Localized Snowpack Models


for Sasse Ridge, Blewett Pass and Snoqualmie Pass

Last site update: Friday, July 09, 2021

The charts linked in the sidebar show the output of localized snowpack models that generate daily ‘virtual snowpits’ for Sasse Ridge and Blewett Pass. I may run the Snoqualmie Pass model from time to time, but it’s hard to maintain so it’s not set to run automatically.



Summer 2021: I hope to post the Sasse Ridge winter charts next ski season. The data sources for the model have been revised but the basic idea is unchanged.

A model of the Sasse Ridge snowpack:

In 2002 I began playing with a quite simple experimental model that estimates the recent additions to the Sasse Ridge snowpack as one ascends from the valley floor. The result is displayed as a bar graph which is much easier to interpret than a long series of numbers. The model and the assumptions on which it is based are discussed here. Since then I’ve added a number of other bits of data to the output; stuff that I find useful.


Data sources:

The Northwest Avalanche Center (NWAC) maintains a large number of excellent telemetry sites in the Cascades, and this data is used for the Snoqualmie model. However, there are no NWAC sites in close proximity to Sasse Ridge or Blewett Pass.


Fortunately there are SNOTEL sites near both the later two locations that provides hourly data which can be accessed via the web. SNOTEL sides are owned and maintained by the USDA National Resources Conservation Service and are intended mainly for water resource management. The NRCS website has a vast amount of information about these sites and is worth looking at to understand how the sensors work.


Note that SNOTEL precip  and SWE sensors report only to the tenth of an inch. By comparison, the NWAC sites report to the hundredth of an inch. For newly fallen snow, a tenth of an inch of precip is roughly equivalent to an inch of new. This means that at SNOTEL sites data scatter is in the order of plus/minus an inch of new snow or more.  This is significant for a skier.


For the 02-03 winter, snow depth monitoring was added at the Sasse SNOTEL site. It seemed to be a useful adjunct, but perhaps because of the location of the site itself and perhaps the nature of the sensor, I think that the general conditions on the ridge were often better reflected by the SWE and precip counters.


Besides data from the Sasse SNOTEL site, other useful information can be gained from the HADS – DCP site at Cooper Pass, just across the valley to the west — if it is still functional. Although the precip gauge has appeared to be erratic for the last few years and not to be trusted, this site has wind speed and direction, as well as temperature. More about this site here. (Access to the Cooper Pass data keeps changing; try a web search.)


Telemetry sites give an idea about conditions at a particular elevation. However, a skier would like to know how the snowpack changes from the parking lot the top of the hill, and that’s what these models try to predict.


Questions or comments, at least friendly ones, welcome at the address at the bottom of the page.


Many thanks to Scott Pattee of the NRCS – Washington Snow Survey Office for inviting me to chat about the snowpack models at the 2004 Snow Survey Workshop in Cle Elum. I’m sure it was good comic relief at least. Credentials? What credentials??  The illustrations for the talk are here, with thanks to Bob Wells for two of his great cartoons.