Advancing today were No. 8 seed Austen Huang of Elk Grove in the boys 18s, No. 1 Sara Choy of Palo Alto in the girls 16s and No. 1 Stefan Leustian of Mather in the boys 14s.
However, No. 1 Katie Volynets of Walnut Creek lost to No. 4 Gabriella Price of Montebello, N.Y., 6-4, 6-1 in the girls 14 semifinals in Tucson.
In Scottsdale, Huang routed No. 10 Jason Lui of Bellevue, Wash., 6-1, 6-3, and Choy beat unseeded Sedona Gallagher of Henderson, Nev., 6-3, 6-4.
Leustian defeated No. 3 Harry Yang of Arcadia 6-1, 6-3 in Tucson.
Huang will face No. 1 William Genesen, a Tulsa, Okla., resident headed for Stanford. Choy will meet No. 2 Hannah Zhao of San Diego, and Leustian will play No. 10 Ryder Jackson of Nicasio.
Top seeds Zummy Bauer of Suwanee, Ga., and Andrew Ton of Milpitas won the boys 16 doubles title. Ton, a diminutive left-hander, also captured the boys 14 doubles title in the 2014 USTA National Clay Court Championships in Fort Lauderdale, Fla., with Brandon Nakashima of San Diego.
USTA NATIONAL WINTER CHAMPIONSHIPS
(Northern California results only)
18 and underAusten Huang (8), Elk Grove, def. Jason Lui (10), Bellevue, Wash., 6-1, 6-3.
14 and underStefan Leustian (1), Mather, def. Harry Yang (3), Arcadia, 4-6, 6-3, 6-1.
16 and underZummy Bauer, Suwanee, Ga., and Andrew Ton (1), Milpitas, def. Ryan Seggerman, Coronado, and Charlie Sharton (8), Wayland, Mass., 6-4, 7-5.
16 and underSara Choy (1), Palo Alto, def. Sedona Gallagher, Henderson, Nev., 6-3, 6-4.
14 and underGabriella Price (4), Montebello, N.Y., def. Katie Volynets (1), Walnut Creek, 6-4, 6-1.
Doubles finalAmanda Chan, Pasadena, and Amy Huang, San Diego, def. Gabriella Price, Montebello, N.Y., and Katie Volynets (2), Walnut Creek, 2-6, 6-4, 6-4.