OR-AMS Dinner Meeting Summary


“Weather Disagreeable: A Look at the Weather the Corps of Discovery Encountered on Their Northwest Journey”


  Twenty members and guests gathered at the Happy Fortune Chinese Restaurant in SW Portland on Saturday evening to enjoy great food, company, and listen to George Miller talk about the weather observations made by Lewis and Clark—the first European-American explorers to enter the interior Pacific Northwest two hundred years ago.  George started with the purpose of the expedition, known then as the Corps of Discovery.


  The Corps of Discovery was sent by President Thomas Jefferson to explore the uncharted lands northwest of the Mississippi River.  Were they adequately prepared or just lucky?  Was Pacific Northwest weather different 200 years as compared with today?  Since Jefferson was a weather buff, he specifically wanted Lewis and Clark to make and record weather observations on their journey.  They noted the weather at sunrise and sunset each day and used short codes to note the weather patterns.  Lewis was the primary observer.  Much collaboration of the writings did occur within the expedition.


  Wind was a frequent problem.  Wind affected canoe travel, Columbia River Gorge passage, and navigating the Columbia River mouth. 


  Their weather observations included changes in wind direction and speed (more qualitative), river white caps and wave action, amount of snow cover on the hills and mountains, fair days, rain days, freezing events, etc.  Their first major weather event was something similar to the Columbus Day Wind Storm and they would have been the first European-Americans to note such an event.


  November 24, 1805 was a crucial decision point: where to camp for the winter, Interior or the Coast?  The Corps of Discovery voted as a group on Fort Clatsop, as the local Native Americans (Chinook) said that game was more abundant on the south shores of the Columbia River.


  Early winter was eventful.  On December 16, 1805, a possible weak tornado (F0) hit near Fort Clatsop, based on the description of uprooted trees flying in every direction.


  Mid-winter was most challenging.  Three major arctic outbreaks occurred on January 25, 28, and February 6, 1806.  They calculate that temperatures plunged to 15 degF using standing jars of water left to freeze overnight.  They saw four to nine inches of snowfall in two weeks.  Freezing rain was noted on February 2-3, 1806.  Local rivers froze.


  On March 30, 1806, they noted rising Columbia River levels due to high flows from the Willamette River (perhaps their peak for the season).  On April 6, 1806, the Columbia River at Rooster Rock was 12 feet higher than when they passed through the previous summer.  Their return passage over the Rocky Mountains was delayed as six to eight feet of snow was still on the ground near Lolo Pass (6000 feet) by late June. 


  George noted the number of “rain days” in their journals for November through March for Fort Clatsop: 128 days.  This value compares very well with 127 rain days during the winter of 2003-2004 and 114 rain days for the winter of 2005-2006 (57 inches, 12 inches above normal).  Despite the claim of Lewis and Clark that the winter of 1805-1806 was “very wet” (perhaps by East Coast standards, as that was the only guide they had at that time), the amount of rain days seems near normal, using present day data. 


  In summary, the Corps of Discovery were not adequately prepared for Pacific Northwest weather, faced a harsh two-week cold spell, far above normal snow pack in the Cascade and Rocky Mountains (due to a rapid barrage of Pacific storms).  Overall, the weather was very similar as we see today (except for the two week cold snap).


  After the talk concluded, George answered many questions from the audience.  George was kind to offer his two books for sale, at a discount, and several folks bought books.


Note-taker: Kyle Dittmer, OR-AMS President