textproduct: Eureka

SYNOPSIS

Rain showers will continue across most of the area through today. Drier weather is expected late in the work week before a colder and stronger system may impact the region this weekend through early next week.

DISCUSSION

A Pacific system moving onshore along the Central Coast of California will continue to bring moisture from the southeast across Northwest California. The bulk of the rain has moved through with showers continuing through today. Expect showers to gradually tapper off from north to south throughout the day today. By the time showers end, the total rainfall amounts are forecast to be from 0.5 to 1.0 for Lake County and extreme eastern portions of both Mendocino and Trinity counties, with the highest amounts expected in Lake. Locally up to 2.0 inches are expected over the higher terrain of Lake and Trinity counties. The Mendocino Coast, interior Humboldt, Del Norte, and western Trinity will more than likely see less than half an inch with the majority of Humboldt and Del Norte unlikely to see even a tenth of an inch.

While this is primarily a rain event for the lower elevations, snow levels will hover around 5500 to 6000 feet, which will continue to bring light snow showers to high mountain passes, like Scott Mountain Pass on Highway 3, through the day.

In addition, increasing east to southeast winds are expected through this afternoon over the interior, focused mainly over Mendocino and Lake counties. Gusts from 25 to 35 mph are forecast over the exposed ridges in Mendocino and Lake counties. However, the easterly winds may aid in funneling gusty winds in Lake County. The National Blend of Models (NBM) 90-95th percentile (high end) indicate a potential for gusts around 30 mph in the lower elevations of Lake County through early this afternoon.

Dry weather is expected for late in the work week as weak high pressure builds into the region. Expect seasonable daytime temperatures and chilly overnight low temperatures. Freezing minimum temperatures are highly probable for valleys in Trinity County. Many areas along the coast will have periods of stratus cover each night and morning along with patchy fog through Friday.

Another unsettled weather pattern will return this weekend and continue into early next week. This system is forecast to be a deeper, more positively tilted, cut-off trough. It will slowly approach shore with a broad surface low over the Pacific. Ensemble models and WPC Cluster Analysis are in good agreement with the low moving near the California Coast over the weekend, bringing a high chance of widespread precipitation. High uncertainty remains regarding the specific details at this time.

Heading through early next week, a potent cold upper-level trough with 500 mb temperatures from -32 to -38C will dig south- southeastward from the Gulf of Alaska toward the West Coast. The most recent operational models are suggesting temperatures aloft at -4C at 850 mb, -15C at 700 mb, and -35C at 500 mb over Northwestern California. The cold airmass will aid in the development of steep lapse rates which will promote heavy precipitation, along with isolated thunderstorms and the potential for accumulating small hail along the coast by early next week.

Some other main concerns with this system are the potential for heavy mountain snow, which would impact highway passes, along with the potential for lower elevation snow. Snow levels are expected to start around 5,000 feet Saturday and gradually drop to around 1,500 to 3,000 feet MSL by early next week. There is uncertainty on just how low snow levels could get due to the probability of convective showers, which has the potential to lower snow levels for localized areas. Heavy snow across the higher ridges could accumulate from 1 to 2.5 feet from Saturday morning through early next week. Travel impacts are anticipated from Saturday through mid next week. Stay tuned! /ZVS

AVIATION...06Z TAFs

VFR conditions prevail as an area of low pressure to the south wraps in light showers. Surface winds at the coastal terminals will be light and mostly variable. The low pressure to the south will bring a risk for low level wind shear and turbulence with easterly winds of 30 to 40 kts near 2000ft AGL for portions of Lake and southern Mendocino counties Wednesday. Winds aloft will quickly subside after 21Z Wednesday for the described areas.

MARINE

Moderate northerly winds remain over the outer waters. Steep, short period seas of 7 to 9 ft will maintain advisory conditions over the northern outer waters into Wednesday night. Relatively calm winds and seas will persist elsewhere until Thursday afternoon into Friday when northerly winds increase again, reaching 20 kts in the southern waters. At the same time, a large long period swell will build in, peaking 10 to 12 ft at 18 seconds Friday. This swell alone will bring hazardous conditions to small craft.

BEACH HAZARDS

Generally mild beach conditions expected through Thursday. Then a steep, northwest long period swell will build in Thursday evening and peak around 12 to 13 feet at 16 seconds on Friday. This swell will align with beaches in Humboldt and Del Norte counties and may produce rapid and unexpected beach run up of over 18 feet. Calmer winds and few short period seas along the North Coast Friday will further enhance set behavior and make waves more sneaky, especially on steep beaches. Take care if going to the beach late in the week. Stay off of rocks, logs, and jetties and never turn your back to the ocean! JHW/DS

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 10 PM PST Wednesday for PZZ470.