Charged Lightning Strike

In line of sight you conjure a 10 foot radius dark storm cloud that crackles with electricity. As an action you end the spell and cause a bolt of lightning to strike a spot you can see within 120 feet of the storm cloud blasting in a 10 foot radius, creatures in the area make a Dexterity saving throw against your spell DC on a save they still take half damage. The spell does 3D10s + D10s equal to your spell casting ability modifier as lightning damage. As a bonus action on subsequent turns until the spell ends you can add a number of D10s equal to 1 + your spell casting ability modifier to the damage.