Here is the situation.  I hunt near Lake Superior which currently has a surface temperature of 38-40 degrees.  The forecast for Saturday, MN Riffle Season opener, is a low of 28 rising to 42.

At day break will thermals be climbing the ridge or sinking towards the lake?  At sunset which direction will they be taking?

Thanks for your knowledge on this one.

-MD

This explains thermals a h*77 of a lot better than I could of... It really comes down to the particulars of the area.  Generally, morning thermals rise and evening thermals fall.   Good luck!

Thermals
Thermals are controlled by the heating or cooling of the air. Typically in hilly or mountainous terrain the warming of the air in the morning creates a "draft" that travels from the valley up towards the ridge or peak. In evenings the cooling air sends that draft down the hill towards the valley. Thermals are different than the prevailing wind by the fact that they're due to temp changes and totally separate from the prevailing wind however the prevailing wind and thermals and how they relate to each other are an important part of stand location,more on that later.

Wind Currents
Wind currents or prevailing wind are not as consistent as thermals and much must be noted that a Northeast wind doesn't necessarily mean that the wind will be blowing that way in all types of terrain. My grandfather taught me to think of the wind going across an area like water. Every hill,rock outcropping,stream bed, etc. will change the direction of that wind. Example: if you have a flat that leads to a creek then on the other side of the creek is a hill most hunters will setup on the hill side thinking their scent will blow over deer positioned on the flat. If the wind is blowing from the hill towards the flat the wind will "eddy" like water bringing your scent down to the creek and across the flat. I've watched many hunters set up on these hills thinking the deer won't wind them only to be puzzled by the lack of deer sightings. Many times that wind will be drawn down to the flat and change direction by 180 degrees. Setting up on the flat itself is a much better option.

How they affect each other
Thermals and wind currents can effect each other to a point where the wind is blowing in a completely different direction from where you parked your vehicle. Example; You want to hunt a ridge line in the morning expecting Bucks to leave the fields below to travel up to their bedding area. The ridge is running from north to south and the prevailing wind is coming out of the North. The north wind will hit these thermals and changed direction traveling towards the ridge at an angle and yes the deer will use this to their advantage so if you want to score you better use it to your advantage. Solution: Position yourself on the opposite side of the ridge from where the deer will be traveling up. Bucks will eventually use this side of the ridge to bed for the wind and thermals traveling up from the valley will "eddy" over top of the hill allowing the deer to smell anything on their blind side and use their eyes for looking down the opposing ridge. This tactic has payed off time and time again in PA for me and hope it gives some of you a little edge.
This topic has so many variables to it that you basically can learn something every time your out and taking note and applying it can be the difference between failure and success when targeting big bucks. I'm no expert and am the first to admit I've failed my way to success many times by learning from those failures and not making the same mistake.Learning to hunt the wind and thermals to me is undoubtedly the most important factor in considering stand location

Mark, how near the lake are you going to be? It's a bit of a relative statement. Steve lives in NY so I could tell him that I live near the lake too, even though I'm 30 miles away.

Steve's post gives some excellent info. But I'm not sure how it will relate to being "very close" to Lake Superior. My thinking is that the closer you are to the lake the more of a chance there will be that the thermals will be rising as the lake will be warmer than the air. That said, I don't know what effect the lake will have on pushing your scent inland.

If you have the time you might try and go out a couple of mornings and lighting an incense to see where the smoke goes. If your hunting very close to home, a small campfire will show you even better.

On the other hand, an inversion could occur in which case the biggest factor will be the direction of the air current.

Inversion (meteorology) - Wikipedia, the free encyclopedia

Probably true LD. Some friends of mine use unscented talc powder in a small squirt bottle to test wind direction. I take a piece of sewing thread and tie it to a tree branch if I'm sitting. I also carry a small spray bottle of talc as I frequently like to still hunt but like to monitor conditions.

Steve,

I will have to do more digesting of the info you gave.

LD,  

I will be between the lake the Sawtooth Ridge line.  Which means I will be a 1/2 mile to a mile inland.  100-250 feet above lake elevation.

-MD

Mark, I won't say that your in a micro condition, but it is at least a bit unique.

Even at 30 miles out I'm very aware of what the phrase "Lake Effect" means. It may be a trial and error experience for you.

Until you are one, you may just have to start talking to the old timers in your area. Some things may be more predictable, and others less under certain given conditions.

Typically in hilly or mountainous terrain the warming of the air in the morning creates a "draft" that travels from the valley up towards the ridge or peak. In evenings the cooling air sends that draft down the hill towards the valley


In the west the valleys warm up first and the thermals climb the ridge.  OK  For Saturday that will probably be the case here by the "inland sea"  but when the air temperature remains colder than the lake does that mean the thermals will be moving towards the lake?

Antidote:  During the summer walking down a trail that drops 50 feet you can actually feel the temperature drop 5-10 degrees.  In this situation the land is warmer than the lake.

-MD

I don't think there's any guarantees to anything weather related. I'd use the string or talc method and spot check the current conditions in the area. You can go in with an idea of what you think *should* be happening based upon conditions but a ton of factors are in play when dealing with air currents.

Yup, I hear ya Steve. There was a time when I  hunted  on my feet only, I think that about as often as not I changed my plans in the morning (made the night before) based on what the air currents were doing. It still happens quite often these days.