Post-Cold Frontal Stratocumulus Clouds Create Recipe for Airframe Icing

Pilots should never allow themselves to be fooled by the snow.

Scott Dennstaedt, Ph.D

Friday, February 21, 2025 at 08:52 AM ET

Verified

Edited By: tccjeremy

Airplane flying high above stratocumulus clouds during the morning sunrise. [Adobe Stock]

Key Takeaways:

Snow-producing clouds can pose a significant airframe icing risk, contrary to common belief, and have been involved in a substantial percentage of icing incidents.
Icing results from supercooled liquid water (SLW), not ice crystals alone; snow-producing clouds can be "mixed-phase," containing both ice crystals and dangerous SLW.
Shallow stratocumulus cloud decks, often found in the wake of cold fronts, are particularly hazardous as they can concentrate high supercooled liquid water content near their tops, leading to severe icing.
Pilots must be vigilant and not assume safety when encountering snow-producing or post-cold frontal stratocumulus clouds, especially during descent where high liquid water content and moderate cloud top temperatures increase severe icing risk.

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Are snow-producing clouds an airframe icing risk? The short answer is yes, which will likely surprise most readers who fly under instrument flight rules. While your mileage may vary, depending on the conditions, heavy ice within snow-producing clouds can even overwhelm an aircraft with a certified icing protection system.

In fact, a study done by Steven Green of Flight Operations Research suggests that if you look at icing accidents and incidents that occurred during which precipitation was reaching the surface, freezing precipitation (freezing rain or freezing drizzle) is present in 33 percent of the total events and snow is present in 32 percent of the events; these conditions are not mutually exclusive, as 7 percent of the events include both.