textproduct: Eureka

KEY MESSAGES

* Slightly cooler, but still hot, interior temperatures are forecast through Wednesday.

* Smokey conditions likely from the MP 18 Fire in the Trinity River Valley.

* Slight chance of interior thunderstorms late this week or over the weekend.

SYNOPSIS

High pressure starts to weaken this week, but slightly above normal temperatures in the interior are expected through Wednesday. Coastal areas continue to have near normal temperatures with overnight stratus clearing in the afternoons along with breezy northwest winds.

DISCUSSION

Smoke from the MP 18 fire continues to impact air quality over Northern California, particularly in the interior valleys of Humboldt and Trinity counties. Depending on fire containment, expect a similar pattern to carry through the week.

The high pressure ridge responsible for the extended period of hot temperatures is finally beginning to weaken. Temperatures will trend cooler as a result, but will still be hot through Wednesday. The heat has greatly dried out the region and fire weather concerns will be elevated with any increase in winds. See the fire weather section below.

There will be a more noticeable drop in interior temperatures Thursday as a troughing pattern settles over the region. High temperatures in the interior valleys will struggle to break 90 by Friday, and will continue to lower through the weekend. Clusters show a potential brief rebound in the ridge late in the weekend before a deeper area of low pressure potentially develops.

The pattern has been analyzed for the potential for thunderstorm formation under the troughing, including from various shortwave disturbances that pass through. These are possible as early as Thursday. Confidence is low, at 5 to 10 percent through Trinity Siskiyou counties. Modeled available moisture and instability has decreased, but the pattern will continue to be closely monitored for deviations in modeled trends.

AVIATION

Winds have switched bearings from Southerly to northerly at KCEC as of 20z with VFR conditions as coastal stratus has scattered and cleared out. Gusts at KCEC are expected to reach 22kts with sustained winds at 10-12kts. Winds are expected to ease at KCEC around 04z and switch bearings, back to southerly into early Tuesday morning, with LIFR ceilings below 500ft and possibly fog or marine stratus advection reducing visibility to 1/2 mile or less. Winds turn northerly again Tuesday morning. KACV not quite as gusty but northerlies with a more westerly component turning southerly after sunset and easing to 5 knots or below. LIFR at KACV will be primarily from ceilings below 500 ft and not as much from lower visibility although 3-5 mile vis with light fog or mist will likely be the obscuration. GFS does have a few hours of 1/2mile vis which usually equates to a few hours of 2sm with BR/mist. /EYS

MARINE

Northerly winds continue to build throughout the afternoon and will peak around sunset. The largest fetch area being in the Northern outer waters with gusts up to 40+ kts. South of Cape Mendocino, the wind field will be wide as it fans out into the southern outer waters with gusts up to 38kts or so. Wind wave action from the northerlies will give 10-12ft wave heights and periods in as many seconds, creating steep and dangerous sea conditions. The Gale Warning for the northern and southern outer waters is extended through Thursday. In addition to the Gale Warning there is also a small craft advisory (SC.Y) for the inner coastal waters, north and south for steep seas. Otherwise, a long period southerly swell with < 1 ft wave height, is due to arrive overnight into early morning Tuesday. /EYS

FIRE WEATHER

Locally critical fire weather conditions can be expected through Monday with the afternoon and evening breezes. Winds will be strongest channeled through the terrain. Additionally, The ridges around the King Range will continue to see strong northerly winds, and there will be a northeast wind surge overnight and into Tuesday for the interior ridges of Del Norte. A similar wind pattern will remain Tuesday.

Minimum RH and overnight recoveries will improve noticeably Tuesday with moistening westerly flow and lower daytime highs from the breakdown of the ridge of high pressure. A troughing pattern then takes shape, which will maintain good recoveries and also increases chances for a deepened marine layer to infiltrate farther into the interior. There is a chance for dry thunderstorms late in the week in the Trinities and Yolla Bolla mountains, and these are possible as early as Thursday. Confidence is low, at 5 to 10 percent through Trinity Siskiyou counties, with the highest chances currently Friday.

COASTAL FLOODING

Sea levels continue to run approximately 0.8 ft above the predicted tide level in Humboldt Bay. Tides will become more amplified early this week following the lunar cycle. The predicted tide at the North Spit is 7.95 ft MLLW at 10:21 pm tonight and then 7.99 ft MLLW at 11:17 pm on Tuesday the 11th. If the tide continues to run at around 0.8 ft above predicted, this could result in minor coastal flooding around Humboldt Bay with minor impacts in King Salmon and possibly a few other locations around the bay. Additional minor coastal flooding will be possible for the 12:10 AM high tide Thursday morning.

EKA WATCHES/WARNINGS/ADVISORIES

CA... Coastal Flood Advisory from 9 PM this evening to 1 AM PDT Tuesday for CAZ103.

NORTHWEST CALIFORNIA COASTAL WATERS... Coastal Flood Advisory from 9 PM this evening to 1 AM PDT Tuesday for PZZ415.

Small Craft Advisory until 9 AM PDT Thursday for PZZ450.

Small Craft Advisory until 3 AM PDT Wednesday for PZZ455.

Gale Warning until 9 AM PDT Thursday for PZZ470-475.