Pacific Northwest Storm Parade, Including Remnant of Typhoon Songda, Could Bring Destructive Winds, Flooding, Huge Waves

Brian Donegan
Published: October 12,2016
A series of Pacific storms, one fueled by a remnant of a typhoon, will hammer the Northwest into the weekend, with the potential for destructive winds, flooding rain, huge waves and coastal flooding in Washington, Oregon and far northern California.
This is the time of year when the dry season leaves the Pacific Northwest behind and the Pacific storm track begins to make its periodic migration south into the Northwest U.S.
The first signs of this pattern are now taking shape, marking the beginning of a parade of storm systems well into next week. A storm system hitting the coast this weekend will be associated with the remnants of western Pacific Typhoon Songda.
(MORE: Where the Planet's Most Intense Tropical Cyclones Most Frequently Happen)
High wind watches and warnings have been issued by the National Weather Service in parts of the West, as far south as the Sierra and east-facing front range.

Current NWS High Wind Alerts

Timing the Storms

The first Pacific front will continue pushing inland into Thursday, bringing a period of rain and wind.

Current Satellite, Winds, Surface Pressure

A stronger impulse of low pressure will push a secondary cold front into the Pacific Northwest later Thursday into Friday, bringing another round of heavy rain and strong winds, especially along the coast and in the mountains.
(MAPS: 7-Day Forecast Highs and Weather)
The third, and strongest, frontal system will impact the Northwest Saturday. This system will be the remnants of Typhoon Songda, with a potentially dangerous threat of damaging winds, flooding rain and coastal flooding.

Here's a breakdown of what to expect and when to expect it:

• Into Thursday morning: A steady period of rain develops from west to east across Washington, central and western Oregon and northwest California.
• Thursday-Friday: A stronger pulse of heavier rain and strong winds surges into Washington, Oregon and northern California Thursday, spreading at least some rain and high-mountain snow into Idaho, western Montana, Nevada and central California. Some very high-elevation snow is also possible from the Cascades (above pass level) into the northern Rockies. High winds are expected along the immediate coast of Washington and Oregon with some strong gusts also possible in the interior later Thursday. Friday should offer a bit of a break in the Northwest.
• Saturday-Sunday: A powerful storm will track near or over parts of the Pacific Northwest Saturday, with effects lingering into Sunday. The strongest winds would occur immediately ahead of and behind the time the front sweeps through, particularly along the coast. Heavy rain, coastal flooding and at least some high-mountain snow are also expected, lingering into Sunday.

(FORECAST: Seattle | Portland | Spokane | Boise)

Destructive Winds, Flooding Rain and Snow Impacts

Of greatest concern is the threat for damaging winds with Saturday's storm, a remnant from Typhoon Songda, known to give rise to destructive Pacific Northwest windstorms in the past.

Potential surface setup for the Pacific Northwest storm.

In this scenario, low pressure deepens rapidly near the Pacifc Northwest coast. The uncertainty is in how widespread the damaging winds will ultimately become. This depends on the exact track of the rapidly-deepening low Saturday.

Two Possible Northwest Windstorm Scenarios

Scenario 1	Low stays much farther offshore, then heads to N. Vancouver Island	Some strong gusts in Seattle-Eugene corridor still possible
Scenario 2	Low moves inland over Washington state or western Oregon	Stronger, more damaging winds inland, including the I-5 corridor.

In either scenario, damaging winds are likely Saturday along the immediate coasts of Washington and Oregon, with power outages and downed trees.
As you can see, an inland track would bring more widespread power outages to the Pacific Northwest, along with wind gusts well over 70 mph. It is too soon to tell if this will occur.
(FLASHBACK: Nov. 2015 Northwest Windstorm)
The heaviest rain is expected to fall near the coast and below snow level in the coastal ranges, Olympics and Cascades, where over a foot of total rainfall is possible through the weekend.
This will trigger flooding, especially in urban and poor-drainage areas, and along flood-prone rivers such as the Skokomish in western Washington.
Leaf-clogged drains could also worsen the situation since leaves are slowly beginning to fall from the trees; water will not be able to adequately flow into storm drains if leaves are clogging them.
(MORE: When Does Your City See Peak Fall Color?)
Farther inland, in places like Seattle and Portland, Oregon, 3 to 5-plus inches of rain is possible, and localized flooding can't be ruled out.

Rainfall Forecast

These strong winds from a parade of storms will likely produce huge waves off the Northwest coast, in excess of 30, if not 40 feet. Pounding surf is likely to lead to coastal flooding, beach erosion and some damage, as well.

Forecast Wave Heights Saturday PM

Some snow could fall over the higher elevations of the Cascades in Washington and the northern Sierra Nevada of California. It also appears some higher-elevation snow is possible in the mountains of Idaho, western Montana and western Wyoming.

MORE: Pacific Northwest Storms