textproduct: Eureka

SYNOPSIS

Isolated showers and thunderstorms are possible in the interior this afternoon. There are additional shower chances each afternoon through Monday. Drier weather returns mid next week.

DISCUSSION

High pressure weakens today as multiple upper lows and trough digging into the northern Rockies interact with each other. Cooler temperatures aloft will support instability over the interior this afternoon. The main uncertainty is if there will be enough moisture to support thunderstorm development, but CAMs are showing a few showers developing over eastern Trinity and the Yolla Bolly's. Saturday, the trough over the Rockies continues to dig westward while a secondary upper low approaches the southern California coast. This pattern looks like it will bring slightly more moisture which could support more shower and thunderstorm development over the interior. The highest chances in northern Lake, eastern Mendocino, and eastern Trinity. The chance for wetting rain (>0.1") is around 20-40% over much of Trinity and eastern Mendocino, with much lower probabilities elsewhere. Additional chances for showers and isolated interior thunderstorms are possible Sunday and Monday afternoons, depending on the positioning of the low. All told, the chance for wetting rain over a 72 hour period from Saturday morning to Tuesday morning is only around 40% for much of Trinity, and 20% outside of Trinity County. At the coast, any precipitation would likely be in the form of drizzle or a stray light shower. Drier and warmer weather is likely to return by mid next week as ridging redevelops. JB

AVIATION

VFR conditions have prevailed through Thursday evening. In contrast to previous nights, however, a robust marine layer is evident on satellite even before midnight. Models suggest MVFR to IFR ceilings will likely (65% chance) at least briefly form along the coast Friday morning, with the greatest chances around Humboldt Bay. Chances are even greater (80% chance) Friday night into Saturday of MVFR ceilings forming even before midnight Friday night. Otherwise, modest north winds during the afternoon will be the only notable feature during the day Friday. /JHW

MARINE

Northerly winds peaked Thursday evening with some gusts in the southern waters recorded in excess of 25 kts. Steep short period seas have built near 10 feet in response. Heading into Friday, moderate to strong northerly winds will gradually shunt further offshore. While some short period wave energy will linger closer to shore, it to will push offshore by the evening with seas near shore falling below 6 feet.

WInds will generally weaken this weekend. Winds will remain gentle for the inner waters, but gusts up to 25 kts will ebb and flow through the outer waters. Seas will be mostly controlled by short period seas, though a mid period westerly swell up to 4 feet will modify the sea state through the weekend. More widespread, calmer conditions are expected for all waters early next week. /JHW

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 6 AM PDT early this morning for PZZ455.

Small Craft Advisory until noon PDT today for PZZ470.

Small Craft Advisory until 3 PM PDT this afternoon for PZZ475.