Area Forecast Discussion
Issued by NWS Eureka, CA
Issued by NWS Eureka, CA
563 FXUS66 KEKA 271206 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 506 AM PDT Thu Jun 27 2024 .SYNOPSIS... An upper level disturbance will produce marine stratus, patchy coastal drizzle, and relatively cooler temperatures today. Lower daytime RHs and slightly elevated windsexpected in interior Trinity, Mendocino and Lake County. Warming and drying trend returns Friday, potentially becoming more intense next week. && .DISCUSSION...Elevated wind gusts are still being observed across eastern portions of Trinity and Lake counties this morning in the wake of a weak frontal boundary. Prominent NW flow will drive diurnally driven winds today as high pressure builds in from the Pacific, enhancing the thermal trough and coastal pressure gradient. With a surge of moisture into the coast contributing to the still 3000 foot marine layer overnight, disorganized offshore stratus is expected to linger this morning before scouring out this afternoon with increasing marine winds and diurnal heating. Patchy coastal drizzle is also possible this morning, especially around Humboldt Bay. The remaining influence of a broad upper shortwave system will continue to contribute to cooler temperatures today. Highs are only expected reach the mid 70`s to low 80`s across the interior while coastal highs continue to be slightly dampened by marine stratus. NBM anticipating some valleys in southern Mendocino, Lake and eastern Trinity counties to rise into the upper 80`s, although probabilities significantly fall off at 90 degrees. Minor upper instability and moist onshore flow may allow for more drizzle within coastal stratus Friday morning. Broad, weak ridging is expected build into the region Friday, driving interior temperatures back into the 90s. NBM exhibits high probabilities of interior valleys >90 degrees on Friday, aligning with short range deterministic models. With increasing temperatures, min daytime RH values can be expected to drop into the mid teens and low 20`s in Lake and interior Mendocino and Trinity counties. Moist NW flow will sustain marine influence for coastal counties through this weekend. Additional upper shortwaves will provide similar disturbances this weekend before potential for substantially warmer and drier conditions early next week. Long-range models indicate anomalous warm ridging building into the eastern Pacific, coupled with potential for min RHs in the teens and single digits by mid- week. Stay tuned for updates on potentially elevated fire weather conditions. && .AVIATION...Coastal stratus has redeveloped along the Redwood Coast overnight, and expanded well up the adjacent river valleys. Although, profilers data indicate the marine layer is quite shallower than previous night. Mainly MVFR ceilings with OVC layer between FL010-FL015 at ACV and CEC early this morning...with brief periods of IFR ceilings at CEC. Otherwise, a dry air mass moving into our area along with increasing northerly are expected by late morning and afternoon as a weak ridging builds in. While VFR conditions prevail at UKI, stratus are expected to lift and mix out with the increasing northerlies during the morning hours. After 17Z, VFR conditions are expected for all aerodromes. Winds from NNW at 5kt this morning, increasing to around 10-20 kt with occasional strongest gusts after 20Z. Short-term model guidance suggests stratus redeveloping again around Humboldt Bay and vicinity later this evening. && .MARINE...Fresh breezes will continue increasing in coverage south Cape Mendocino this morning. Northerlies strengthen and spread from south to north across the coastal waters this afternoon into Friday, with the strongest winds across the southern outer waters and leeward Cape Mendocino. Wind driven seas will generate steep short period NW seas around 6 to 9 feet across the southern waters today. Winds are forecast to ramp up on Friday with near gale to locally gale force gusts across the outer waters and in the fan of Cape Mendocino on Friday. Short period seas will pick up to around 8 to 10 feet at 8 to 9 seconds Friday afternoon as result. Winds slightly diminish from north to south throughout the weekend as another upper level trough moves over the area. However, elevated northerly winds and steep seas will persist over the southern waters. && .EKA WATCHES/WARNINGS/ADVISORIES... CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 9 PM PDT Saturday for PZZ455-475. Small Craft Advisory from 11 PM this evening to 3 PM PDT Saturday for PZZ470. && $$ 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