A Phish (Traffic) Jam

From HoCo PD:

On Saturday, Aug. 15th, motorists are advised to expect delays in the area of
Merriweather Post Pavilion and The Mall in Columbia due to a concert that is
expected to draw large crowds.

Starting at 10 a.m., police will be directing traffic on Little Patuxent Parkway,
Brokenland Parkway, South Entrance Road and Hickory Ridge Road.

Little Patuxent Parkway from Brokenland Parkway to South Entrance Road will
be closed to through traffic from approximately 3–7 p.m.

Motorists are advised to plan ahead and allow extra travel time.

What could the be object of such interest? The return of Phish.