At least I am pretty sure this is dame's rocket. Even though it's technically an invasive species, I think it's fairly nice looking.
Dame's Rocket is known as hesperis matronalis and is native to Eurasia. It was brought here because it is a nice looking flower but like many things brought for gardens or whatever, it has escaped into the wild.
The flower tends to bloom in early to mid spring but with the odd weather we've been having, I'm not surprised it is blooming now.
It is a prodigious breeder and tends to crowd out the native species.
It is prohibited in Colorado, Connecticut and Massachusetts. It is restricted in Wisconsin.