Elk and Thermals

[NealS02]

This question is not generically about thermals or prevailing wind, but about experience with hunter horizontal orientation on a slope and thermals. A theoretical situation, but one that I’ve encountered is approaching an open feeding area (8500 ft) in the morning, on a slope that is east facing (ridgline running N to S), with ridge peak at 9000 ft and valley floor 8000 ft.

The elk typically bed below and work up to this feeding area before going up further in elevation to bed towards the ridgeline peak, moving E to W. In this scenario, I plan to start my hike S of the feeding area, climb in elevation while moving N, and position myself to the south of the feeding area for morning ambush at the same level or elevation that the herd will move to.

Assuming that morning thermals are moving downhill W to E into the elks’ face and prevailing winds are not impacting this and no shift in thermals, how far offset to the south (distance from the feeding area) do I have to be to not have thermals carry my scent to the elk moving E to W up in elevation and perpendicular to my S to N movement?

I can clarify if needed. Thanks in advance!

 

[mad_angler]

Is this correct? Are you asking "what is the orange distance?"

 

[NealS02]

You nailed it! Thanks for the illustration. I know that if I sit directly on the green feeding area, the thermals are gonna go downhill to their face. That orange line distance and what would be appropriately safe is what I was looking to get feedback on.

 

[Chris in TN]

Tagged. I don't think there's an actual answer based on any sort of calculations beyond 'how far away can you see to shoot from'.

I have an idea of a very similar scenario could play out, and the answers to this interest me. I am thankful that we have 3-4 days, hopefully, to do a crash course in wind and morning thermals, next week, hopefully away from any actual elk. I literally just want to sit for the first hour of the day somewhere with a wind checker bottle and sit and learn.

 

[LCguy]

I have gotten a shot at a cow elk from 50 yards with a muzzleloader in basically this exact same scenario. Just check the wind constantly. and keep a lookout that no elk are getting directly above or below you. What will get you in trouble is if the wind starts running perpendicular to the thermal.

 

[Dos Perros]

In my experience the directionals in the west are generally southwest to northeast in September, and then sometimes cold fronts come through and it switches from northwest to southeast. Based on that usually I think you'd want to be to the north of the feeding feature, except in cold front situations. I also think if you have the wind right, and it is consistent, you can be pretty damn close to the feeding feature. Bow range type close. If you have a rifle no need to be any closer than what you need to cover the whole thing though.

 

[TaperPin]

At ground level, prevailing winds may not be felt, but they are always there, at least a little with swirls, dips, curls, flows around points and down draws. I imagine that is all going on above the tree tops, and can and does mix in with what’s happening at ground level, which is why a cross wind elk 500 yards away can get our scent and take off.

It helps to remember down/up slope gravity winds are air currents that occur at ground level - the down/up slope movement of air has to be resupplied from air that’s near by. It can be a big circular path.





The speed of down/up slope winds is greatest near the surface, but goes away to zero or even starts to flow the opposite direction a tree length or two or three or four up.

 

[Chris in TN]

At ground level, prevailing winds may not be felt, but they are always there, at least a little with swirls, dips, curls, flows around points and down draws. I imagine that is all going on above the tree tops, and can and does mix in with what’s happening at ground level, which is why a cross wind elk 500 yards away can get our scent and take off.

It helps to remember down/up slope gravity winds are air currents that occur at ground level - the down/up slope movement of air has to be resupplied from air that’s near by. It can be a big circular path.



View attachment 944391

Does this also imply that it is possible to have a morning thermal flowing downhill but then rising and going right over an elk's head (or some other direction, not into his nose) so that even though you perceive a wind blowing from you, downhill towards the elk, it's never actually reaching them if they're maybe a couple hundred yards away?

 

[patagonialuke]

I regularly run into this situation (or vice versa on a W-facing slope in the evening) during archery season. If we can keep tabs on the elk's movement and the wind is consistently pulling downhill, we've occasionally been able to set up within bow range.

However, it's a lot trickier if I can't see / hear the elk (especially a big herd), since they almost never follow the exact same route up the hill, and one cow could easily shift a bit N or S and end up downwind if trying to set up a pure ambush at archery range. As a result, we usually aim to set up 100-400 yds away from the anticipated ambush setup and cut the final distance via careful sneaking and/or calling. The specifics vary a ton, but the wind is always my primary focus throughout.

One thing I always look out for is smaller terrain features along the face. Little ridges and gullies often act as funnels for the thermals, so they can sometimes help us get closer while decreasing wind risk. E.g., the primary thermal might be pulling directly E, but if there's a gully that runs NW>SE, the wind in the gully will often be going to the SE in the morning.

 

[Skerhunter]

With thermals it will depend on the smaller terrain features on that face. Without the topo image it’s had to say exactly how close is too close.

If everything to the south of the feeding area is slightly lower you probably can walk right up to it. If it’s slightly higher then you will get busted before you know it. Staying 1-2 topo lines is a safe bet 50-100’ in elevation.

 

[Jethro]

I don’t have a number, but IMO I think the distance you’re asking about is small. Meaning if your scent is not blowing “AT” the elk, they don’t smell you.

The closer you hunt to that line though, the more failures are possible. Roll/dip in terrain, Sun/shade spot, or a swirl can end it real quick.

 

[TaperPin]

Does this also imply that it is possible to have a morning thermal flowing downhill but then rising and going right over an elk's head (or some other direction, not into his nose) so that even though you perceive a wind blowing from you, downhill towards the elk, it's never actually reaching them if they're maybe a couple hundred yards away?

Not really. The elk will still be in the same air you are in. Return air going the opposite direction is not an abrupt wall of air as the return arrow would imply as it is drawn, but it gradually sheds off the top of the moving air.

A cool extreme case is what happens during the heat of the day on glaciers. There will be warm air going upslope from the valley floor on up, but over the glacier the air cools and at ground level there can be downslope flows, while just overhead the warm air is still going up hill.