Area Forecast Discussion
Issued by NWS Eureka, CA
Issued by NWS Eureka, CA
848 FXUS66 KEKA 292150 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 250 PM PDT Fri Aug 29 2025 .SYNOPSIS...Near seasonal average temperature will continue through the weekend. Increasing heat across the interior early through mid next week, with interior widespread Moderate to locally Major HeatRisk. && .DISCUSSION...Stratus eroded back to the coast with the daytime heating early this afternoon, while high level clouds stream eastward across the forecast area. Warm and dry weather will continue through the Labor Day Weekend as a closed low well offshore the Oregon Coast continue to track northward. Interior high temperatures generally in the mid 80`s to mid 90`s, while mid 60`s to low 70`s along the coast. Expect coastal stratus every morning with a deep marine layer, before erode back and mix out by late morning/early afternoon. Smoke from the active wildfires in Siskiyou County will continue to be pushed toward northeast with the southwesterly breezes aloft through this evening, bringing some improvement in the air quality for areas in the northeastern portion of Humboldt counties, including Orleans. Air quality is expected to deteriorate across the northeastern portion of Trinity County as the surface winds increase from south to southwest later this afternoon and push the smoke from the Peak Fire in Trinity and 5-4 Fire in Shasta County toward the area. HRRR model indicates smoke will spread into the northeast this weekend each afternoon again with the southwest winds aloft. High pressure begin to build back to the West Coast with 850 mb temperatures warming for the Labor Day (Monday). This will bring a warming trend early this week, with Moderate HeatRisk returning across the interior valleys on Monday and continue through mid week. ECMWF Extreme Forecast Index (EFI) highlight highs in the 60th-90th percentile above normal temperatures on Tuesday and Wednesday across the interior. Interior high temperatures in the mid 90`s into 100`s are expected to return across across the warmer locations of Trinity, Lake, interior Mendocino, and northeastern Humboldt. The heat is forecast to peak on Wednesday with locally major heat risk in Trinity, Lake and northeastern Mendocino counties. There is a 40 to 70% chance of high temperatures greater than 105F across the hotter valleys, with the higher chances for Hoopa and Big Bar in Trinity County. In addition, a southerly reversal low will form off the Central California Coast on Monday, before becoming on a negative tilt as it moves northward through the area Tuesday through Thursday, and bring some threat of interior thunderstorms. There is a high uncertainty with the exact timing/location at this point, with a non- zero probability of convection expected Tuesday and Wednesday. See the Fire Weather section below. /ZVS && .AVIATION...(18Z TAFs)...MVFR conditions with light variable winds along the Redwood coast this morning. Overcast ceilings forecast scatter out late this morning (18Z-20Z) as the influence of a shortwave trof deepens the marine layer, increasing daytime mixing. Marine layer expected again tonight (onset: 02Z-04Z) with a 60-70% probability of ceilings below 1kft AGL at the coast and in adjacent river valleys. Visibilities more likely than not to remain favorable. VFR expected inland with terrain driven winds. && .MARINE...By this afternoon, northerly winds are expected to increase to 5-15kt with the strongest winds South of Cape Mendocino. These winds are expected to continue to increase in the southern waters Saturday afternoon with an area of 15 to 20 kt winds, especially downwind of Cape Mendocino. Models are in good agreement that the wind in the northern waters will remain light. On Sunday however, the winds may increase slightly more, especially in the southern waters. Some models suggest they may reach close to 20 kt while others remain around 10 kt. Northerly winds are expected to persist, and potentially even increase next week as well. Marginal small craft advisory conditions are possible Sunday in the far southern outer waters (PZZ475). That said, there is still fairly good model agreement on them remaining below gale force. Waves remain calm, around 2 to 3 feet. This is mostly from a southerly at ~17 seconds. These waves are generally expected to continue through the weekend with the addition of short period wind waves as the winds start to pick up. There is a small threat for some sneaker waves along SW facing beaches, but with the southerly swell expected to be comparatively small and not too long of a period, the threat is not expected to be very significant. && .FIRE WEATHER...Elevated to locally critical fire weather conditions due to low RH and breezy southwesterly winds over the higher terrain in zones 277, 283 & 264 Today and this weekend. Surface observations reported daytime RH values in the single digits to mid teens across Trinity, Lake and interior Mendocino counties this afternoon. Winds will continue to be light and terrain driven. Otherwise, a brief period of increasing wind is expected today and this weekend by late afternoon with westerly to southwesterly breezes. More wind prone areas could sees gusts up to around 25 mph. The onshore marine moisture will bring a slight improvement in the overnight RH recoveries across the interior, but these are expected to remain poor over the higher terrain with values in the 30`s in Trinity, Lake and eastern Mendocino counties. Warming and drying trend is expected early through mid next week as the high pressure build in, with high temperatures across the interior valleys peaking in the 90s and into 100s on Tuesday and Wednesday. The afternoon RH values will likely be in the teens and even in the single digits across Trinity, Lake and eastern Mendocino counties. Humidity recoveries will gradually diminish through the weekend and early next week, with locally very poor recoveries by Tuesday. A southerly reversal low will bring some threat of thunderstorms for Tuesday and Wednesday. There is a high uncertainty with the exact timing/location at this point, with a non- zero probability of convection expected Tuesday and Wednesday. At this point there is a 10% chance for thundertorms over the Trinity Horn for Tuesday and Wednesday afternoon. /ZVS && .EKA WATCHES/WARNINGS/ADVISORIES... CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... None. && $$ NOTE: The full forecast discussion is now regularly issued between 10 am/pm and 1 pm/am. Additional updates will be issued as needed. 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