I've been in contact with R, A's associate, and he assures me that all packages that were scheduled for yesterday will in fact go out today. TN's will most likely go out at the same time as always later tonight. As always, and if you haven't already done so, sign up for a UPS MyChoice account, which will provide pending delivery alerts, most often hours before you would otherwise receive them from the vendor. Either way, I would assume that it will be at least 4:00 pm Pacific time before packages are dropped off and information becomes available.
As for the "why" portion, there is a great deal of discussion of this topic in most of the SY vendor threads, including both this thread and that of R. The short answer is that shipping / order fulfillment is centralized with this vendor group, A and R included. As such, they do not physically prepare your order for shipment and drive it to the UPS facility or drop box. They are front line customer service people, "franchisees" of a sort, if you will, and occasionally there are delays in order fulfillment. Sometimes it's a matter of order volume for the day, which in this case would make a measure of sense with a mid-week holiday and many customers ordering earlier than normal to account for it. Just remain patient, and A will take care of you. This vendor group has the best track record in the industry, hands down, so no need for concern.
If I receive any further updates, I will post them accordingly.