ARgon is giving good advice here!
MA doesn't allow out-of-staters to bring guns/ammo into MA (unless they have a NR LTC) for casual shooting or to keep in the car (unless you're driving thru with no intent to "delay yourself here" under Fed'l law). There are exceptions for attending a match (informal plinking doesn't qualify) or a gun show.
If you are otherwise legal to have firearms with you in MA, YES you can leave them locked in the car (not within reach of anyone in vehicle . . . or locked case in rear of SUV or other vehicle with no trunk). The law about unloaded handguns in unattended motor vehicles (referred to above) was changed in 1998 to specifically allow handguns to be unloaded and locked in an unattended motor vehicle.
I am also unclear if you mean you are here today 11/6 or tomorrow 11/7. I have commitments 11/7, but could be available with some warning today.