Marine Weather and Tide Forecast for Ukiah, CA

DISCUSSION
Water vapor satellite imagery shows a potent upper-level trough positioning over the Pacific Northwest with its core low anchored in the Gulf of Alaska. The accompanying cold front is moving ashore early this morning, deepening the marine layer and introducing mid- to-high-level cloudiness.
Periods of light rain and drizzle will expand across the northern tiers today. Model guidance shows a 60% probability of wetting rain (0.10 inches or greater) for Eureka proper, with a near 100% probability across Del Norte County and a 50 to 90% probability for northern Humboldt County. Areas south of Cape Mendocino and east into the southern interior will remain largely dry, seeing only isolated sprinkles or light drizzle.
The primary impact for southern and eastern zones will be the thermal and wind response. Temperatures will drop significantly today, with afternoon highs running 10 to 20 degrees cooler than earlier in the week, limiting interior valleys to the 70s. As the cold front passes this evening, a tightening pressure gradient will unleash breezy west-to-northwest winds across the interior. The strongest winds are expected along the ridges of Lake, eastern Mendocino, and Trinity counties, where gusts could hit 35 to 40 mph.
The core of the upper-level low will remain north and east of our area. However, the coldest temperatures aloft will be centered around 06Z Sunday as the trough axis passes through. This will destabilize the mid-levels sufficiently to maintain a 10% chance of thunderstorms over northeastern Trinity County and interior Del Norte County Saturday afternoon. Any cells that form will be steered rapidly eastward by the ambient flow. Clearing skies Saturday night will couple with the cold air mass to support localized frost in the colder basins of Trinity and eastern Humboldt counties. High pressure returns Sunday, starting a steady warming trend back into the 80s by early next week.



AVIATION
The marine layer continues to deepen ahead of the cold front.
Coastal terminals (KACV/KCEC) may toggle between MVFR and IFR ceilings overnight with patchy fog and developing light rain. There is a low-confidence potential for brief LIFR ceilings at KCEC Friday morning. By mid-to-late morning on Friday, incoming rain and drizzle will lock in persistent MVFR conditions, with ceilings occasionally dropping below 1,000 feet as the main front moves inland.
For the interior (KUKI), VFR conditions prevail through the early morning hours with some high clouds. Winds will back to the west- northwest by Friday afternoon and become gusty, reaching 20 knots at times. Stratus will make a push inland along the river valleys Friday night, bringing lower ceilings to interior terrain, though KUKI is expected to remain largely clear of low terminal stratus.



MARINE
Northerly winds and steep wind-driven waves will continue to diminish early this morning as a cold front approaches the waters. In the pre-frontal environment Friday morning, winds will briefly shift out of the south to southwest at 5 to 10 knots, primarily across the northern waters, accompanied by light rain.
Following the cold front passage, strong north winds will return quickly on Saturday afternoon, rising to 15 to 20 knots. Building seas will follow this wind surge. As high pressure builds rapidly behind the exiting trough on Sunday, a sharp pressure gradient will form along the coast. North winds will surge to 20 to 25 knots across all waters by Sunday afternoon, with near-gale to gale-force gusts up to 35 knots expected south of Cape Mendocino. This will build hazardous, steep, wind-driven waves peaking near 10 to 12 feet by Monday and Tuesday. Winds are expected to begin moderating by mid- week.



FIRE WEATHER
A major pattern shift takes place today as a strong cold front pushes through the region. While this system brings critical wind speeds to parts of the interior, the fire weather threat is significantly mitigated by a substantial influx of moisture and high relative humidity values.
Wetting rain is a certainty across coastal Del Norte County (90 to 100% chance) and remains highly probable across northern Humboldt County (50 to 90% chance), including a 60% chance for Eureka proper.
Drier interior zones to the south and east will miss out on meaningful wetting rain, but will still experience a dramatic 10-to- 20-degree drop in temperature.
The main operational focus centers on Friday evening and Saturday across the mountains of Lake, eastern Mendocino, and Trinity counties (including the Yolla Bollys). Strong westerly winds developing behind the front will sustain speeds of 10 to 20 mph, with ridge-top gusts frequently exceeding 30 to 40 mph. Fortunately, minimum relative humidity values on Saturday afternoon will remain high, primarily between 40 and 60% across the interior, and up to 80% along the coast. Exceptional humidity recoveries of 80 to 100% are forecast for Saturday morning, keeping fuel flammability low despite the high winds. Localized destabilization will support a 10% chance of thunderstorms across northern Trinity County and interior Del Norte County on Saturday afternoon, though lightning coverage will be isolated. Warmer and drier conditions return Sunday as high pressure builds.



EKA WATCHES/WARNINGS/ADVISORIES
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
Small Craft Advisory until 3 AM PDT early this morning for PZZ455-475.