Here is a link as to how it works.. Interesting.. 180 of 30 could see england sturggleWell, according to Cricinfo the cut-off time is 4:30pm local (currently 3:19pm local).
That seems rather weird as the finish time is scheduled for 5:15pm local. I would imagine no play possible after 6:30pm local, meaning we would need to start 20 overs at 5:00pm local.
Buggered if I know what that means for the overs.
EDIT - clarification is we must start by 4.30pm local time if we are to get 20 overs in.
It looks like we will get underway in about 20 minutes, which will give us another 45 minutes of play. That gives us another (45/80)*20 = 11 overs... so the Pickup Prediction for the runchase is 183 off 31 overs.
EDIT 2 - Sky tell me they are aiming for a 3.50pm restart: therefore 179 off 30 overs.
Isn't maths fun?
Duckworth-Lewis.com - Calculator