Flood warnings now issued for some rivers

Flood warnings now issued for some rivers
SEATTLE -- Someone needs to tell Mother Nature there is a happy medium.

After 23 consecutive days of at or below normal temperatures, we swing to the other end of the pendulum with a very wet and warm "Pineapple Express" type storm that promises a solid 48 hours of nearly non-stop rain for western Washington.

But aside from the rain, snow levels will rise quite high -- to 5,500-6,000 feet, meaning it'll be raining heavily across the mountains as well, adding water to the rivers instead of sticking to the hills in the form of snow.

FLOOD WARNINGS are now in effect for several rivers, meaning flooding is occurring or imminent. Here are the forecasts for those rivers currently on Flood Warning. All others remain on Flood Watch:

Near Record Crest:

Newaukum near Chehalis

Major Flooding Forecast:

Tolt near Carnation
Snoqualmie near the Falls
Snoqualmie near Carnation
Skokomish near Potlatch
Bogachiel near La Push

Moderate Flooding Forecast:

Skagit near Concrete
Skagit near Mount Vernon
Stillaguamish at Arlington
Puyallup near Orting

Minor Flooding Forecast:

Stillaguamish (S. Fork near Granite Falls)
Nooksack at N. Cedarville
Nooksack (S. Fork at Saxon Bridge)

Forecasting models suggest as much as 10-20 inches of rain could fall on the southwest and west facing slopes of the Olympics, and 5-12 inches could fall in the Cascades.

In the lowlands, we could see 4-6 inches of rain along the coast and southwestern Washington, around 2-4" in the Puget Sound region (higher totals as you go south and east) and 1.50-3" in the North Sound Interior and along the Kitsap Peninsula, where the Olympic Mountains will provide a bit of an umbrella in the form of a rain shadow.

(Quick aside to show how much moisture that is, if you use the general calculation, had this been snow, 4-6" of rain would equate to nearly 3-5 feet of snow)

Rain will begin heaviest from about Seattle north through Tuesday, putting most of the initial rains in the Olympics and North Cascades. As we get into day 2 Tuesday night and Wednesday, the "hose", if you will, will drift south and continue soaking the Olympics but now add heavy rain to the central and southern Cascades.

Flooding is possible on all mountain fed rivers, and we could see some urban river and creek flooding as well. Rain will taper off during the day Thursday.

In addition, winds will be gusty with the storm as well. We've had a wind gust recorded at 61 mph at Alki Beach; 52 mph at Magnolia and Sand Point, 51 mph in Issaquah and 48 mph along the 520 Bridge. Most other areas have been continually gusting to 35-40 mph. A Wind Advisory is in effect through Wednesday morning as the storm will keep it gusty in about this range through the afternoon and night.

The wind has knocked out power to a few areas. Puget Sound Energy reported isolated outages in Factoria, Issaquah, Enumclaw, Mercer Island and northeastern King County, but didn't have exact numbers.

Landslide Risk Is Considerable

The heavy rain, combined with the soaking effect of the recent and long-lasting dense snowpack, has really saturated soils. Thus, the risk for landslides is considerable for the rest of this week. Those who live on steep hills or near cliffs should monitor the surrounding area for signs of a slide.

Also, those who have rail travel plans should plan for potential delays as if a slide blocks a rail track, service will be automatically suspended for 48 hours.

Avalanche Danger Extreme in Mountains

The Cascades have seen several feet of snow in the past few days, and now adding rain on top of that snowpack will make for a very unstable situation.

An AVALANCHE WARNING is in effect for the Cascades. Backcountry hiking or travel is extremely discouraged, and mountain pass highways could face continuing occasional closures for avalanche control.

However, ski resorts remain open and safe as the ski runs are constantly monitored and controlled to mitigate any potential avalanches.

However, going into any out of bounds area or ignoring warning signs and skiing in marked off areas is extremely risky.

Flooding Resources

Current Weather Information:

General Flooding Information:

What is a "Pineapple Express"?

The "Pineapple Express" is when we have a weather system that has its origins from the Hawaiian tropics (Get it? 'Pineapple' for Hawaii? Who said weathermen don't have a sense of humor?)

You can usually see it on a satellite photo, where the band of rainfall stretches from the Pacific Northwest all the way southwest to near Hawaii.

These tend to be the wettest-type of storms we get around here -- bringing between 1-2" of rain per day for Seattle and much more near the mountains -- as it has an abundance of warm, tropical moisture.

It also brings high potential for flooding, as the warm air tends to raise snow levels quite high around here. That has two compounding effects:

1) It means precipitation falls as rain instead of snow in the mountains, increasing the run-off into the local rivers.

2) It will also begin to melt the snow at lower mountains altitudes, adding even more liquid water into the mix.

Why Is The North Sound Getting Less Rain?

This storm will not be quite as wet for the North Sound area, due to the Olympic Rain Shadow.

The Olympic Mountains act as a wall that protects the northeastern Olympic Peninsula and San Juan Islands from the bulk of the rain that moves into the Pacific Northwest.

The dominant airflow during this storm will be from the southwest. As that air runs into the southwestern face of the Olympics, the mountains push the air upward.

As the air lifts, it condenses and squeezes out its moisture -- think of it as the mountains acting like a sponge soaking up and then squeezing out the rain. That's the reason there are vast rain forests on the southwestern side of the Olympics. They receive over 200 inches of rain a year.

On the flip side, once the air reaches the Olympic Summit, now it's pretty much lost its moisture. As it goes over the top of the mountains and comes down the northeastern slopes, it sinks. And just like rising air condenses, sinking air dries out as it encounters warmer air near the surface. So you already have semi-dry air becoming even drier.

Here is a forecast model chart of the expected rain at 5 a.m. Wednesday. I put red arrows to simulate the air flow over the mountains. Note the cone of dryness over Seattle and the North Sound, stretching west toward Sequim.

And, of course, Sequim sits on the northeast side of the Olympics, so they are almost always in this dry slot -- although the shadow affects Port Townsend and the San Juan Islands as well. Sequim only gets about 18 inches of rain a year. Meanwhile, just 90 miles to the west, Forks receives over 120 inches of rain a year.

One interesting statistic: Port Angeles receives about 27 inches of rain a year. However, for each mile you go west of that city, you pick up an extra inch of annual rainfall. And again, looking at that chart, you can see how the area along the Strait of Juan de Fuca gets wetter as you go west.

When Do We Dry Out?

The rain should taper off as we get into the midday hours Thursday. It then looks like Mother Nature finally finds that "happy medium" as we go dry for a few days, with near normal temperatures.

Better late than never!

Specific River Flooding Information and Forecasts:

Bogachiel near La Push
Carbon at Fairfax
Cedar near Landsburg
Cedar near Renton
Chehalis near Grand Mound.
Cowlitz at Packwood
Cowlitz at Randle
Deschutes near Rainier
Newaukum near Chehalis
Nisqually near National
Nooksack at Ferndale
Nooksack at N. Cedarville
Nooksack (S. Fork at Saxon Bridge)
Puyallup near Orting
Puyallup at Puyallup
Satsop near Satsop
Skagit near Concrete
Skagit near Mount Vernon
Skokomish near Potlatch
Skykomish at Gold Bar
Snohomish near Monroe
Snohomish near Snohomish
Snoqualmie near the Falls
Snoqualmie near Carnation
Stillaguamish at Arlington
Stillaguamish (North fork near Arlington)
Stillaguamish (S. Fork near Granite Falls)
Tolt near Carnation