textproduct: Eureka

KEY MESSAGES

* A one more day of high temperatures with bring Moderate HeatRisk across the interior through the week.

* A developing trough will bring much cooler conditions by Friday and the weekend.

* Strong, gusty north wind close to shore and along ridges this weekend.

* No wetting rain forecast for the next 10 days.

SYNOPSIS

Much warmer and drier than normal conditions will persist Thursday with shallow marine influence along shore. Much more seasonable cooler and moister conditions arrive by the weekend alongside strong north winds near shore. Chances for wetting rain remain near zero.

DISCUSSION

Much warmer than normal conditions continue to linger under the influence of weakening high pressure. Many interior valleys again hit just shy of 100 on Wednesday with similar temperatures again most likely one more time Thursday. Such conditions will continue to support moderate to isolated major HeatRisk across the interior but especially Mendocino and Lake Counties. Meanwhile, an especially shallow but strong marine layer will remain along shore with low marine fog and clouds and scattering out in the afternoon.

By Friday, weak low pressure moving over the eastern Pacific will weaken heat and bring generally much more seasonable conditions. On Friday, highs will drop back into the lower 90s with a deeper marine layer along shore. A broad trough and associated surface cold front will further cool conditions by Saturday and into Sunday. High temperatures will drop back into the 70s. Despite the front, essentially no models show any moisture associated with trough. Very light coastal drizzle will be the only precipitation potential as the marine layer gets lifted.

As the trough dips south, there is strong model agreement that there is potential for unusually (EFI values of 0.75) strong north winds Saturday and Sunday. Winds could be particularly enhanced by low pressure detaching from the trough and moving south, though this scenario remains uncertain. NBM shows most likely wind gusts along shore of 35 mph on Saturday. The strongest winds would be on coastal ridges and headlands during the day Saturday. There is a 70% chance of gusts over 45 mph over the King Range and in the coastal waters, though that chance is only 10 to 20% for more populated areas like Crescent City and Humboldt Bay. Winds will most likely keep marine air scattered out along the coast, especially as winds turns slightly easterly by Sunday morning and into early next week.

As winds weaken, clear skies and dry air may allow for freezing conditions in the morning by Monday (20% chance for eastern interior valleys). Ensembles remain dry throughout the extended forecast period (next 10-14 days), though much weaker high pressure will generally result in more seasonable temperatures. /JHW

AVIATION...06z TAF

A very shallow marine layer is again impacting the coast, bringing a thin band of LIFR fog and ceilings to near coastal terminals. LIFR conditions will most likely persist overnight before slowly pulling back by mid morning Thursday. Most models show the pattern finally beginning to weaken this evening with high pressure slowly breaking down. Still, most models still show LIFR marine fog forming Thursday night, albeit slightly less dense. VFR conditions will continue across the interior. /JHW

MARINE

As high pressure continues to stall, moderate winds will remain isolated to the far outer waters. That said, stronger winds just outside the waters will continue to generate some steep mid period seas up to 9 feet. These seas will mostly effect the outer waters with much calmer conditions close to shore. There continues to be be very minor, southerly longer period swells from distant tropical storms.

North winds will quickly increase Friday and push closer to shore as low pressure pushes east of the area. Gusts will most likely be near gale conditions with a 40% chance of proper gales south of Cape Mendocino by Friday evening. Of course, steep short period seas will rise in response. Winds will continue to strengthen Saturday as broad trough dips north of the area. By Saturday, there as 80% chance of gusts over 45 kts in the southern outer waters with gale conditions in the inner waters. Very windy conditions will then persist until at least next Monday. Around Sunday a long period swell around 5 feet at 22 seconds will augment the sea state. If short period seas were not so steep, such a swell would create a significant sneaker wave risk. /JHW

EKA WATCHES/WARNINGS/ADVISORIES

CA... Heat Advisory until 11 PM PDT this evening for CAZ110>114- 118>120.

NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from 9 PM Friday to 3 PM PDT Saturday for PZZ450.

Small Craft Advisory from 3 PM to 9 PM PDT Friday for PZZ455.

Gale Watch from Friday evening through Saturday afternoon for PZZ455.

Small Craft Advisory until midnight PDT Friday night for PZZ470.

Gale Watch from late Friday night through Saturday afternoon for PZZ470.

Small Craft Advisory from 9 PM this evening to 9 AM PDT Friday for PZZ475.

Gale Watch from Friday morning through Saturday afternoon for PZZ475.