textproduct: Eureka

SYNOPSIS

Unseasonably warm and dry conditions will build through midweek especially on the coast. Light rain is most likely to return this weekend,= mostly focused on the northern half of the area.

DISCUSSION

A moderate ridge, currently centered over California, will slowly meander just east of the area over the next two days. At the moment, this has promoted shallow marine fog near shore and mostly calm winds.

As the ridge pushes east through midweek, it will help generate persistent, moderate easterly wind. This will promote dry and clear conditions, even at the coast, Tuesday through Thursday. Coastal conditions are likely to be unseasonably warm. Wednesday and Thursday, there is 30% chance of highs reaching 70. There is slight potential (about 15%) on Thursday of reaching the high temperature record for the day in Eureka of 73. Highs in the interior will also be warm, though not record breaking, most likely in the mid 70s for warmer valleys such as Ukiah and in Lake County.

There is high ensemble agreement that an elongated, but weak trough will sweep across the area around Friday and into the weekend. The first effects of the trough will increasing cloud cover and generally cooler and more moist condition by Friday. A thin band of moisture will be pulled onshore, most strong around Cape Mendocino, behind the trough. This band, however, appears very weak in ensembles and will have little instability to work with, limiting any high end rain potential. That said, model ensembles still place about a 70% chance of wetting rain all along the coast around Saturday and Sunday. Rainfall would be mostly focused along the the North Coast with most likely rainfall amounts of 0.1 to 0.5 inches. This initial round of rain would be mostly light and associated with little wind.

Deterministic models currently support a much strong and deeper trough then crossing the area as soon as Sunday into early Next week. There is much more uncertainty with this system compared to Saturday. While there is much greater high end potential, only about 50% of ensemble members support robust enough moisture to constitute a weak to moderate atmospheric river event. Because of that, there is a very wide range in current precipitation forecasts. About 20% of models show no rain at all with a mostly likely rainfall range of 0.4 to 1.6 inches along the coast. In higher end scenarios, precipitation could reach near 3 inches at higher elevations. There is good agreement, that the greatest chances of heavier rain are isolated to the northern most part of the area, with a narrower mostly likely range in Mendocino and Lake Counties of 0.2 to 1.0 inches. Should the determinist models prove right, this system could have the potential for some impactful winds over 45 mph and possible snow levels as low as 3000 feet, but too much variability remains to really nail down scenarios for those variables quite yet. /JHW

AVIATION

Coastal cloud cover is much less widespread this morning as compared to last night. Patchy IFR to LIFR condition are expected along the coast into the morning hours. Interior areas will also see some fog formation overnight in the valleys with gradual mixing to VFR by the afternoon, though the Ukiah valley should remain clear. Winds will remain light across the region with high pressure building aloft. /RPA

MARINE

Westerly swells are now subsiding and will continue to decrease in height through the day on Tuesday into Tuesday night. High pressure over the region will keep winds light across the coastal waters Tuesday and again on Wednesday. The next westerly swell will build into the waters Thursday into Friday allowing seas to build back to around 10 feet. The models have been trending down with the magnitude of this swell, so the potential for small craft advisory conditions is a little more questionable than what seemed more likely only 24 hours ago. /RPA

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... None.