736 FXUS66 KEKA 090703 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 1203 AM 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. && .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...(06Z TAFs)A shallow marine layer remains in place this morning, but is mainly limited to the immediate coast and very near coastal valleys. This is expected to keep it out of KUKI tonight. KACV and KCEC are expected to remain LIFR overnight. It is uncertain if they stay down around 1/4 mile vis or not. This marine layer is expected to push back to the immediate by mid to late morning, but much like today is expected to move back in quickly. Thunderstorms occurred over the inland areas Sunday evening. These could return early this morning and move out towards the coast. This is highly uncertain and will need to be monitored. MKK && .MARINE...Northerly winds are expected to start to slowly increase this morning to around 10 to 15 kt by late this afternoon. This will increase the steep wind driven waves, but only to around 3 to 4 feet. In addition to these waves there is a northwest swell building to around 3 to 4 feet at 10 seconds. Tuesday winds are expected to pick up to around 15 to 20 by the late afternoon, with the stronger winds mainly beyond 10 nm. These are expected to persist on Wednesday. In addition Monday night and Tuesday there is expected to be a small southwest swell of 3 feet at 17 seconds. This could present a small sneaker wave threat on south facing beaches if it ends up coming in this big. Late in the week winds are expected to be continue to increases, but gales are not expected, aside from a few localized gusts, through the work week. Over the weekend some of the models are showing some larger areas of gale force gusts, but this isn`t particularly consistent among other models. MKK && .FIRE WEATHER...Isolate thunderstorm threat continues for Trinity, Del Norte, and Northern Mendocino counties tomorrow. While soundings look dry in the lower levels, there is still a chance for pop-up thunderstorms to form with middle level moisture. These thunderstorms could send some lighting strikes out before collapsing. Relative Humidity recoveries expected between 65% for the bottom of inland valleys, with a forecasted mid-slope thermal belt forming between ~3000-5000ft keeping RH recoveries around 45% within those elevations. Down-valley winds expected overnight with High Resolution models showing speeds of 10-15mph with gusts up to 20mph possible at times. && .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