The most popular method for surfers to forecast whats going to happen over the next 120 hours is this WAM script. The closer the colour to 1 on the key the flatter the swell, the further away from 1 the bigger the swell.

Obviously this doesn't take into account wind etc, so this script is best used in conjunction with a good wind model. See below.

Used in conjuntion with the WAM script above this gives you a good idea of wind speed and direction.