Tuesday, November 20, 2012

Storms Slam into Pacific Northwest

While most of the country has enjoyed tranquil weather for the last week or so (evidenced by the many gray dots on the CoCoRaHS national map), the Pacific Northwest has been pounded by a series of storms that have brought hurricane-force winds, torrential rain, and heavy snow. Flooding closed roads, winds toppled trees which in turn brought down high voltage power lines, heavy rain caused mudslides, and the avalanche danger was high from the heavy snow.

The first of these storms moved ashore from the Pacific on Saturday, followed by another on Monday.

Surface map for Saturday, November 17 (L) and for Monday, November 19 (R).
 The 7-day precipitation accumulation map shows accumulations ranging from five to more then ten inches all along the Oregon and Washington coasts.  Most of that precipitation came with Monday's storm, which has been the most intense one so far.

7-day precipitation accumulations through 5:00 a.m. PST November 20
CoCoRaHS observers in Oregon reported more than nine inches of rain.

CoCoRaHS map for Curry County in southwestern Oregon for November 20.
A number of observers in Oregon noted that today's rainfall was the highest 24-hour amount they have ever recorded. The general nature of the rain and flooding apparent from this comment from the CoCoRaHS observer at Oakridge 4.6 NE in Lane County who measured 4.03 inches of rain:

Nope that's not a typo, we did get over 4" and almost all of that came after 5 PM. It rained off an on during the day but never heavily, less than a 1/2" before 5, and then it started really raining. We don't get flooding up here to speak of. Compared to other areas what we have right now is minor, but it is significant for us. I marked the flooding as minor because on an absolute scale that's what it is, but it is not typical for us. Last time I saw this sort of general standing water on our property was the heavy rains the winter of 05-06. We have had heavier flooding in the area, but from creeks overflowing, not just general standing water. The creeks are high right now, but not overflowing. 

Washington also received heavy rain, and there were a number of new daily rainfall records, including daily rainfall records at the Seattle-Tacoma International Airport (2.13", old record 1.23" in 1962) and at the National Weather Service Office 2.60". old record 1.16" in 2003).

CoCoRaHS map for King County, WA for November 20.
There were many wind gusts in excess of 70 mph reported yesterday with this storm. Here are a few of those gusts.

114 mph      Naselle Ridge in the mountains of southwest Washington
106 mph      Mt. Hebo nearTillamook, Oregon
101 mph      Astoria bridge, Washington
101 mph      Megler, Washington 
  98 mph      Yaquina Head, Oregon
  92 mph      Astoria, OR
  90 mph      Garibaldi, Oregon

It appears the stormy weather will continue through the end of the week. A third storm will hit the Pacific Northwest Wednesday, and yet a fourth storm is forecast to arrive on Friday. Additional rainfall of one to three inches is expected from Washington south through northern California and a foot or more of new snow in the high Cascades and the northern Rockies by Wednesday night.

Forecast surface map for the morning of Wednesday, November 21


  1. Nice summary, thanks! I live in Lane County (about 50 miles from Oakridge) and it is nice to get the bigger picture of what went on during that storm. We are bracing ourselves for the next one, which is being heralded by a rainbow over the Willamette Valley.

  2. Thanks for the comment, Sue. It's been a rough week for all of you out there. After a brief respite this weekend, it looks like storms will start moving in from the Pacific again next week. Rain gauges will get a workout!