textproduct: Eureka

SYNOPSIS

Clearer and more dry conditions will settle across the area this weekend with some particularly cold mornings with lows near freezing. Conditions will slightly warm and moisten next week with increasing chances of wetting rain late in the week.

DISCUSSION

A cutoff low continues to move south along the California Coast today, helping to turn wind offshore and pull in generally drier air. Skies have gradually cleared, even along the coast, as a result. Cold air building just east of the area will continue to reinforce offshore flow into the evening. This will allow for more consistently clear skies and very dry conditions with daytime RH possibly dipping into the teens, especially at some higher elevations.

Clear skies and dry air will enable cold overnight conditions, particularly Friday and Saturday nights. Highs will most likely be right around freezing. Friday night, there is a roughly 20 to 40% chance of interior valley lows below 30 degrees with a 10% chance closer to the coast. Chances increase Saturday night with interior probabilities of 40 to 70%, though near coastal probabilities remain low near 10%, likely thanks to shallow fog formation. Such temperatures could pose a risk to sensitive outdoor plants and those without housing.

Conditions will slightly warm but greatly moisten early next week as a weak warm front alongside a push of southerly winds crosses the area around Tuesday. Increasing midlevel clouds will generally limit the high temperature potential. There is high model agreement that a weak and quick moving trough will cross the area behind the warm front sometime around Wednesday. This trough will bring the first real chances of wetting rain since the first week of January.

Rain will most likely be relatively evenly spread across the area from North to South with only a slight focus on the North Coast. There remains very high model spread in terms of rain amounts. For low elevations, model means over 48 hours are around 0.2 to 0.5 inches, though there is a 10% chance of greater than 1.5 inches or even greater at higher elevations. At the same time, the bottom 30% of models still show no rain at all. In any case, more moist conditions are essentially certain, even should no rain occur, and even the very high end of forecast will pose little to no flood risk given the recent dry period.

Long range ensembles show generally good agreement that a wetter pattern will then continue through the end of January. Again, model spread remains high with round of light to moderate rain being most likely through next weekend. /JHW

AVIATION

Stratus has been clearing out over Humboldt bay and at KACV this afternoon. This trend to mostly VFR conditions will continue into this afternoon, but some mist and low clouds may redevelop specifically around Humboldt and in the Eel delta by mid evening. Offshore flow will likely limit the chances of widespread stratus development tonight, especially for KCEC area where offshore flow will be strongest. Around Humboldt Bay and Eel delta some stratus may linger overnight before scouring out Friday morning. Now for southern Mendocino, particularly at KUKI, guidance is suggesting a chance for IFR by early Friday morning as a southerly push develops in the wake of transient trough. Some low ceilings and vsbys for KUKI may occur (30% chance) early Friday morning. Confidence KUKI will have LIFR remains low with boundary layer humidity from some of the more reliable models no more than 80%. Otherwise, expecting VFR to prevail except for fog and low clouds in the interior river valleys late tonight and early Fri morning. Northerlies aloft increase after 23/06z and shallow low level turbulence and/or low level wind shear will become a hazard for small aircraft, primarily over Humboldt county from KACV southward, more specifically over the King Range.

MARINE

Northerly winds have gradually increased through the day. Gusts up to 20kts have been observed int he inner waters with gusts closer to 30 kts in the outer waters. Winds will continue to increase overnight with a 60 to 70% chance of gusts over 34 kts by midnight tonight. 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. Seas are unlikely to reach 10 feet but will still be very steep between 8 and 9 feet.

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 until 10 PM PST this evening for PZZ470-475.

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