The annual radiothon for the National Symphony Orchestra sponsored by WGMS-FM/AM (103.5/570) will feature a sing-along with Mitch Miller at White Flint Mall tomorrow.

Miller's 1:30 appearance will be a highlight of the 33 hours of music, celebrity talk and auctions that begin at 6 tonight and continue until midnight Sunday. Also scheduled to participate is actor Werner Klemperer, who will be at the mall at 11 a.m. tomorrow. Several NSO musicians will appear Sunday, including the Capital Woodwind Quintet at 10 a.m., the Brahms Horn Trio at noon and associate conductor and pianist Andrew Litton at 5 p.m.

The radiothon, which it is hoped will raise $225,000 for the orchestra, is continuous except for the "Texaco-Metropolitan Opera" program tomorrow at 2 p.m., the overnight shows starting at 11 p.m. and "Delta's World of Opera with Paul Hume" Sunday at 1 p.m.

In the contribution corner, WAMU-FM (88.5) is kicking off its annual week-long spring fundraiser tomorrow at 3 p.m. Last year the public radio station raised $245,000 in this seasonal drive. Irish Smiles and Songs

WAVA-FM (105.1) will be be participating tomorrow in the St. Patrick's Day "Rally in the Alley" for Martha's Table, an organization that feeds the homeless. The event takes place between L and M streets and 18th and 19th streets NW . . . A number of personalities will be participating in various parades this weekend: Mac McGarry of WWRC-AM (980) will again be the emcee at the District's St. Patrick's Day parade Sunday at 1 p.m. Joining him will be WWRC's Felix Grant and Bill Hickok. Don Geronimo and Mike O'Meara will lead the WAVA cars and van; the team from WRQX-FM (107.3) will be in their Irish regalia. Over in Alexandria, the parade begins at 10 a.m. tomorrow, and Jim London and Mary Ball of WMZQ-FM (98.7) will be riding on a float.

On the holiday Monday, WASH-FM (97.1) will take its "Continental Breakfast" crew to Rumors for a remote from 5:30 to 10 a.m. . . . WBMW-FM (106.7) will throw a party at the Pierce Street Annex starting at 3 p.m. Crockett will do his show live from the annex from 7 to 11 p.m. with cut-ins from nearby Flaps and Sign of the Whale . . . Dave Arlington and Dave Adler of WLTT-FM (94.7) will emcee a party for their listeners at the Hyatt Regency on Capitol Hill, beginning at 5 p.m. Music will include Tom Lofgren's band, the Newkeys . . . Jeff Baker and David Burd of WCLY-FM (95.5) will host a party at 5:30 p.m. at the Hyatt Regency in Crystal City . . . WASH will celebrate at the Radisson Mark Plaza Hotel in Alexandria at 8 p.m. The next day Arthur Crofton and Linda Sherman will be there for an early morning remote.

On the music side: Ed Walker will feature Bing Crosby, Dennis Day and other Irish performers Sunday; on St. Patrick's Day, Diane Rehm of WAMU will include music from Ireland and Scotland by the Pratie Heads on the second part of her 10 a.m. show . . . All of Monday will be turned over to Irish music on WWDC-AM (1260) . . . John Chester of WGMS will feature Irish music from 10 a.m. to 2 p.m.; then Karl Haas will continue the celebration; Win Clearwater will play Harty's "An Irish Symphony" at 7 p.m. . . . David Chadwick of WGAY-FM (99.5) will present "When Everyone Is Irish" at 7 p.m. . . . WHUR-FM (96.3) couldn't decide what to do for St. Pat's so Jesse Fax, program director of the black music station, has scheduled an hour of Al Green at noon.

And speaking of parades and Monday, that is the deadline for entries for the annual Gross National Parade of WMAL-AM (630). News Specials

Jack Sheehan, the morning news anchor at WWRC, will take a five-part look at PCP abuse next week each morning at 7 a.m. . . . Beginning Monday WTOP-AM (1500) will feature "Tax Tips," a 22-part series by Paul Hencke of the Research Institute of America. The weekday reports will be broadcast at 6:53 a.m., 11:57 a.m. and 3:55 p.m. . . . WETA-FM (90.9) will carry the address of Rep. John Dingell (D-Mich.) at 1 p.m. Tuesday from the National Press Club; then from the same podium on Thursday, Sen. John Heinz (R-Pa.) and Sen. George Mitchell (D-Maine) . . . Ernest White, host of "Crosstalk" on WDCU-FM (90.1), will discuss the images of the urban poor in literature with writer Rosa Guy on Thursday. On the same day D.C. Councilman William Spaulding will answer questions from listeners about proposed sites for a new prison. Staff Changes

Lucy Crider has joined WINX-AM (1600) as the morning news person and Jamie Dupree as the afternoon news anchor . . . Bob Sweeton, known professionally as Maxx, has been named to the overnight shift at WRQX. The Datebook

Bill Mayhugh of WMAL will be doing periodic broadcasts from Raleighs on Connecticut Avenue today from noon to 2 p.m. This is a warmup for the Leukemia Society radiothon March 23 . . . WMAL has rescheduled the final cook-off in its contest to fatten up Bullets star Manute Bol to Monday night at Jameson's restaurant in Bethesda.