if they are running on snow or ice, there are mechanics for that. can reduce movement speed additionally for steep inclines.
For skill checks, I might take the average of your PCs 2 highest Climb, Swim, or Survival skills and use that figure for rolls. maybe a Con check for being winded from running all out away from impending tidal wave of snow and trees. reflex to avoid rough patches, trees etc.
I'd reference the rules for running a Chase encounter and modify that to suit your challenge. Made the snowmass the pursuer trying to catch the PCs.
Source: Paizo Blog
A frozen lake, a sheen of thick ice on a dungeon or cavern floor, or some other cold and slick surface, slick ice can be hard to traverse, but can also increase the speed of creatures that are agile or foolhardy enough to utilize its surface's lack of friction.
A creature traversing slick ice at more than half speed is required to make a DC 15 Acrobatic check at the start of the movement. Failure causes the creature to fall prone at the start of the movement. Running or charging on slick ice increases the DC by 5, with the same effect on a failed skill check. A creature that succeeds at this check by 5 or more can increase its move across the ice by 10 feet, but is considered flat-footed until the start of its next turn. Creatures (like those with enough levels of barbarian or rogue) that can't be caught flat-footed at the start of combat are immune to this flat-footed effect as well.
I'm running my first avalanche tomorrow, and was wondering if there are any mechanics I should be aware of?
I've looked through the GM's guide but can't see a relevant bit.
Any advice/stats/mehcanics anyone has pre-made, please feel free to link/post bits.
Mrs. Camelot (Noob GM)
Core rule book page 429.
Edited: Apperantly I am suppose to put here "ninjad by nezthalak" ?
Awesome, thanks all.
Hopefully the clerics channelling will stave off hypothermia until they can be dug out by the snowcasters.
Hopefully this will get the players back on track. :)
In this instance, I'm using the avalanche to explain why the players don't just go back through the gate/hang around until it's recharged and ignore the module.