'Significant' Thursday Snow: What the Forecasts Models Say

SEATTLE, WA - The National Weather Service released a grim-sounding winter storm watch for all of Western Washington Tuesday night - from just east of Bellingham to the Oregon border - that goes into effect Thursday morning. The watch says we're in for "significant" snowfall of up to 4 inches on the east side of Puget Sound and up to 7 inches out on the Hood Canal. Not to mention, there's talk of sleet and high winds.

To predict weather around the region, meteorologists use several different models. The two main ones are the American model and the European model. Here's what the models are saying about what's coming Thursday:

• American model: There are a few different scenarios with this one, which some meteorologists see as less reliable than the European model. In one scenario, the approaching storm moves up the Washington coast to Vancouver, which would bring a strong windstorm to Puget Sound. That would push cold air out of the area, which means no snow. But that scenario is unlikely according to this model. For snow, it's predicting anywhere from 1 to 4 inches in Seattle.
• European model: Meteorologists are calling this model "consistent" - meaning that for a few days, it's been steadily predicting between 3 and 5 inches, and about 4 inches in Seattle.

University of Washington meteorologist Cliff Mass has said that a key to this storm is how long cold air sticks around. The approaching storm will push cold air out of Puget Sound, but how long that takes will determine how much snow we get. The longer the cold air stays, the longer the snowfall. The National Weather Service storm watch says it could be a 12-hour snow event.

Right now, the storm appears to begin around rush hour Thursday with snow, which will then turn to rain overnight into Friday. But the forecasts are still shifting.

"This situation is more threatening than Monday, since we will have cooler and drier air in place and the amount of precipitation is greater," Mass wrote on his blog Tuesday.

Photo of 2008 Seattle snowfall by Flickr user Alex Wu