Assessment of crown fire conditions calls for two important judgments: (1) identifying conditions for the onset of severe fires, and (2) predicting the spread rate, intensity, and size of expected crown fires. This paper addresses the second problem and provides methods for making a first approximation of the behavior of a running crown fire in fuels and weather conditions of the northern Rocky Mountains in the western United States. Rate of spread is developed from field data correlated to prediction of Rothermel's surface spread model. Energy release from surface fuels is obtained from Albini's burnout model. Fireline intensity is estimated from Byram's model. Flame lengths are estimated from Thomas' model. Energy rate, or power developed by the fire and ambient wind, is developed from Byram's equations and used to ascertain the possibility of a wind-driven of plume-dominated fire. The characteristics of these fires and dangers to fire fighters are discussed. The paper is oriented for use by well-trained fire behavior analysts to use in the field without the aid of computers at assess the characteristics of running crown fires.