959 FXUS66 KEKA 092044 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 144 PM PDT Mon Jun 9 2025 .SYNOPSIS...Isolated thunderstorm threat for Trinity, Del Norte, and NE Mendocino County continues this afternoon into the evening. Warm temperatures continue today, however, a cooling trend will keep temperatures cooling steadily through the week. && .KEY MESSAGES... * Isolated afternoon and early thunderstorms in the interior, primarily Trinity County, today and Tuesday. Cloud-to-ground lightning strikes and gusty erratic flow winds possible. * Interior heat risk diminishing and becoming low on Wednesday. High temperatures generally decreasing each day this week along with cooler overnight low temperatures late this week. * Gustier afternoon and evening westerly and northwesterly breezes expected in the interior mid to late week. * Gustier northerlies for coastal areas mid to late week. && .DISCUSSION... A ridge the the south and an anomalously high ridge to the north are sandwiching (for lack of better terms) NW California allowing for a change in our daily weather. First and foremost, there is CAPE aloft allowing for daytime heating to pop into thunderstorms over the interior mountains. The GFS is showing "Most Unstable CAPE" values in the 100-150J/kg range over Humboldt Co. tonight and over Del Norte, Trinity, and Northeastern Mendocino County tomorrow. Wetting rain, lighting, and small (pea- sized) hail is possible with these storms. The lifting mechanism remains uncertain for these storms. Yet, the GFS is showing a moderate amount of vorticity in the 850mb level, which could possibly help these thunderstorms start their life. Monday has a slightly increased chance in Trinity county for thunder with NBM probabilities 20 to 35%, especially in the Trinity Horn. Mid-level moisture availability and consistently warm temperatures contribute to potential instability. Potential for gusty winds and dry lightning could be a fire weather concern for these areas. Chances for storms decreases on Tuesday with less available mid level moisture - convective development looks to stay much further east of CWA in southern OR and NE CA, potentially reaching the Trinity Horn. Brief ridging on Tue may be followed by a deeper trough Wed and Thu next week. This trough looks quite dry and main impacts appear to be a return of stronger gusty winds and cooler temperatures. Inland valleys will struggle to break 90F on Wednesday through the week. This comes a relief after what has been a warm couple of weeks to start meteorological summer. These cooler temperatures will also be accompanied by stronger winds with gusts around 15-20mph in the later portion of the week. && .AVIATION...07/18Z TAFs...A slightly deeper marine keep blanketed the West Coast this afternoon, with IFR/LIFR ceilings between FL003- FL005 impacting KACV and KCEC. The McKinleyville and Bodega Bay profilers indicates the marine layer is about 2000 feet MSL. Visible satellite imagery depicts multi size scale cyclonic eddies along the coast keeping the shoreline with low clouds moving in and out, helping with an improve of visibility at the coastal terminals. A brief window of improve conditions is possible. Otherwise, expect mainly LIFR conditions with visibility in mist/fog redeveloping late this afternoon and evening. VFR conditions is expected to prevail at UKI. Surface winds will remain generally out of the west at 5-10 kt. && .MARINE...Gentle to moderate northerly breezes across the coastal waters. Northerly winds will continue to slowly increase with moderate to fresh breezes tonight and Tuesday, before strong breezes develops south of Cape Mendocino on Wednesday. This will increase the steep wind driven waves, but generally around 4 to 5 feet...5 to 7 feet in Z470. In addition, a long period southwest swell of 3 feet at 17 seconds will build tonight and Tuesday. This could present a small sneaker wave threat on south facing beaches if it ends up coming in this big. Mid to late week, winds are expected to steadily increase with some near gale to gale force gusts possible by Friday. There is a 30-50% chance of gale force gusts downwind Pt St George and Cape Mendocino. && .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