We consult 2 main forecasts for wave predictions for the Donegal Bay so make sure you understand what they mean and you will know what to expect when you rock up at the beach most of the time (sometimes it doesn't relate well as it is data derived from a model and predicting the wave size at a break is not the same as the swell size in the open ocean which is the information provided) 

 

The swell direction is fundamental to get the most of the small swells. The best waves conditions for beginners and improvers using Tullan Strand and Rossnowlagh would be a West swell with 1 m and 2 m, RESPECTIVELY, with a wave period of 8 to 12 seconds with light winds Bt 1-3. Remember Rossnowlagh is safer as the rips are weak in general whereas Tullan Strand has stronger currents and is ill-advised for beginners without supervision.

 

Here is the 72 hours forecast provided by Windguru and the more fancy display of Magicseaweed for Bundoran.