The best powder day of the season was Friday Feb 16th. The day the Seattle Snowstorm ended. The following weekend was fantastic too. Friday March 2, after the earthquake, was also an outstanding day. Schick - On powderwatch This forecast page updates every couple of days.
Skiing can be great without an alert.
Powder Alerts can also be sent out when I darn well feel like it. If you have already signed up in the past, you don't need to sign up again.