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Flattop Mountain SNOTEL - Snow Water Equivalent Water Year 1999

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These materials prepared by the Climate Change in Mountain Ecosystems Program -- U.S. Geological Survey, Glacier Field Station.  Dan Fagre, Program Coordinator, email: dan_fagre@usgs.gov.  For more information, visit the Glacier Field Station - Climate Change in Mountain Ecosystems program (CCME) web site. 


SNOTEL (SNOw TELemetry) sites are operated by the US Department of Agriculture, Natural Resources Conservation Service (NRCS) and used for forecasting water availability. These stations measure Snow Water Equivalent (SWE), the weight of snow equivalent to inches of water at the site.  The graph below plots data from the Flattop Mountain site, located at approximately 6300 feet in elevation along the upper edge of the McDonald
drainage in Glacier National Park, Montana.  SWE has been recorded daily since 1 October 1969, the beginning of Water Year 1970.  The first of October is considered the start of a water year, which runs from 1 October - 30 September of the follwing year.  Logan Pass is located at 6646 feet elevation along the upper edge of the McDonald drainage, approximately 10 miles southeast of the Flattop Mountain SNOTEL station.

The data plotted below includes:  the long-term average SWE, 1970-1998;  the water year with the maximum snowpack, 1972;  the water year with the minimum snowpack, 1992;  and the current water year snowpack, 1999.  The animation is set at a weekly interval running from 1 October 1998 - 22 July 1999.  Notice how the snowpack progresses from virtually no snow present on 1 October 1998 and surges upward beginning in late November.  In February 1999, average daily snow water accumulation was 0.4" with daily increases between 1/4" to 3/4", while in February 1972 average daily accumulation was closer to 0.6" with daily increases between 1/2" to 1".  The nice weather of March & April is quite obvious as level spots in the graph (SWE was nearly constant at approximately 56" for the weeks of 11, 18, & 25 March).  Maximum SWE at Flattop Mountain typically occurs on the 27th of April, maximum SWE in water year 1999 was 60.1" on 18 May (on 17 April 1999 Flattop Mountain SWE was 59.9").  This year's spring melt-cycle was slightly prolonged, with snow covering trails in Glacier National Park well into July & even August in a few spots.  To see how this years snowmelt patterns affected streamflow visit the USGS, Montana Current Streamflow Conditions web page for current & historic stream info.

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Click here or on the image above to view an animatedversion of this graph.


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