textproduct: Eureka

KEY MESSAGES

* Tropical moisture arrives today and may bring a few showers to Mendocino & Lake Counties this evening through early Friday afternoon.

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

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

SYNOPSIS

Tropical moisture arrives today, bringing slight chances for showers to 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

Tropical moisture from the remnants of Tropical Storm Iselle starts to stream into the area this afternoon and evening. This will primarily affect the southern portions of the area (Lake and southern Mendocino Counties). Some rain may reach the ground with precipitable water values approaching 1 inch, but dry low levels will limit precipitation to a few sprinkles. The first chances for showers would be late this afternoon and early evening. CAMs are not in agreement if these will form, however CAPE of around 100-200 J/kg, while limited, may allow for a few showers to tap into the moisture and a stray lightning strike cannot be completely ruled out. Overnight into early Friday, moisture continues to surge into the southern half of the area, though most models show instability declining to near zero. This will limit any impacts to virga or a stray shower through early Friday afternoon. Moisture moves east Friday afternoon. It should be noted the chances of either showers or thunderstorms are very slim (15% for any rain and less than 5% for thunderstorms), but this is being watched closely as conditions change.

Interior temperatures will be moderated somewhat by this moisture push and the associated mid and high cloud cover. Most interior areas are likely to see high 80s to low 90s. The continuation of the troughing pattern will support a deeper marine layer near the coast while additional moisture will support drizzle overnight along the coast. Stratus is likely to clear, at least partially, in the afternoons through the weekend as breezy northwest winds develop in the afternoons and the marine inversion remains elevated and weak. Coastal high temperatures are likely to remain in the low 60s through the weekend and into early next week as this pattern continues.

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! /JB

AVIATION...(18Z TAFs)

Stratus has retreated to the immediate coastline, but has continued to bring occasional IFR ceilings and visibility impacts into the early afternoon. This is likely to continue though the afternoon until rebuilding this evening, returning more consistent IFR to LIFR stratus impacts. Drizzle will result in lowered visibilities and support fog formation at times through the night. /JB

MARINE

Northerly winds increase today, especially south of Cape Mendocino where widespread gusts of 20 to 30 kts are likely in the lee of the Cape. Winds increase further this weekend over the outer waters with near-gale force gusts possible by Saturday night. Nearshore winds remain lighter with peak gusts of 10 to 20 mph, with locally higher winds in the lee of Cape Mendocino. Steep seas will be associated with these winds and will likely occasionally bring propagate into the inner waters, especially south of Cape Mendocino. 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 Friday to 9 PM PDT Saturday for PZZ455.

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

Small Craft Advisory until 3 PM PDT Sunday for PZZ475.