Halloween will generally be chilly and rainy. Spotty rain showers are likely across the area, with the highest chances found in Del Norte, Humboldt, and Trinity Counties. Interior Mendocino and Lake Counties have a better shot at staying dry, with rain probabilities around 30%.

Clear and cool conditions will become increasingly cloudy this evening and overnight ahead of an approaching warm front. Gusty southerly winds will accompany periods of moderate rainfall Wednesday as a front moves through the region. Cloud cover will continue to increase and descend overnight as a strong surface low in the Gulf of Alaska propagates a fast-moving frontal boundary toward the coast. The leading edge of precipitation is expected to begin around sunrise before becoming moderate to heavy by late morning. Deterministic weather models are showing higher 24 hour precipitation values for regions north of Cape Mendocino. The heaviest precipitation will fall from 11 am through 6 pm - High Resolution models are indicating some areas of 0.5 inch/3 hour totals in the coastal ranges (particularly wind facing slopes of the King Range and higher elevations of Del Norte). Rainfall will be lighter but still impactful further south, with 0.25 to 0.5 inches expected in southern Mendocino County and 0.15 to 0.25 inches in Lake County. The cold upper low will continue to cycle above the strong associated surface low, providing continued forcing for precipitation to continue Thursday and Friday. Precipitation accumulation updates will follow as weather models resolve this system.

A wind advisory is in effect from 7AM to 5PM Friday for Del Norte and Humboldt counties. South-southeast winds from 20 to 30 mph with gusts of 40 to 50 mph are forecast along windward ridges and exposed coastal headlands. Tree branches may be blown down and may result in a few power outages. Strong wind gusts could make driving difficult.

A strong warm frontal boundary will move through the waters today, producing strong southerly winds and periods of gale gusts through the afternoon. A large NW swell will fill into the waters Thursday, peaking late Thursday into Friday at 15 - 17 feet at 13 - 14 seconds. Winds expected to shift northerly as seas diminish through the weekend.