Strong December Storm to Strike Pacific Northwest

10:30pm WINDSTORM UPDATE —- The 0z models this evening are stronger yet with tomorrow nights storm. The GFS now brings a 971mb low to the NW tip of Washington overnight tomorrow night. There is a forecasted 20mb pressure gradient from Eugene to Olympia. If this trend continues, areas from Salem north to Seattle will see the biggest windstorm since December 14th 2006. Winds could gust to 55mph in Portland after 10pm Sunday evening. With all the rainfall as of late, there will likely be power outages with falling trees. More details tomorrow morning.

Holiday travelers take note. After a “snow tease” this morning across Portland, a strong December storm just now developing in the Pacific will bring with it the potential for strong winds, followed by more low elevation snowfall across the Pacific Northwest beginning Sunday evening and lasting through Tuesday. Computer models are now coming into better agreement on the path and strength of a system slated to arrive Sunday evening. This system is currently developing well off the Washington and Oregon coast. The path of this system will ultimately determine the outcome of who will see the strongest winds and the best chances for low elevation snowfall Monday night after the storm passes. This will be the strongest system to strike the Pacific Northwest this fall season.

This storm system is currently forecast to take a similar path to that of the December 14th 2006 Hanukkah Eve storm which tracked into extreme southern Vancouver Island. The depth of the December 2006 system was approximately 970mb at its peak, which is nearly identical to what is forecast yet again tomorrow night. The December 2006 storm brought with it winds as high as 50mph in Portland and 75mph across some locations near Seattle. The system was then followed by much colder air aloft and some low elevation snowfall across the region. When comparing these two systems, there are some similarities as well as some differences as of Saturday afternoon. At this point there are still a few more model runs to look at when assessing this storms potential. If the track remains the same as currently forecast and the storm develops deeper than anticipated, the concern for a more widespread damaging wind event similar to December 2006 is possible. The next run of models will come out approximately 9pm PT this evening and will better help clarify the exact forecast track and strength of this system.

Regardless of the potential for strong winds, the system will pass by Monday morning, followed by much colder air and lowering snowfall levels. Anything that falls from the sky will be scattered in nature and not likely to cause any travel issues at the lowest elevations. The air mass that follows this system is forecast to be as cold if not colder than what we see over the area today. So, again I expect snow to fly (at least in the air) at all elevations Monday night and Tuesday morning. Hills above 750-1,000ft will likely see some sticking snow. Tis the season, right? The Cascade mountains will see several feet of new snow between now and Wednesday. This will cause holiday travel problems over the mountain passes, just as schools let out for the winter break. Longer range models continue to show colder than normal temperatures across the Pacific Northwest with more storm systems on tap next week. Snow levels will also remain below pass levels. Below is the path of the December 2006 storm (courtesy, Wolf Read), followed by forecast track of tomorrow night’s storm from the WRF-GFS and MM5-NAM models. As you can see, there is quite a bit of agreement on the path and depth of the storm system.

At the present time I do not expect damaging winds in the Portland area as the tightest pressure gradient remains offshore or just to our north, but that could change with this evenings models. In 2006 I recorded a 21mb pressure difference between Eugene and Olympia. That netted Portland wind gusts of about 50-55mph. This time it looks like 15mb or so as of the latest model runs. If the old Jim Little theory still works it goes something like this — PI x Max Eugene to Olympia gradient = max wind gust potential in Portland. With that in mind, Portland is looking at maybe 45mph right now (3.14 x 15mb = 47mph). Seattle is another story. The pressure gradient will be tighter up there. Could see some 60mph+ gusts up there if things develop just right. I would like to see a more northerly track to this system for strong winds in Portland. These west-to-east traveling systems rarely bring Portland anything exciting. Then there is the old Steve Pierce theory. When my right knee hurts, we are in for a storm. Right now my knee feels fine. So as I always say, “stay tuned!” If tonight’s models show a 965mb monster taking the same path, that will get my attention fast.

Steve Pierce, President
Oregon Chapter of the American Meteorological Society (AMS)


Steve Pierce

Steve Pierce

Steve Pierce is widely known as Oregon and Washington's "go-to-guy" when it comes to fast, accurate historical meteorological research and forecasts. Steve is currently the President of the Oregon Chapter of the American Meteorological Society (AMS). Steve is also recognized as a regional weather commentator and blogger who can be heard on local radio stations and seen in print media outlets across the Pacific Northwest. His Weather Blog is hosted by the Columbian Newspaper in Vancouver. Check it out! He is a third generation resident of Vancouver, Washington and holds a degree in Communications. Both sets of Steve's grandparents migrated to Vancouver during World War II. One set traveled from Lenox, Iowa to work in the Kaiser Shipyards supporting the war effort. The other set came to Vancouver from Olympia, Washington to work as educators for the rapidly expanding Vancouver School District. When the war was over, both sets of grandparents decided to stay in Vancouver and continue raising their families, as did thousands of other families at the time. Those who are most familiar with Steve can attest to the fact that weather is his true passion. His love for "all things weather" began at the age of 7 when Mt. St. Helens erupted in 1980. He was fascinated with which direction the ash plumes were headed. Then came the very powerful windstorm of Friday, November 13, 1981, also referred to as the "Friday the 13th" storm. This was the strongest storm to hit the Portland / Vancouver area since the great Columbus Day Storm of 1962! At age 11, he was asked to publish an extended weather forecast for his elementary school's weekly newsletter. In the 1980's, at age 14, Steve was the youngest of KGW-TV's local "weather watchers" and would phone in his daily Vancouver weather stats to then television meteorologist Jim Little for use on-air. Steve has lived through all of the major Pacific Northwest weather events of the past 30 years, and then some. The most notable events include; the bitterly cold winter of 1978-1979, the record setting snow storms of January 1980, the summer heat wave of August 1981, the windstorms of November 1981 and December 1995, the severe arctic blast of February 1989, the record flood of February 1996, the historic ice storm of January 2004, the Vancouver tornado of January 2008 and the record setting snow storm of Christmas 2008. Not to mention every Mt. St. Helens volcanic eruption in between. With access to the most extensive set of historical weather records available to date, Steve has personally designed and integrated a proprietary system that gives him the ability to quickly locate and manipulate weather data as far back as the 1800's. As one local Meteorologist put it, "Steve has fast access to historical weather data that is needed for media, agriculture, business, personal, historical and other climatological needs. He can quickly manipulate the data in many different ways. His forecasts are also quite accurate, especially at longer lead times." Steve also provides local storm assessments, narratives and weather presentations to the general public, as requested. In his spare time, Steve enjoys spending time with his family, the outdoors, vacationing at his family's coastal cabin and just relaxing! By the way, do you like your weather on the "extreme" side? So does Steve! Whether it is collecting damage assessment data & photos after record setting 125 mph winds at the coast in December 2007, being one of the first on the scene after the January 2008 Vancouver tornado, or feeling (literally) the awesome power of 100 mph wind gusts at Oregon's Crown Point in January 2010, Steve has experienced it all! As Steve says, "don't just love weather, live weather!" Check out Steve's personal weather website at:

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