No foolin': Mother Nature sends another potent storm

No foolin': Mother Nature sends another potent storm
Thursday 10:30 p.m. Update:

The Thursday evening model runs are in and do not show any major changes to the forecast for Friday's anticipated wind and mountain snow event. There is still a little bit of discrepancy in exact track and strength of the storm, but they are all in the realm of the current forecast.

The way it is shaping up, the strong, potentially damaging winds gusting to 60 mph along the Coast and North Interior are pretty much a given and still in the same time frame as the forecast listed below. High Wind Warnings remain in effect for these locations.

However, strong, damaging winds for the Puget Sound area and Southwestern Washington still are not as certain.

If current forecast models were to verify, this is still not looking like a major event for the greater Seattle area -- more along the lines of a "typical" wind storm with gusts of 40-45 mph, maybe some gusts to 50, but even then, as we mentioned, with trees more leafier now, that might cause more damage than a usual storm of this magnitude in the dead of winter.

But since the storm is rapidly developing, there's always a chance it could develop more than anticipated, so the National Weather Service is maintaining a High Wind Watch for the Puget Sound area and Southwestern Washington for a while longer to watch the storm's development, but if everything stays the course, it will likely be converted to a lesser Wind Advisory.

Winter Storm Warnings remain for the Cascades and Olympics. Big snows and strong winds are still on for these areas.

Original story:

SEATTLE -- Mother Nature's April Fool's trick? Moving the calendar five months back without telling us.

We just turned the calendar to April, but looking at the weather charts, you might feel we just waltzed into November instead as a very strong storm is expected to roll into Western Washington on Friday, bringing not only a round of drenching rain, but strong, gusty winds and copious amounts of mountain snow. In fact, the mountain passes could see blizzard conditions Friday afternoon and evening, making pass travel extremely treacherous.

The National Weather Service says it could be the strongest late-season storm since 1997 when a gusty storm rolled in on March 30.

Forecast models show a storm rapidly developing in the Pacific Ocean Thursday, with the storm center coming ashore somewhere between Central Vancouver Island and Forks on Friday morning.

The Windy Details:

In the lowlands, the most noticeable event will be the wind. High Wind Warnings are now in effect for the coast, Northwest Interior and areas along the Strait of Juan de Fuca. A High Wind Warning means sustained winds of 40 mph and gusts to 58 mph or higher are imminent.

The rest of Western Washington, including the greater Seattle/Puget Sound area remains in a High Wind Watch, as there is still enough uncertainty in the storm's track that winds of that magnitude are not a given, but still in the realm. (A Watch means conditions are possible, but not certain.)

Forecast models show the wind will develop along the coast around 3-5 a.m. Friday morning and will be southerly of 30-40 mph sustained with gusts to 60-65 mph possible. Just offshore over the ocean waters, marine Storm Warnings are in effect for gusts to 65 mph near the coastline and 70 mph for spots more than 10 miles off the coast.

Wind will then pick up in the Northwest Interior just before daybreak Friday morning. These will be southeasterly at first and could gust as high as 55-60 mph, although exposed spots on Whidbey Island could see 65 mph gusts.

Once the storm begins to move inland, southerly winds will rapidly increase in the Seattle/Puget Sound area and points south. As of now, the timing window on this surge to begin is about 11 a.m. to 2 p.m. for gusts to begin to roll in.

Paul Deanno's 4W update on the storm.

Here, forecasted wind speeds are a little tricky. Just glancing at the computer forecast models, wind gusts are probably looking at 40-50 mph with maybe a few gusts to 55 mph in exposed spots. That is on the fringe of the "High Wind Watch" criteria so depending on what the models show Seattle could get downgraded into a lesser Wind Advisory. (Read more in the "Meteorological Mumbo-Jumbo section below.)

During this time, it'll still be windy in the Northwest Interior, just the wind direction will veer closer to due south.

By late afternoon, wind speeds will be decreasing in most areas with a few big exceptions: The North Coast, Strait of Juan de Fuca, and Whidbey Island. Depending on how the storm goes, we could get a surge of west wind that rolls along the North Coast, down the Strait and into Whidbey Island. This is always a challenge to forecast, but if things go right, we could see winds of 40 mph gusting to 60 mph in these areas in the afternoon.

For Whidbey Island, this gives you a triple whammy of strong southeast winds ahead of the storm in the morning, strong south winds during the storm in the midday hours, and strong west winds in the storm's wake in the afternoon.

Now, these expected wind speeds are not on par with major windstorms of the past. In fact, in many areas, it might mirror the storm Sunday night. But with trees in bloom, they are more susceptible to toppling over at lower wind speeds.

In other words, a 45 mph wind storm in Seattle in April could do more damage than a 45 mph wind storm in January with blank trees.

