textproduct: Eureka

SYNOPSIS

Breezy to strong gust winds this afternoon, followed by strong to damaging south winds tonight into Sunday. Light to moderate and locally heavy rain, and mountain snow for elevations above 4500 feet on Sunday. Another frontal system is expected to bring a prolonged period of moderate to heavy rain and gusty winds Monday through Tuesday night.

KEY MESSAGES

* Strong to damaging southerly winds will bring an increased risk of downed trees and power outages today through Sunday morning. Strongest winds expected tonight into Sunday.

* Light to moderate and locally heavy rain on Sunday, with the heaviest amounts in Del Norte and Humboldt counties. Snow levels beginning about 4500 feet, rising to above 6000 feet Sunday evening.

* Another frontal system will bring moderate to heavy rainfall, mountain snow above 6000 feet, and strong gusty winds Monday through Tuesday night.

* Increased risk for minor flooding of small creeks and streams and urban areas with poor drainage early next week.

DISCUSSION

A 989 mb surface low, located well offshore of the Northern California and Southwest Oregon coasts (near 41N 130W), is strengthening rapidly while tracking north- northeast toward the NEPac. Breezy to strong gusty south winds are occurring over the coastal headland and exposed ridges, as well as a long the channeled terrain, especially in Del Norte and Humboldt counties. Gusts from 40 to 55 mph have been observed this afternoon over the coastal headlands and exposed ridges in Del Norte, Humboldt and northern Mendocino. Even around the Humboldt Bay, strong gusty winds up to 40 mph have been reported. As of 1 PM PST, the strongest wind reported was 64 mph at the Upper Bear River Road station in Cape Mendocino. These southerly winds are promoting afternoon temperatures up to 10 degrees warmer compared with yesterday's readings, especially along the North Coast.

Southerly winds will continue to increase and spread southward into Mendocino Coast through late tonight, with the strongest gusts expected tonight into Sunday with a strong pressure gradient along the NW California coast. Gusts up to 50 mph is expected for the Humboldt Coast, Mendocino Coast and northern Mendocino Interior. Up to 70 mph gusts are forecast for the coastal headland and exposed ridges in Del Norte and Humboldt County, with locally up to 80 mph possible over the more prominent exposed ridges. Even Del Norte Coast is expected to be impacted by damaging winds up to 60 mph tonight into Sunday. A High Wind Warning remains in effect for interior Humboldt, the King Range, and Del Norte County, including the coast. A Wind Advisory is in effect for the Humboldt Coast, Mendocino Coast, and portions of Northern Mendocino Interior.

Precipitation chances will increase Sunday morning as a frontal system couple with southwest moisture flux begin to move onshore. Rain with high elevation snow is expected with this event. CAMs continue to show a narrow line of organized convection activity approaching the area early Sunday. A few thunderstorms are possible with this line with shallow instability Sunday morning, especially over the coastal waters and nearshore coast. Expect light to moderate and locally heavy rain, with the heaviest rainfall expected in Del Norte and Humboldt counties. The HREF probability of 6 hours precipitation greater than 1 inch is around 45 to 75% for localized and confined to the southwest facing higher slopes in Del Norte County from 5 AM to 11 AM Sunday (2/22) local time. Rainfall total amounts with this system range from 1.5 to 2.5 inches in Del Norte....although it is expected to drop off fairly quickly. Meanwhile, 0.5 to 1 inch in Humboldt county, with locally up to 1.5 in the King Range. The lowest amounts may be less than a half of an inch is forecast for the valleys in Trinity, Lake county and Mendocino with this system.

Snow levels continue to gradually rise up to 4000 to 4500 ft by this evening and into Sunday. This will limit snow impacts mainly to Highway 3 at Scott Mountain Pass, where up to 10 inches of snow is expected. A Winter Storm Warning is now in effect for elevations above 4500 feet from 10 PM this evening to 4 PM Sunday. Snow levels continue to rise and are likely to be above 6000 ft by Sunday night. Snow levels continue to rise to above 8000 ft into early next week.

The next frontal system along with a moderate Atmospheric River (IVT's greater than 500 kg/m/s) is expected to impact the area Monday through Tuesday night. This have the potential to bring widespread moderate to heavy rainfall. There remain regarding the specific details at this moment. 48 HR NBM probability now indicates an increasing 60-90% chance of precipitation exceeding 2 inches across Del Norte, Humboldt, southern Trinity and northern Mendocino counties from 4 AM Monday through 4 AM Wednesday, and a 25-40% chance for around Humboldt Bay and lowest elevations in southern Mendocino and Lake counties. In addition, this system is expected to bring another round of gusty to strong south winds Monday night into Tuesday, especially for the coastal headlands and exposed ridges along the North Coast. Stay tuned! /ZVS

AVIATION...18Z TAFs

Main threats are low level wind shear and turbulence. A frontal boundary will bring periods of moderate rainfall to isolated and brief heavy rainfall after 12Z. VFR to MVFR CIGs and VIS will be maintained outside of TEMPO heavier precipitation rates.

A passing strong area of low pressure and frontal system is increasing southerly winds. Wind gusts of 30 to 40 kts will are occurring over much of Del Norte and Humboldt counties. Winds aloft near 2000 ft AGL of 50 to 70 kts will create a high risk for dangerous low level wind shear and turbulence. Winds aloft and through the surface will slowly begin weakening after 14Z Sunday, but southerly winds of 35 to 45 kts near 2000ft AGL will remain a hazard into Monday morning. Downsloping southeasterly winds are raising ceiling heights. Chances for MVFR ceilings increase to 55 percent after 12Z Sunday. JJW

MARINE

Storm conditions are underway over the outer waters and around Cape Mendocino, wile solid Gale gusts and localized Storm gusts continue in the inners. Southerly winds will be particularly strong in the northern outer water (zone 470) where high end storm conditions with gusts up to 60 kts are likely occurring. Satellite estimated winds (scatterometer) estimated sustained winds of 45 kts at the 11:30 am pass, and further strengthening is highly likely to have occurred since then. Seas are very steep, large, and hazardous. Seas will be particularly large in zone 470, up to 25 ft through Sunday morning. Winds and seas will slowly subside Sunday, but gale strength gusts will linger over portions of the waters through Sunday.

A secondary front will begin increasing southerly winds to better coverage of 34 kt gusts Sunday night through Monday. An extension of the Gale Warnings in st least zone 470 may be required to cover this. A Hazardous Seas Warning would be required otherwise for multiple zones for steep seas of 13 to 15 ft.

Another strong front will crank up the southerly winds Monday night through Tuesday, with sustained winds up to 34kts. A Gale Warning can be expected through that period. Winds and seas will finally begin to subside late Tuesday. This break in large seas and strong winds looks to carry through much of next week as a shift to northerly wind direction develops. JJW

EKA WATCHES/WARNINGS/ADVISORIES

CA... High Wind Warning until 10 AM PST Sunday for CAZ101-102- 104>106.

Wind Advisory until 10 AM PST Sunday for CAZ103-109-110-112.

Winter Storm Warning from 10 PM this evening to 4 PM PST Sunday for CAZ107.

NORTHWEST CALIFORNIA COASTAL WATERS... Gale Warning until 11 AM PST Sunday for PZZ450.

Gale Warning until 1 PM PST Sunday for PZZ455.

Storm Warning until 4 AM PST Sunday for PZZ470-475.

Gale Warning from 4 AM to 11 AM PST Sunday for PZZ470-475.