Jon launches a bolt of lightning toward the left most skeleton, causing it to arc towards the second.Spoiler(2 actions) Electric arc doesn't specify how close the two targets have to be to each other, so if both are within 30 feet of Jon, then I think he can hit both.
(1d4+3)[4] electricity damage, basic Ref save DC16
1 action step 5 ft back to let the melee take the brunt of the assault coming