I suspect it will be a lot quicker than 3 days. The small grocery store near me probably has 20,000 living within 10 miles of it.
I use Florida hurricanes as an example. It takes a day to empty out the stores.
The one grocery here always has empty shelves. They play games with the chain’s weekly ads claiming the item didn’t make it in on the truck. “The truck” is their go to blame. Of course, when you demand something or ask for them to go to the back, it magically appears. If they’re this bad now, imagine what it’d be like when it does hit the fan. Because of their little games, I wonder how many customers have wised up and started stocking so they do have enough on hand to stay ahead of “the truck”? I’ve been waiting for them to put tuna on sale for Easter. They haven’t done it the last 5 years so I’m not holding my breath. Not that “the truck” would make it.
remember that blackout that occured about 7 years ago that affected most of the north east coast for several days? I don't think it affected you but it did us here in S.E. Michigan. It took me 4 hours to get home that day because all the street lights were out. By the next afternoon, the local supermarkets such as Meijers and Kroger were out of all non perishable essential foods, water and beverages.
That was a really strange time. There is an 8 lane highway about a half mile away that was dark and devoid of traffic and eerily silent once the sun went down.