Picture: Spill at Pathfinder Dam, North Platte RiverJune 2011
Missouri Basin Forecasters Meeting – February 20-21, 2013
Cara McCarthyNatural Resources Conservation ServiceSnow Survey and Water Supply Forecast ProgramNational Water and Climate CenterPortland, OR
Entry to Geneva Park Snow Course, South Platte, for February 1st, 2013 Measurement,60% of Normal
• Water Supply Forecasts/Current Conditions• A SNOTEL site you should not use for SWE• Snow Course Reductions• Change to 1981-2010 SWE Medians
Sawtooth Snow Course, South PlatteFeb 1st Measurement
February 1, 2013
Feb 1, 2013
February 1, 2013Snow Water Equivalent
as % of Normal (Median)
SNOTELMonth-to-Date Precipitation
% of Normal
February 18, 2013
Feb 18, 2013SWE
% Normal
Feb 1, 2013SWE
% of Normal
Change in SNOTEL Snow Water Equivalent since February 1
Month-to-Date Guidance Forecast Change as Percent of 1981-2010 Normal
Feb 18, 2013
From Lucas Zukiewicz, NRCS SSWSF Montana DCO 2/7/2013
Pike Creek SNOTEL May 2009
Pike Creek SNOTEL May 2009
Bear Basin Snow Course 2006
39 Snow Course Reductions in Montana DCO Area
New Normals this Year
• Every decade the 30 year normals change periods.• This year we go from the 1971-2000 period to the
1981-2010 period.• The change is meant to keep pace with current
climatic conditions as the most recent years are said to represent the current conditions.
• Most data types are calculated as a straight average except Snow Water Equivalent which is “median” or “middle value”
Why will SWE use a median?
Lewis Lake Divide SNOTEL Site Yellowstone NP January 16, 2013
Effect of Change to Median SWE 1981-2010
http://www.wcc.nrcs.usda.gov/reportGenerator/
Questions?
www.wcc.nrcs.usda.gov
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