Snow

The Snow Load Analysis for Oregon was first published in 1971 and updated in 1978.  A third edition was published in 2007, with additional updates in 2010.  Based on a 33-year mean recurrence interval, the snow load data was presented in graphical form with county areas with similar ground snow load versus elevation relationships grouped together.  With the help of the Oregon Climate Services at Oregon State University, the Structural Engineers Association of Oregon (SEAO) created a new ground snow load map for the State of Oregon based on a 50-year mean recurrence interval (MRI), making the load probability consistent with the ASCE Standard.  The new map loads are the result of 36 years of additional data and were generated using the latest climate modeling technology, PRISM. Along with the map, the SEAO Snow Load Committee updated the Snow Load Analysis for Oregon and published this third edition with the new map in December 2007.

Coming Soon:  Electronic Version of the Map hosted by OSU

Shortly after publication of the book and map, areas of northwestern Oregon experienced record setting snowfall in the winter of 2007-2008.  The SEAO Snow Load Committee began reviewing the data in early 2009 to see if it would affect of the 50-year snow load at certain sites.  After researching the snowfall from that winter we found that the 50-year predicted snowfall for a number of mid-elevation sites exceeded those predicted on our map.  We also realized that the 50-year station values for some locations on the map were much lower than the surrounding snow load contour lines.

 Upon finishing our review, we concluded that some of the snow data needed to be revised and incorporated into an updated map. An enormous volunteer effort has been completed to revise the snow load data and determine new station values for 50-year MRI ground snow loads to input into Prism to develop the new map.  In addition to updating some of the snow data, the current project consists of an effort to develop an electronic version of the snow load map.  We are currently waiting for BCD funding to facilitate OSU’s portion of the project including a new PRISM run with our revised data.

For more information on the current snow load updates, see the snow load manual page.

As noted above, we are currently waiting for funding from the State of Oregon Building Code Division (BCD) to facilitate OSU’s PRISM run with our revised data.