509 FXUS66 KEKA 132152 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 252 PM PDT Sun Apr 13 2025 .SYNOPSIS...Warm and calm weather will continue through Monday with cooler and gustier conditions through the rest of the week. There remains little to no chance of wetting rain through the end of the week. && .DISCUSSION... KEY MESSAGES: -Warm, calm, and dry conditions persist through Monday with potential for interior highs over 85 and coastal highs near 70. -Cooler though still Sunny conditions return for the interior midweek with potential for isolated Thunderstorms over high terrain Tuesday and especially Wednesday afternoon. -Cool and gusty onshore winds return for the coast Wednesday and Thursday. WEATHER PATTERN OVERVIEW: Weak and transient upper level ridging has spread over the area today. Compared to the last couple days, high pressure has gradually weakened winds and has allowed interior temperatures to warm into the low 80s. Low pressure forming off the central coast has helped gradually turn gentle wind offshore, greatly drying out conditions. High pressure will continue to build Monday with interior valleys in the mid 80s. Offshore flow has a slight chance (20%) of allowing temperatures as high as 70 along the coast. High pressure will gradually weaken by mid next week as a shallow shortwave dips along shore. The largest impacts of this patterns will be temperatures cooling back into the upper 60s for the interiors with a return of more gusty north wind along shore, though there is little chance (10%) of gusts of similar strength to the past couple of days. Resurgent moisture and onshore flow will likely help rebuild the marine layer Tuesday morning. Additionally, some moisture pulling from the south combined with more unstable air aloft and strong solar heating may help generate diurnal afternoon thunderstorms. The greatest chance (20%) of showers is over the Yolla Bollys and Trinity Alps late Wednesday afternoon. There is some forecast uncertainty by the end of the week as a cutoff low is forecast to travel south along shore, but essentially no model ensemble members show any measurable precipitation along the low. FORECAST CONFIDENCE AND DEVIATIONS: Forecast confidence is high at least through early next week with not real hazardous scenarios of note. As is normal, the greatest forecast variability in the short term is related to the chance of a marine layer forming alongshore tonight into Monday. The greatest chances (30%) will be around Humboldt Bay with any layer most likely to be very shallow. Related to this chance, Monday has the greatest uncertainty in coastal high temperatures. Though most models show highs in the mid 60s, about 20% show the potential for highs reaching 70 if marine air burns off quickly and offshore flow is strong enough. Beyond that, the greatest uncertainty will be for interior thunderstorms Tuesday and Thursday and near shore winds around Wednesday and Thursday. For the Thunderstorms, EFI shows a weak signal for elevated CAPE, mostly around the Yolla Bollys. There is significant uncertainty weather or not moisture will be sufficient to form storms, SREF currently shows 30% chance of isolated storms though NBM is much lower around 10%. The overall ensemble moisture spread remains high, but the potential is certainly there as soon as Tuesday afternoon with the greatest chances Wednesday afternoon over high terrain. For near shore wind, there is a consistent signal of gustier north wind returning near shore, but their strength remains very variable with about 40% of ensemble members showing gusts below 15 mph but a group of about 30% showing gusts near 30 mph. The overall distribution is roughly bimodal for wind. Otherwise although the exact detail of temperature and wind have high uncertainty by late in the week, essentially no models indicate wetting precipitation. /JHW && .AVIATION...Conditions at all the terminals are VFR this afternoon. Offshore winds have cleared skies across Northwestern California. Models are showing a shallow marine layer developing tonight, which does bring the potential for IFR/LIFR fog/stratus impacts to the coastal terminals. NBM is showing around a 40% and a 70% chance for IFR ceilings at ACV and CEC, respectively, early Monday morning. Weak offshore flow aloft is also forecast tonight, which could keep all stratus impacts offshore. Regardless, any stratus that does develop will likely lift and scatter out by the late morning. UKI is forecast to remain VFR for the next 24 hours. JB && .MARINE...Winds and seas have gradually eased today and will continue to ease into Monday. Strong northerly breezes and steep seas are still forecast in the outer waters into tonight, with lighter winds expected nearshore. Seas are still steep nearshore early this afternoon north of Cape Mendocino, hovering around 6-7 ft at 6 seconds. Seas are forecast to ease by the late afternoon and evening. Nearshore winds and seas are forecast to be mild for much of Monday. Northerly winds increase again Monday evening into Tuesday, with strong breezes to gale force gusts possible in the outer waters, especially north of Cape Mendocino. Seas will respond with 13-15 ft significant wave heights in the outer waters. Lighter winds are forecast nearshore, but conditions could still be hazardous to small crafts with steep seas of 7-10 ft and gusts of 20-25 kts by Wednesday. JB && .EKA WATCHES/WARNINGS/ADVISORIES... CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 9 PM PDT this evening for PZZ450. Small Craft Advisory until 3 PM PDT this afternoon for PZZ455. Small Craft Advisory until 9 AM PDT Tuesday for PZZ470-475. Gale Watch from Tuesday morning through late Tuesday night 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