The description of each spell:
Hail of Thorns (concentration): The next time you hit a creature with a ranged weapon attack before the spell ends, this spell creates a rain of thorns that sprouts from your ranged weapon or ammunition. In addition to the normal effect of the attack, the target of the attack and each creature within 5 feet of it must make a Dexterity saving throw. A creature takes 1d10 piercing damage on a failed save, or half as much damage on a successful one.
Conjure Barrage (Instant):You throw a nonmagical weapon or fire a piece of nonmagical ammunition into the air to create a cone of identical weapons that shoot forward and then disappear. Each creature in a 60-foot cone must succeed on a Dexterity saving throw. A creature takes 3d8 damage on a failed save, or half as much damage on a successful one. The damage type is the same as that of the weapon or ammunition used as a component.
What I want to do is cast hail of thorns as a bonus action and then cast conjure barrage. Each creature that I'm firing on must make two dexterity saves — the first save for conjure barrage, the second for hail of thorns.
To me the only way this would work is if conjure barrage is a ranged weapon attack. To me it seems as though it is, because I'm firing a piece of nonmagical ammunition. And hail of thorns doesn't make my ammunition magical, it just causes thorns to explode out from them on a hit. What I picture happening in game is my character shooting an arrow, the arrow flies out and then multiplies as it goes in a cone, and then each arrow in the cone hits a target and then sends thorns going everywhere.
Can the spells stack that way?