Finland. For guaranteed snow, skiing (maybe not challenging enough for good skiiers, but great for beginners and families), cross-country skiing, snowmobiling, reindeer-drawn sleighs, husky rides, ice fishing and the Northern Lights.
We've been to Ruka twice, in 2016 and 2018, in February half term holidays, but in fact if you can get there before then, now that Christmas is dying down, the second half of this month will be very quiet, and relatively cheap. We stayed in RukaSuites both times, but there are many other options too.
https://www.ruka.fi/en/rukasuites
The accommodation is feet away from the ski lifts, and lots of restaurants and bars. There is also a great English-speaking ski school, ski hire, and all of that can be booked online independently.
The first time we went, we went on a Crystal Ski package, flying from Gatwick to the nearby airport at Kuusamo. Flights once a week from Gatwick and Manchester. The second time, we booked independently, and flew FinnAir to Kuusamo via Helsinki.
We're not going this year because we're off to the Caribbean at the end of March. I think we were spoilt with snow in each of the last two winters; I'm really missing my snow fix this winter!
They recently had some exceptionally mild weather in Finland, which caused the snow to fall off the trees, but it will come back. There's still 60cm of snow on the ground, though. Just before Christmas the place looked absolutely amazing!
https://www.vuosaariwebcam.com/ruka/archive-yr.php
Relatively cheap? ,well maybe to you,but looks expensive to me,had a look for 2 adults and a child in febuary,around 1500 euros that’s just the accommodation,flights,ski hire ,and lift would be extra I would think.