textproduct: Eureka

SYNOPSIS

Above-normal tempeartures through Today, followed by a cooling trend this weekend and into early next week. Isolated thunderstorms possible in Trinity County this afternoon. There is a chances of wetting rain for Del Norte and northern Humboldt counties Monday through Tuesday. Northerly winds will begin turning strong again by Monday afternoon, and likely remaining breezy through mid next week.

KEY MESSAGES

- Chance (10-15%) of isolated mountain showers and thunderstorms across Trinity County this afternoon and evening.

- Gradual cool trend and lighter winds this weekend and into early next week.

- Coastal stratus will become more stubborn to scatter out through the weekend.

- Light to locally moderate showers are forecast on Monday/Monday night, with lingering showers through Tuesday.

- Breezy to gusty northwest winds returns next Tuesday.

DISCUSSION

High pressure over the Northwestern Pacific has begun to weaken, while a weak shortwave trough develops over Northern California overnight. Satellite imagery depicts coastal stratus and patchy fog around Humboldt Bay and along much of the immediate coast. Low clouds and fog are expected to become more stubborn to scatter out nearshore today and through the weekend.

Interior temperatures are expected to be slightly cooler with the onshore flow; however, highs are forecast to be in the upper 80s to low 90s. Coastal areas are forecast to be generally in the mid 50s to low 60s with the sea breezes. The afformentioned weak shortwave will bring a slight chances (10-15%) of isolated thunderstorms for Trinity County this afternoon and early evening, with the west-nortwest flow keeping the cells over the eastern portion.

Cooler temperatures are expected for this weekend and early next as the shortwave trough persist over the area and the flow aloft become more zonal. A lingering chance (below 10%) 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. /ZVS&JJW

AVIATION...(06Z TAFs)

Coastal stratus has developed around the Humboldt Bay and vicinity, promoting IFR ceilings at KACV. Low clouds are expected to continue developing nearshore and push northward into KCEC overnight with light south winds. These should bring IFR/LIFR from 10Z through at least 19Z for KCEC, before the NW winds increase. Short-term guidance suggests low clouds scattering for KCEC, allowing VFR conditions after during the afternoon hours, while low clouds will be stubborn to scatter out onces again at KACV. Light S winds overnight, becoming NW at 10-15 kts for the coastal terminals during the afternoon with higher gusts, especially at KCEC. Meanwhile, prevailing VFR conditions for KUKI. /ZVS

MARINE

Strong to gale-force gusty winds persist across the outer waters through tonight, with the strongest winds in the northern outer waters. Gale-force gusts are forecast to redevelop onces again around Pt St George, with near-gale force gusts in the lee of Cape Mendocino. These winds will continue to generate steep to very steep, hazardous seas across the waters into the weekend.

Northerly winds are expected to diminish this weekend as the high pressure shifts eastward and the pressure gradient relaxes. Seas will also subside this weekend and into early next week, and are forecast to be below 5 feet across the waters by Sunday night.

Monday, winds shift to west-northwest as a cold front from the Northeastern Pacific (NEPAC) moves through. Seas for the Memorial Day will be relatively calm around 4-6ft expected. Wind shifts to northerly and increase in the wake of the front Monday night through Tuesday. A NW swell around 7-11 feet at 12 seconds is expected to build in Monday night. This NW swell is forecasted to be up to 14-16 feet at 12 seconds at its peak on Tuesday/Tuesday night. High confidence (80-10% chance) for gale- force gusts redeveloping on Tuesday for the southern waters. The chances for gale-force gusts increase to the northern waters Tuesday night/Wednesday. /ZVS

FIRE WEATHER

A weak shortwave trough developing over the area today will bring a slight chances (10-15%) of isolated mountain showers and thunderstorms this afternoon and early evening for Trinity County. 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. CAMs shows moderate return across the eastern portion of Trinity County. A lingering chance (below 10%) 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. Breezy to gusty northwest winds will then expected 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.