Use of Cooper Pass Telemetry Site Data
For planning a trip to Sasse Ridge, the Cooper Pass telemetry site can be useful for confirming temperature trends and for the wind speed and wind direction data with the following caveats.
Note the differences in elevation, as well as the effects of solar heating when comparing temperature readings from this site with those from Sasse Ridge. The Sasse Ridge site is at ~4300 feet (not 4200 feet as listed on the NOAA website) and is located on a bench facing west. It’s largely surrounded by high trees. The Cooper pass site is about 1000 feet lower and faces north.
The winds at Cooper Pass are not directly comparable to those at Sasse Ridge because of the topography.
At Cooper Pass, the winter winds tend to blow either up from the Kachess River valley, or down the Cooper River valley, bending around to go through the pass.
On Sasse Ridge during the winter there are a number of different wind patterns. Storms from the south and southwest often blow up lake Cle Elum, with very strong winds crossing the low point on the ridge top in a more westerly direction.
North of Sasse Mtn., storms approaching Sasse Ridge sometimes come directly out of the Cooper River valley instead of up Lake Cle Elum. Perhaps this is the reason for the distinct increase in the valley snowpack as one progresses north of the French Cabin Creek Road.
Occasional winter storms come from the east, but more commonly light easterly winds in the winter months often foretell excellent skiing on the front-side or west face of Sasse Ridge, where new snow is deposited without significant wind transport.
Northerly winds generally follow the Cle Elum River, but they become northwesterly as they pass over the ridge.
Later in the spring, easterly down slope winds occur in the evening hours and often persist through the night. When the day has been warm I suspect these light easterlies are katabatic winds which represent the downward flow of air that was forced upwards during the heat of the day. If the barometer is stable, such winds at night often signal good weather for the next morning.
From these observations, it is not possible to directly transfer the wind speed and direction data from Cooper Pass to Sasse Ridge. Nonetheless, with frontal passage, high winds at Cooper Pass suggest that there will likely be significant wind transport of snow on Sasse Ridge and the wind direction from the Cooper Pass site may give a hint regarding the direction of snow transport. The graphic display of wind speed and direction on the top right of the Cooper Pass web page is quite useful in this regard.
The Sasse Ridge SNOTEL site also reports wind speed data, but during storms it‘s not of much use. To some extent, the Sasse SNOTEL site is down in a hole surrounded by tall trees. Strong ridge top winds may not register at all. On the other hand, flat calm and new snow, especially when confirmed by the Cooper Pass wind speed data is very suggestive!
Exactly where the snow goes when it‘s windy, and the associated risk is a subject I’ll skip right now! (An easy way to say it’s too complicated for me.)