Mt. Rainier NP Snow Data and Information
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MPG V2.8, January 2013

Above is the winter snow data for the current season at the NRCS' Paradise SNOTEL site, southeast of Paradise. This is the snow-water equivalent (SWE), meaning the inches of water of the snow. The depth on the ground is found at the Website. This is what water resources managers use to assess the water of the river basins and the area.

Snow Season

The snow season in Mt. Rainier NP can start in early October with snow storms which rarely leave lasting snow on the ground. The seasonal permanent snow usually doesn't start until November at the low to mid elevations, but will start to accumulate above 5,000 feet in mid-late October, and earlier in some years.

The peak snowpack occurs late April to early May, usually the first two weeks in May, with drought years occuring in the latter half of April and extreme snowpack years in mid-May, always before Memorial Day. The speak lasts one to seven days before the onset of snowmelt for the season. This is the time most people begin to watch the snow reports to see when the trailheads will open and the mid to higer elevation trails are clear.

The snowmelt season is highly variable and isn't much related to the snowpack, but is related to the late spring weather in June and the early summer weather in July. The end of the snowmelt, meaning all the snow has melted, varys from early June to late August, but normally occurs in mid July, somewhere around July 15th plus or minus a week or so.

Once melted, snowfall may occur anytime in the mid-upper elevations through the summers but won't accumulate except in rare years when the summer temperatures are cooler than normal through July into September. This occurred in 2011 when the snow persisted until the last week of August and snowfall began in early October.

Snow Sites

The NRCS Water Climate Center is the agency in the US government with the mandate to operate snow sites. Other agencies can operate similar sites for specific purposes for the agencies, eg. NWS or USCE, or its customers, eg. USGS, but the NRCS is the agency with the broad scope to assess the snow and water resources of the areas in the western US, namely the mountain ranges of the western states.

In the Puget Sound and Cascace Mountains in Washington the NRCS operates an extensive network of sites. These sites are located above the lowest elevation where snow is usually permanent through the winter season after any early season rain/snow storms, usually above the 2,500-3,000 foot elevation.

This is due to the dynamic weather in western Washington where you have to operate weather data collection sites with real-time telemetry through the extreme ranges of temperature between 1,000 and 2,500 feet elevation where rain/snow storms and thawing and freezing are difficult to operate field sensors, data collection instruments and real-time telemetry equipment.

It's easier to collect snow data once the seasonal snow is present and the temperatures are consistently near or below freezing where thawing isn't a significant problem through the winter season. It seems backward but practical experience shows it's true, and why there is a lack of snow data sites below 2,500 feet elevation. These sites are usually observation sites instead of instrumented sites, usually operated by the NWS or state or local agencies.

The other reason is that you want to know the snowfall and snowpack as high in basin as realistically possible to colllect. This provides the range of snow data from the upper most to the lowest elevation for water resources management of basin. This can only be done by the NRCS, their sites in and around Mt. Rainier NP listed below.

• Paradise, southeast of the Jackson Visitors Center.
• Mowich Lake, west of the NP boundary at the Mowich Lake entrance.
• Cayuse Pass, east of the NP boundary on highway 410.
• Corral Pass, northeast of the northeast corner of the NP and north of Crystal Mountain Resort.
• Skate Creek, south of the southwest area near Skate Creek road between Ashford and Packwood.

These sites will provide you a good picture of the snow in Mt. Rainier NP, where you can data all the data for the site. You can locate them on the map of weather sites, see blue tags.

Snow Data

There are different types of snow data which can be confusing to readers where it's easy to misunderstand the numbers cited in the literature, magazines and newspapers and on Websites. These are snowfall, snowpack and snow water equivalent.

The term snowfall is obvious. It's the snow that falls measured in inches. This where the NPS publishes the annual figures (through 2015 - PDF). It's the most often cited statistic about the snow at Mt. Rainier NP. The data is usually determined at a site or from field instruments or by observors.

The term snowpack is also obvious. It's the depth of the snow on the ground, again measured in inches (US). This data, shown for the Paradise site, is also from a site either with marked poles or pressure sensors. This number changes during the season from a variety of reason, including new snowfall, snowmelt to runoff, ablation, compaction and melting-refreezing from barometric pressure.

This is often the snow collected at and transmitted from remote sites in the NRCS's SNOTEL network of sites. It's often the easiest to collect and transmit, but it also requires calibration to be converted to Snow Water Equivalent (SWE) to be useful for a variety of water resources purposes.

The term SWE isn't so obvious and is defined as the equivalent of inches of water for a specific snowpack. This is where scientists visit the remote sites and take snow samples from the depth to the soil and then measure the depth (snowpack) and weight (as water). This is then converted to an equivalent water in snow, in inches.

This number determines the density of the snow, meaning the number of inches of water per foot of snow (or the reverse for other calculations). Usually dry snow is about 2-4 inches of water per foot of snow. Wet snow is 6 or more inches per foot. Mt. Rainier normally get wet to very wet snow where the Rocky Mountains get dry to very dry snow.

This number determines the amount of potential runoff in inches of water in the snowpack. It's important for water resources managers for spring snowmelt models into reservoirs for reservoir management and for water management in river basin. It's also used with rain and rain-on-snow models for storm events and floods.

The work for snow forecast reports and mountain snowpack reports starts in January, the beginning of the seasonal permanent snowpack and goes through the final snowmelt in June-July when it's gone from at or below about 6,000 feet elevation.

Additional Resources

The next important information is where to find information and links, which are listed below.

• Books in Print
  • Northwest Mountain Weather by Jeff Renner
  • Pacific Northwest Weatherby Cliff Mass
• Websites
  • NPS NPS Information
  • NWS Mountain Forecast
  • NRSC Snotel Sites
  • NWAC Mountain Data
  • USGS Weather data

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