Median/Extreme Date of Last Snowfall
Conterminous United States

Statistic: 30-year median/extreme date of last measurable (>=0.1" or 2.54 mm) snowfall in Spring 
Time period: 1961-1990
Time interval: annual
Spatial format: grid
Data format: ARC/Info ASCII GRID

 Projection: Geographic
Spatial resolution: 1.25 arc-minutes (~2 km)
Spatial Extent: Conterminous United States
Units: Julian Day
Date created: August 2000
Methods: Statistical derivation from mean wet-day temperature, mapped with the PRISM modeling system, and Gaussian filter resolution enhancement. See FGDC-compliant metadata for details. 

Examples 
 
Median date of last snowfall
Features
  • Reviewed and approved by the US National Climatic Data Center 
  • Incorporates topographic effects on timing of snowfall
  • Includes coastal and lake effects on timing of snowfall 
  • Accounts for temperature inversions on coasts and in inland valleys 
  • Uses upper-air temperature data to capture high-elevation patterns 
  • Consistent treatment and spatial quality control of station data 
  • Consistent coverage across all state boundaries 
  • "Universal" geographic (latitude/longitude) projection allows conversion to any other coordinate system 
  • Data format allows for easy import into ESRI's GIS products, as well as MAPINFO and Intergraph's GeoMedia 
Data used in analysis
  • 5,426 National Weather Service stations for date of last snowfall 
  • 6,358 stations for mean wet-day temperature
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