textproduct: Eureka

SYNOPSIS

Rain showers and coastal flooding continue for this afternoon and evening, mainly over Del NOrte and Humboldt counties. Another round of rain and wind is expected tonight through Monday, before a break on Tuesday. Light rain and mountain snow are possible again Wednesday.

DISCUSSION

Current radar imagery shows a line of convective showers moving across the coastal waters and strengthening while approaching the northern portion of the area ahead of a frontal boundary. This round of showers will be almost exclusively focused on Del Norte and Humboldt counties through late this evening. Periods of moderate to locally heavy rainfall is expected. Southerly winds will continue to ramp up, with gusts 25-35 mph expected over the coastal headlands and exposed ridges. Localized gusts up to 40 mph are possible through the evening as the front nears the coast.

A somewhat more prominent shortwave and associated surface low pressure will approaches the area tonight into Monday, while the moist plume sags southward into Central California. This is expected to bring a more widespread precipitation spreading the area from the southwest. Some organized convective cell with brief heavy downpours and/or thunderstorms is expected to move onshore from the southwest along the Mendocino Coast and perhaps into the Cape Mendocino late tonight into Monday morning. HREF probability of 6-hours precipitation exceeding 1 inch indicate there is a 20-40% chance from the King Range and long the Mendocino Coast from 4 AM to 10AM Monday. In addition, there is the potential for some isolated waterspouts near shore late tonight/ early morning as well. Gusty winds from 25 to 35 mph are also expected to developed over the coastal headland and exposed ridges in Mendocino and Lake counties tonight through Monday morning.

Snow levels are expected to be around 3,500 to 4,000 feet with this system, but confidence is low on this. This could bring notable snow to Highways 3 and 36. A few snowflakes along the highest passes on Highway 299 in Trinity County are possible, but little accumulations are expected. Meanwhile, a Winter Storm Warning is now in effect through 4 PM Monday for elevations above 5000 feet where the heaviest snow are expected to continue.

Tuesday is generally expected to be dry, although there may be some lingering showers around. Wednesday another system is expected to move through. This is expected to have lower snow levels, possibly around 3,000 to 4,000 feet. The amounts look fairly light at this point, but this will need to be watched as this could affect the passes along Highway 299 (along with Highways 3 and 36). Rainfall amounts are also fairly light, with less than a half inch currently forecast across the area.

Thursday there may be a few lingering showers in the morning, but high pressure is expected to building in. This is expected to bring clear skies and dry conditions for Friday and Saturday with night and morning valley fog in the interior. NBM is showing some higher probabilities for freezing temperatures starting for Friday and Saturday morning for much of the area, even coastal areas, but moist conditions from recent rains are likely to nudge temperatures upward. ZVS/MKK

AVIATION...18Z TAFs

A passing area of low pressure is bringing light showers and rainfall over the region Sunday. Ceilings are forecast to remain mostly VFR to MVFR. Areas of moderate to locally heavy rainfall will move in this evening and will bring a threat for at least TEMPO IFR VIS and CIGS. The axis of moderate to heavy rainfall will remain from northern Humboldt and southward into Monday night as another area of low pressure clips the region. Southerly winds will remain gusty through Sunday evening. The threat for turbulence and low level wind shear will be much lower than Saturday, with only a slight risk Sunday afternoon for portions of Del Norte County where 35 kt southerly winds will reach down to 1500 ft AGL. Winds will be much lighter on Monday as the low departs southward. There is a chance for some thunderstorm activity near the southern Mendocino coast Monday afternoon, but terminal coverage is anticipated at this time. JJW

MARINE

Southerly winds will diminish through the night and early Monday. Monday afternoon and overnight high pressure starts to build in and northerly winds start to build into the area. Tuesday night and Wednesday winds are expected to diminish briefly and veer to the SW as a little system moves by the area. After that, northerly winds are expected to continue through Friday. A moderate northwesterly swell will continue through the week, peaking at around 16 feet Friday morning.

COASTAL FLOODING

A Coastal Flood Advisory is in effect for Monday for Humbold Bay. High tides are forecast to be at 8.04 feet at the North Spit tide gauge at around 12:28 PM local time. High tides combined with surge and tidal anomaly will result in water levels between 9.3 to 9.5 feet MLLW (Mean Lower Low Water). Minor coastal flooding around Humboldt Bay, including King Salmon and Jackson Ranch Road in the Arcata Bottoms, will be likely between 10 AM and 2 PM. /ZVS

EKA WATCHES/WARNINGS/ADVISORIES

CA... Flood Watch through Monday afternoon for CAZ101-102.

Coastal Flood Advisory until 2 PM PST this afternoon for CAZ101-104-109.

Flood Watch through Monday evening for CAZ103>106-108>115.

Coastal Flood Warning until 2 PM PST this afternoon for CAZ103.

Winter Storm Warning until 4 PM PST Monday for CAZ107.

NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 10 PM PST this evening for PZZ450-455-470-475.