It's been said already, griz range is practically all over the west part of the state, but they're not behind every tree. I've seen only one in about 15 years, but it was a big boss. It ran from me, and I was thankful for that. That said, I just always carry spray when I'm in the mountains. From what I've read it's statistically more likely to deter an attack, but it's not a magic bullet. Speaking of bullets, bears can/have been shot and still inflict I great deal of damage while they're dying. Anyway, every near I've ever seen, black and griz, blessedly ran like hell when they saw or smelled me.
As far as tactics, I tend to see bears where dark brush, green grass in patchy timber, and a water source converge. Grab a vantage point and be mentally prepared to spend a lot of time behind your binoculars. But seriously, in my mind bears are not real easy to pattern or anticipate. You might see them anywhere and at any time of day, or you might not see a thing. I've probably seen most just coming out grazing on the tender green grass in mid to late afternoon. And they can be remarkably elusive - you might be sitting there looking at a clearing, look down to pick your nose or something, look back up and there's a bear that seems to have coalesced out of the ethers. And bears have ADHD. Most don't stop moving long and for no apparent reason might just suddenly jump up and sprint away - I've seen this more than once and figure they probably just got a whif of something they didn't like.
Do not underestimate their sense of smell. I'm of the opinion it's even more keen than a deer or elk, but they really don't seem to see that great. You gotta be down wind when you approach, there's no other way.
If/when you shoot one, pay very close attention to where it ran (assuming it didn't go down within sight). I've watched lots of bears, but the only one I ever shot ran immediately for the thick stuff. It didn't go far with a 165gn Federal TBT through both lungs but it left very minimal sign and hardly any blood. That was because her thick, shaggy spring coat soaked it up like a sponge.
You asked about weather. Man, expect anything. Montana springtime can be highly schizophrenic. I do tend get rained frequently in the spring, but it can go from rain to snow in minutes.
Good luck on your adventure. I hope it goes well.
