


Area Forecast Discussion
Issued by NWS Eureka, CA
Issued by NWS Eureka, CA
104 FXUS66 KEKA 161207 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 507 AM PDT Wed Apr 16 2025 .SYNOPSIS...A weak weather system will bring near normal temperatures, coastal clouds and a slight chance for afternoon mountain thunderstorms. Clearing skies and slightly warmer temperatures are expected Thursday and Friday. Continued seasonal temperatures and dry weather are expected into next week. && .DISCUSSION...The upper level low off the central CA coast is continuing to bring moisture and mid level clouds to much of northern CA. An upper level trough is approaching from the north and this will help to push the upper level out of the area and usher in some cooler and drier air. Before this dry air moves in there is a small window for a few thunderstorms over the interior mountains again this afternoon. Lapse rates aloft are still steep, between 7.5 and 8 c/km and the models are showing some instability. At the coast this afternoon northerly winds are expected to start picking up again. This, combined with the dry air aloft is expected to help clear out much of the coastal stratus north of Cape Mendocino. However farther south is expected to remain cloudy. Wednesday night into Thursday morning easterly winds are expected to develop aloft and this is expected to start clearing out the coastal clouds with most areas clear by the afternoon. Offshore flow is expected to return again Friday morning with east winds of 15 to 25 kt at 925mb and 850mb. This is expected to bring mostly clear skies to the area. This will also allow temperatures to drop and will likely be the coolest morning of the week in the calm valleys. Some frost is possible in the coldest valleys of Trinity county. Friday night into Saturday the offshore flow decreases and this may allow some fog or stratus to form again in the coastal areas. A weak front is expected to move across the area on Saturday bringing cooler temperatures to mainly Humboldt and Del Norte counties. All of the ensemble clusters are showing the rain remaining north of the area. Sunday and into early next week the flow remains northwest or westerly with occasional weather systems moving through the flow and bringing an increase in clouds and slightly cooler temperatures. There is good agreement that the weather will be dry through the period. Temperatures are expected to be near to slightly above normal with upper 50s at the coast to upper 60s in the warmer interior valleys. MKK && .AVIATION...IFR ceilings prevail at the coastal terminals early this morning, with a deeper marine layer along the coast. The McKinleyville profiler indicates a marine layer depth up to around 2,500 feet MSL. Patchy drizzle has been occurring along the North Coast as result of this uniform saturated layer. Otherwise, stratus are expected to gradually lift and scatter out during the morning and early afternoon as an approaching cold front destabilize the marine layer. After 16Z, VFR conditions with clearing skies are expected at CEC as northerly winds increase nearshore. Winds will become N at 5-10 kt at 16Z, increasing after 18Z to around 15-25kt with gusts from 25-35kts...with the strongest winds from 16/21Z- 17/03Z. Northerlies ease after 17/03Z, but will remain breezy into Thursday. For ACV, conditions are expected to improve to VFR after 19Z as low clouds scatter out. HREF model indicate MVFR to IFR conditions redeveloping in the vicinity of Humboldt Bay after 17/02Z, with a 70% chance of ceilings below of 2kft at ACV at 17/05Z. Winds will remain very light and variable through 18Z, becoming WNW from 5-15 kts after 20Z with occasional gusts. Meanwhile, MVFR ceilings and calm winds will persist at UKI through late morning. After 18Z, low clouds are expected to lift and scatter out to aid in VFR conditions. Winds will peak from SE around 5-10 kts with occasional gusts after 19Z, becoming variable after 2Z. HREF indicates the marine layer deepening along the Mendocino Coast after 00Z, with a probability of ceilings lower than 2kft at UKI about 20-40% around 17/02Z increasing to 70% after 17/05Z. && .MARINE...Gale force northerlies and very steep northerly waves are forecast to increase through early evening over the northern outer waters after the passage of a relatively dry cold front. Chance for gale force northerlies (35-40kt) is forecast to expand into portions of the northern inner waters this afternoon and evening, primarily near and downwind of Pt St George. A few gusts to 50 kt are possible (20% chance) as a thermal trough takes shape nearshore. Very steep northerly waves are forecast to build over the northern outer waters tonight, and peak around 15 kt this afternoon and evening. These steep waves will spread into the southern waters outer waters and northern inners this afternoon and evening, and probably persist into the overnight hours. Hazardous Sea Warning remain in effect for the northern inner waters and southern outer water. Very steep waves will likely persist on Thu before winds and seas trend downward by Friday. Northerlies and very steep waves will most likely ramp up again over the weekend after passage of another dry cold front. DB && .EKA WATCHES/WARNINGS/ADVISORIES... CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 4 PM PDT this afternoon for PZZ450. Hazardous Seas Warning from 4 PM this afternoon to 3 AM PDT Thursday for PZZ450. Gale Warning until 3 AM PDT Thursday for PZZ470. Small Craft Advisory until 3 PM PDT this afternoon for PZZ475. Hazardous Seas Warning from 3 PM this afternoon to 3 AM PDT Thursday for PZZ475. && $$ 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