South Dakota NWS to change Grassland Fire Danger Formula

The National Weather Service Offices in Aberdeen, Sioux Falls, and Rapid City will start using a new index for the South Dakota Grassland Fire Danger Statement and Grassland Fire Danger map on March 15, 2011.  The Grassland Fire Danger Statement itself will not change.

The Grassland Fire Danger Index (GFDI) is based on a mathematical formula that uses temperature, relative humidity, wind speed, and curing data.  Curing is related to the “greenness” of the plant material.  Grass is a light-weight fuel that reacts quickly to changing weather conditions, which have a large and immediate effect on fire potential.  The GFDI also better represents the role of wind speed.  Recent studies have shown that wind often has the greatest effect on the overall fire danger for grasslands.

The Grassland Fire Danger Statements and South Dakota Grassland Fire Danger map are issued once a day during the fire season around 5 AM Mountain Time.  The fire danger is described by one of five categories, which correspond to the likelihood that grass fires will get out of control:
   Low Fire Danger
   Moderate Fire Danger
   High Fire Danger
   Very High Fire Danger
   Extreme Fire Danger

The grassland fire danger forecasts can be used by emergency managers and fire officials for decision-making on issuing burn permits or burn bans. It may also be used for planning prescribed burns.

If you have questions or comments, you may contact the Rapid City NWS office Fire Weather Focal Point.

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