If you're facing a line of thunderstorms, taking a longer deviation around the upwind side of the storm might be a good idea. Here's why...

1) Turbulence Avoidance

Generally speaking, you'll find the best chance for clear, smooth air on the upwind side of a thunderstorm. That's in part because the air is less disturbed by the convection found within the storm, and spreading out downwind.

2) Precipitation Falls On The Downwind Side Of The Anvil

As winds aloft blow the thunderstorm downwind, the anvil begins to spread out. Precipitation usually falls on the downwind side, and odds are you won't find conditions nearly as clear.

3) Clear-Air Hail

Many pilots have experienced dangerous, large clear-air hail by flying beneath overhanging anvil clouds. This hail is essentially sucked upwards through primary updrafts near the core of the storm, and then spit out with the direction of the wind.

4) Other Hazards Occur Downwind Too

Severe or extreme turbulence, lightning, and strong straight-line winds can exist outside of the visible thunderstorm. Most of the time, these elements occur downwind of the thunderstorm, in the direction of its movement.

5) Storms Move Fast, And Your Radar Data May Be Delayed

When you're on the ground planning your route, pay close attention to the storm's direction, and how fast it's moving. Satellite-based weather radar will have latency, so it's likely the storm will move significantly downwind by the time you approach it. If you're worried an upwind route may take too long, it's likely you can plan to cut the corner closer than you think due to the direction of the storm.

6) Finding A "Gap" Can Be Risky

The worst outcome is to plan your flight around the downwind side of the storm, or through a small gap, which could close with little warning. If you have to pick your way through cells or a small gap, be cautious as cells can join together rapidly. On top of that, some of the worst turbulence can be found right between building cells.

7) Fuel Planning Becomes Tough

If you're planning to fly down the line of storms and cross around the downwind side, the storm direction isn't working in your favor. A deviation can get much longer than planned as you try to find a clear spot, leading to fuel constraints.

If you approach a line of storms and you're faced with a "should I turn right or left?" moment, turning toward the upwind route is typically the best decision. Have you faced this decision before? Tell us about it in the comments below.