The Rain:

Steady rains will develop around midnight and last through evening, then taper to showers. Snow levels are low enough that river flooding is not a concern.

Mountain Snow:

As was the case earlier this week, this storm will bring gobs of new snow to the mountains. But aside from the snow comes the wind and this could cause some real headaches.

A Winter Storm Warning is now in effect from Friday morning through Saturday morning for as much as 1-3 feet of snow in the Cascades and Olympics.

Snow levels will be around 2,500 feet, so it'll be very snowy in all mountain passes. The passes themselves are protected a bit from the southeast and southerly winds during the storm passage, but they are very susceptible to a high west wind in the storm's wake. We could see west wind gusting 40-60 mph in the passes, making for potentially blizzard conditions up there.

This is bad timing with all the Easter holiday travel in the works, so if you need to get over the passes, I'd say either go Thursday night or by Friday morning, as conditions will deteriorate through the day with the brunt of it Friday afternoon and evening. It'll still be snowy on Saturday, but should be much less windy, if waiting until then is an option.

Skiing and hiking will be a challenge too Friday as winds could gust to 80 mph on exposed ridgetops.

The Meteorological Mumbo-Jumbo

In what is indeed looking like a page straight out of November 1st, a strong storm is developing in the Pacific Ocean and heading toward the Pacific Northwest.

As usual with wind events, the storm's track and intensity is key in determining who gets the strong winds and how strong they will be.

The strongest winds are typically associated within the area just to the south of the storm center. Thus, a classic windstorm for our area has a storm tracking right over Forks or southern Vancouver Island, and moving east/northeast to about Vancouver, B.C., putting that strong surge over Western Washington.

A stronger storm intensity that moves farther north can have similar effects as a weaker storm that moves in over this classic path. If a storm goes in too far south (say, the southern or central Washington coast), the Seattle area and points north are typically spared the strong winds and it becomes more of an Oregon storm as the surge passes to our south.

So, what about this storm? One forecast model has it fairly potent (central pressure of 976 mb, or 28.82" on the typical home barometer) making landfall around central Vancouver Island, then brings the storm up north of Whistler. That setup is really windy for the coast and Northwest Interior, but marginally damaging windy for Seattle as it appears the storm will be too far north when its surge comes through. In this case, I'd say winds for Seattle would be on par with Sunday night/early Monday -- gusting 35-45 mph.

Our other main model has been pushing the storm center farther south of late with each successive model run -- the latest model showing a 986 mb storm (29.11") making landfall just north of Hoquiam and pushing across Port Angeles through Bellingham. This storm is weaker but closer to home so it could bring similar wind speeds. The caveat here is that with the model trending this storm south, if it keeps up that theme, we could end up with the scenario where it goes *too* far south and this is a non-event for Seattle north, and mostly an Oregon/SW Washington deal.

None of these events spell a major widespread "name that storm" type of event (which is too bad it's not today because an "April Fool's storm" would be kinda neat). To compare, past historical Top-of-the-chart windstorms typically have had central pressures between 955 and 970 millibars. Another trick I've talked about in prior wind storm events is gauging the pressure difference between Portland and Bellingham, which is not a perfect measure of a wind storm as there are plenty of other factors involved, but I like using it for general comparison's sake.

Our big kahuna wind events have had these differences be between 18-22 mb with the record being the 2006 Hanukkah Eve storm that reached 23.2. I'd say a "typical" wind event has this number in the low teens, and models now gauge this storm between 11-13 mb. So noticeable, but not looking catastrophic.

That said, we always have to keep our eye out as anytime you have a storm rapidly developing and forecast to make landfall somewhere between Hoquiam and Central Vancouver Island, it bears watching in case it develops more than the models think it does. We'll have our eyes glued to the satellite, surface weather charts, and latest forecast models. (This is where not having land out to our west is a big disadvantage. It'd be nice to have more than just a few ship reports and buoys out there to let us know some pressure readings where the storm is developing. If only whales could e-mail!)

What Happened In The 1997 Storm?

We alluded earlier that the National Weather Service says this at least has potential to be the strongest late-season storm since March 30, 1997.

Not to say this storm will be on par with that storm, but here is the storm report from the National Climatic Data Center, to give an idea of how strong storms can be in early spring:

That storm had two deaths -- one from a fallen tree onto a pickup truck and a canoeist who died when his canoe overturned on Burley Lagoon. About 160,000 lost power and three homes were damaged by fallen trees. Gusts on the coast reached 60-70 mph, the Hood Canal Bridge hit 71 mph and Bellingham hit 60 mph.

Calming Saturday

By Friday night, rain and wind will be tapering off, although snow will continue to fall in the mountains. By Saturday, we are expecting just a mix of showers and sunbreaks -- something a little more typical of April.