Area Forecast Discussion
Issued by NWS Eureka, CA
Issued by NWS Eureka, CA
120 FXUS66 KEKA 172024 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 124 PM PDT Thu Jul 17 2025 .SYNOPSIS...Conditions will remain hot and dry inland, while a deepened and a relatively persistent marine layer keeps temperatures cooler along some portions of the immediate coast. && .DISCUSSION...Upper troughing to the north has continued to suppress inland temperatures from hotter values. A coastal shortwave is maintaining a deep marine layer. A moderate to strong inversion combined with transient coastal wind eddies are also contributing to persistent diurnal coastal stratus. Models currently show a better shot of clearing and more coastal sunshine on Saturday, but the inversion still looks to be on the strong side. Conditions are also favorable for overnight light coastal drizzle. There is a very slight chance (less than 5%) for dry thunderstorms in far northeast Trinity County Thursday afternoon. Model soundings show very limited to no elevated instability and available moisture, with a good amount of CIN. The trough will subtly give way to the dominant Four Corners region high Friday and Saturday, allowing for a slight uptick in some of the inland valleys. This will introduce some isolated Moderate HeatRisk. The warming will prove to be very short lived as the trough reestablishes its dominance with a deepening progression down the Pacific Northwest and into Northern CA. Inland temperatures will drop by up to 10 degrees by Monday. The cooling influence of the trough will likely last most of next week before the Four Corners high attempts to expand. Clusters identify the potential for more troughing however. JJW && .AVIATION...(18Z TAFs) Coastal clouds are well entrenched with little clearing expected over the next 24 hours or so as a strong inversion remains in place over the marine layer. LIFR to IFR will likely persist at coastal terminals through Thursday. Winds will remain light at the coast. The wind direction is the main forecast challenge with strong coastal eddies evident on satellite. Northerlies winds are expected to reform on Friday, possibly leading to an improvement in categories as coastal stratus gets mixed out. Farther inland, VFR conditions are likely for interior areas on Thursday with only a 30% chance of clouds reentering the Russian river valley all the way to KUKI tonight into Friday morning. && .MARINE...Light winds and low combined seas are expected today with the thermal trough located off the Northwest California coast. On Friday into this weekend, as high pressure re-builds over the eastern Pacific Ocean, the pressure gradient should tighten over the coastal waters allowing northerlies to strengthen again. Moderate to strong northerlies and steep seas due to wind waves are likely over the weekend with small craft advisories possible, most likely in the outer waters. /RPA && .FIRE WEATHER...Conditions will remain hot and dry into the weekend. A deep marine layer and onshore winds will continue to maintain marine influence farther inland from the coast, with some coastal drizzle. There is a 5% or less chance for dry thunderstorms with gusty outflow winds over far northeast Trinity County mountains Thursday afternoon and evening. Anything that manages to form may remain in Siskiyou County. South to southwest winds are breezy in Lake and Southern Mendocino County Thursday afternoon with a weak shortwave trough along the coast. Minimum RH values will drop to the mid to low 20s Thursday, but overnight recoveries will be very strong, into the upper 60s to 70s. Inland temperatures will trend much cooler, up to 10 degrees, Sunday and into next week with a deepening trough to the north. This feature will increase the pressure gradient, strengthening the westerly winds in response, particularly south in Lake and southern Mendocino County. JJW && .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