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1991-2020 Normals Dashboard - Nevada and Eastern Sierra
On October 1, 2021 the NRCS updated its 30-year normals period from 1981-2010 to 1991-2020. The NRCS uses normals in a variety of products to represent data as a percent of normal. Changing normals impacts percentages and requires users to re-calibrate themselves.
The following data types have normals:
- Daily and Monthly SNOTEL Snow Water & Accumulated Precipitation
- Peak SNOTEL Snow Water & Peak Date (new)
- SNOTEL dates for Snow Onset &Melt-out (new) - click here for explanation
- Monthly Snow Course, Streamflow Volumes & Reservoir Storage
A Technical Summary about the new normals is available from the National Water and Climate Center.
Overview Presentation
The following video presentation highlights how the normals update impacts Nevada. For a pdf of the presentation slides click here.
Key Points about 1991-2020 Normals in Nevada:
- The median is the new default normal used in all NRCS products.
- Most 1991-2020 medians for snow, precipitation and streamflow in Nevada are less than 1981-2010 normals (exceptions exist).
- The main impact of a smaller normal is it produces a larger percentage.
- The reason 1991-2020 medians are less than the 1981-2010 normals is due to a combination of shifting the climate periods (1981-2010 to 1991-2020) and the statistical change from average to median.
- Streamflow forecasts have been re-calibrated with 1991-2020 data.
- New medians do NOT change SNOTEL data collection methods.
Tips for Adjusting to New 1991-2020 Medians
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Pay attention to how percentages are reported – median vs. average. External sources may mis-label data.
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Don’t expect as much water from a given percentage snowpack.
- Think like a water manager. Concentrate on streamflow volumes not on percentages.
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Investigate the new normals yourself using the tools lower on this page.
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Use tools that compare current data with historic years without percentages. Examples include:
Investigate the 1991-2020 Normals
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Normals Technical SummaryThis Technical Summary of 1990-2020 Normals was produced by National Water and Climate Center and explains calculation methods and additional information. |
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Basin Snow Water Normals Comparison |
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Basin Precipitation Normals Comparison |
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SNOTEL Snow & Precipitation Normals Comparison |
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April-July Streamflow Normals ComparisonFor help accessing historic time series and histogram plots click here. |
Retrieve 1991-2020 Normals
Interactive Map:
Snow: Today's Median / Average | April 1 Median / Average
Precipitation: Today's Median / Average | Water Year Median / Average
Streamflow: Seasonal (April - July) Median / Average | Water Year (Oct-Sep) Median / Average
Update Reports by Basin:
Snow and Precipitation: Today's % of 1991-2020 Median | Today's % of 1991-2020 Average
Month to Date Precipitation: Today's % of 1991-2020 Median | Today's % of 1991-2020 Average
Snowpack % of Peak: Today's % of 1991-2020 Median | Today's % of 1991-2020 Average
Tabular Reports:
See "Retrieving 1991-2020 Normals" link here