textproduct: Eureka

SYNOPSIS

Dry and warm continues today. Interior showers and isolated thunderstorms are possible Friday through early next week.

DISCUSSION

High pressure continues to dominate today bringing pleasant weather to the area. High temperatures in many interior valleys could reach the high 70s to low 80s. Coastal temperatures are likely to be cooler with morning stratus potentially persisting into the afternoon and breezy northerly winds in the afternoon. Highs from the mid to high 50s are expected for the coastal areas.

This pattern changes Friday as a trough dips down into the Pacific Northwest. This trough will advect moisture into the area, bringing anomalously high PWATs values of 0.7-1.0". Interior rain showers are possible starting Friday afternoon and evening. CAPE of around 500 J/kg may bring isolated thunderstorms, mainly to northern Trinity and around Siskiyou County, though drier air aloft could stunt thunderstorm growth. Conditions Saturday are similar, if not slightly better for thunderstorm development, with slightly more moisture aloft and more instability. Chances increase Sunday as the low moves southward and brings more moisture into the area. CAPE of around 500 to 750 J/kg will support more widespread shower thunderstorms for much of the interior, including in Trinity, interior Del Norte, interior Humboldt, eastern Mendocino, and northern Lake. Ample moisture with high PWATs does present a low-end flash flood risk should training storms develop, though confidence is low at this point. Bulk shear of around 20 kts could support a few stronger thunderstorm cells bringing frequent lightning, hail, and strong winds. This will need to be watched should this trend continue. Generally east flow aloft is likely to bring these interior showers to the coast by the evening. Thunder may even be heard at the coast! Wetting rain (>0.1") chances are around 50-60% for much of the area outside southern Mendocino and southern Lake Sunday. Additional showers are possible Monday across the northern half of the area. NBM actually has low end chances (20%) of over an inch of rain in the mountains of Del Norte and the King Range Sunday afternoon to Monday afternoon. Showers taper off as ridging likely returns Tuesday into Wednesday. JB

AVIATION...06Z TAFs

In a very similar setup that occurred over the previous 24 hours, stratus has expanded from Humboldt Bay and into the coastal terminals. Southerly return flow from a coastal eddy will also embed stratus up the Del Norte coast into CEC. Unlike last night, a subtle increase in mid level heights will bring higher probabilities (50 to 70%) of lowering to IFR levels after 12Z Thursday. Moss guidance is introducing a chance for a more briefer period of LIFR near 14Z, but confidence is not high (20-30%). MOSS guidance has been too low with CIGS recently. Northerly winds will increase Thursday afternoon, with gusts of 15 to 20 kts forecast. Winds may be lighter around Humboldt Bay where northwesterly flow and moisture pooling looks to lock in the stratus longer throughout the day. If CIGS do manage to lower to IFR heights, improvement to MVFR or VFR would be expected after 20Z.

MARINE

Northerly winds continue to be strengthened over the waters, along with steep seas. Steep seas of 7 to 9 ft are pulsing into the inners as well. Near gale to gale conditions will periodically develop over the waters through Saturday morning. Gale strength gusts will be more persistent around and south of Cape Mendocino. Hazardous Seas Warnings remain over the outer zones to cover the periods of gales and large, steep seas. Conditions hazardous to small crafts are forecast for the inner zones for winds up to 21 kts and periods of steep seas of 7 to 10 ft. An area of low pressure will approach the area Saturday, and the northerly winds will subside through Saturday evening. This will begin an extended period of lighter winds and smaller seas which may carry into next week. An up to 21 second small, long period westerly swell will begin filling in Saturday afternoon. The swell is forecast to peak Sunday at 4 to 7 ft at 17 seconds.

BEACH HAZARDS

On Sunday, a long period northwest swell of around 3 to 6 ft at 16 seconds will arrive. This swell will need to be watched as it may pose a moderate risk of sneaker waves to the area. Should this swell continue as modeled, a Beach Hazard Statement may be needed. Sneaker waves are relatively large, unexpected waves that can sweep across the beach without warning. There may be 30 minutes of smaller waves before a sneaker wave arrives. Avoid steep beaches and jetties and stay much farther back from the ocean. Never turn your back on the ocean! JB

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 9 AM PDT Saturday for PZZ450-455.

Hazardous Seas Warning until 9 AM PDT Saturday for PZZ470- 475.