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Updrafts and Downdrafts: How Much Vertical Wind Moves Your Impact

Air moving up or down pushes the bullet exactly as far as the same crosswind pushes it sideways. Numbers from 300 to 800 yards, an updraft over only part of a canyon, and the updraft behind a 0.7 mil high miss at 370 yards.

5 min readSolved with the Ballista engineUpdated October 2026

A common question on long-range forums goes like this: a shooter takes a 370 yd shot across a canyon, about 15° downhill, with a strong wind blowing up the slope, and the bullet hits 0.7 mil high. Is there a rule of thumb for updrafts? There is, and it’s one you already carry. Air moving up or down pushes the bullet the same distance as the same speed of crosswind pushes it sideways. A 10 mph updraft lifts a 6.5 Creedmoor’s impact 21.7 in at 600 yd. A 10 mph full-value crosswind moves it 21.7 in sideways.

A vertical wind works like a crosswind

The bullet doesn’t ride the air. Drag acts along the bullet’s velocity relative to the air around it. When that air moves sideways, the relative airflow comes slightly from the side and drag gains a small sideways part. When the air moves up, the same thing happens in the vertical plane: drag gains a small upward part. Gravity pulls the bullet down the same way whether or not the air is moving, so it doesn’t change the result. What sets the push is lag time, the same quantity behind crosswind drift, as the lag time article shows.

How we computed it

The Ballista engine takes wind in the horizontal plane only, so it has no input for vertical air. We wrote a small point-mass integrator that follows the engine’s own equations (the same G7 drag table, drag formula, Runge–Kutta steps and zeroing) and lets the air move in any direction. Run with a 10 mph horizontal crosswind, it matches the engine’s drift to within a thousandth of an inch at every 100 yd out to 1,000 yd. Then we turned the same wind to point up.

The updraft and crosswind columns agree to the hundredth of an inch at every range. The shift is also proportional to the wind: 5 mph gives half of 10 mph to the hundredth of an inch. One thing is left out. A crosswind makes a spinning bullet jump vertically a little, and by the same physics a vertical wind makes it jump sideways a little. That’s small and doesn’t change the vertical numbers here.

The .308 moves 1.52 times as far as the 6.5 at 600 yd, the same ratio as its crosswind drift. A bullet that holds its speed well is less sensitive to air moving in any direction.

So the rule of thumb is: your crosswind hold for a given speed is also your vertical hold for an updraft or downdraft of that speed. Hold low for an updraft, high for a downdraft.

How strong an updraft has to be to matter

A vertical air speed of a few mph over the whole path is enough to cost a plate at long range. Inside 300 yd it takes a strong updraft along the full length of the shot to move the impact half a mil.

When the updraft covers only part of the path

Across a canyon, the air may rise only over part of the bullet’s path, for example where the flight crosses a sunlit slope. Position matters. For the 6.5 at 600 yd, a 10 mph updraft over the whole path lifts the impact 21.7 in. The same updraft over only one third of the path gives:

• near third, by the rifle: 11.0 in
• middle third, over the canyon: 7.7 in
• far third, by the target: 3.0 in

The three parts add up to the whole. The same weighting applies to crosswind, and the muzzle wind or target wind article explains why air near the rifle counts most.

The 370-yard case

Back to the opening question: 370 yd, 15° downhill, 0.7 mil high. We don’t know that shooter’s load, so here are both reference rifles. On a slope, the part of the vertical wind that counts is the part across the line of sight, about cos 15° of it. The integration shows the same: at 370 yd the downhill shot gets 96% of the flat-ground lift.

A 0.7 mil miss at that distance needs a strong, steady updraft over most of the path. If the measured slope angle or range was off, or the wind also had a crosswind part that pushed the shot sideways, those errors would have added to it. A vertical miss of that size at 370 yd is worth checking against the range, the angle and the rifle’s zero before blaming the air alone.

Using this on the mountain

You can’t see vertical wind directly. You can see where it’s likely: air pushed up the face of a slope, spilling over a ridge, sinking on the far side. Ballista’s wind is a speed and a clock direction in the horizontal plane, so there’s nothing to enter for the vertical part. Enter the updraft’s speed as a full-value wind from 3 or 9 o’clock and the wind hold the Shot screen gives is your vertical hold.

1. Know your crosswind hold for 5 and 10 mph at the ranges you hunt. It’s also your updraft hold.
2. When the wind runs up or down a slope across your line of fire, estimate how much of it is vertical where the bullet passes.
3. Hold low for rising air, high for sinking air, by that amount.
4. Weight the part of the path nearest you more heavily.
5. After a miss high or low, check range, angle and zero first, then consider the air.