions will further ease Friday, especially with the help of upper level clouds. Highs will pull back closer to the 90s with RH over 20 percent.

The greatest forecast challenge remains thunderstorm potential Friday. A strong plume of midlevel moisture is already entering the area and will peak early Friday morning and through the day. At the same time, a strong southerly jet forming offshore and aligning with topography could provide and lift and enhance instability to allow for thunderstorms. Even with this dynamic forcing, however, few models are showing any instability. A couple of high resolution models today are showing areas of minor MU CAPE less than 100 J/Kg. Soundings reveal very narrow areas of mixing into the freezing layer that will make lightning formation unlikely. There remains a very slight (5-10%) chance of lightning in northern Trinity and eastern Humboldt Counties Friday morning and afternoon, but coverage would be sporadic and very isolated. Any lightning that does occur will be dry, increasing fire risk. /JHW

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... None.