NDFD-SnowFall.mxd<br/>

The National Digital Forecast Database (NDFD) was designed to provide access to weather forecasts in digital form from a central location. The NDFD produces gridded forecasts of sensible weather elements. NDFD contains a seamless mosaic of digital forecasts from National Weather Service (NWS) field offices working in collaboration with the National Centers for Environmental Prediction (NCEP). All of these organizations are under the administration of the National Oceanic and Atmospheric Administration (NOAA).

Snow Amount is the expected total accumulation of new snow (in inches) during a 6 hour period. A snow accumulation grid will be specified whenever a measurable snowfall is forecast for any hour during a valid period.Valid periods for the NDFD begin and end at 0600, 1200, 1800, and 0000 UTC.

This feed consumes NDFD’s files and calculates the snow accumulation, cumulative snowfall, and amount snowfall over time for the next 72 hours

Source: http://weather.noaa.gov/pub/SL.us008001/ST.opnl/DF.gr2/DC.ndfd/AR.conus/VP.001-003/ds.qpf.bin

Organization: NDFD (National Digital Forecasted Database) POC:

Scale/Resolution: 1KM

Update Frequency: The Data Increments: 3 hours Refined: Hourly Downloaded: Hourly

Area Covered: CONUS (Continental United States)


Access and Use Constraints:This data was derived from NDFD, who state that the data is “Public Domain.”



This work is licensed under the Web Services and API Terms of Use.
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This map is provided for informational purposes and is not monitored 24/7 for accuracy and currency.

Processing: The data is downloaded from the NDFD using The Aggregated Live Feed Methodology

Live Feed Script Automated Process:

• Check source location for updates and then download
• Extract Floating Point Raster and Shapefile files from binary download, returning a list of files to process
• Enable Arcpy and Spatial Analyst Extension
• Setup workspaces (File Geodatabases)
• Prepare Raster objects and time space details from list of files to process, augment (injecting new Raster objects if Morphing is required)
• Process each Raster object
• Negate NoData and Zero/Null values in Raster
• Re-Project Raster to output projection while increasing cell size and smoothing with bilinear interpolation
• Vectorize Raster
• Reclassify Raster using predefined symbology
• Convert Raster to Polygon Vector Featureclass
• Add Fields
• Calculate new field values
• Drop unwanted fields
• Create or Append to output
• If accumulation of data is required (to create an accumulated Snow Fall layer for instance)
• Drop Negation (zero out all cells < zero) for proper map algebra addition
• Add to accumulation Raster
• Export current accumulation Raster using ‘Vectorize Raster’ process above
• Add Spatial and Attribute indexes to output Featureclass(es)
• Add Spatial and Attribute indexes to output Featureclass(es)
• If required
• Archive File Geodatabase and distribute to S3
• Deploy File Geodatabase to Live location

Attributes:There are no attributes because the final product is a map service. This service does show snow accumulation, cumulative snowfall, and amount snowfall over time for the next 72 hours by using a color ramp.

Symbology:
View Legend