A significant ice storm is expected for much of Washington and parts of Oregon over the next couple days, with significant impacts possible for the Seattle and Portland metro areas.
As of 8:00 PM Thursday, freezing rain has already begun around Portland, and has been reported as far north as Grays Harbor County in Washington.
Expect freezing rain to start from 11 PM to 4 AM from Seattle southward, and later in the morning north of Seattle. Freezing rain will taper west of the Cascades by Friday evening. Freezing rain will impact Eastern Washington on Saturday, and will impact the Cascades and Columbia River Gorge from Friday through Saturday.
This has potential to be a high-impact event, with significant travel disruptions (including shutdowns of PDX and SeaTac), widespread power outages, and a significant tree damage potential.
Below is the European model forecast for total freezing rain accumulation.
The European model forecast shows 0.25-0.5 inches of ice accretion from the Willamette Valley to Seattle and on the coast. This would be very disruptive. The Columbia River Gorge and Snoqualmie/Stevens Pass get very bad freezing rain totals of 0.5-1.25 inches. Eastern Washington will pick up 0.1-0.25 inches of freezing rain, but likely on Saturday.
Next, let's look at the GFS model forecast for total freezing rain accumulation.
The GFS forecast shows 0.1 to 0.3 inches of ice for areas from Seattle to the Willamette Valley, the WA Coast, and Whatcom County. This forecast likely overdoes the freezing rain in the mountains & Gorge, since 1.5-3 inches of ice seems unreasonable.
Next, let's look at the high-resolution Canadian model, the RDPS.
The RDPS shows a similar situation as the Euro, with most freezing rain (0.25-0.5") from Seattle to Eugene, plus 0.3-0.5 inches on the Coast and Whatcom County.
Finally, the HRRR forecast.
This is the highest-resolution forecast available, and it paints a good picture showing the localized differences in freezing rain. The HRRR shows 0.25-0.5 inches of freezing rain from Seattle south into the Willamette Valley, in Mason and S. Kitsap Counties, in Whatcom County, and 0.5-1" in the Columbia River Gorge. On Saturday, 0.05-0.4 inches is possible across Eastern Washington, highest near Wenatchee and Walla Walla.
Some areas will receive snow before a changeover to freezing rain. Let's take a look at the European model forecast for snow prior to the changeover.
Expect a trace to 1 inch from Seattle to Everett and on the Kitsap Peninsula. Eastern Washington will get 1-4 inches, and areas from Mount Vernon northward into BC will get 2-6 inches.
This graphic below from the National Weather Service talks about how dangerous freezing rain can be.
With power outages possible, below is a list of local public utilities sites to monitor:
As always, the best place to get frequent updates is Twitter (linked on top right of blog site), local news stations, Pacific Northwest Weather Watch on YouTube, and NWS Seattle.
Stay safe & stay tuned. More active (but wetter & warmer) weather is ahead through the end of December.
No comments:
Post a Comment