textproduct: Eureka

KEY MESSAGES

* 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

Strong north winds will impact the area through the weekend. Dramatically cooler temperatures arrive Saturday, with chances for frost or sub freezing temperatures for the interior through late next week. Chances for wetting rain of at least 0.1 inch remain near 0.

DISCUSSION

High pressure is finally beginning to break down across the area, spelling the end of 6 days straight of much above normal temperatures and shallow marine fog 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, few models show any moisture with front. Some very light coastal drizzle is possible as the marine layer lifts, but chances of wetting rain are below 10%. SOme high resolution models show showers forming along the Sacramento Valley around Sunday, an offshoot of much broader convection in Southern California. That said, general lacking precipitable waters and little to no instability make virga and weak radar returns the most likely outcome.

As the trough dips south, there is strong model agreement that there is potential for unusually (EFI values of 0.85) strong north winds Saturday and Sunday. Winds may be particularly enhanced by low pressure detaching from the trough and moving south, though actually instability with this low is tenuous at best. 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 80% 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). Even the coast has good chances of lows int he low 40s, the coldest of the year so far. 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

The lingering shallow stratus scattered out Friday with the approach of a trough and front. The front will disrupt the marine layer, decreasing the chances for LIFR developing Friday night. IFR to MVFR is more likely at this point earlier in the night. The front may actually effectively scatter out the stratus going into Saturday morning with increasing northerly flow.

Inland areas can expect VFR conditions will gusty afternoon westerly to northerly winds. Winds could be erratic near terrain as well, possibly causing Low Level Turbulence near terminals. The there are some indications that the passing front could drive stratus eastward over the higher terrain and into UKI, potentially bringing a ceiling below 1700 ft AGL. Confidence is low at this time. DS/JJW

MARINE

Strong northerly winds and gale conditions are ongoing over the waters. These winds will strengthen through Saturday, with gusts to 40 kts. Near Storm force gusts will develop south of Cape Mendocino. Steep and hazardous seas of 12 to 15 ft are developing as a result. In addition to very steep short period seas, a moderate, very long period westerly swell will impact the waters around Sunday while gale conditions remain in the outer waters and around Cape Mendocino. Winds will gradually subside early next week while the long period swell very slowly weakens.

FIRE WEATHER

Prolonged much hotter and drier than normal conditions will finally begin to ease today. However due to the lagging nature of heavier fuels, ERC values will crest near the 90th percentile on Friday and Saturday. Such values will most likely be record breaking for October. At the same time, strong north winds gusting 30 to 40 mph will build near shore and along exposed ridges Saturday. Passing low pressure may aid in more moderate winds mixing into usually protected valleys Saturday afternoon. Winds will turn more easterly by early Sunday, helping to further dry conditions and produce poor RH recovery at high elevations. Although by Saturday, conditions will be much more seasonably cool and moist (highs in 70s and RH around 30 percent), the lack of any rain chances and recent drying will still support near record breaking Burning Index values for October around Saturday. All that said, there is potential for much above average fire activity through the weekend. /JHW

BEACH HAZARDS

The first long period swell of the season arrives this weekend. The west-northwests swell will arrive in the Northern California waters Saturday evening with a period over 25 seconds. Swell will then build through Sunday, peaking Sunday afternoon and evening at around 5 feet at 19 seconds. This very long period swell will result in a heightened chance for sneaker waves and run-ups of unusual size through Monday evening.

While the threat for sneaker waves will be persistent throughout Sunday and Monday, the highest risk is expected during periods of incoming tides. With high tides along the California coast at around 11am to 1pm Sunday and Monday along N CA coast. A possitive tidal anomaly is yieling tides around 1 foot higher than predicitons on top of higher than usual tides, adding to the threat.

COASTAL FLOODING

A new moon lunar cycle is bringing higher than usual tides. A positive tidal anomaly of over 1 foot will yeild high tides that will near or reach advisory levels of 8.8 ft for Humboldt Bay Saturday, Sunday, and Monday.

North Spit high tide estimates: Saturday: 8.5 ft at 12:03 pm Sunday : 8.8 ft at 12:32 pm Monday : 8.6 ft at 1:01 pm

EKA WATCHES/WARNINGS/ADVISORIES

CA... Beach Hazards Statement from late Saturday night through Monday afternoon for CAZ101-103-104-109.

NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until midnight PDT tonight for PZZ450.

Gale Warning from midnight tonight to 9 PM PDT Saturday for PZZ450.

Small Craft Advisory until 3 PM PDT this afternoon for PZZ455.

Gale Warning until 9 PM PDT Saturday for PZZ455.

Hazardous Seas Warning until 9 PM PDT this evening for PZZ470.

Gale Warning from 9 PM this evening to 9 PM PDT Saturday for PZZ470.

Gale Warning until 9 AM PDT Sunday for PZZ475.