textproduct: Eureka

KEY MESSAGES

* Tropical moisture has arrived and cause a light shower or two for Mendocino & Lake Counties through early Friday afternoon.

* Interior areas continue to experience near or slightly below normal temperatures through this weekend.

* Coastal areas continue to see overnight stratus with afternoon clearing.

SYNOPSIS

Tropical moisture has arrived, very slightly increasing the chance for light rain showers for Mendocino & Lake Counties through Friday. Generally mild, seasonable weather continues across the area with slightly below normal interior temperatures and coastal areas seeing overnight stratus.

DISCUSSION

Water Vapor IR satellite imagery shows a stream of moisture flowing over the region this morning as the remnants of Tropical Storm Iselle move downstream along the upper level flow. Moisture is remaining mostly over Mendocino and Lake County as of right now. widespread rain is not forecasted for this evening, yet some rain showers are possible in the southern portions of the CWA. Any rain that does fall will likely be beneficial. The forcing of this flow is an upper level trough sitting over the NE Pacific Ocean. This trough is also the cause of the temperatures inland being at or just below normal for late August. The marine layer remains deep due to this feature as well, increasing the likelihood of afternoon clearing due the weak marine inversion. Weather through the weekend is likely to remain calm with this pattern remaining in place.

Model guidance is showing a trough dropping far south off the coast of the Pacific Northwest and possibly forming a cutoff low right off the northern California coast by Tuesday. This is several days out, so this has time to change, but this could give the northern half of the area some light rain. NBM is showing around a 20% chance for the North Coast to see a tenth of an inch of rain while chances in Del Norte are around 40%. Should this trough move northward, there is also the potential for a return of tropical moisture early to mid next week. Stay tuned!

AVIATION

Overcast skies with a deep marine layer of IFR-MVFR is expected through the monring with calm southerly winds for the coast. Winds expected to shift northerly during the day with slight chance of clearing during the peak of the day. Overcast conditions expected to return tonight. Inland areas can expect VFR conditions with increased middle to high cloud coverage. Northerly winds are expected to channel through the valleys.

MARINE

The surface pressure gradient between the land and water is expected to increase this afternoon resulting in an increase of northerly winds today. The increase is forecasted to begin south of Cape Mendocino where widespread gusts of 20 to 30 kts are likely. Winds increase further this weekend over the outer waters with near-gale force gusts possible by Saturday night. Nearshore winds remain lighter, especially in sheltered areas with peak gusts of 10 to 20 kts. These winds will force steep seas to form, especially in the outer waters. Steep waves will also propagate into the inner waters. A small craft advisory has been issued for the southern inner waters where as the northern waters remain clear, yet will continue to monitor the situation as these winds build through the afternoon. The northerly winds will decrease quickly early next week as another trough approaches the area.

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from 9 AM this morning to 9 PM PDT Saturday for PZZ455.

Small Craft Advisory from 3 PM Saturday to 10 PM PDT Sunday for PZZ470.

Small Craft Advisory until 10 PM PDT Sunday for PZZ475.