JACKSON, Wyo. — Spring has arrived and it’s time to start thinking about how this year’s snowpack will affect the upcoming whitewater rafting season. Read on to learn how winter snowpack, spring temperatures and the timing of snowmelt all influence the spring runoff, then submit a prediction for the 2021 high mark through Dave Hansen’s High Water Heydey Contest for a chance to win a new raft!
Currently, we can see that snowpack is slightly below average across the Snake River Basin based on snow-water equivalent measured hourly at numerous locations in the surrounding mountain ranges.
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Peak winter snow depths relative to average
First, there is the obvious connection between peak snow depths and peak river levels. Typically, if the snowpack is above average, peak river levels will also be above average.
However, sometimes this is not always the case. In 2019, the snowpack was above average and peak river levels were below average. The explanation for the lower stream levels in 2019 is that temperatures were colder than average temperatures in May, which slowed the rate of snowmelt.
Spring temperatures relative to average (particularly in May)
Spring temperatures have a significant influence on snowmelt rates, which in turn influences river levels. Snowmelt rates are at their highest during the month of May, so temperatures relative to average during May are the most highly correlated to river levels.
WHEN snowpack reaches its maximum depth
The other key factor that influences river levels is when the mountain snowpack reaches its peak. Years when the snowpack reaches its peak before April 1 tend to result in lower river levels compared to years when snowpack peaks later.
Predicting the High Water Mark for 2021
The remaining question mark is what happens with temperatures over the next six weeks, and particularly in the month of May. Below average temperatures in May could negate a heavy snow year and contribute to a low runoff season. Long-range weather forecasting beyond two weeks out is difficult, to say the least. NOAA’s latest long-range outlook is predicting slightly above average temperatures during May, which would favor a higher runoff.
Using the above data and based on the average river high mark of 19,218 CFS, what do you think the high mark will be during 2021?
Enter Dave Hansen’s High Water Heydey Contest here or below to guess the highwater mark for 2021 and for a chance to win a NRS STAR Outlaw 140 Self-Bailing Raft! The deadline to submit entries is May 15.
Dave Hansen’s High Water Heyday Contest
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