You are correct that the overall flow field is nearly parallel to the line of flight, however, because it is NOT parallel, I can chose whatever coordinate system I like and apply additive vectors to get the net flow direction (i.e. I take one step forward and one left, I end up moving 1.41steps at 45degrees). So, instead of saying I'm in a 2046mph I can say I'm in a 2045mph head wind with a 15mph cross wind, and have the same effect. In either case, the magnus effect would be virtually the same, because the perpendicular component of the angular flow field is ALWAYS 15mph, whether I say it's 2045.5mph at .46 Seconds of angle or I say it's 2045.45mph head on and 15mph side on.

Accounting for yaw angle isn't necessary if you do this addition. The advantage of it, however, is the ability then to account for the boundary layer buffering and shedding, which I've not yet seen a formula for that doesn't take more calculus to do than I can do in 5min sitting at the computer, and constants for directional drag coefficients or magnus coefficients that would be specific to each individual case.

Also, if I'm reading the figure and text you pointed out correctly (which I think is the same exact figure as one on the site I pointed out above), then the following will happen in my hypothetical 150grn .30-06 bullet...in which the center of pressure WILL be behind the center of gravity, as the relatively large cylindrical body will draw the center of pressure to it, while the center of gravity is shifted slightly forward because of the mass of the tip (assuming that you neglect the density difference in the copper jacket and the lead core, which would shift the Cg rearwards).

This also explains why the magnus force would only temporarily lift a bullet...

The magnus forces would start working, it would lift the bullet, but also turn it to become parallel to the overall flow field (turning your bullet into the wind), this would reduce the magnus lift force considerably...However, it would also be turning your bullet tip INTO the wind, which won't have a net positive effect because of the mass-mass impact of the x-wind and the bullet bluff body...Honeslty, I think there would be no net force in that direction, but more of a torque, so your bullet would become unstable because of the wind and start to gyrate.

So, basically what that figure shows, projectiles will be turned tip wise by a cross wind in addition to their lift, both caused by the magnus effect...this would have a LOT of results, drawing your bullet into the wind (negated by the wind PUSHING back), pointing your bullet into the wind (destabilizing it's flight), and reducing the lift force created by the rotation.

Like I said, no, it's not likely you'll ever see any net positive LIFT due to it, but the force is real, and given the right combination of oddities-which COULD be possible in a hunting environment-it could happen that the magnus force overcome the force of gravity momentarily.

Cut-throat (eldeguello) is correct about the bullets dropping SOONER (fall per foot traveled) in cold air vs. dense air, but I don't really agree with how he said it...

Bullets don't drop FASTER (per time) in cold air than hot, they just don't fly as fast so they drop SOONER (per distance traveled)...Meaning, the rate of fall isn't any FASTER, it's just that they don't travel as far horizontally per second as they would in less resistive hot air...The rate of fall is constant, the gravitational constant, 32.174ft/s.

Truth be told, the rate of fall would be SLOWER in cold air than hot (miniscule amounts) because of the density change...the more dense the air, the more bouyant force it exerts on the bullet...but this is a very small change, so it is over shadowed by the huge increase in drag force which slows the bullet and makes it fall sooner (in feet).

People miscommunicate that because they see their groups hitting lower at 100yrds in December than they did in June...they assume this means their bullet is dropping faster, but this is impossible, since the gravitational constant is a CONSTANT.

It's like the figure Bilge posted earlier, the dropped bullet and the fired bullet---no matter the speed--hit the ground at the same time.....it's just that the bullet in cold air isn't going to fly as far as the bullet in hot air.

Which I'd imagine is often also exaggerated by the fact that many modern powders are temperature sensitive, and will burn more efficiently at higher temps (giving higher pressure and muzzle velocity)...so you've got less resistive air and higher muzzle velocity, cold air shooting sucks.