textproduct: Eureka

SYNOPSIS

Shallow coastal stratus and fog will persist along the immediate coast with limited afternoon clearing through Friday. Inland areas will remain dry and hot under a building upper-level ridge.

DISCUSSION

An upper-level ridge over the Southwest US is expanding westward over Northwest California. Subsidence aloft is compressing the marine layer, keeping it shallow and confined to the coast and adjacent lower valleys. Inland areas will experience warming, with afternoon high temperatures in the mid to upper 90s becoming widespread across the interior valleys of Trinity, Mendocino, and Lake counties this afternoon.

Early next week, the placement of the upper ridge will determine the track of potential monsoonal moisture. Current guidance indicates a continuing warm trend for the interior, with a low probability of thunderstorm development over northeastern Trinity County.

AVIATION

A compressed marine layer has brought low ceilings and reduced visibilities to coastal locations. At KACV, IFR to LIFR conditions in stratus and fog will persist through mid-morning before gradual clearing. Temporary southerly surface winds at KACV and KCEC overnight indicate localized coastal eddy development rather than a sustained southerly wind pattern. Clear skies are forecast for KUKI.

MARINE

The surface pressure gradient between an offshore surface high pressure system and an inland surface thermal low is tightening. South of Cape Mendocino, sustained northwest winds of 20 to 25 knots are generating steep, wind-driven seas. A Gale Watch is in effect for the southern outer waters starting at 5 AM Thursday morning through Thursday evening due to potential gusts up to 40 knots, with conditions being monitored for a potential upgrade to a Gale Warning. For the northern outer waters, winds of 20 to 25 knots combined with steep 9-foot waves at short 8-second periods satisfy advisory criteria. All coastal marine zones are currently under a Small Craft Advisory.

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 11 AM PDT Friday for PZZ415-450.

Small Craft Advisory until 10 PM PDT Friday for PZZ455-470.

Small Craft Advisory until 5 AM PDT early this morning for PZZ475.

Gale Watch from 5 AM PDT early this morning through this evening for PZZ475.