A Pilot's Guide to Inflight Icing
Module I - Before You Fly
Know the Situation
Section: Weather - Geographic Effects
Start This SectionGeographic Effects Weather
The geography near the intended route of flight can provide important cues to the severity of the associated icing threat.
Icing can occur anywhere. However, the likelihood of encountering icing is greater near large bodies of water. Large bodies of water can add heat and moisture to overlying air masses, increasing the water content and inducing instability, which increases the risk of icing in these areas.
Icing Potential (November - March)
Geographic Effects Weather
Moist air that is forced upwards as it flows over a mountain range can produce a serious icing hazard. The risk of a serious icing encounter is greater when the route of flight traverses or is along the windward side of a major mountain range such as the Sierras, Cascades, Appalachians, or Rockies.
Mountainous terrain can also limit your options for escaping from icing conditions. In mountainous areas, it may not be possible to safely descend out of icing conditions.
Moist air forced upwards by mountains can produce ice.
Geographic Effects Weather
Pilot Action Recommendation
IF: Your planned route is along the windward side of a mountain range and icing is forecast.
ACTION: Consider flying along the leeward side to reduce your risk, but watch out for mountain wave turbulence.
WHY: Moist air on that is forced upwards on the windward side of terrain may cool abruptly and produce a serious icing hazard.
Always consider routes or altitudes that limit your risk of an icing encounter. In many cases, small alterations to your planned route can substantially reduce the risks.
Fly along the leeward side to reduce the risk of icing