There is a growing likelihood of a heavy freezing rain the next day.
Freezing rain can make driving dangerous and lead to widespread power outages.
As described in my previous blog, freezing rain occurs when temperatures warm above freezing but the air below freezing remains near the surface. Raindrops fall into the air below freezing and can supercooled below freezing, but remain liquid. Such drops can freeze on contact on cold surfaces.
Nowaday situation
Temperatures are well below freezing throughout the region, as shown on the 2 p.m. temperature map below.
A hot front approaching the coast, accompanied by rainfall, was detected by the Langley Hill Radar near the coast (see radar image). Clouds from the approach system have begun to spread across the western part of the region and rainfall has now reached the southwest coast of WA.
Precipitation will start as snow, then hail, then freezing rain and finally rain.
Let me show you some event forecast graphics (just produced by meteorologist Dave Ovens) from UW’s high-resolution modeling system.
First, west Washington.
At 10 p.m. tonight, much of the hinterland will see snow (blue), but cold rain (yellow) will move toward the coast.
By 4 a.m., freezing rain will cover much of the lowlands west of Washington, while snow will appear over the Cascades and eastern Washington.
And by 07 o’clock tomorrow, the hail ends, the rain turns to the area.
The possibility of freezing rain is even greater in the Columbia Gorge and in the western part of the northern Willamette Valley. Why? Because there will be an abundant supply of cold air moving westward in the Gorge.
Below is the forecast for cumulative freezing precipitation according to NOAA’s HRRR modeling system through 8 a.m. tomorrow. Lots of freezing rain south of Seattle and in the Willamette Valley.
But while the icy rain ends in western Western Australia tomorrow morning, it continues in the Columbia Gorge and the Willamette Valley, with huge amounts of ice. And cold rain will continue in the WA Cascades. Not good.
On Saturday, warm, humid air will overwhelm the area and this cold/frost/snow will sweep across the western side of the area.
