textproduct: Eureka

KEY MESSAGES

* Thick smoke remains stuck around the Hoopa Valley stretching from as far north as to Orleans as far south as Burnt Ranch. Weak transport winds will keep smoke here through the week.

* Interior temperatures peaking Tuesday will ease through the week with persistent marine influence along shore.

* Another trough is expected to bring below normal temperatures and very slight potential for a isolated thunderstorms Friday.

SYNOPSIS

Warm temperatures will ease through the week thanks to increasing marine influence. Marine clouds will persistent along shore with some slightly better clearing chances late week.

DISCUSSION

High pressure hung on a bit longer than initially forecast with the warmest interior valleys again grazing 100 today. Besides a thin and slow to recede marine layer near shore, clear skies and gentle west winds have persisted. Smoke has continued to sock in valleys around the MP18 fire in Hoopa with smoke pushing up the Trinity River with afternoon terrain winds.

An elongated trough will gradually approach shore through the end of the week. This will help push marine influence further inland and weaken high pressure, allowing interior highs to pull back into the upper 80s by late in the week. Increasing marine influence will most likely help strengthen and deepen the marine layer along shore. A deeper and slightly more unstable marine layer may allow for better scattering in the late afternoons. The trough will certainly bring a string of high clouds across the area around Friday, helping reinforce cooler temperatures. There is potential for very isolated, weak thunderstorms along the trough Friday, but instability appears lacking in all models. Although there will be gusty southerly winds aloft, no model shows them mixing to the surface where weak north and west winds will persist. Most long range models show high pressure then at least briefly rebuilding this weekend. /JHW

MARINE

Moderate north winds in the outer waters have just started to begin easing today. Though some stronger winds will remain in the southern waters, few gusts over 20 kts are expected in the northern out waters by late tonight. Steep short period seas will remain in the outer waters through early Thursday, before calming significantly through the day. Beyond short period seas, a very minor 2 foot, mid period southerly swell and a mid period, 2 foot, westerly swell are augmenting the sea state. North winds gradually ease through the week with particularly calm conditions in the northern waters by Friday. /JHW

FIRE WEATHER

Hot and dry weather held on for one more day longer than initially forecast with the hottest valleys reaching near 100 F and some RH values in the upper teens. Thermal belts, however, are expected to begin weakening tonight, slightly improving poor mid and upper slope recoveries. Winds remain weak and terrain driven. Conditions will generally ease through the end of the week with increasing marine influence. Weak transport wind will continue to allow smoke accumulation around the MP18 fire in Hoop and up the Trinity River Valley, creating some extra, localized moderation of conditions.

The greatest forecast challenge remains thunderstorm potential around Friday. There is high ensemble confidence that a strong stream of midlevel tropical moisture will push across the area from the southwest early Friday morning and through the day. At the same time, a strong southerly jet forming offshore and aligning with topography could provide and lift and enhance instability to allow for thunderstorms. Even with this dynamic forcing, however, few models are showing any instability. A couple of high resolution models today are showing areas of minor MU CAPE less than 100 J/Kg. Soundings reveal very narrow areas of mixing into the freezing layer that will make lightning formation unlikely. There remains a very slight (5-10%) chance of lightning in northern Trinity and eastern Humboldt Counties Friday morning and afternoon, but coverage would be sporadic and very isolated. Any lightning that does occur will be dry, increasing fire risk. This forecast could quickly change if a source of instability materializes. /JHW

EKA WATCHES/WARNINGS/ADVISORIES

CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 5 AM PDT Thursday for PZZ455.

Small Craft Advisory until 9 PM PDT this evening for PZZ470.

Small Craft Advisory until noon PDT Thursday for PZZ475.