textproduct: Eureka

KEY MESSAGES

* Red Flag Warning in effect for all towns and areas within Lake County Saturday for critical fire weather of strong winds and low relative humidity.

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

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

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

A trough and associated front will enter the area today, 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 10-20% 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 this afternoon for 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 today, 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

AVIATION

Nighttime IR Satellite Imagery shows a weak stratus deck developing along the Del Norte coastline. This feature is keeping the forecast optimistic for VFR through the early hours of the morning for much of the North Coast. Light winds are expected through the morning before westerlies at ACV and southerlies at CEC form. Inland, WNW winds will funnel through terrain with heightened chances for gusts in Mendocino and Lake County, especially near elevated terrain. VFR is expected in areas away from smoke from the Lucas Fire in Lake County. Rainshowers are possible for Del Norte and N. Humboldt Co, yet models show continued VFR ceilings with periodic MVFR possible.

MARINE

An incoming upper level through is ushering a weak cold front to the coastal waters by tomorrow. This front will weaken the surface pressure gradient allowing for the weakening of northerly winds through the overnight hours. Localized areas, such as those downwind from points or capes can expect northerlies to last slightly longer. Gentle breezes expected through Saturday with gentle to moderate breezes. Fresh to strong northerly breezes return Sunday and continue through early next week. Near-gale force gusts possible south of Cape Mendocino Monday.

FIRE WEATHER

A troughing pattern will bring breezier winds, much cooler temperatures, and a deeper marine layer through the weekend. Wetting rain is possible for Del Norte and far northern Humboldt. Stronger winds are forecast this afternoon with gusts up to 35 mph are possible in Lake, southern Mendocino, and eastern Trinity Counties, especially for higher, N-S orientated terrain. 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. In the few hours before the winds increase, hot and dry conditions are possible, increasing the likelihood of critical fire weather conditions for 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 increase 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 of California 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.

EKA WATCHES/WARNINGS/ADVISORIES

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

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