textproduct: Eureka

SYNOPSIS

Stratus remains over coastal areas Monday. A cold front approaches the area Monday evening bringing light rain and cooler temperatures with gusty winds. Chances for thunderstorms increase Tuesday and Wednesday.

DISCUSSION

Stratus remains persistent as coastal eddies recirculate the marine layer towards the lower elevations along the coastline. Stratus will keep temperatures chilly along the North Coast. Inland areas can expect more normal temperatures between 75- 80F. Southerly winds will increase through the day as a cold frontal boundary approaches NW CA.

This cold front will increase the likelihood for rain in Del Norte and Humboldt counties beginning this afternoon. Rain totals look mostly benign through the storm with even the more extreme models (75th percentile) showing between 0.25-0.5" in Del Norte Co. and <0.25" for Humboldt County. Little to no rainfall is forecasted for areas outside of coastal Humboldt and Del Norte County. Winds will increase in the wake of the front beginning Tuesday and Wednesday afternoon with gusts up to 30mph likely and up to 40mph possible. Temperatures Tuesday will be below normal before a warming trend forms through the end of the week.

The back side of the approaching low will also prime the atmosphere for continued convective thunderstorm activity. The upper level trough will increase atmospheric instability over the area. PWAT values are forecasted below normal which seems to be the limiting factor for thunderstorm development. That said, a few thunderstorms are possible each afternoon Tuesday through Friday, especially in Trinity County. DS

AVIATION

Another night of status remains as the marine layer holds strong. IFR to LIFR conditions are forecasted for tonight through most of the day tomorrow. A cold front approaching around 22- 00Z will most likely deepens the marine layer to MVFR levels. Slight visibility degradation is possible from the beginning of the frontal passage until around 04-06Z, especially for the North Coast. Prefrontal southerly winds, with increased likelihood of LLT (25kts @ 2.5 kft AGL), will shift quickly to W-NW surface flow in the wake of the frontal boundary. Inland areas outside of large river valleys can expect VFR until this frontal boundary Monday afternoon. DS

MARINE

Moderate southerly breezes expected through Monday morning. Seas are dominated by a decaying NW swell at around 3 to 5 ft. A fairly dry, weak cold front will pass over the coastal waters Monday evening. Prefrontal southerly winds will increase with brief gusts up to 20kt before shifting to breezy NW winds in the wake of the front. Seas are expected to rapidly increase as strong NW winds continue to fill in behind the front. Buoys in the Northern Pacific are recording seas over 18ft as northerly mid period waves build with local wind waves. These are the first observations associated with this frontal system and will help impact the wave height forecast based on future observations. Nevertheless, expect seas early this coming week to build substantially. The largest seas and strongest winds are forecasted for the southern outer waters where there is an 80-100% probability of gale force winds developing by Tuesday with gusts up to 45kts possible Tuesday and Wednesday afternoon. Winds are likely to remain strong for much of the next week. Expect multiple warnings to be hoisted if this forecast stays on track. DS

FIRE WEATHER

A cold front is expected to arrive to the area Monday night. All but the most aggressive models show not enough CAPE for storm activation today. Values increase Tuesday for Trinity County and Wednesday for Del Norte and Lake counties. Sustained winds around 25mph with gusts up to 40mph at ridgetops late Tuesday evening pick up again Wednesday afternoon for Del Norte and Lake. Low to moderate CAPE values coinciding with the gusty winds in Lake county for zones 418 and 421. RH values down to 25% with the possibility of wet convective cells. /EYS

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from 9 PM this evening to 3 AM PDT Wednesday for PZZ450-455-470-475.

Gale Watch from late Tuesday night through late Wednesday night for PZZ475.