Logan Styler scored in double overtime as Castlegar beat Nelson 5-4.
Everett Hicks scored a hat trick as Castlegar beat Nelson 5-1 to tie the series.
Devin Allen had 53 saves as Nelson won Game 1 of the playoff series.
Nelson's 5-2 win over Grand Forks means the Leafs face Castlegar in the playoffs.
The 2-0 win keeps Nelson in contention for third place.
Dale Howell scored and had two assists in Nelson's 5-3 win against the Fernie Ghostriders on Saturday.
Nelson dropped a 5-3 result to the Columbia Valley Rockies in Invermere on Friday night.
The Atoms finished second at a Trail tournament, while Nelson also hosted a PeeWee tournament.
Castlegar downed Nelson 3-2 in the last regular season game at the NDCC.
Mitch Foyle scored with only a minute left in regulation to lift the league-leading Beaver Valley Nitehawks past the Leafs 4-3 on Saturday.
The former teammates passed away on Christmas Day.
Fernie's Keagan Kingwell scored 3 goals in the 5-3 victory Saturday.
Grand Forks' Mitch Turko scored with a minute left in regulation to force double-overtime.
Castlegar scored five goals in the second period en route to an 8-2 win.
Six different players scored as Nelson overwhelmed Spokane on Sunday.
Hunt's goal against his former team came during Nelson's fourth straight game that went to overtime.
Nelson sent the forward to Revelstoke to bolster its defensive corps at the KIJHL trade deadline Tuesday.
Nelson fought back from a 3-0 deficit but fell 4-3 to rival Creston.
Sawyer Hunt had two goals and Logan Wullum scored in overtime to give Nelson a 3-2 win over Golden.
Grand Forks scored five unanswered goals to romp past Nelson.
