The annual competition, held near Washington, D.C., started Tuesday with 281 contestants from around the globe, all under the age 16.
That number had dwindled to 42 earlier today, and more contestants were eliminated as the semi-finals continued this afternoon.
The final rounds will begin at 5 p.m. PST and will be broadcast live on ESPN.
Audrey Bantug, 13, of San Ramon, was the last of three Bay Area contestants to remain in the bee today, after correctly spelling "oread," "umami," and "prosciutto" to advance to Round 6.
The previous rounds included written tests, including on the meaning of words -- a new feature at the bee.
However, she was eliminated after misspelling the word "polytocous," an adjective meaning having more than one offspring at a birth.
Another Bay Area contestant was 13-year-old Cecilia Trujillo from Chualar, a community in Monterey County near Salinas, who spelled "Holi" and "legato" correctly before she was eliminated in Round 3. Cecilia is an eighth-grader at Chualar Elementary School.
Cupertino resident Neha Konakalla, 13, was also knocked out of the bee in Round 3 after correctly spelling "kohlrabi" and "eccrinology."
Both Neha and Cecilia fell short of the points they needed in the vocabulary portion of the bee to advance.
Neha's classmates at Sam H. Lawson Middle School, where she is a seventh-grader, were following her progress this week, principal Jeff Bowman said.
More information about the spelling bee is available at www.spellingbee.com.