textproduct: Eureka

SYNOPSIS

Cool and clear conditions will continue Saturday. Winds turning onshore will likely help form a marine layer early Sunday with light drizzle and rain along the North Coast. Clearer conditions will return early next week alongside another risk of interior frost.

DISCUSSION

Cool and clear conditions have built all across the area. Clear skies have returned even for the coast with conditions modestly warming into the upper 50s to mid 60s. Patchy frost mixed with fog this morning in some interior valleys in Trinity and Mendocino Counties. Some frost will be possible (30% chance for valleys in Trinity and Northern Mendocino) again tonight, but significantly warmer temperatures combined with similar dewpoints in the upper 30s will most likely make frost coverage relatively limited. Still, the need for a frost advisory will need to be watched closely this evening should coverage expand and offshore flow become stronger.

Clear and slightly warmer conditions will persist Saturday, especially if offshore flow continues through the day. Winds quickly turning onshore ahead of a weak trough passage to the north will most likely promote a coastal marine layer to form early Sunday morning. The marine layer lifting through the day may allow for light rain and drizzle just along the immediate coast Sunday afternoon and evening. Rain chances are greatest in Crescent City where there is a 25% chance of wetting rain (> 0.1 inches) and a 90% chance of at least light drizzle. Chances drop by Humboldt Bay where there is only a 20% chance of even light drizzle.

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. 70% of 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. 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, 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

AVIATION...(18Z TAFs)

Northerly winds have filled in as of 20z with VFR conditions prevailing at the coastal terminals. A reduction in visibility from haze at KCEC and KACV, will bring periods of MVFR. There is a low probability (17-22%)of ceilings lower than 6500ft for the coastal terminals. With light winds expected tonight, there could be some ground fog development but dry easterly flow could limit development overnight into Saturday early morning. Light northerly winds through the TAF period is expected for KUKI, likely lasting into Saturday morning with prevailing VFR categories. /EYS

MARINE

Northerly winds continue through the evening and fill in to all area waters into Saturday. A westerly swell with wave heights of 10-12ft at 16-17 seconds will occupy area waters for the next few days, slightly diminishing by Sunday to 10ft at 15 seconds or so. Wind waves with a square profile around 8-10ft at 8-9 seconds will also be in effect and combine to make seas 11-14ft, with the larger waves in the outer waters 10 - 60nm. Northerly winds 15-20kt this weekend will ease by Sunday night 10-15kt but return Monday at 15-20kt. Milder conditions are forecast to return Tuesday evening. /EYS

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 7 AM PST Sunday for PZZ450-470.

Small Craft Advisory until 3 PM PST Sunday for PZZ455-475.