To grill the corn:

Peel back the corn husks and leave them attached at base of each ear of corn.   Remove the silks and close the husks over the corn cobs.  Soak the corn in cold water for 10 minutes.  Drain and pat dry.

Preheat the grill to medium-high heat.  Place corn on grill and cook.  Turn every 3 to 5 minutes, until all sides of the corn are cooked, about 15 minutes.   Slice the kernels off the cobs and set aside.

To make the dip:

1. In a large bowl combine the yogurt, mayonnaise, lime juice, garlic powder, onion powder and salt.  Set aside some of the corn, scallions and jalapeno for topping the dip.  Add remaining corn, scallions and jalapeno to the bowl and stir to coat.  Chill for at least 1 hour.
2. To serve, spread chilled corn dip in a bowl and top with reserved corn, scallions and jalapeno.  Sprinkle with cheese and garnish with cilantro.  Serve with tortilla chips.