textproduct: Eureka

SYNOPSIS

Another cold morning is in store as clear skies persist inland. A marine layer will likely build along the coast early today with coastal drizzle incoming by the evening. Cool and dry weather will return Monday and Tuesday.

DISCUSSION

Offshore flow continuing overnight combined with drier air may allow for patchy frost formation in interior valleys of Trinity and NE Mendocino counties early this morning. That said, the addition of moisture to the environment from the recent rain is already enabling the formation of fog, which reduces the likelihood of frost formation. Frost concerns through this morning remains low (less than 10% via HREF/REFS probabilities). Closer to the coast, the marine layer has steadily been forming through the evening hours. This cloud layer will insulate the coastline, stopping the chance for frost early this morning. Interior highs will generally return to the low to mid 60s this afternoon through Thursday.

Most ensemble members show a weak trough moving onshore well north of the area later this afternoon/evening through Monday morning. Most members show light rain and drizzle along the North Coast in Del Norte and Humboldt counties with a 90% chance of at least trace rain amounts in Crescent City and an increasing probability (~20- 30%) of any amounts over 0.3 inches. In the Humboldt Bay area, there is about a 40% chance of no rain at all and only a 20% chance of greater than a wetting rain (>0.10"). High pressure will then again most likely briefly build with about 70% of ensemble members showing another cold, cutoff low storm system entering the area late next week.

Clearer skies and offshore flow will quickly reassert themselves early next week with another 50% chance of light frost in the interior by Monday morning. Most ensemble members continue to show a cold, cutoff low pressure system impacting the area mid to late next week, though potential timing is very uncertain. At least some rain is very likely, but the range is large (most likely 0.5 to 2.0 inches) because many models focus the system north. Compared to previous model runs, more now show the system staying north of the area (about 50%). Should rain occur, it will focus on the North Coast. NBM shows snow levels of 3000 to 4500 feet on the back end of the system into next weekend, which could bring some of the lowest elevation (albeit very light) snow of the season so far. There is little ensemble support (less than 20% over 45 mph) of any impactful winds with the system. /JHW/DS

AVIATION...(6Z TAFs)

Stratus has developed along the coast north of Cape Mendocino and up the river valleys. This is expected to continue to expand overnight and may even make it into the Russian River valley and KUKI towards morning. Sunday these clouds are expected to take their time clearing, but most areas should be VFR by midday or early afternoon. This will be shortlived as a frontal boundary moving by to the north of the area is expected to bring MVFR or IFR conditions to the KACV and KCEC along with some light rain or drizzle. This is expected to linger for much of Sunday night. COnfidence is low on how far inland this will make it. Monday is expected to see clearing again. MKK

MARINE

Northerly winds are gradually diminishing as a weak frontal boundary moves toward the area this morning. There may be a brief period of southerly winds in the northern waters later this afternoon and evening. The current swell has built in to around 11 to 12 feet at 15 seconds. This swell is expected to gradually diminish, dropping below 10 feet by early Monday. In addition there are some smaller wind driven waves that are gradually diminishing as well.

Early on Monday northerly winds are expected to build back into the area. These are expected to peak around 20 kt Monday afternoon and evening before they start diminishing again Monday night. Tuesday and Wednesday are generally expected to see fairly light winds. Wednesday afternoon these are expected to start becoming southerly again as a frontal boundary approaches the area. There are still some discrepancies in the models on how strong these winds are expected to get on Wednesday night and early Thursday, but generally they are expected to peak around 20 kt in the northern outer waters with lighter winds farther south. Friday stronger northerly winds are expected to return and models are in fairly good agreement on this. Over the weekend the models start to diverge with some bringing in another weak weather system and others bringing stronger northerlies.

The swell is expected to continue to diminish Tuesday and Wednesday with swell heights only around 4 to 6 feet at 10 seconds. The wind driven waves are expected to diminish Tuesday night setting up a very calm day on the water for Wednesday. Total wave heights look to be around 4 feet with a dominant period of 12 seconds. The next swell is expected to build in Thursday morning. MKK

BEACH HAZARDS

The long-period WNW swells continue to move through the waters today. Periods are around 15 seconds and some set behavior is expected to continue. These will pose a moderate risk of sneaker waves through the day Sunday. Breaking wave heights may reach 17-19 ft. Be cautious visiting beaches and jetties and remember to never turn your back to the ocean!

EKA WATCHES/WARNINGS/ADVISORIES

CA... Beach Hazards Statement through this evening for CAZ101-103- 104-109.

Frost Advisory until 9 AM PST this morning for CAZ106>108- 110-111.

NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until noon PST today for PZZ450.

Small Craft Advisory until 6 PM PST this evening for PZZ455- 475.

Small Craft Advisory until 11 PM PST this evening for PZZ470.