The NREL maps are reliable for serious prospecting, and can be used as a rule of thumb.  Especially when thinking about the region as a whole.  Individual sites still have to be measured and/or calibrated to reliable long-term measurements.  I'm trying to think of who up there would be worth talking to, as that's a good way to get a current lay of the land.  But speaking with NREL might also prove valuable.  There'a a program called Wind Powering America which has also been involved with some of the tribes up there, some of whom have refurbished older turbines if i recall.

"Life shrinks or expands in proportion to one's courage." - Anaïs Nin