You're rebooking your outbound leg which means you'll have to be reticketed. That means you cancel your existing reservation and will be subject to penalties for cancelling per the fare rules with any remaining money available to credit to your new itinerary. The new fare for the 11/2-11/4 weekend which will likely be high since it's so close to departure.

I would suggest as another option that you get to the airport (you did not mention which of the DC area airports you're actually leaving from) as early as you can and go stand-by on the first available flight if it looks like there will be weather issues, especially later in the day.

Nearly all CO tickets allow stand-by on domestic reservations.