Belgingur uses weather forecasts to estimate how sulfur dioxide and ash would distribute in an eruption on the Reykjanes peninsula. There are many populated areas in the close vicinity of the expected eruption site. The countries largest international airport is relatively close by, and parts of the capital area are within 20km of distance. Consequently, a high-quality dispersion forecast may provide valuable information to decision-makers if/when an eruption starts. WRF-Chem atmospheric model is used to simulate the dispersion of volcanic ash and SO2 from a hypothetical eruption on the Reykjanes peninsula in SW-Iceland. The forecast is run on a horizontal grid with a 3km resolution and goes out for nine hours. A new forecast is created every hour using input data.