textproduct: Eureka

SYNOPSIS

Dry weather and above normal daytime temperatures will continue through much of the upcoming week. Overnight and morning temperatures will remain chilly with patchy dense fog along the river valleys and around Humboldt Bay.

DISCUSSION

Resilient high pressure continues to dominate the region, leading to dry weather and above-normal temperatures. Abundant clear skies are observed across NW California this afternoon, with the exception of coastal stratus that remains stubborn to scatter around Humboldt Bay. A shallow marine layer up to 2,000 feet is expected to redevelop quickly along the coast late this afternoon and evening, with low clouds lapping the coastal areas into Tuesday. Low tempearures tonight/Tuesday morning are forecast to remain chilly with areas of fog and patchy dense fog along the shelter valleys. If you are interested in catching a glimpse of the aurora tonight, your location matters! Low coastal stratus clouds will likely hinder viewing for those along the coast tonight. Meanwhile, clear to partly cloudy are expected for the interior areas, offering a much better opportunity between 10 PM and 2AM tonight.

The 500 mb blocking flow pattern will continue to result in dry weather for NW California through the end of the week. A shortwave trough will undercut the block on Wednesday, resulting in a deeper marine layer with some low clouds pushing into the interior river valleys. Ensemble guidances shows the ridge rebuilding Thursday and Friday, with offshore flow strengthening. This dry offshore flow will most likely reinforce the chilly overnight low temperatures.

Beyond Friday, global models are now trending drier across the region. NBM probability for light rain or drizzle (0.01 inch or more) is around 15-25% for Del Norte and northern Humboldt on Sunday. Probabilities for 0.1 inch or more is less than 10%. Generally dry and above normal daytime temperatures are expected to continue through the next 7 days. /ZVS

AVIATION...(18Z TAFs)

LIFR and IFR conditions have persisted around Humboldt Bay over KACV trough much of the day on Monday. Conditions may improve some by late afternoon or early evening, however LIFR visibility and LIFR ceilings are expected to quickly redevelop by mid to late evening and overnight. Greatest disruption to airport operations appears to be highest for KACV where duration of 1/4SM in fog is forecast to be over 6 hours. The timing of 1/4SM in fog remains uncertain and statistical guidance has been utilized. Fog could also create disruptions to airport operations for KCEC as well, however confidence of long duration 1/4SM in fog is not as high. Otherwise, fog and LIFR ceilings in the valleys of Trinity, Humboldt and northern Mendocino counties will likely redevelop tonight and Tuesday morning. These LIFR conditions will pose a landing and take off hazard for smaller airports with no terminal forecast. Conditions should improve at these non-TAF terminals late morning and afternoon on Tue. Now for KUKI TAF, there are not any signs for LIFR in fog or even an IFR/MVFR stratus deck at this time and VFR with light wind is expected.

MARINE

Northerly winds (strongest south of Cape Mendocino around 15 kt) will continue on a downward trend tonight through Tuesday. Steep northerly wind waves around 4-5 ft (also south of Cape Mendocino) are forecast to trend down tonight and Tuesday as well. A long period westerly to northwesterly swell will build to 2 to 4 ft at 18 seconds late tonight and early Tue morning, and then to 5 to 6 ft near 16 seconds for the remainder of Tue. A secondary swell group around 3 to 4 feet at 12 seconds from the west-southwest will also add to the total sea state for max significant wave heights around 6 to 8 feet on Tuesday. Pressure gradients remain loose and wind fields light Tue into Wed before high pressure rebuilds and gradients tighten Wed night-Fri. Northerly winds increase by Thu with high probabilities for gusts to 25-30 kt on Thu and lower chances for gale gusts over 34 kt in the outer waters. The main hazard may end being steep northerly wind waves which are forecast to build on Thu and eventually to reach 8 to 10 by Fri. These deteriorating marine conditions will be hazardous for small craft and at a minimum an advisory for small craft will be necessary.

BEACH HAZARDS

A moderate risk for sneaker wave will arise during the early Tuesday morning hours. A Beach Hazard Statement, BH.S, has been issued for two separate arrival times of a westerly swell 4- 6ft with a period around 16-17 seconds. The earliest estimated arrival is 12z on Tuesday January 20th for Coastal Del Norte, Northern Humboldt Coast, and Southwestern Humboldt ending around 04- 05z Wednesday. The sneaker wave threat for the Mendocino beach zones will arrive around 15z on Tuesday January 20th, ending around 05- 06z. /EYS

EKA WATCHES/WARNINGS/ADVISORIES

CA... Beach Hazards Statement from late tonight through Tuesday evening for CAZ101-103-104.

Beach Hazards Statement from Tuesday morning through Tuesday evening for CAZ109.

NORTHWEST CALIFORNIA COASTAL WATERS... None.