textproduct: Eureka

AVIATION...00Z UPDATE

VFR conditions persist this afternoon for the coast, before MVFR to IFR of BKN-OVC ceilings develop overnight as an incoming trough deepens and weakens the marine layer. An approaching front will also turn winds southerly near CEC, which may lead to continued VFR ceilings. Interior areas are likely to remain VFR for the next 24 hours with stronger gusty afternoon breezes expected tomorrow, primarily out of the NW. Smoke will continue to be an issue in Lake County increasing potential for mountain visibility issues. The first round of light rain showers is likely to arrive tomorrow afternoon to CEC, yet MVFR to VFR is expected to remain as this system is trending further north than CA.

PREV DISCUSSION

/issued 135 PM PDT Fri Sep 11 2026/

KEY MESSAGES...

* Much cooler interior temperatures likely this weekend.

* Chances for light rainfall for Del Norte and northern Humboldt Saturday.

* Elevated fire danger each afternoon through Saturday for the interior.

* Red Flag Warning in effect for Lake County Saturday for strong winds and low relative humidity.

SYNOPSIS...Cooler temperatures are expected through into the weekend. Light rain is possible for the Del Norte and northern Humboldt Saturday. Westerly to northwesterly winds will bring elevated to critical fire danger for the interior Saturday.

DISCUSSION...Interior temperatures will will be over 10 degrees cooler Friday as troughing from the NW begins to influence the region. The trough and associated front will swing through on Saturday, considerably lowering interior temperatures to the 70s and 80s. The front will also bring a chance for rain to Del Norte and northern Humboldt Counties. Del Norte has around an 80-90% chance to see measurable rain, while northern Humboldt has around a 20-40% chance, mainly north of Eureka. The chance for wetting rain (over 0.1") is around 20% in northern Humboldt and 60-70% in Del Norte. There is some instability modeled with this system, which may allow for a thunderstorm to develop in an especially strong shower.

Post frontal westerly winds will strengthen Saturday afternoon to the eastern portions of the area. The probability of wind gusts over 30 mph are above 50% for much of eastern Lake County, eastern Mendocino, and the Trinity River Valley in eastern Trinity County. This will elevate fire weather concerns, particularly over Lake County where the strongest winds will coincide with dry conditions. A Red Flag Warning is in effect for Lake County Saturday, but elevated fire weather conditions will exist for all the interior areas listed above. There are also chances this fire threat continues Sunday night and Monday for the far eastern portions of the area. See the Fire Weather section below.

An omega-block pattern is likely to develop right off the Pacific Northwest coast, with troughing remaining far east and far west. Slightly over half of ensemble members do show an elongated positively tilted trough or cutoff low over the area Wednesday. This will contain little moisture and may only result in a slightly deepened marine layer and perhaps some modest instability in the higher terrain. Regardless, a dry, near-normal pattern looks likely for the following week as the omega block stalls any storm track for NW California. /JB

MARINE...Northerly winds increase across the southern waters Friday while easing some in the northern waters north of Cape Mendocino. Localized gale conditions can be expected around and south of Cape Mendocino this afternoon and evening. Short period seas up to 10 ft will be generated in the lee of Cape Mendocino from these winds. Winds and seas quickly ease Saturday as a trough moves in. This will bring thunderstorm chances to the northern waters, mainly closer to the Oregon border.

FIRE WEATHER...A troughing pattern will bring breezier winds, much cooler temperatures, and a deeper marine layer. Wetting rain is possible for Del Norte and far northern Humboldt. Breezy afternoon winds continue today with gusts of up to 20 mph in Lake, eastern Mendocino, and eastern Trinity Counties. This will elevate fire weather conditions as afternoon RH remains in the teens and 20s. Saturday, stronger winds are forecast with gusts up to 35 mph are possible in Lake, southern Mendocino, and eastern Trinity Counties Saturday afternoon. RH will rise with this onshore push of winds to the 20s and 30s, but much stronger wind gusts of 25 to 35 mph will support critical fire weather conditions, particularly in Lake County. A Red Flag Warning has been issued in Lake County from 10 AM Saturday to 2 AM Sunday. Other areas outside Lake County will still see elevated fire danger, including eastern Mendocino and Trinity County, despite not being within the Red Flag Warning area.

Winds ease Sunday and RHs tick up slightly into the high 20s to the high 30s for the eastern interior. Areas closer to the coast could see afternoon RHs in the 50s with a much deeper marine layer. Sunday night into Monday, an increase of northerly winds down the Central Valley may elevate fire conditions again for the eastern portions of the area, particularly eastern Lake County should the winds end up on the stronger end. RH does trend upwards, so the threat may be muted somewhat, but it is something to watch. /JB

EKA WATCHES/WARNINGS/ADVISORIES

CA... Red Flag Warning from 10 AM Saturday to 2 AM PDT Sunday for CAZ418>421.

NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 3 AM PDT Saturday for PZZ455-475.