textproduct: Eureka

SYNOPSIS

Light to moderate rain through this evening with snow levels around 5,000 feet. The heaviest rain is expected late this afternoon and evening in Mendocino and Lake counties. Monday a few showers are expected as colder air moves in. Monday night and Tuesday snow is expected above 1500 to 2500 feet impacting most highways through the interior. Lighter rain and low elevation snow are expected Wednesday and Thursday

KEY MESSAGES

* Moderate to heavy rain through this evening, especially in Mendocino and Lake counties where localized flooding is possible. Snow levels remain over 5000 feet.

* Monday night through Tuesday night heavy wet snow will generate dangerous travel conditions, downed trees and possible power outages. This is expected to impact mountain passes highways 199, 299, 36, and 3. This may also impact highway 101.

* Small hail accumulation expected for low elevations along NW California Coast with heavy showers, especially on Tuesday.

DISCUSSION

A surface low and an associated cold front off the NW California Coast are bringing widespread rainfall across the area. Generally light to moderate rainfall is being observed this afternoon. An enhancement in precipitation is expected to occur late this afternoon and evening as a deep upper-level troughs moves over the region. Expect moderate to heavy rainfall, especially in Mendocino and Lake counties, where additional 1 to 2 inches is expected in around 12 hours. This may cause some minor flooding of small streams, streets and low lying areas. Snow levels are expected to be over 5,000 feet through tonight.

Tonight and Monday, precipitation will become more showery as the first system weaken and moves into Central California. Rainfall amounts are expected to be mainly less than a quarter of an inch. Snow levels are expected to start falling through the day on Monday, dropping to around 3,000 to 4,000 feet by late afternoon.

A major winter storm is expected to move into the region Monday night and continue through Tuesday. This system will bring significant and potentially major weather impacts to our area through at least Wednesday. A colder air mass is expected to move into the area as early as Monday evening, and will likely be in place when the heavier precipitation starts in the late Monday night into Tuesday. Snow levels are expected to fall rapidly to around 1500 to 2500 feet with a significant colder airmass moving across the area Monday night into Tuesday. Heavy snow is anticipated for all major mountain pass as the snow level drop rapidly throughout the event. Additional impacts expected include downed trees and possibly power lines. The current forecast is showing over a foot of snow on Hwy 299 at Berry Summit and on Hwy 199 at the Collier Tunnel. Snow fall amounts are slightly less on Hwy 299 at Oregon Mountain and Buckhorn Summit with less precip that far inland. Smaller roads such as Mattole Road and Shelter Cove road as well as numerous county roads farther inland will likely also see snow. A Winter Storm Warning remains in effect from Monday evening through Wednesday afternoon for elevations above 2000 feet in Del Norte, Humboldt and Trinity Counties. For Mendocino and Lake counties, less snow amounts are expected with snow level above 2500 feet. Expect 2 to 4 inches of snow amounts is forecast for Hwy 101 at Rattlesnake Summit and Hwy 175 at Cobb from Monday afternoon through Tuesday. A Winter Weather Advisory is now in effect for elevations above 2,500 in Mendocino and Lake counties from Monday night through Wednesday. Additional impacts expected with this storm includes accumulating small hail at lower elevations, which can create slippery "ice rink" conditions on the roads in a matter of seconds. Have to hoisted a Winter Weather Advisory for accumulating small hail in Del Norte Coast and Humboldt Coast. Uncertainties remain for accumulating small hail along the Mendocino Coast with temperatures in the mid to upper 40s on Tuesday. This need to be re-evaluated and may need to extended the winter weather advisory for Mendocino Coast due to accumulating hail.

Showers and low snow levels are expected to continue on Wednesday and Thursday although at this point amounts look quite a bit lighter. There will likely be some breaks in the rain and snow even though the current forecast broad brushes the pops due to uncertainty on timing. Additional rain and snow are expected on Friday, although snow levels are expected to start rising. /ZVS

AVIATION.

Rain has arrived to the area as an area of low pressure spins off the northern California coast. Ceilings have remained MVFR to VFR as ceilings remain elevated. Some of the heavier showers have brought lower visibilities, however, but these are largely brief. Mendocino and Lake Counties will see the heaviest rain today and the bigger potential for more impactful conditions. UKI could see conditions below airport minimums at times today from heavier rain showers. Showers taper off at the coast overnight, but still VFR conditions with periodic MVFR ceilings are expected. UKI is likely to see rain for much of the night, potentially tapering off around sunrise Monday. JB

MARINE

Southerly winds continue early this afternoon with sustained winds at 15 to 20 and widespread gusts of 20 to 30 kts. Brief gale force gusts were recorded on some buoys this morning. The southerlies will begin to ease by the early evening, but could remain breezy south of the Cape with gusts of 15 to 25 kts. The center of the low pressure will move through the waters Monday, bringing stronger northerly winds behind the low. Gale force gusts, starting late Monday morning or early afternoon, are likely south of Cape Mendocino depending on the location of the low. Winds turn westerly Tuesday and are likely to remain breezy with gusts of 20 to 30 kts. Isolated thunderstorms with small hail, gale force gusts, and isolated waterspouts are possible Tuesday morning. Winds turn northerly and begin to ease by midweek as the low pressure moves out of the area. However, a northwesterly large, steep mid period swell of around 15 to 18 ft at 14 seconds will build in Tuesday and Wednesday. This will keep seas elevated into Thursday.

EKA WATCHES/WARNINGS/ADVISORIES

CA... Winter Weather Advisory from 10 PM Monday to 7 AM PST Wednesday for CAZ101-103.

Winter Storm Warning from 7 PM Monday to 4 PM PST Wednesday for CAZ102-105-106.

Winter Storm Warning from 10 PM Monday to 4 PM PST Wednesday for CAZ104.

Winter Storm Warning until 4 PM PST Wednesday for CAZ107- 108.

Winter Weather Advisory from 10 PM Monday to 4 PM PST Wednesday for CAZ110-111-114-115.

NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from 10 AM Monday to 3 PM PST Tuesday for PZZ450.

Small Craft Advisory until 1 PM PST Monday for PZZ455.

Gale Warning from 1 PM Monday to 10 AM PST Tuesday for PZZ455.

Small Craft Advisory until 3 PM PST Tuesday for PZZ470.

Small Craft Advisory until 10 AM PST Monday for PZZ475.

Gale Warning from 10 AM Monday to 10 AM PST Tuesday for PZZ475.