textproduct: Eureka

KEY MESSAGES

- Winds remain light through the holiday weekend, but trend much stronger Monday afternoon.

-Chances for light rainfall or light drizzle increase early next week.

-Isolated thunderstorms possible in Trinity County Friday afternoon, which would bring a lightning risk to early holiday weekend outdoor activities.

-Morning coastal stratus and fog will persist, with increasing chances for longer duration coastal stratus and possibly fog through the weekend.

DISCUSSION

Coastal stratus was clinging along the immediate coast for the afternoon, with full sunshine elsewhere. This pattern will continue through the weekend, with light north- westerly winds and coastal eddies locking in the coastal low clouds more effectively. Interior temperatures will slower moderate through the weekend as high pressure ridging is flattened from troughing to the north.

A weak upper disturbance is passing through from the north. There are big questions in available moisture/instability in regards to potential subsequent afternoon thunderstorm activity for Trinity County Friday. There will be a strong capping inversion in place, but convective allowing models have in more recent runs depicted breaking of the cap and thunderstorms over Trinity County. With run- to-run deterministic and ensemble congruity, have increased thunderstorm chances for Trinty Friday afternoon. There is a small, low confidence chance a lone storm may form out there this afternoon. A lingering chance for convective activity may carry into Saturday afternoon for far northern Trinity County if the cap can break.

A deeper trough will work farther south Monday. A late season, weak front off the low has been forecast to clip the area and deliver some light rainfall or drizzle to the northern portion of the region Monday and possibly Tuesday. With a slightly more southerly track modeled, chances for a wetting rainfall (over 0.1 inch) have increased to 30-50%; however, these types of systems usually underperform when arriving into such dry antecedent conditions. Ensemble spread is still quite high, ranging form nothing to 0.4 inches for Del Norte, and this is typical modeling for late season systems.

The deep trough will progress SE through the Pacific Northwest/Great Basin region later Monday through Wednesday. With Northern Pacific high pressure strengthening against it, the northerly to westerly winds will once again begin turning strong by Monday afternoon. The strongest winds will initially be focused over the eastern portion of the area, through Trinity and Lake Counties. Chances for gusts over 35 mph are notably high for Lake County Monday afternoon and evening, at 60-75%. Wind gusts over 40 mph are also looking probable (40 to 50%) for the ridges and locations around Clearlake. On Tuesday, these strong northerlies expand westward over the coastal regions. Chances for wind gusts over 30 mph are pretty solid for the exposed coastal headlands Tuesday afternoon, at 40 to 60%. This pattern will not likely quickly breakdown through Wednesday, but chances for stronger gusts are much lower Thursday. JJW

AVIATION

Stubborn stratus is keeping IFR ceilings at the North Coast with periods of VFR at KCEC and KACV. IFR is forecasted to return tonight around 03Z as ceilings reform and drop with ~70% confidence. After 12Z, North Coast ceilings are more likely than not to be LIFR if they do form. The daily clearing pattern is forecasted to repeat again Friday. VFR elsewhere through the TAF period.

MARINE

Buoys in the inner waters report slightly calmer winds off the NW CA coastline today. However, near gale force gusts off SW Oregon and in the outer waters are creating steep, short period seas for our waters. Sea heights are much higher in the southern waters as the northern winds continue and fetch grows. A Gale Warning is active for the northern outer waters through tomorrow evening as is a Hazardous Seas Warming for the southern outer waters. Inner waters are reporting large, steep waves with dangerous conditions for small crafts through tomorrow as well.

Into the weekend, the synoptic weather pattern changes as a weak frontal system passes overhead. This front will do two things for the coast waters. Firstly, expect light winds as the surface pressure gradient weakens over the area. Gusts up to 20kts are expected, which is a nice chance after multiple days of gales. Secondly, a large swell will build Sunday into next week with the storm travelling across the Northern Pacific. This NW swell is forecasted to be up to 14ft@12s at its peak on Tuesday. Seas for this holiday weekend will be calm before this swell builds in with seas of 5-7ft expected. DS

FIRE WEATHER

There is a small, low confidence 5-10% chance for an isolated thunderstorm over far eastern Trinity County this afternoon. Chances for isolated thunderstorms increase Friday afternoon for Trinity County (10-20%). There will be a strong capping inversion in place, but convective allowing models have in more recent runs depicted breaking of the cap and thunderstorms over Trinity County. With run-to-run deterministic and ensemble congruity, have increased thunderstorm chances for Trinty Friday afternoon. A lingering chance for convective activity may carry into Saturday afternoon for far northern Trinity County if the cap can break.

After some light rain/drizzle chances Monday for mainly Humboldt and Del Norte counties, northerly to westerly winds will quickly increase Monday afternoon. Winds will initially be strongest in east Trinity through Lake County, with moderate to high chances for gusts over 35 mph (60-75%) Monday afternoon and evening. Wind gusts over 40 mph are probable (40-50%) for the ridges of Lake County and around Clearlake. Winds will then increase across the entire region Tuesday, and will likely remain breezy through Wednesday. Minimum RH is currently forecast to drop to the mid to low 20s with these winds. JJW

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 11 PM PDT Friday for PZZ450-455.

Gale Warning until 11 PM PDT Friday for PZZ470.

Hazardous Seas Warning until 11 PM PDT Friday for PZZ475.