Mt. Rainier NP Snowpack Data and Information
Above is the winter snow data for the current season at the Natural Resources Conservation Service's (NRCS') Paradise SNOTEL site, southeast of Paradise. The graph is the Snow Water Equivalent (SWE), meaning the inches of water of the snow. The depth of snow on the ground is found at the Website. The SWE is what water resources managers use to assess the water of the river basins and the area.
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.
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.
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.
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.
While several federal government agencies, along with many state and local government agencies, universities, and organizations collect snow data, the Natural Resources Conservation Service (NRCS) is the primary agency responsible for collecting snow data in the western U.S. The NRCS operates a network of sites throughout the western U.S. for the benefit of water resources managers and anyone with interest in snow.
The technique to collect and calculate SWE data involves two parts, field instruments and fielc calibration trips. From the data collected by the field calibration the data collected with the instruments can be converted to SWE from the depth or weight of the snow, depending on the sensors and instrumentation at each site. Snow is measured with a rain/snow tube, an ultrasonic sensor, or a snow pillow, each providing different data which can be converted to SWE.
To calibrate field instruments, the NRCS conducts snow surveys for each site to check the site, the equipment and instruments and conduct the field tests of the snow using snow tubes which are weighed before and after the tube is driven into the snow to ground level.
The difference in weight is the snow which is then recorded with the snow depth. This provides the data to compute the snow water equivalent to calibrate the data from the instruments. Each calibration is taking the accumuluated data for the snow from the changes during the winter season which they can adjust the data from the series of calibrations over the season.
The data collected from the field instruments is transmitted in near-realtime through various transmission modes to downlinks and then into computers for processing from the field data to compute SWE which is then transferred to the Web page for everyone to view and use the data. You should remember the data is always provisional and subject to change during the winter season.
Paradise Snowpack Data
The NRCS operates five SNOTEL sites in and around Mt. Rainier NP, but the Paradise site off the Pinnacle Peak trail is perhaps the most important one along with the NPS site, in cooperation with the NWS, at the Jackson Visitors Center at, Paradise. These two sites are within a few miles of each other at about the same elevation, 5,120 feet for the NRCS site and 5,500 feet for the NPS site.
The NPS sites provides the snow depth data at Paradise for the late fall through spring visitors to understand the snow conditions for their visit and get an idea of the road and trail conditions in the NP. It is the NRCS site, however, that is key for water resources maanagers for the SWE data along with the snow data.
It is also clear the NRCS site, current water year data show in graph at top of Web page, shows the variability of snow at Mt. Rainer NP. Using the NRCS SWE data for 1981-2015 (no data 1982 and 1983 water years) I looked at several characteristics of the snow, not just annual water year (October 1 to September 30) SWE amount, but the timing of the first seasonal permanent snow, peak snow, onset of snowmelt and end of snowmelt.
The summary of the data is present here in PDF, shows the year to year variation with a few obvious observations. In the last 10 years, including 2015, seven years were above average, 111% to 144% and two others were above 95%. Only the record low for 2015 is significantly different, as seen in the comparison graphs of 2014 and 2015.
This compares with the the data which shows only eight years of the previous 23 years were above average, including the two record years, 1997 with 163% and 1999 with 155%, with the intervening year of 1998 with 97.8%. In short 9 of the last 10 years were normal or higher with the anamoly being 2015 with 36.1%.
What the data also suggests is that the data of the onset of seasonal snow, the peak, the onset of snowmelt and the end of the snowpack are not related to the amount of snowpack, either as the depth or snow water equivalent, but related to the overall seasonal weather pattens of the Cascade Mountains from late fall to early summer.
In addition the onset and rate snowmelt, and the corresponding end of snowmelt, does not relate to the amount of the snowpack, either as snow depth or SWE, but relates entirely to the late spring weather of June and early July. As noted some years of high snowpack had a faster snowmelt and some years of lower snowpack years had a longer snowmelt.
This web page was included for personal reasons as I follow the snowpack every year from the earliest snowfall to the last day of snow on the ground. It determines everything that happens in the following spring and summer as seen in the summer of 2015 with the early snowmelt, and the early and prolonged wildflower season.
The next important information is where to find information and links, which are listed below.
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