* Some hepcats won't make the beach scene during this glorious long weekend -- don't want to get sand in their fur, you see. Instead they'll be doing the wop-bop-a-loo- bop at a couple of concerts around town.
* In Old Town this Monday you can purr along to tunes at Alexandria's Memorial Day Jazz Festival. The lineup starts off with the Doc Dikeman Big Band at 11 a.m., followed by the U.S. Navy jazz ensemble "The Commodores" at noon, the Jazz Masters at 1, Explorer Jazz at 2, the Post Nuclear Jazz Society at 3, Kaleidoscope at 4, and finally The Bob Lewis Orchestra from 5 to 6. Jazz- announcer Felix Grant of WWRC (980 AM) radio will host the day of hot tunes. It's at Market Square in the 300 block of King Street. Call 838-4343; free.
* The Pavilion at the Old Post Office will hop all weeknd starting on Friday at 7 p.m. when the Post Nuclear Jazz Society plays its contemporary brand of jazz. Saturday from 2 to 4 the D.C. Jazz Workshop Orchestra will perform; the Difficult Run Jazz Band plays at 2 on Sunday; and on Monday the bluegrass band The Sprouts of Grass will perform with the Cranberry Cloggers at 1. To wrap it all up, Second Story will play traditional folk music from 4 to 6. The Old Post Office is at 1100 Pennsylvania Avenue. 289-4224; free.