Does Thunderwave hit the 8 adjacent squares or 3×3 squares in front of the caster?

@chrisperkinsDnD we need a ruling. Does Thunderwave hit the 8 adjacent sqs or 3×3 sqs in front of the caster?

— Alan Drake (@vsdrake20) October 21, 2015

The caster is on the edge or corner of a 3 x 3 sq area. https://t.co/4ZvU2jH5Ht

— Christopher Perkins (@ChrisPerkinsDnD) October 23, 2015