textproduct: Eureka

KEY MESSAGES

* High pressure offshore builds tonight into Monday, increasing northerly winds.

* High pressure is expected to bring warmer temperatures and dry weather Monday and Tuesday.

* Cooler temperatures and a 5 to 10 percent chance of thunderstorms in Trinity county are expected Wednesday afternoon and overnight.

SYNOPSIS

Surface high pressure building offshore will strengthen the onshore pressure gradient against the interior thermal low into early next week. This pattern will keep a shallow marine layer pinned along the coast while bringing dry, seasonable warmth back to interior valleys. An upper low will bring cooler temperatures and slight chance for interior thunderstorms Wednesday afternoon and overnight.

DISCUSSION

An upper level trough is moving through the Pacific Northwest. This brought a few showers to Humboldt and Del Norte counties this morning. As of 1:30 PM just a few clouds remain. Later this afternoon and tonight these clouds are expected to diminish with the loss of daytime heating and high pressure starting to build into the area. This will bring some offshore flow to the coastal areas. The temperatures aloft remain cool making the marine inversion weaker. Still it looks like there will be some coastal stratus that forms around Humboldt Bay and the Eel River Delta, but confidence is low on the extent of the coverage of this. Farther inland will see cooler overnight temperatures and there is a slight chance for frost in the valleys of eastern Trinity county, especially Hayfork. Currently the forecast is around 37 and frost is not expected, but it will be close.

Monday and Tuesday as weak high pressure builds in and afternoon temperatures warm up again in the inland areas. After today's highs in the 70s inland temperatures are expected to warm by 10 degrees in many areas with highs in the mid 80s to low 90s Monday and slightly warmer on Tuesday.

Wednesday evening an upper level low drops south over the area. This is expected to keep temperatures a few degrees cooler on Wednesday and could bring some clouds to the area. At this point it looks to remain too dry to see much rain, although a few convective showers are possible in the evening. There is some instability which could bring the potential for a thunderstorm or two late Wednesday afternoon or overnight. The highest chance looks to be in Trinity county, but this will need to be watched as it gets closer. Currently there is only a 10 percent chance of a thunderstorm even in Trinity county. The models are still struggling on the exact location of this low and even a small shift could change the potential for precip or thunderstorms. So this will need to be watched as it gets closer. Thursday the low will keep temperatures slightly below normal, but it generally looks dry as the low starts to move out of the area. If it starts to slow down this could possibly allow some precip to linger into Thursday morning.

Seasonable warm inland temperatures and dry weather area expected to return Friday and into the weekend. MKK

AVIATION

There are a few lingering clouds in Humboldt and Del Norte counties this afternoon. These could impact ACV and KCEC briefly this afternoon, but more likely they will remain farther inland. These clouds are expected to diminish quickly when the sun goes down. Tonight some offshore flow and a weak inversion is expected to keep the marine clouds fairly limited. They may form briefly around sunrise at KACV and with a low chance at KCEC. Monday afternoon breezy afternoon winds are expected as high pressure builds into the area. MKK

MARINE

High pressure is building into the area and this is expected to switch winds to the northwest and then more northerly tonight. These are expected to increase to around 25 to 30 on Monday with the stronger winds in the southern waters. A few gale force gusts are possible in the lee of the capes, but at this point they are not expected to be widespread enough to warrant a gale warning. The winds do make their way into the southern inner waters Monday afternoon, but will likely push farther offshore Monday night. The northern inner waters are not expected to see widespread winds over 20 kt to warrant a small craft advisory, but the steep seas could exceed 6 feet and this may require a small craft advisory.

Wednesday winds and seas are expected to rapidly diminish. For now it looks like this will happen Wednesday evening and overnight, but this may still change slightly. A small upper level low is dropping south over the are and a small shift in the track could change the winds quite a bit. Thursday and Friday fairly light southerly winds are expected before northerly winds return and start to increase for the weekend. MKK

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from noon Monday to 3 AM PDT Tuesday for PZZ455.

Small Craft Advisory from 3 AM Monday to 3 AM PDT Wednesday for PZZ470.

Small Craft Advisory from 6 PM this evening to 3 AM PDT Wednesday for PZZ475.