The DC Caucus is tomorrow, February 14, from 10:00 am to 4:00 pm.
Unfortunately, this timing is not good for those who observe the Sabbath - they will not be able to vote without breaking the Sabbath.
However, the DC Democratic State Committee will allow those who observe the Sabbath to vote TODAY, February 13, until 5:00 pm.
You can vote at the DCDSC headquarters (499 South Capitol Street, SW - Room 412). The DCDSC HQ is a short walk from the Capitol South or Navy Yard Metro stops.