The climate in the parts of Alaska where people live is actually not really exceptional at all. Not including Fairbanks. But Anchorage winters are similar to Minneapolis winters (potentially even a little milder) and Minneapolis has two parks - granted one is inside. Juneau is comparable to Vancouver and the Pacific Northwest, ie. mild year-round. So climate isn't a gigantic issue. They could always opt for an indoor park. The bigger problem is population. Anchorage doesn't even have 400k people in a 100 mi radius. Juneau and Fairbanks don't even break 100k by the same metric.
For comparison (I'm using
this so take it with a grain of salt, but the numbers seem generally accurate to me):
Wonderland (Amarillo): 550k
Joyland: 700k
Silverwood: 850k
Arnolds Park: 1.2 million
Adventureland (Des Moines): 1.7 million
Holiday World: 3.3 million
Michigan's Adventure: 3.5ish million
(For even starker comparison: Cedar Point's figure is close to 12 million)
If we were to see a park in Alaska, it would definitely serve Anchorage. Obviously there's a big tourism industry there, but it thrives in nature, not urban amenities - who would go all the way to Alaska to ride roller coasters? So I doubt it would benefit all that much from tourist activity. So at best, we're looking at a park like Wonderland in Amarillo. Could happen, I guess, but probably wouldn't be anything to write home about. The customer base just isn't there. Maybe a small indoor park at a resort? Maybe.. I don't know.