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Snow Pack and What it Means

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A forest service employee checks on snowpack at a SNOTEL site. Photo by Kevin Davis A forest service employee checks on snowpack at a SNOTEL site. Photo by Kevin Davis

The science of snowpack

The science of snowpack predictions and weather forecasts is a complex notion (not to mention that it often sounds like a foreign language) and maybe even a bit of an art. Regardless of complexity though, many agencies and organizations are highly dependent upon these predictions and measurements for the operation and/or management of their businesses or charges.

Let’s take a look at snowpack predictions in the Panhandle and in the Clark Fork Basin for the upcoming spring and what is left of the winter. Temperatures have been fluctuating wildly - no surprise, we hardened and wise Westerners are used to this sort of thing (“don’t like the weather? Wait five minutes”). 

Snowpack, just to make sure we are all on the same page, is essentially all of the snow that accumulates in mountain areas. So far this winter we are just a little below normal. If you can remember back that far, it was a very wet November, followed by a normal December, a dry January and a wet February. The “water year,” commencing October 1, is off to a fairly wet start, as levels of snow water are near normal due to the wet November and February, even after the dry January. 

Patrick Maher, Senior Hydro Operations Engineer for Avista, the utility company that operates the Noxon Rapids and Cabinet Gorge hydroelectric facilities on the Lower Clark Fork River, notes that, from a generation standpoint, this is a pretty decent position. “The wet November saturated the ground and filled up the reservoirs to give a good start to the year,” he says.

In the Clark Fork and Bitterroot drainages, snowpack is at approximately 85 percent of normal, according to “SNOTEL” (Snow Telemetry) stations, automated snow measurement sites that measure many parameters, including snow depth, snow water equivalent, rainfall, temperature and soil moisture in real-time data. The data is sent by radio waves through the air to National Resource Conservation Service offices, where the information is made available on the Internet. 

There are about 780 SNOTEL sites in the Western US. The SNOTEL shows that everything south of us (Snake River, Boise area) is dryer than normal, and everything north of us (Kootenai, Moyie area) is wetter than normal. 

The National Weather Service’s River Forecast Center, as of February 15, projects that the Clark Fork drainage runoff will be about 95 percent of normal. Another division of the National Weather Service, the Climate Projection Center, is projecting a wetter than normal season for April, May, and June in the west. 

So how does this information affect Avista? Maher states that probably the biggest factor with respect to how much generation is available for the summer is how warm the weather is in late spring and how much it rains at that time. “This actually trumps the amount of snowpack,” he says. 

Last spring, for example, there was above average snowpack in the late spring, but three days of temperatures in the 90s in May peeled off most of the remaining snow, resulting in a below normal snowpack thereafter. In June, however, near record rains produced plenty of opportunity for hydropower generation. 

“Peak runoff for our drainages usually occurs around June 1,” says Maher. “If May and June are cool, then we have more hydro generation left for late June and July when temperatures are warmer and loads are higher.”

On the other side of Lake Pend Oreille, we have Albeni Falls Dam, operated by the U.S. Army Corps of Engineers. Project Manager, Joe Summers if Albeni Falls says that he doesn’t really look at snowpack with a “critical eye” until forecasts for spring are a bit more reliable. “Using the weather and snow pack information, our reservoir control folks can run their models and give us a better idea of how the snow will melt and what our refill rate [should be],” he says.

Spring lake elevations for Pend Oreille are mostly driven by Mother Nature, and like Avista’s projects, Albeni Falls’ refill fate is limited by weather and snowpack. “With warmer weather, the flows increase and the lake naturally fills,” says Summers. “Constrictions at Dover and along the river limit how much water can leave the lake at any given elevation.” As the lake fills, more water can exit the lake at Dover and pass through the powerhouse (and/or spillway as necessary). 

“We try and keep the last foot or so available for the final runoff from Montana that comes late in June and early July,” says Summers. “Without this cushion there is potential for flooding around the lake as the last peak inflows arrive.” 

Aside from power generation, other agencies, such as the US Forest Service, utilize and even contribute to predictions and measurements. Craig Neesvig, hydrologist for the Trout Creek/Cabinet Ranger Station, manually takes measurements once a month at three “snowcourse” stations in the Rock Creek drainage. He has been collecting data with NRCS personnel for four years at the three sites. The snowcourse station is similar to the aforementioned “SNOTEL” station, but is not as fancy, meaning measurements must be taken manually, and it measures only snowpack. This can be quite difficult when winter or spring conditions make access a challenge. Neesvig says that the measurements are ultimately used to get at how much water is in the snowpack, also known as “snow water equivalent.”

“Although this information is mainly used for drought/flood forecasting, it has many applications spanning from recreational uses to long-term climatic trends,” says Neesvig, who is working on getting a SNOTEL station in Sanders County, Montana. 

Though there are many SNOTEL stations in Idaho and Montana, no current sites in operation accurately represent the Lower Clark Fork Valley. The specific location for the much-anticipated SNOTEL station has yet to be determined, though it would most likely be in one of the three snowcourse station sites. These sites are: 1) Chicago Ridge at 5,900 feet elevation. As of the beginning of February, Chicago Ridge had a snow depth of 95 percent of average, and a SWE of 107 percent of average. 2) Government Saddle, at 5,200 feet elevation, had a snow depth of 123 percent of average, and a SWE of 139 percent of average. 3) Rock Creek MDWS, at 3,400 feet elevation, had a snow depth and a SWE of 110 percent of average. 

Last summer the NRCS converted an old manual snow course to a SNOTEL site on Ragged Mountain, in Idaho just East of Mount Spokane and North of Rathdrum. This site now remotely provides information for snow melt into Spirit Lake and Twin Lakes. 

Kevin Davis, also a hydrologist for the US Forest Service at the Sandpoint Ranger Station, points out that though predictions and forecasts are important, they are looking further out than one spring runoff to the next, as they manage for a landscape scale, ecosystem-wide approach. “We don’t really alter our management based on runoff predictions,” says Davis. “But we do long-term management for risk,” such as infrastructure issues like the building of roads, installing culverts, and planning bridges. 

 So there you have it, a quick glimpse into the snowpack predictions and measurements, and how that information is processed by various businesses and agencies here in the land of lots of water. Information like this is certainly valued in regions such as ours, where a lack of foresight, planning, and information could easily be our undoing. 

Excited about the prospect of a SNOTEL? I’ll let you know when and where that extraordinary machine comes to be. For more information on snowpack or temperature predictions, see the NRCS SNOTEL sites, or the National Weather Service River Forecast Center. Seeing as how it is dumping snow as I am finishing this article, you just might need another snowpack update shortly. Always a pleasure.

Kate Wilson is a project journalist for Avista’s Clark Fork Project. She has been interested in environmental issues and the great outdoors since she was a youngster. 

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Author info

Kate Wilson Kate Wilson Kate Wilson is the Project Coordinator for the Pend Oreille Basin Commission

Tagged as:

snowpack, Snotel, Patrick Maher, Kevin Davis

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