When it snows or rains heavily, runways can become slippery. Pilots need accurate, timely information about runway surface conditions to make safe decisions about landing and takeoff. The SNOWTAM (weather information) and runway condition report formats exist precisely for this purpose.
A runway condition report describes the surface state: dry, wet, slush, snow cover, contamination, and friction coefficient. It's reported using a standardized code so that every pilot understands it the same way.
The format includes:
  • Runway designation — which runway (e.g., "RWY 27").
  • Extent of contamination — how much of the runway is affected (e.g., "less than 10%", "10-50%", "more than 50%").
  • Depth of contamination — if snow or slush, how deep it is (e.g., "0-5 cm", "5-10 cm", "more than 10 cm").
  • Friction coefficient — a numerical code (e.g., "0.60" indicates poor braking action, "0.40" is very poor and unsafe for most aircraft).
  • Remarks — any special notes, such as "snow banks on edges" or "icy patches near threshold."
A typical runway condition report might sound like this:
"Vienna Tower, F-ABCD, requesting runway condition. — Vienna, F-ABCD, RWY 34 Left, more than 50 percent snow coverage, approximately 3 centimetres depth, friction coefficient 0.40, ice patches near threshold. — Copied, friction coefficient 0.40, F-ABCD."
This information is critical. A friction coefficient of 0.40 means the runway is effectively slippery, and many aircraft will refuse to land. The pilot must evaluate whether their aircraft can safely land with that braking action. Light aircraft might not be able to stop safely; heavy jets might barely be marginal.
A SNOWTAM is a formal notice issued by Austro Control or the national authority when significant snow, ice, or contamination affects one or more runways. It's distributed to all pilots and repeated on ATIS so that arriving aircraft receive the warning proactively. A SNOWTAM supersedes normal weather reporting and is treated with the highest priority.