954 FXUS66 KEKA 061145 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 445 AM PDT Mon Sep 6 2021 .SYNOPSIS...Above normal temperatures are expected across the interior through mid week. A low moving north of the area Tuesday will bring a chance of showers and coastal drizzle. Smoke will be guided more north and northeasterly by Tuesday night. && .DISCUSSION...An upper high is building over NV today. A closed cutoff low which has been spinning in place west over the Pacific will begin to be nudged NE ahead of a NE Pacific trough. The low will just pass our coastal CWA as an open wave Tuesday afternoon. High clouds can already be seen streaming in from the south as southerly flow has already developed ahead of the trough. Mid to upper moisture will continue to stream in, guided between the western periphery of the high and the incoming open wave. Guidance has held the bulk of the forcing and instability to remain offshore as it passes, with even NAM now giving way to this solution. Some light showers and coastal drizzle will be possible along coastal northern Humboldt and Del Norte counties Tuesday afternoon and evening. Weak elevated CAPE and high PWATs up to 1.5 inches will arrive as well, but thunder chances continue to look very low for this period, 5% or less between NBM, HREF and SREF. A line of weakly defined baroclinic instability and frontogenesis will trail behind the low as it progresses over Oregon through Tuesday evening. This will linger over the CWA as a stalled frontal boundary through Wednesday, with some remaining mid-level moisture along it. The upper high will have backed off SE over the four corners region, allowing temperatures to moderate some. Another plume of mid level moisture may blossom up Thursday, but instability looks to very low. The timeframe will require watching however, as deterministic models and cluster analysis diverge on the strength of the high and amplitude of an approaching trough. Smoke in northeast Humboldt and Trinity Counties will continue to produce poor air quality, though the increased southerly winds should help to disperse the smoke. Regarding heat, the valleys of southern Mendocino and Lake counties have the highest chances of reaching or just breaking 100. Areal extent of any heat risk threat in those zones was low, and locally confined. Overnight lows have also been exceeding model expectations, but the usual caution is still advised with outdoor exposure. && .AVIATION...VSBY down to 1/4SM in fog with VV002 at KCEC continues this morning. Expect LIFR conditions with visibility in fog down to 1/4SM at KCEC and possible for KACV as well through the morning hours. The stratus and fog should once again burn off a late this morning, but will likely linger near the shoreline all day again. Smoke and haze from inland wildfires may impact KUKI with periods of MVFR visibility, otherwise VFR is expected through the period. /MKN && .MARINE...Northerly winds are expected to increase to 15-25 kts across the outer waters through late Monday night, mainly in the southern outer waters. Nearshore winds will be light to gentle breezes, with localized stronger winds downwind of Cape Mendocino through Monday morning. Steep seas are forecast to reach 6 to 7 feet in the lee of Cape Mendo this morning as winds increase. A series of NW swells are moving across the waters and are expected to build to around 4 to 6 feet by Monday morning. On Tuesday, winds will gradually diminish into weak winds with low seas as an upper level low moves through. In the wake of the passing low, northerly winds are expected to increase again as high pressure rebuilds back into the NW coast. /MKN && .FIRE WEATHER...Fire weather monitor has once again light up with many stations flirting with red flag criteria this afternoon. It does not take much wind (gusts 10-15 mph) when RH's are in the single digits and teens. RH recoveries tonight will once again remain poor over the ridges and slopes. Temperatures will continue to warm through Monday with the hottest valleys in the 90's to around 100 again. A cut-off low churning to our southwest for the last several days will slowly eject north-northeastward Mon-Tue in response to an upstream kicker. Some high will spread over the area in southerly flow aloft on Monday. Stable conditions are forecast to persist. The ridge will likely hold over the area on Tuesday as the cut-off becomes absorbed by the upstream trough. Some elevated instability will develop offshore and near the coast on Tuesday as the mid level moisture increases. The forcing for elevated storms appears to far offshore to pose a substantial threat for storms. HREF should shed more light on this once within range of the CAMS. This trough will also induce stronger westerly to southwesterly breezes Tuesday afternoon and evening with some afternoon gusts around 20-25 mph on ridges and wind channeled valleys of Humboldt and Trinity Counties. With dry air continuing, locally critical conditions are expected, though nothing widespread enough to justify a red flag warning at this time. Cooler temperatures and improved recoveries are expected toward the latter portion of the week. Models currently hint at a troughing pattern and maybe another round of showers and possible thunderstorms Friday across the eastern and northeastern portion of the forecast area; the Trinity ALPS and YOLLA BOLLY wilderness area. && .EKA WATCHES/WARNINGS/ADVISORIES... CA...None. NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory until 3 AM PDT Tuesday for PZZ470-475. && $$ Visit us at https://www.weather.gov/eureka Follow us on Facebook and Twitter at: https://www.facebook.com/NWSEureka https://www.twitter.com/NWSEureka For forecast zone information see the forecast zone map online: https://www.weather.gov/images/eka/zonemap.png