My list of ski areas/resorts with opening dates before Thanksgiving got pretty long. There are also quite a few opening up on Thanksgiving or for the Thanksgiving long weekend. Timberline in WV is opening on Wed, then staying closed on Thanksgiving, and re-opening on Friday. I'm sure that's to allow the employees to enjoy Thanksgiving with their families.
Clearly there are resorts that choose to wait to announce an opening date, as opposed to picking a date months or weeks in advance. This season the destination resorts in the Rockies and Tahoe were able to meet or beat opening dates that were announced long before winter weather forecasts were meaningful.
Note that my interest this early season didn't include the PacNW or the southwest. I paid more attention to regions where I've skied in December or am thinking of going for an early or late season ski safari some time in the future.
11/14: Copper, CO
11/14: Cataloochee, NC - announced 11/14
11/14: Sugar Mountain, NC - announced 11/14
11/16: Park City, UT - announced 11/12, was 11/18
11/17: Killington, VT - announced 11/15, Nov 17 for pass holders only
11/17: Sunday River, ME - announced 11/17, was 11/24, Nov 17-18 for pass holders only
11/18: Crystal, WA - Nov 18-20 for pass holders only
11/18: Palisades Tahoe, CA - 4 days early
11/18: Grand Targhee - MCP but not Ikon
11/18: Eldora, CO
11/18: Alta, UT
11/18: Snowbird, UT - was 11/30
11/18: Snowbasin, UT - was 11/25, Nov 18-20 for pass holders only
11/18: Afton Alps, MN
11/18: Gore, NY - announced 11/17
11/18: Hunter, NY
11/18: Belleayre, NY - tickets online start 11/25 as of 11/17
11/18: Stowe, VT
11/18: Wildcat, NH
11/18: Sugarloaf, ME - announced 11/17, a week early
11/18: Appalachian, NC
11/19: Aspen/Snowmass, CO - was 11/24
11/19: Purgatory, CO
11/19: Lutsen, MN - weekends until 12/9
11/19: Ski Brule, MI - delayed from 11/11, snowmaking started 11/13, then Thanksgiving
11/19: Whiteface, NY - announced 11/17
11/19: Sugarbush, VT - on website 11/15
11/19: Okemo, VT
11/19: Stratton, VT
11/19: Bretton Woods, NH - announced after 11/16, was 11/11
11/20: Mount Snow, VT - announced 11/19, was 11/11
11/22: Snowshoe, WV - 11/22 for passholders only
11/23: Big Sky, MT- a day early, on website 11/15
11/23: Beaver Creek, CO
11/23: Crested Butte, CO
11/23: Steamboat, CO
11/23: Sunapee, NH
11/23: Loon, NH - announced after 11/18
11/23: Wachusett, MA - snowmaking started 11/15
11/23: Blue Knob, PA - announced after 11/20
11/23: Timberline, WV - closed 11/24, re-open 11/25
11/24: Telluride, CO
11/24: Taos, NM
11/24: Boyne Mountain, MI - announced 11/19
11/24: Nub’s Nob, MI - announced 11/22
11/25: Sugar Bowl, CA
11/25: Jackson Hole, WY
11/25: Jay Peak, VT
11/25: Beech Mountain, NC
11/25: Greek Peak, NY - snowmaking started 11/14
11/25: Jiminy Peak, MA - weekends until 12/16, snowmaking re-start 11/17
11/25: Massanutten, VA - snowmaking started 11/16