textproduct: Eureka

SYNOPSIS

Chance for light rain and drizzle is forecast for mostly Del Norte and Humboldt Counties late Saturday night and Sunday. Otherwise, dry and stable weather is forecast to continue through most of next week.

DISCUSSION

Pleasant weather will continue into the weekend with mild temperatures and low angle sun. Mid to high level clouds do indicate the approach of a low pressure system that will just barely clip the northern most areas of the CWA. Probabilities of wetting rain Sunday seem to diminish with every model run, though some light precipitation is still being forecasted.

The high and mid cloud cover will likely counteract the longwave cooling for the interior valleys while higher elevations respond to the large scale adiabatic warming. A strong nocturnal inversion and moist grounds will likely result in fog and low clouds early Sat for mostly Trinity, Humboldt and northern Mendocino Counties.

Decaying frontal boundary will bring a chance for light rain or drizzle to primarily Del Norte and Humboldt Counties late Saturday night or after 2-4 AM Sunday. Light rain or drizzle chances increase after 4 AM Sunday. Highest chance for 0.25 inches in 12 hours end 4 PM Sunday is forecast for Del Norte County, around 40-50%. Chance for > 0.25 inches in 12 hours ending 4 PM Sunday is much lower for most of Humboldt, 10-20%. Chance for > 0.10 inches in 12 hours is not very much higher for most of Humboldt, generally around 30-40%. That is a long way of saying not much rain is expected. Chances for 0.01 to 0.08 inches are higher (>60%) and will impact outer activities and projects that cannot get wet. Timing and duration still remains somewhat uncertain, but highest chances seem to be from 4 AM to 12 PM Sunday. The rain may not last as long either as the forecast seems to suggest. Other portions of the forecast area, Trinity and Mendocino may see some light rain or drizzle too on Sunday, but right now we are talking a trace to perhaps a few hundredths. Southeast Mendo and Lake Counties will most likely not get any measurable rain. Said another way, an 85% to 95% chance for less than 0.01 inches in 24 hours. The shortwave trough lifts out to the northeast by Sunday evening and precip chance will start to dwindle except for perhaps residual drizzle.

High pressure aloft will spring back up by Monday and then dominate most all next week resulting in multiple days of dry and stable weather. A shallow moist air push behind the front and N-NW surface flow may result in fog and low clouds overnight Sunday into Monday morning in the interior valleys. Otherwise, a general warming trend is forecast for much of the area early to mid next week. Highs are forecast to warm up into the lower to mid 70's in the interior next week. South facing exposures and higher terrain stand the best chance for highs in the 70's, while valleys trapped under the nocturnal inversion with night and morning fog may not warm up even into the lower 60s, especially in Trinity and northern Humboldt. The sun angle is low and many narrow valleys do not get much or any sun light this time of year. As is common for this time of year, overnight low temperatures will remain on the chilly side with subfreezing minimums highly probable for valleys in Trinity and perhaps portions Humboldt, Lake and northern Mendo. Longer range models are suggesting a break-through in the westerlies or undercutting of the blocking ridge late next week and next weekend. This could bring us some rain. Details on the timing and amounts are elusive at this point. NBM 24-hour probability of exceedance for 1" is not very high, only 5 to 20%, ending 4 AM Sunday. Stand by for more in this next week.

AVIATION

Light offshore flow has continued to promote VFR conditions all across the area this evening with broken clouds around 20 to 25 kft being the only notable feature. SOme very shallow haze will be possible (20% chance) on the coast around sunrise, but otherwise more calm and VFR conditions will persist Saturday. This increased potential for light coastal rain and MVFR conditions along the coast by early Sunday morning. /JHW

MARINE

Currently gentle southerly winds throughout the waters will persist through Saturday. That said, a persistent series of long period westerly swells will maintain a steep sea state. Combined seas have dropped below 10 feet, but another westerly swell will build in and keep seas no shorter than about 8 feet into the weekend. A weak front crossing the area Sunday will rebuild steep short period seas at least for the northern waters. Yet another round of steep, long period swells will build behind the front Sunday once again building over 10 feet into early next week. /JHW

BEACH HAZARDS

Two long period (>16 seconds) westerly swell groups will spread into the coastal waters this weekend. The first one will arrive on Saturday with heights building to 4 to 6 ft at 17 seconds by late afternoon. A decaying west swell around 6 feet at 11 seconds will also be present and should mitigate the sneaker wave risk. Another long period swell train is forecast to arrive on Sunday with significant swell heights building to 12 feet with periods near 16 seconds. Breakers up to 16 feet for west and northwest facing beaches on Sunday are forecast based on average beach slope profiles. Beachgoers venturing near the surf zone should remain vigilant. Avoid rocks, jetties and steep beaches.

COASTAL FLOODING

Chance for minor high tide flooding of low-lying areas around Humboldt Bay will be possible Saturday and again on Sunday. Highest chance (40%) for salt water inundation of normally dry areas will be on Saturday, followed by slightly lower chances of 30% on Sunday. Impacts are not expected to be as severe as the King Tide flooding observed in early January. More nuisance road flooding is likely in areas like King Salmon. Storm surge model has been fluctuating around from 8.7 to 8.9 ft MLLW for Saturday again on Sunday. Strong southerly winds (>35 kt) and large surf (>20 feet) will make coastal flooding much more significant with greater impacts. That component of the storm surge continues to be lacking and therefore impacts will most likely be minor with road flooding in King Salmon. We posted a graphic on our web page to call attention to this.

EKA WATCHES/WARNINGS/ADVISORIES

CA... Coastal Flood Advisory from 8 AM this morning to noon PST today for CAZ103.

NORTHWEST CALIFORNIA COASTAL WATERS... Coastal Flood Advisory from 8 AM this morning to noon PST today for PZZ415.

Small Craft Advisory from 8 AM Sunday to 3 AM PST Monday for PZZ450-455.

Small Craft Advisory from 4 PM this afternoon to 3 AM PST Monday for PZZ470-475.