textproduct: Eureka

SYNOPSIS

Temperatures will continue to cool through Friday with marine influence deepening and pushing more inland. Scattered dry thunderstorms will impact high terrain locations over the interior Friday.

DISCUSSION

Cooling will continue Thursday as a broad trough approaches the area. The trough will help generate some upper level clouds and pull in more marine influence, helping to drop interior high temperatures into the 80s. A deepening marine layer is expected along the coast Thursday morning.

The trough will also aid in increasing upper level instability. Combined with a moisture surge up the Sacramento Valley, there is a chance (10%) of isolated, mostly dry thunderstorms over eastern Trinity Thursday evening. Thunderstorm potential will increase Friday with a 20% chance of isolated dry storms Friday afternoon over northern Humboldt and Trinity counties with a lesser chance extending as far south as the Yolla Bollys. Otherwise, temperatures will bottom out Friday with slight warming into the weekend. Seasonably warm and dry conditions are anticipated this weekend, with mostly unimpactful conditions. Long range models indicate potential for a moderate heatwave next week. /JHW

AVIATION

An upper level low will affect area terminals through the end of the work week. Early this morning, most models indicate a coastal marine layer quickly resurging to create LIFR coastal conditions, though marine layer lifting may push ceilings closer to IFR. Satellite is already showing lower clouds starting to form along the coast. The upper level low will aid in deepening the marine layer through this morning. This means that marine influence will push further inland. In particular, marine stratus could surge up the Russian River Valley this morning which could result in IFR conditions for KUKI.

MARINE

Strong north winds in the outer waters have gradually weakened and continue to push further offshore into very early Thursday morning with short period seas slowly falling mostly below 6 feet by Friday. Winds will be mostly calm Friday with moderate north winds rebuilding and pushing close to shore Saturday and Sunday. /JHW

FIRE WEATHER

A now receding heatwave has left fuels much drier than they were just one week ago with ERC broadly near the 90th percentile across the interior. ERC is forecast to remain high despite increasing RH over the coming days. Overall weather conditions will greatly moderate through Friday with highs mostly in the 80s, increasing marine influence, and RH closer to 30 percent. Winds will remain gentle and terrain driven.

That said, the approaching trough set to bring cooler and more moist conditions to Northwest California will also pull some tropical moisture combined with increasing instability. In combination, these two factors could create some very isolated, mostly dry, thunderstorms Thursday afternoon in far NE Trinity County (10% chance). Small waves rotating around the trough may trigger convection overnight. Some high resolution models hint at weak storm activity in the early morning hours (also 10% chance Friday. Much more robust activity is likely (25% chance) across northern Humboldt and Trinity Counties by Friday evening with lower chances as far south as the Yolla Bollys. Storm motion appears slow and isolated overall, but ignitions are still very likely given the current ERC values. Any storms could also produce some rain and gusty erratic outflow winds. /JHW

EKA WATCHES/WARNINGS/ADVISORIES

CA... Fire Weather Watch from late Thursday night through Friday evening for CAZ403-406-409-410.

NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 3 AM PDT Thursday for PZZ450-470- 475.