173 FXUS66 KEKA 162155 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 255 PM PDT Wed Apr 16 2025 .SYNOPSIS...Coastal clouds, seasonal temperatures and mostly dry weather expected into early next week. && .DISCUSSION...An upper level low off the central CA coast is continuing to bring mid level moisture in wrap around flow to the eastern and southern portions of the forecast area today. An upper level trough is approaching from the north and this will push the cut- off low out of the area tonight, ushering in drier northerly air. Before this dry air moves in there is a small window for isolated and very weak thunderstorms over the interior mountains this afternoon, particularly in SE Trinity, NE Mendocino and NRN Lake counties. Main hazard from this high based convection will be isolated cloud-to-ground strikes and perhaps gusty outflow winds. Low cloud cover has cleared out along the Del Norte County today in response to much stronger northerlies and drier air mixing down to the surface. Northerly winds have been gusting to 37 mph at Crescent City ASOS and should hit 40-45 mph by 6pm per HREF (an 80% chance). The strong winds were very localized with winds at Crescent harbor gusting only to 25 mph. Stratus has persisted longer into the afternoon hours over the Humboldt Bay area and Eel delta, but has been slowly eroding and should clear out by late afternoon. BUFKIT boundary layer humidity profiles are favorable for stratus redevelopment this evening and overnight around Humboldt Bay area and Eel delta. In fact, visible satellite imagery already showed new slivers of stratus forming offshore this afternoon. Meanwhile, a small scale eddy in the lee of Cape Mendocino will most likely keep stratus locked-in tonight into Thur along the Mendo coast. Deep marine layer conditions and low cloud cover will probably push into the southern interior of Mendocino County again (Ukiah area) tonight. Chance for longer lasting clearing is expected to increase Thu and Fri as northerly and northeast flow continues over the area. There is considerable uncertainty with amount of clearing along the Mendocino coast and stratus intrusion via the Russian river valley in southern Mendocino county. Models have not been resolving small scale circulations very well. With the passage of an upper trough tonight and ridge building aloft, extensive cloud cover should diminish on Thu. A weak front is expected to move across the area on Saturday and may generate another deep push of low clouds and perhaps a few spats of North Coast drizzle. Otherwise, seasonal temperatures and low chances for measurable precip are expected. There is considerable variability in possible outcomes with a series of transient shortwave troughs early to mid next week. These troughs could create a favorable environment for interior showers sparking up with daytime heating or may even generate some rain. Greater uncertainty arises mid to late week with potential for an even colder and wetter scenario. So far there isn`t a clear signal from the NBM on this yet. DB && .AVIATION...A deep marine layer finally scattered out most of the north coast this afternoon as northerly winds increase, while ACV is still holding on to a patch of overcast MVFR ceilings. Gusts exceeding 30 knots are likely at CEC through late afternoon, while ACV will be more shielded with 10 to 15 knot gusts - brief MVFR scattering is likely before 00Z as well. The marine layer will remain destabilized by a dry cold front descending into NorCal this evening, but will likely rebound after 03Z for ACV and UKI as northerly winds diminish. HREF has a 50 to 60% probability for ceilings <1000ft persisting through late Thursday morning. Offshore breezes will likely keep most coastal stratus at bay for CEC. && .MARINE...Gale force northerly winds and steep wind waves continue in the outer and northern waters this afternoon. Gusts exceeding 35 to 40 knots are expected through this evening, including near Point St. George, before winds begin to diminish overnight. Conditions in the inner waters will quickly fall below advisory levels while seas in the outer waters will remain steep and hazardous through Thursday afternoon. Fresh to strong breezes will likely persist in the northern outer waters through Friday before widespread strong northerlies return this weekend. NBM has 50 to 75% chance for gale gusts approaching 40 knots developing by Saturday evening in the outer waters, although uncertainty increases early next week for longevity of these gales, especially in the southern waters. && .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 until 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