textproduct: Eureka

SYNOPSIS

Dry weather and above normal daytime temperatures will continue through the early next week. Overnight and morning temperatures will remain chilly with patchy dense fog along the river valleys and around Humboldt Bay. Chance of precipitation increase by mid next week.

DISCUSSION

A cut-off low is currently located approximately 250 miles off the Central California, which continues to track southward. High pressure will rebuild in the wake of this low through Friday, leading to drier offshore flow. This will promote clearer sky conditions today, with clear skies across much of NW California Friday and into the weekend.

A dry offshore flow will most likely reinforce chilly overnight lows, bringing a chance of near-freezing or freezing temperatures to coastal areas and adjacent valleys Friday night into Saturday morning. Granted places where winds stay up all night, temperatures probably will not even fall below 50F. Lower dewpoints, clear skies and light winds at night will allow for ideal long wave cooling again. Freezing or near-freezing temperatures are probable Friday and Saturday morning, both along the coast and in the wind- sheltered coastal valleys. Sub-freezing temperatures are a sure thing in interior valleys, especially Trinity and northern Mendocino.

Dry weather is expected to persist through the weekend and into early next week as the high pressure persist over the Eastern Pacific, though the ridge weaken. A weak shortwave trough will bring increasing cloudiness Saturday night and Sunday. Coastal stratus are anticipated to redevelop, with a slightly deeper marine layer along the North Coast. Aside of some patchy coastal drizzle, generally dry conditions and above normal daytime temperatures are expected to continue through the early next week.

Long-range models continue to suggest an increasing chance of precipitation from mid- to late next week. Uncertainties remain high in the details. Stay tuned for updates as the timing of this shift become clearer. /ZVS

AVIATION

Low pressure passing to the south has continued to raise ceilings along the coast while also increasing offshore flow. Both factors have allowed for mostly VFR conditions this evening. There is a decent chance (25% chance) that some shallow IFR fog will form around sunrise, with the greatest probability around Humboldt Bay. Otherwise, more robust clearing to VFR is expected during the day Thursday with clearer conditions than the coast has seen in several days. Shallow radiation fog may bring a return to patchy IFR conditions Thursday night. Besides high level clouds, mostly clear and calm conditions will otherwise prevail across the interior. /JHW

MARINE

Currently calm conditions will give way to increasing northerlies Thursday as a mid level shortwave trough and NW flow aloft moves across the Pac NW. High resolution ensemble guidance indicates high chances for gusts to 25-30 kt (80% chance or more) with gale gusts over 34 kt much more probable (>60% chance) for the outer waters. Gale gust coverage increases after 8-10PM with very steep seas building to 9-11 ft overnight into Friday. Combined seas will build to 10 to 14 feet in the outer waters by Friday afternoon. Ocean conditions will also deteriorate Thursday night and Friday for the inner waters. Gale gusts are certainly probable around notorious wind prone locations such as Cape Mendocino and perhaps around Pt St George, but the primary hazard for the waters appears to be large steep waves arising from the strong northerlies offshore. Confidence seas will be sufficiently elevated and very steep for a warning (10 feet or more) across the inner waters is not high, but seas will be steep regardless.

Conditions look to gradually improve over the weekend as the axis of strong north wind shifts outside of NW California waters and steep wind waves gradually subside. In this mix of steep short period waves will be a long period (>16 seconds) westerly swell on Thu that will decay through Fri. A mid period swell near 14 second follow on Fri, followed by third mid period group on Sat. None of these appear to pose a risk for sneaker waves at this time. /JHW

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from 7 PM this evening to 3 AM PST Saturday for PZZ450.

Small Craft Advisory from 10 PM this evening to 3 AM PST Saturday for PZZ455.

Small Craft Advisory from 10 AM this morning to 10 PM PST this evening for PZZ470-475.

Gale Warning from 10 PM this evening to 3 AM PST Saturday for PZZ470-475.