textproduct: Eureka

SYNOPSIS

An occluded frontal system will bring moderate to locally heavy rain, high mountain snow, and gusty winds this afternoon into tonight. Major coastal flooding will be possible today and Saturday during high tides. Bouts of rain and gusty winds are forecast to continue Sunday and likely next week.

DISCUSSION

A frontal boundary continues to approach the area bringing breezy winds to the area this afternoon. Rain is also starting to spread north. A round of showers is expected ahead of the front this afternoon. This may help to bring some of the stronger winds down to the surface. Gusts of 40 to 50 mph are expected along much of the coast and in some of the interior areas. The higher terrain, especially along the coast is expected see gusts of 60 to 70 mph. The first round of winds is expected to peak this evening and early tonight as the front passes through the area. This first round of rain is expected to be heaviest in southern Humboldt, Mendocino and Lake counties. One half to 1.5 inches is expected in most areas with local amounts. For details on the flooding potential see the hydrology section. Later this evening and overnight there is expected to be some thunderstorms in the stronger showers. These may enhance rainfall and winds.

There is expected to be a brief break in the winds late tonight and early Saturday morning. The second round of winds is expected later Saturday morning and peaking later in the afternoon and evening. This second round of winds is driven by a surface off the coast dropping to around 990 mb. The NAM and the GFS both are starting to fill as it approaches the coast. The center of the upper low is getting closer and bringing some colder air aloft into the area. This will create more unstable conditions and allow some of these stronger winds to mix down to the surface. This will be a longer period of stronger winds starting Saturday morning and lasting through Sunday morning. This is due to the upper level low stalling off the coast. A high wind watch remains in effect for coast Del Norte due to the uncertainty on how much wind will mix down to the surface with this second system. Rainfall amounts with this system are expected to generally be 1 to 3 inches with local amounts of 6 inches in the mountains and higher terrain. This system is expected to bring heavier amounts to the northern portion of the area. The ensembles are in fairly good agreement that IVT will be near 500 kg/m/s. This is slightly higher in the south on the first system and slight higher in the north on the second system.

Snow levels are forecast to start around 5500 feet on Saturday, lowering to 4000 ft into early next week. However, the heavy snow is most likely expected for elevations above 5000 feet. Snow impacts currently look mostly confined to Scott Mountain Pass in Northeast Trinity County. Total snow accumulations up to 1 foot possible for Scott Mt Pass. Higher amounts over the Trinity Alps. A Winter Storm Watch is in effect from Saturday morning through Monday afternoon for elevations above 5000 feet in Northern Trinity. Confidence is remains on this as snow levels have trended slightly higher. So will hold off on upgrading to a warning at this point.

Sunday and Monday additional rounds of rain are expected before a drier day on Tuesday. Wednesday may see another weather system. These later systems generally look colder.

AVIATION...18Z TAFs

Southerly winds are strengthening with an approaching strong storm system. South winds aloft are strong as well, up to 65 kts through 2000 ft AGL, and this brings a high level threat for low level wind shear and turbulence. The strong southeast downsloping winds are generally keeping ceilings higher. Ceilings are forecast to lower into MVFR levels, and periods of moderate rainfall will bring a chance for at least TEMPO IFR. Rainfall will generally become lighter after 9Z Saturday, but oceanic to coastal thunderstorm activity will increase at that time and will create more localized lowering of CIGS and VIS. Thunderstorms may push far enough inland to impact UKI as well, particularly Saturday through Saturday night. Very strong southerly winds will develop again near 18Z Saturday at the end of this TAF period. JJW

COASTAL FLOODING

A period of very high tides will continue through the 4th. The north spit tide gauge already recorded an impressive 10.01 ft high tide Friday morning, which is preliminarily the highest tide ever recorded since the tide gauge went in in the late 70s. The storm surge model continues to show slightly higher tides The storm surge model is now continuing to show 1 to 2 feet of storm surge on top of the already high astronomical tides. The surge is expected to be slightly higher Saturday than Friday with the longer duration of southerly winds and possible local wave action. Sunday the high tides are slightly lower and the southerly winds are expected to diminish.

Strong winds and surf could cause waves to wash onto roads exposed to the surf including Highway 101 south of Crescent City, Pebble Beach in Crescent City, Moonstone Beach parking lot, Centerville Beach road and parking lot, low spots along Highway 1 on the Mendocino coast, and other near coast infrastructure. At this time surf isn't expected to be exceptionally large, so elevated locations like the homes in Shelter Cove are less likely to be impacted but it isn't out of the question if seas are larger than expected. MKK

EKA WATCHES/WARNINGS/ADVISORIES

CA... Wind Advisory until 10 AM PST Saturday for CAZ101-102.

Coastal Flood Warning from 9 AM to 1 PM PST Saturday for CAZ101-103-104-109.

Flood Watch from Saturday morning through Sunday afternoon for CAZ101-102.

High Wind Watch from Saturday morning through Sunday morning for CAZ101-102.

Coastal Flood Watch from Sunday morning through Sunday afternoon for CAZ101-103-104-109.

Wind Advisory until 10 PM PST Saturday for CAZ103-105-106- 109-110-112.

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

High Wind Warning until 7 AM PST Sunday for CAZ104.

Winter Storm Watch from Saturday morning through Monday afternoon for CAZ107.

Wind Advisory until 4 PM PST Saturday for CAZ113>115.

NORTHWEST CALIFORNIA COASTAL WATERS... Coastal Flood Warning from 9 AM to 1 PM PST Saturday for PZZ415.

Gale Warning until 7 AM PST Saturday for PZZ450.

Storm Watch from Saturday morning through Saturday evening for PZZ450-470.

Gale Warning until 11 PM PST Saturday for PZZ455.

Storm Warning until 11 PM PST this evening for PZZ470-475.

Gale Warning from 11 PM this evening to 7 AM PST Saturday for PZZ470.

Gale Warning from 11 PM this evening to 11 PM PST Saturday for PZZ475.