Reason for cancellations, baggage allowance after downgrade.

My Flight UA6314 SAN-MMH for March 14 has been cancelled.

Agent over the phone alleged "weather". I find that unbelievable, given that California is having wonderful weather and these small aircrafts don't go too far.

1. Where to find online what the official reason for cancellation is?

2. I had upgraded to First (offered at online check-in) to take advantage of the free checked bags and paid $49. Now I am in coach to SFO, then on First to MMH. I am afraid that airport agent in SAN will try to make me pay for my checked bags. Can she? Phone agent assured me I should not be charged for checking bags, since I was booked in first when the irrops occured. Otherwise, how do I ask for a refund of my $49 if I am forced to pay baggage fee at airport?

3. Can I get on the upgrade list for the flight to SFO?

4. If in fact it was some other reason that entitles some sort of compensation (I am losing my lift ticket for example), should I ask for it at the airport? or...????

Sorry if this has been asked somewhere else, I don't come to this forum very often, not elite with UA.

Thanks,