Had my 9AM LGA-ORD today (Fri) flight canceled at 6PM EDT yesterday (Thurs). The soonest UA could rebook me was 6AM Saturday. Reason for cancellation was "severe weather in our route network". I have tickets to Lollapalooza that I cannot use or sell, because the tickets are wristbands and not electronic. I would like to seek reimbursement for the Lollapalooza tickets due to the following reason:

1. How can they cancel a flight 15 hours before departure due to "severe weather". They certainly could have dead-headed a plane to replace the flight.
2. UA had 8 other flights that could have gotten me to Chicago in time for the concert. They automatically rebooked me on Saturday, when I called last night, they said they couldn't rebook for Friday.
3. Weather is clear at flight time - both LGA and ORD. There was no severe weather in the area for several hours prior to my original flight time.

Do I have any shot at getting reimbursement, and if so, are there any steps I should follow?