Most likely outcome: KL861 gets CANCELLED by Jan 6, 8am CET. You'll rebook to KL863 (Jan 8 13:00) and land at Narita Jan 9 morning. You lose 1 day, but Japan waits.
If miraculously operating: Expect 3–8 hour minimum delay. De-ice queues + crew chaos = late board, early Jan 8 arrival at NRT.
Do NOT expect on-time (5–15% odds = don't count on it). Schiphol historically sucks at snow recovery. Once in crisis mode, it's 5–7 days minimum to stabilize.