Our most recent snow storm caused great gnashing of teeth as some areas not expected to receive much snowfall got 8-12 inches! The featured chart attempts to explain why this surprise happened. The GFS forecast model is one of the models used by forecasters to predict the weather. The model is run four times daily and each run produces a forecast out the next week or so. The featured chart presents the model forecasted precipitation for a grid cell over the Des Moines Airport. The top bar displays what was observed. If you focus on the third column in the grid where the most intense precipitation fell, you will see that the model went from a dry solution for Des Moines to having a storm to then again dry and the runs made on the 26th ramped up the totals tremendously. These changes are due to storm track differences as the model moved the storm initially south of Des Moines and then brought it back.

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Tags:   model