From April 20 to April 21, the center of low pressure moved from Des Moines to Detroit. What city would you think it would be over on April 22 if it continues to move in the same manner? What type of air mass was over Washington on April 21? What type of air mass was over Washington on April 22? How do you think conditions changed in Washington, DC from April 21 to April 22? Include the general changes in temperature, dew point temperature, wind direction, and air pressure. In order to answer the question, you could look at the conditions in a city, such as Indianapolis, IN, before and after the cold front passed through.