textproduct: Eureka

SYNOPSIS

Periodic coastal drizzle continues for areas of the North Coast through mid week. A generally dry and warm weather pattern is expected to prevail across NW CA mid to late week, with record warmth likely for the interior.

DISCUSSION

Satellite imagery shows areas of stratus and fog in many of the interior valleys late this morning. Low cloud cover will gradually lift and scatter out today, giving way to a fairly pleasant December afternoon. The main exception will be at the northern Humboldt and Del Norte coasts, where stratus and drizzle is likely to return this afternoon and evening. Precipitation amounts are minimal with up to a few hundredths of an inch of drizzle possible in Del Norte.

The persistent ridge of high pressure responsible for blocking Pacific storm systems will strengthen and nose eastward through the week. Significant warming for the interior will occur as a result. The current forecast yields interior high temperatures reaching 10-20F above climatological norms midweek through the weekend. NBM shows a high probability (70% or higher) for the warmer interior valleys, including Ukiah and much of Lake County, to exceed 70 F Thursday and Friday. NBM probabilities for exceeding 75F around Ukiah is around 50% for Thursday and Friday. This would break the high temperature record of 72F from 1958 for Ukiah on Friday if the forecast holds.

Ensembles and clusters are hinting at the weakening of the stubborn ridge through the weekend. Precipitation chances start to increase through the latter portion of the weekend. However, any meaningful breakdown of the ridge or zonal flow may not occur until early next week.

AVIATION...(18Z TAFs)

Fog and stratus have started to lift and scatter across the area, ushering in MVFR to VFR conditions for the terminals. An approaching front to the north will bring a chance for drizzle or light rain, and likely gradually bring ceilings down to MVFR or IFR for the coastal terminals. The weak marine inversion could lead to scattering near sunrise at ACV, but shallow ground fog is still a possibility. LIFR fog and stratus may return for the interior valleys, including UKI, again tonight. Any stratus and fog is likely to lift and scatter by mid-morning Wednesday. JB

MARINE

Northerly winds are forecast to ramp up south of Cape Mendocino this afternoon and evening and persist through at least Friday. Wind gusts peak around 20-30 kts in the lee of Cape Mendocino, with breezy winds reaching nearshore areas at times. Steep wind waves of 5-7 ft are possible with these winds. North of Cape Mendocino, winds remain light and southerly through at least Thursday. North winds return late Thursday into Friday and could be breezy in the outer waters. The sea state remains dominated by mid-period northwest swells, with additional swells filling in tonight into Wednesday and again Thursday. These will keep the sea state elevated and combined seas could exceed 10 ft at times, especially south of the Cape where the swell will combine with the steep wind waves. Winds ease this weekend as high pressure weakens. JB

BEACH HAZARDS

An increased threat of sneaker waves is expected for the Del Norte, Humboldt, and Mendocino coastlines this Thursday. A mid-period westerly swell generated by a storm currently located near 45N,160W will enter the coastal waters early Thursday morning. A lack of local wind waves will allow this swell to dominate the sea state over an existing swell, creating beach conditions that could look deceivingly calm. Forecast confidence will grow as the swell passes NOAA/NDBC buoys Wednesday morning. Remember to never turn your back to the ocean, and to avoid steep beaches, jetties, outcroppings, and rocks during these events. DS

EKA WATCHES/WARNINGS/ADVISORIES

CA... Beach Hazards Statement from Thursday morning through Thursday evening for CAZ101-103-104-109.

NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from 3 PM Wednesday to 10 AM PST Thursday for PZZ455.

Small Craft Advisory from 3 PM Wednesday to 2 AM PST Friday for PZZ475.