textproduct: Eureka

SYNOPSIS

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

KEY MESSAGES

- Temperatures ease through Saturday with only minor HeatRisk

- Slight chance of dry thunderstorms over high terrain of northern Humboldt and Trinity counties Friday morning.

- Warming trend returns next week.

DISCUSSION

An upper level trough approaching the area has helped to more rapidly decrease temperatures today. Most interior valleys have struggled to even reach 80 with increasing marine influence pushing RH over 30 percent. The trough will cross inland tomorrow and bring more cloud cover and further warming.

The trough will also help increase upper level instability. Combined with a moisture surge up the Sacramento Valley, there is potential fro thunderstorms as early as sunrise on Friday morning. High resolution models show a weak convective signature, but chances of actual lightning remain low to moderate at best (15%). Models generally focus convection over northern Humboldt and Trinity counties though just a few want to put storms as far south and west as the King Range. Uncertainty remains very high, as many model sounding show moisture too high in the unstable layer with weak forcing, making lightning potential questionable. That said, these setups or normally poorly resolved by models in both over and under forecast directions. Isolated, surface based storms are possible in the afternoon though chances have generally dropped for those (10%).

Otherwise cool conditions will bottom out on Saturday with gradually warming and non-impactful weather next week. Though temperatures will return to the 90s only moderate HeatRisk is expected. /JHW

MARINE

Winds have generally dropped to gentle or even calm across all waters. Moderately steep short period seas are gradually falling and will generally fall below 6 feet Friday morning. Beyond the wind waves, there is a minor but persistent mid period northwest swell around 4 feet that may be more obvious with the calmer seas. North winds will gradually increase again this weekend with near gale force gusts in the outer waters by Sunday afternoon. These winds will pull closer to shore brining steep short period seas to all waters through early next week. /JHW

FIRE WEATHER

Fire weather conditions have eased substantially all across the area. Temperatures have struggled to get above 80 and RH has risen over 30 percent even for drier valleys. Winds remain generally light.

Increasing cloud cover will help further ease temperature and RH on Friday. That said, ERC values remain around the 85th percentile due to the past heat wave and there is a risk of dry thunderstorms Friday morning. The chance of storms is greatest between about 5 AM Friday and noon. Storms in this period are most likely to form over northern Trinity and Humboldt counties with just a few models (less than 10% chance) placing thunderer further south and closer to the coast. These morning storms would be mostly dry and fast moving. That said, uncertainty remains high with a 50% chance of no convection at all. Storms chances are more limited in the afternoon with less chance for ignitions. /JHW

EKA WATCHES/WARNINGS/ADVISORIES

CA... Red Flag Warning from 8 AM to 7 PM PDT Friday for CAZ403- 406-409-410.

NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 5 PM PDT this afternoon for PZZ450-475.

Small Craft Advisory until 5 AM PDT Friday for PZZ470.