Generally why do you overcall? It is for a number of reasons including:
- to compete for the part score
- to tell partner the lead
- to find a good sacrifice
- to make life difficult for the opps
Opposite a passed hand, when you are vulnerable against not, and RHO has opened a strong 1NT, and you have 5 points and a ropey suit, bidding 2
♠ achieves none of these objectives.
Instead you are offering the opposition the chance for a juicy double, telling them that suits are breaking badly, warning them about a weakness.
So I think this overcall is misjudged.
Instead just pass and lead a spade. You never know, partner may have
♠Kx and the suit will run. Once you've bid they'll never play in 3NT when it's wrong.
However, once you've bid I'd still lead a spade as it's the best chance to beat the contract.
Paul