123 FXUS66 KEKA 102153 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 253 PM PDT Thu Jul 10 2025 .SYNOPSIS...High pressure is building and generally hot and dry weather is expected for the next week or so. The hottest temperatures will start in the south on Friday and work their way north on Saturday and Sunday. Northeast winds overnight on Thursday and Friday will help to limit the stratus and potentially bring warmer temperatures to the coast. && .DISCUSSION...High pressure continues to build over the area and hot temperatures are starting to take hold in Mendocino county. A thin strip of stratus remains in place as of 2pm along portions of the coast. If this clears out it may take considerable time to come back tonight. Offshore flow tonight is expected to limit the coverage of clouds up the river valleys and this should facilitate skies clearing on coast. The heat advisories start Friday afternoon in Mendocino and Lake counties as the temperatures warm more quickly down there, although there is quite a bit of warming in the north as well and the argument could be made to start the advisories in Humboldt and Del Counties as well. Trinity county warms more Saturday as this heat continues to build. This is expected to be the start of a more extended period of hot weather so have issued an excessive heat warning. Sunday the ridge starts to shift east slightly and it looks like this will allow some marine air to start to intrude on Mendocino county. This may also bring some stratus to the immediate Mendocino coast. So the heat advisory ends for the Ukiah and Willits zones on Saturday evening. Also on Sunday the models are showing some increasing moisture aloft and the potential for a thunderstorm over northern Trinity county. For now this only looks to be around a 10 percent chance, but did add that to the forecast. One potential challenge in this forecast is the presence of smoke may keep temperatures cooler than expected. General went with the idea that the smoke would not be sufficient to keep temperatures cooler over a large area. Monday the ridge continues to shift east and the marine layer may start making its way north and starting to cool off portions of Humboldt and Del Norte counties. There is still some uncertainty on how much of the heat will linger in eastern Mendocino and Lake counties so the advisories may need to be extended there. Tuesday hot weather continues, but it is expected to be more confined to areas well away from the coast in Trinity county. Wednesday an upper level trough approaching the area continues the slow cooling trend, but most areas are expected to still be in the 90s. MKK && .AVIATION...Stratus along the Del Norte and Humboldt coasts has started to lift and scatter early this afternoon. Breezy northerly winds are likely this afternoon and evening, with strong winds at CEC possibly exceeding 25 kts. Mostly clear skies will follow for across the area into the evening, apart from wildfire smoke. Stratus is likely to return this evening and overnight to the Humboldt coast, with a shallow marine layer bringing LIFR/IFR ceilings and visibilities. Northerly winds will likely ease overnight for most of the area, aside from CEC. Southerly winds are possible along the immediate coast between ACV and CEC, which would advect stratus northward. If northerlies remain strong overnight at CEC, stratus will likely hit a barrier before affecting the terminal. NBM is showing around a 60% chance for IFR or LIFR ceilings and visibilities for CEC. Interior areas, including UKI, are expected to remain clear aside from smoke and haze. JB && .MARINE...Northerly winds have started to ramp up as a tight pressure gradient sets up along the coast. Gale force gusts are likely in the outer waters starting this afternoon into Friday. Nearshore waters could see gusts of 20-25 kts in the afternoons, but are largely insulated from the strongest winds. Steep, elevated seas in the outer waters are likely to in nearshore Friday afternoon, bringing steep seas of 8-10 ft. Winds begin to move further offshore Saturday, especially south of Cape Mendocino. North of the Cape, near-gale to gale force winds are likely to continue into early next week. High pressure begins to break down by mid next week, which will likely ease winds and seas. JB && .FIRE WEATHER...High pressure is building and offshore flow is expected with the warming and drying inland and near coastal areas. This is keeping just a very thin strip of stratus along the coast this afternoon and even this may erode later this afternoon. Areas below the marine layer inversion, which is currently around 2500 feet, are expected to see good RH recoveries while areas above it will be much drier and see breezy northeast to east winds. This inversion is expected to lower over the next couple days as high pressure strengthens. The NBM is likely too high on the rh due to the pattern shift from a deep marine layer. So it has been lowered it by blending it with the FV3 model. This may not be low enough, but it appears to push it in the right direction. 850 and 925 mb winds are around 10 to 20 mph overnight with rh recoveries only around 40 to 50 percent on the ridges again. Warmer dry conditions are generally expected on Saturday, although portions of Mendocino county closer to the coast may start to see more marine influence as the flow aloft weakens starting on Saturday. Smoke across the area will mainly be pushed south from the Butler Fire. This will trend more towards the west overnight and back to the east in the afternoon when the winds become more northwesterly. The eastern portions of the area may also see some smoke from the Green Fire north of Redding in the afternoons. This general pattern is expected to continue over the next several days depending on how much smoke the fires output. MKK && .EKA WATCHES/WARNINGS/ADVISORIES... CA... Extreme Heat Watch from Saturday morning through Sunday evening for CAZ102-105-106. Heat Advisory from 11 AM Friday to 11 PM PDT Sunday for CAZ107-108-111-114-115. Heat Advisory from 11 AM Friday to 11 PM PDT Saturday for CAZ110-113. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 11 AM PDT Saturday for PZZ450. Small Craft Advisory until 3 AM PDT Friday for PZZ455. Gale Warning until 11 PM PDT Saturday for PZZ470. Gale Warning until 11 AM PDT Saturday for PZZ475. && $$ NOTE: The full forecast discussion is now regularly issued between 10 am/pm and 1 pm/am. 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