Marine Weather and Tide Forecast for Mendocino, CA

DISCUSSION
In the near term, afternoon satellite imagery reveals a cumulus field and colder cloud tops over Humboldt and Del Norte counties. An approaching shortwave trough is bringing some weak elevated instability and moisture this afternoon. Moisture is lacking, but a low chance (up to 5%) exits for isolated dry thunderstorms this afternoon and evening for mainly Humboldt and Del Norte counties as this feature interacts with the higher terrain. Colder cloud tops and a cumulus field are observed on satellite over Humboldt and Del Norte counties this afternoon. There are some weak radar returns over the ocean well offshore and over the interior. Some light showers with virga (precipitation evaporating before reaching the surface) are also confirmed on the cams. A secondary shortwave trough axis and front will swing through Monday afternoon, slightly lowering daytime high temperatures and bringing similar low- chances for a couple showers or lone thunderstorm over far NE Trinity County.

Weak ridging will begin building in behind the trough. Inland valley temperatures will warm into the low to mid 90s, with some upper 90 in Lake County on Wednesday. Temperatures will trend lower next Thursday will another weak shortwave trough passing. Initial analysis of this trough does not show much chances for convective impacts, but features as this always bear watching this time of year. A seasonally anomalously strong trough is then forecast to dive south into the region next Friday. There is currently a low chance for some light showers with a cold upper low and front. There is the potential some of this precipitation may be in the form of thundertorms with steep lapse rates and elevated instability. The clusters unanimously bring down a cold trough, but show differences in the heights and depth of the low. Much cooler temperatures may be in the forecast, but there is time to work out the details. JJW



AVIATION
(18Z TAFs)A layer of coastal stratus from a deepened marine layer due to an overhead shortwave trof is beginning to give way to daytime VFR conditions. Breezy northerly winds are expected with elevated FEW/SCT clouds. Sounding data shows ample daytime mixing inland, potential resulting in gusts at or around 20kts this afternoon. Tonight, a return of coastal stratus is forecasted after sunset. This layer will be elevated due to the passing trough and should linger tomorrow through the morning.

Confidence: High resolution models show high confidence (>90%) for clearing out later this morning along the coast by 19Z. Low winds and increased atmospheric moisture shows a likely probability (for a return to IFR-MVFR conditions at KACV. Model data shows the shortwave trof overhead most likely deepening the marine layer deep enough to keep terminals out of LIFR categories (<10%) with ample visibilities over 5SM (<20%) through tonight at KACV.



MARINE
Strong to near gale force gusts are forecast to continue through the weekend, with the strongest winds across the outer waters and southern inner waters. Locally gale force gusts downwind of Cape Mendocino and Cape Blanco. The sea state will be largely dominated by steep short period wind waves. Winds are forecast to gradually decrease and retreat to the southern waters early next week. Next week as the winds die down, a small mid-period NW swell enters the water early Tuesday morning.

FIRE WEATHER
An approaching shortwave trough is bringing some weak elevated instability and moisture this afternoon. Moisture is lacking, but a low chance (up to 5%) exits for isolated dry thunderstorms this afternoon and tonight for mainly Humboldt and Del Norte counties as this feature interacts with the higher terrain. Colder cloud tops and a cumulus field are observed on satellite over Humboldt and Del Norte counties this afternoon.
There are some weak radar returns over the ocean well offshore and over the interior. Some light showers with virga are also confirmed on the cams. this will be watched closely through tonight as the axis of concentrated forcing progresses from the SW to NE through Humboldt- Del Norte. Trinity County has a brief chance this afternoon and a second chance in far NE portions of the county Monday afternoon for an isolated shower or thunderstorm as the trough axis passes.

Northerly winds are increasing in southern Mendocino and Lake County this afternoon. These winds will further increase Monday afternoon over the interior ridges, mainly in southern Mendocino and Lake counties. These mainly diurnally driven afternoon winds will trend slightly lower Tuesday, but will increase again late next week with a stronger trough and front. Minimum RH values will trend lower early to mid next week, with some values in the mid to upper teens Wednesday. Locally elevated to some brief critical fire weather conditions will develop with these afternoon wind pulses and lowering RH. JJW



EKA WATCHES/WARNINGS/ADVISORIES
CA...
None.
NORTHWEST CALIFORNIA COASTAL WATERS...
Small Craft Advisory until 11 PM PDT this evening for PZZ450-470.

Small Craft Advisory until 10 PM PDT Monday for PZZ455-475.