Definition
A form of precipitation consisting of transparent or translucent pellets of ice, 5 mm or less in diameter, that bounce when they hit a hard surface and make a sound on impact. Ice pellets form when raindrops or partially melted snowflakes refreeze while falling through a layer of below-freezing air beneath a warmer layer aloft. In a METAR, they are reported with the code PL, sometimes preceded by an intensity sign such as -PL (light) or +PL (heavy).
Plain English
Small, hard pieces of ice that fall from the sky and bounce when they hit the ground. On a weather report, they show up as the code PL.
Context Anchor
Seen in the weather section of a METAR, where short codes describe what is falling from the sky at the reporting location.
Derivation
PL comes from the Latin word for ice pellets used in international weather coding. The two-letter code follows the standard METAR convention of pairing letters to label each weather phenomenon.
Why Pilots Care
Signals possible airframe icing and slippery runway conditions that affect takeoff and landing performance.
Analogy
Ice pellets are like tiny bits of hard ice falling from the sky, not soft snowflakes and not liquid rain.
Grounding Statement
If PL appears in a METAR, picture small frozen pellets hitting the windshield, ramp, or runway at the airport.
Intuition Check
Do not read PL as hail or freezing rain. Ice pellets are already frozen when they reach the ground; freezing rain is liquid when it falls and freezes on contact.
Example Sentence 1
The METAR reported -PL, so the pilot suspected a temperature inversion with freezing rain possible at higher altitudes.
Example Sentence 2
With PL reported at the destination, the crew planned for possible de-icing before departure.