I think MM's main point was, unless she seems to be in distress or otherwise ill this close to delivery it's not good to cause her any additional stress, and a vet visit will definitely be stressful on her. Also, without an exact date of conception it's all pretty much just a guessing game so your vet may not be able to tell you anything that you don't already know.I wouldn't bother with a vet trip, unless the vet sees a lot of pregnant cats they aren't experienced at guessing dates.
However, if you are concerned about her then by all means take her. You just have to weigh the pros of what you may find out with the cons of the uncertainty of the situation and the added stress on her. By way of example, i brought in a foster that was huge and the vet was certain she would pop any minute- she kept me waiting 4 more weeks! On the other hand, I had another who they weren't even sure if she was pregnant (and if she was it was very early on) only to have her go into labor a few hours later. Sometimes even the most seasoned vets misjudge the time!
In the end, only you know what you need to do. I hope the babies come tonight so you don't have to decide! Be safe during the storm.