Definition
A report of actual weather conditions encountered by an aircraft in flight, transmitted by the pilot to a ground facility (such as a Flight Service Station or Air Traffic Control) and then disseminated to other pilots and forecasters. A PIREP typically includes location, time, altitude, sky conditions, visibility, temperature, wind, turbulence, icing, and any other significant weather observed.
Plain English
It's a quick weather report that a pilot makes from the cockpit, telling controllers and other pilots what the weather is actually like up there right now.
Context Anchor
You may hear PIREPs on the radio, give one to air traffic control, or see them during a preflight weather briefing.
Derivation
Short for Pilot Report. The 'PI' is from pilot and 'REP' is from report. The label stuck because it's quick to say on the radio.
Why Pilots Care
Supplies real-time, firsthand weather details that official forecasts may miss, allowing pilots to avoid unexpected hazards such as icing or turbulence.
Intuition Check
Do not treat a PIREP as a forecast. A PIREP is a pilot’s firsthand report of weather already being observed or experienced from an aircraft.
Example Sentence 1
Cessna 4-2-Charlie, request a PIREP — any reports of icing between 6,000 and 9,000?
Example Sentence 2
Before takeoff the briefer reviewed recent PIREPs showing moderate turbulence over the mountains.