370 FXUS66 KEKA 250731 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 1231 AM PDT Fri Jul 25 2025 .SYNOPSIS...Thunderstorms are possible in the interior Friday. Near normal to slightly below normal temperatures expected this week. Temperatures trend slightly upward early next week. && .DISCUSSION...Early Friday, there are hints of showers from the Sierras moving into Lake or eastern Mendocino counties in the early morning. These are likely not going to be thunderstorms, but a stray shower is possible. In general, the upper-low inches more northeasterly, bringing a similar setup to yesterday for Friday, but moves slightly south and east. Confidence has increased on thunderstorms forming across Trinity County, eastern Mendocino, and northern Lake Counties. CAPE may be even higher Friday (nearing 1000 J/kg) with DCAPE remaining near 1000 J/kg. Higher shear in the Yolla Bollys may allow for some longer-lasting storms, but elsewhere shear remain weak. Storms will likely form and collapse quickly, bringing gusty outflow winds possibly in excess of 50 mph. PWATs of an inch could support periods of heavy rain. The low moves to the east Saturday, bringing most mid-level moisture with it. Thunderstorm chances significantly decline, and if any form, the Trinity Horn is the most likely area. Sunday and into the middle of next week high pressure is expected to generally remain east of the area. This will keep temperatures near seasonal normals with highs in the upper 80s to low 90s. Thunder potential generally looks to remain low. Ensembles are hinting at another upper-low forming right off the coast, which may return thunderstorm chances mid next week, and this will need to be watched. JB && .AVIATION...(00Z TAFs) Fog entering the river valleys shows a 40-50% probability of reaching KUKI up the Russian River early Friday morning leading to potential IFR conditions. This will depend largely on how quickly light the north wind will decrease, and perhaps become variable or even turn to the south. Stratus is expected to be stubborn along the coast for Friday, and any clearing will be short- lived. Visibility will be a difficult call for the coast, but LIFR conditions should be primarily as a result from low ceilings more than low visibility. DS/MH && .MARINE...An upper level cutoff low will lurk off the Central California Coast and will remain in the vicinity through Friday and develop into an open trough for the weekend. This will continue to weaken the surface pressure gradient, holding winds to gentle to moderate levels. Seas 2 to 5 feet are expected, with the lightest conditions expected nearest the coast. Winds will be broadly northerly with south/southwest winds likely directly adjacent to the coast, especially overnight. The northerlies will begin to slightly increase Friday, mainly through the southern outer zone, and likely remaining mainly below 20 kts through the weekend, except for a small area south of Cape Mendocino where wind gusts will increase to 20 to 25 KTS from the north/northwest. DS/MH && .FIRE WEATHER...Friday, isolated to scattered thunderstorms shift south and east with the highest confidence in Trinity, eastern Mendocino, and northern Lake. Isolated storms are possible in eastern Humboldt, as well. Again gusty, erratic outflow winds of 50 mph are possible and a brief heavy downpour is not out of the question. A Red Flag Warning has been issued for abundant lightning in Trinity, eastern Mendocino, and northern Lake Counties. Thunderstorm chances decrease this weekend. Outside of thunderstorms, winds are generally expected to be fairly light and terrain driven. Interior Temperatures are generally expected to be around or slightly below seasonal normals with highs in the 80s to low 90s. Dry afternoon RHs in the 20s are possible in the eastern portions of the area, but good overnight recoveries are likely. JB && .EKA WATCHES/WARNINGS/ADVISORIES... CA... Red Flag Warning from 11 AM to 11 PM PDT Friday for CAZ212- 277-283. 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