An updated weather advisory from the National Weather Service said wintry conditions will likely continue throughout Thursday night and into Friday morning. But the temperature is expected to climb into the mid-40s by Friday afternoon, bringing more rain to the region into Friday night and Saturday morning.
That mixture of warmer temperatures and anywhere from a half inch to two inches of rain will create river and lowland flooding.
The warm up will cap an historic week of weather that left its mark on the region.
Falling ice-covered trees and branches knocked out power to some 300,000 people, most of them Puget Sound Energy customers.
Officials with the utility said crews were scrambling to restore service to more than 270,000 homes and business. About 150 line crews were already working on restoration efforts, and another 140 crews were being brought in from California.
No estimated times for restoring power were given, but officials said it could be days for some customers due to the wide-spread damage and sheer number of outages.
Other power providers were dealing with comparatively smaller outages, but Snohomish PUD, Tacoma Power, Seattle City Light and Mason County PUD were all trying to restore service to thousands of customers.
In addition to the chance of more freezing rain overnight, a flood watch kicks in Friday afternoon for several counties of Western Washington, including Grays Harbor, Clallam, Island, Jefferson, San Juan, Skagit, Whatcom, King, Kitsap, Lewis, Mason, Pierce, Snohomish, Thurston. The flood watch will continue through Saturday afternoon.
The Skokomish and Chehalis rivers are expected to rise above flood stage between Friday night and Saturday evening. All areas could see excessive surface runoff with ponding of water, ponding around clogged drains or culverts and small streams going over their banks.
The hardest-hit spots will be in the areas of deep lowland snow and heavier rain, such as the Southwest Interior.
Many school districts have already announced that they will be closed on Friday due to the continuously treacherous conditions.
The updated forecast comes after an epic Pacific Northwest ice storm swept in, coating snow-covered Western Washington with freezing rain on Thursday and bringing much of the state to its knees.
Roads and highways were closed and Sea-Tac Airport temporarily halted all flights for several hours. The airport also said fluctuating weather conditions are forcing it to cancel 50 flights on Friday.
One man was killed by a falling tree near Mirrormont.
Gov. Chris Gregoire proclaimed a winter storm emergency that would allow the activation of the Washington National Guard, if needed, and free up state agencies to take extraordinary steps to help local jurisdictions during the current winter storm.
City of Seattle officials urged anyone still working in the city to get home before darkness and ice conditions get worse, and Tacoma officials declared a state of emergency as the city remained coated in ice.
In McCleary, the roof covering half of a school building annex collapsed under the weight of snow and ice. The building is used for storage and no one was inside at the time, officials said.
The National Weather Service initially issued a rare ice storm warning for the region through noon, then later extended it until 2 p.m. After it expired, a winter weather advisory was issued for a variety of conditions through 4 a.m. Friday.
Freezing rain followed heavy snow in Western Washington, causing dangerous travel, power outages and threats that buildings could collapse. Freeways were closed intermittently by jackknifed semis and untold numbers of spinouts and accidents.
"It's a very dangerous situation," with a major impact on roads, said Brad Colman, the meteorologist in charge of the Weather Service office in Seattle. "We're expecting a significant impact on power. ... We have to worry about any infrastructure that can't bear the load," he said.
A rare and historic winter storm
The ice storm was the worst the area has seen in decades. The last time the region had anything close to the intensity was in 1996 when an ice storm struck the Eastside and southeastern foothills in the wake of a major winter storm then.
But even veteran forecasters said they couldn't remember such a widespread and intense ice storm in the Puget Sound region.
The freezing rain was caused by a mixture of arctic air blowing in from Canada in the wake of Wednesday's snow storm combining with a mild and wet weather system moving in off the Pacific Ocean.
The heavier cold air remained entrenched on the ground as the lighter warm air moved in over the top. As snow falls from the clouds, it would melt in the warmer layer before refreezing in the cold air near the ground.
Areas north of the warm air received just another round of heavy snow while areas in southwestern Washington which had received 10-20 inches of snow Wednesday were dealing with just plain rain.
With another weak weather system racing ashore Thursday night into Friday morning and the north wind continuing to reinforce the cold air, we aren't expecting a changeover to rain until early Friday morning now but once it does so, we'll remain warm and wet for the rest of the weekend.
Periods of heavy rain Friday through Saturday on top of the snow blanketing all of Western Washington could cause river flooding in southwest Washington and urban and small stream flooding throughout the area.
Uncertainty is high with this expected flooding event and the snow melt is a big part of that uncertainty - in addition to the usual question of exactly how much and how intense the rain will be.
Snow melt can act in such a way as to hold the rainwater and then melt and release the water in a relatively short period of time which would greatly increase the river runoff. It is extremely difficult to say how the snow will melt.
In addition, river computer models do not always handle these situations very well so specific river forecasts may not fully indicate the existing flood risk.