FXUS66 KEKA 031249 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 449 AM PST Mon Feb 3 2025 .SYNOPSIS...Rain continues with the possibility of low elevation snow and mixed precipitation as a colder air mass looms. Minor flood stage for the Eel river at Fernbridge is possible tonight through Tuesday. && .DISCUSSION...Warm moist air that is being siphoned to the southern zones of the CWA via IVT transport, will be displaced by a cold airmass with less moisture. The Atmospheric River continues to bring rain and high elevation snow but this will be interrupted as the cold core Low pressure system continues southbound from the BC/Washington offshore track. Low temperature anomalies are being signaled by EFI guidance for Tuesday night, compared to seasonal climatological norms. This will bring low elevation snow and possibly mixed precip to the coastal areas by mid morning Tuesday. That said, a second round of rain is due today through midweek which adds to the complexity as tropical moisture will dominate the shallow cold air at the surface. This will help drop snow levels quickly by tonight into Tuesday. Snow levels will drop first and most consistently on the western side of the Coastal mountains. By mid morning Tuesday, about 60% of the ensemble members show freezing levels as low as 1500 feet with 90% as low as 2500 ft at along the coast. Similar freezing levels will filter inland and further south as far as northern Lake County through Tuesday into Wednesday. Without as much terrain enhancement and little to no instability to speak of, precipitation efficiency will likely be poor. That said, even a small amount of moisture could create substantial snow. Best estimate currently show heavy snow impacts on highways 299, 199, and 3 during the day Tuesday. Accumulation 3 to 9 is most likely at Collier Tunnel, 12 to 24 inches at Scott Mountain, and 1 to 3 inches at Berry Summit all by early Tuesday. A second, more consistent pulse of snow showers is expected Tuesday into early Wednesday, bringing more snow to highways passes and pushing a bit further south. This time period will see more light snow along the northern passes down to 2000 feet and about 2 to 4 inches along the highway 36 corridor. Wednesday also has the greatest risk of small hail along the Humboldt and Del Norte coast with surface temperatures in the 30s and models showing a sliver of instability (50 to 100 J of CAPE). The risk of snow and rain will continue through the week with the current most likely forecast showing moderate snow down to 2000 feet early Thursday. /JHW /EYS && .AVIATION...VFR/MVFR conditions are present this morning at forecasted terminals due to elevated ceilings and minimally degraded visibilities. LAMP Probabilities currently show a high chance (>70%) of ceilings dropping below 3kft AGL by midday today for coastal terminals. Winds are forecasted to remain light and slightly from the west allowing marine moisture to infiltrate terminal spaces today. Tomorrow evening however, Hi-Res Model Guidance shows easterly offshore flow, clearing our terminal spaces bringing VFR conditions with a chance of a few lingering low clouds. Inland at KUKI, model guidance is suggesting ceilings will remain in MVFR (3000-1000ft AGL) and visibilities between 3-6SM. Rain will continue possibly leading to more intense degraded conditions. DS && .MARINE...Winds out at sea are forecasted to remain moderate as a stationary front just south of Cape Mendocino inches its way farther south. These northerly winds will create steep wind waves in the northern and southern outer waters as well as the southern inner waters today and tomorrow. A small craft advisory has been issued due to a mixed sea state with steep wind waves interacting with multiple swells from the NW and SW. Conditions this work week are expected to remain rainy with multiple wind shifts and a confused sea state. Winds are expected to shift southerly on Wednesday then back to northerly by Friday morning, building into the coming weekend according to GFS and ECMWF models. DS && .HYDROLOGY...We are currently monitoring the Eel River at Fernbridge. The river is currently (0347 PST) at 11.10ft and climbing. CNRFC forecasts show a 43% probability of reaching Minor Flood Stage of 20.0ft and a ~30% probability of reaching Moderate Flood State of 22.0ft on Tuesday @0800 PST. Due to these probabilities and the continuing rainfall moving south into the Eel River Basin, a Flood Watch has been issued for the Eel River Delta from 2100 PST 2/3 until 1600 2/4. DS && .EKA WATCHES/WARNINGS/ADVISORIES... CA... Winter Storm Warning until 4 AM PST Wednesday for CAZ102- 107. Flood Watch from this evening through Tuesday afternoon for CAZ103. Winter Weather Advisory until 4 AM PST Wednesday for CAZ105. Winter Weather Advisory from 4 AM Tuesday to 3 AM PST Wednesday for CAZ106-108. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from 3 PM this afternoon to 9 AM PST Tuesday for PZZ455-470. Small Craft Advisory until 9 PM PST Tuesday 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