Marine Weather and Tide Forecast for Westhaven-Moonstone, CA

DISCUSSION
Chilly temperatures have set in for the interior areas, with near-freezing temperatures possible in the coldest valleys. A frost advisory has been issued for northern Mendocino and Lake Counties. Satellite imagery and fire watch cameras show that inner valleys have some fog developing, trapping heat and keeping temperatures above the values needed for frost. When daytime comes around, dry weather is forecasted with pleasant temperatures for the inner valleys.

Tuesday night through Wednesday, an upper level trof moving into the interior PacNW will extend southward, leading to windy and rainy conditions for NW CA. Breezy southerly winds up to 30mph are possible for Del Norte and Humboldt counties. Rainfall amounts have continued to trend upwards in the models for this storm system. The current NBM is showing rainfall amounts around 1.00" for Crescent City and Del Norte. The northern area of the CWA will receive the most rain as the front rapidly moves southward and weakens. Rainfall will be light with periods of moderate intensity for the Humboldt Bay area. Lighter rain intensity and totals are forecasted for Trinity and northern Mendocino counties. Less than a tenth of an inch is expected in southern Mendocino and Lake counties. As per usual, the mountain areas will have more rain than the surrounding valleys. The bulk of the colder air for this system is forecasted to be more in southern OR and NE CA. This means that snow levels are still expected to be ~5,000 feet for most of the precip, but may drop below 3,000 feet as the precip comes to an end Wednesday evening. As the frontal system continues southward, breezy west winds in excess of 30 mph are possible Wednesday evening in Lake County.

Wednesday night into Thursday morning shows cold air moving over the area lowering snow levels down to 2,000 ft, leading to cold temperatures. The NBM is showing lows in the 20s in northern Lake, northeast Mendocino, and much of Trinity county. While this is certainly possible, fog and low clouds from the added moisture may develop in some of the valleys, limiting the radiational cooling.
Thursday afternoon, clear skies and dry conditions are expected with a slight warming trend. This will likely set up Thursday night to be the coldest night as even the coast may see frost.

Global models show another frontal system passing on Saturday night through Monday. At this point, model rainfall totals have risen slightly. The probability of rain totals over 0.5" for The weekend is over 75% for Del Norte. Humboldt and Trinity county has around a 50-70% chance for over 0.5", while the southern half has around a 20- 50% chance. Chances for over an inch in 48 hours are around 50% in the mountains of Del Norte and the King Range.
Details of this system will continue to become clearer over the coming days.



AVIATION
(06Z TAFs)...Terrain induced cumulus has dissipated as previous TAF discussions predicted. Light rain at KCEC by noon has low chance but still exists as moisture continues to sweep into the area and likely to clip Del Norte and produce precip for KACV as well KUKI at a lesser amount in the thousandths.
Tuesday late night into Wednesday will likely produce decent rain amounts with reduced visibility and ceilings around 5000ft, keeping VFR categories despite steady showers. Saturday and into Sunday looks to be wet as well which cold set up ground fog development next week if the cloud cover is minimal. /EYS



MARINE
Northerlies have increased today with the pressure gradient tightening behind a departing frontal system at the same time as high pressure builds off the coast. This has resulted in some small craft conditions in the southern water zones today that will persist into tonight. Winds will decrease on Tuesday as the front/trough continues to move inland and the next storm system approaches the Pacific Northwest. Winds will briefly turn out of the south starting Tuesday into Tuesday night ahead of the next frontal passage. A few areas in the north could see nearly small craft conditions ahead of the front. However, winds will sharply turn back out of the north as the front passes through the waters on Wednesday with small craft and possibly gale conditions developing Wednesday night into Thursday and Thursday night. /RPA



EKA WATCHES/WARNINGS/ADVISORIES
CA...
Frost Advisory until 8 AM PDT this morning for CAZ110-111- 114-115.

NORTHWEST CALIFORNIA COASTAL WATERS...
Small Craft Advisory until 5 AM PDT early this morning for PZZ455-475.