This work focuses on the overall effect of blade positions in a wind farm. Assuming that there are no synchronization forces in a wind farm, the distribution of blade position of the turbines of a wind farm is derived. The crossing of blades in front of its turbine tower is modeled as a Poisson Process. The variability of the wind farm power output due to tower shadow and the probability of extreme conditions (such as simultaneous tower shadow events at all turbines of a wind farm) are estimated in the time domain. Index Terms-wind power, flicker, power fluctuation