Buy incrementally. Buy 1/4 of your total desired immediately on Monday morning - that way if it continues the momentum (most likely) you catch some of it. Then if it continues upward, go ahead and buy another 1/4 if it goes up $1/share from your original entry price. Then wait another day and buy another 1/4 Tuesday or Wednesday - if it continues upward. Then the final 1/4 the following Monday.
This way you ease into it, don't get caught if it drops back a little.
If it starts going down, then you are only in it for 1/4 of your total desired shares. If it drops another $1 then you can buy another 1/4 (though I would wait at least a day in this case to see what the momentum is doing). If it was going down further, I'd wait until next Monday to buy the 3rd 1/4. Then the 4th 1/4 the following Monday.
If it stays flat, then you can buy 1/4 each day without issue.
This way you manage your risk, participate some in the upside, guard against downside while still increasing your position.