The PIREP, the Real-Time Gap in Every Weather Forecast, and the Report Most Pilots Never File
PIREPs are real-time in-flight weather observations that fill the critical gap between ground-based forecasts and actual conditions pilots encounter in the air.
Your preflight weather picture - TAF, METARs, winds aloft, AIRMETs - comes entirely from ground-based sensors and forecast models. PIREPs, or Pilot Weather Reports, are the only source of real-world, in-flight conditions reported by actual pilots flying actual routes. Without them, you have no direct information about what the airspace between airports looks like right now.
What Is a PIREP and Why Does It Matter?
A PIREP is a weather observation made by a pilot, from the aircraft, during flight. That distinction is what makes it uniquely valuable.
METARs and TAFs describe conditions at specific airports at specific times. They cannot tell you what conditions exist at 8,000 feet over the plains, inside an overcast layer, or at any point between reporting stations. The ground-based weather picture has a hard ceiling - and you’re going to fly above it.
When conditions are changing rapidly, or when there’s any question about icing, turbulence, or actual cloud layers, a recent PIREP from a pilot who just flew your route can be worth more than everything else in your briefing combined. The FAA Aeronautical Information Manual (AIM), Chapter 7 covers PIREPs in detail, and the Airman Certification Standards (ACS) for the private pilot knowledge test expect you to read and interpret them.
Where Do You Find PIREPs?
In your Electronic Flight Bag (EFB), PIREPs appear as overlaid map icons. In ForeFlight, they display as colored markers - purple for standard PIREPs, red for urgent. Tap any icon for a decoded, plain-English version. Garmin Pilot and most other EFB applications follow the same setup.
You can also access PIREPs through the Aviation Weather Center at aviationweather.gov, or by calling 1-800-WEATHER-BRIEF for a standard briefing.
Age is the most important variable. A PIREP from four hours ago in rapidly changing conditions has limited value. A PIREP from thirty minutes ago, from a pilot flying your exact route at your planned altitude, is the most current real-world data available. Always check the timestamp.
How Do You Decode a Raw PIREP?
On an oral exam, an examiner may hand you a raw PIREP and ask you to interpret it. The format follows a consistent structure.
UA at the start identifies a routine pilot report. UUA identifies an urgent PIREP, issued immediately when a pilot reports severe turbulence, severe icing, or a tornado.
After the type identifier, the report includes:
- Location - referenced to a VOR or GPS fix (e.g., OVR COU means over the Columbia, Missouri VOR)
- Time - always in Zulu (e.g., /T0930 means 0930Z)
- Altitude - where the aircraft was when the observation was made, not where the clouds began or where turbulence started
- Aircraft type - critical context for calibrating the report
- SK - sky condition, including cloud bases, tops, and coverage
- TA - temperature in Celsius
- WV - wind direction and velocity
- TB - turbulence intensity
- IC - icing intensity and type
- RM - remarks, for anything the coded format doesn’t capture
The aircraft type field matters more than most pilots realize. A turbulence report from a Cessna 172 and a report from a Boeing 737 describe fundamentally different experiences. What a jet crew logs as light chop may be moderate turbulence in a light trainer. Always calibrate accordingly.
What Do Turbulence Intensity Levels Actually Mean?
The intensity scale runs from none through light, moderate, severe, and extreme.
Light turbulence produces slight, erratic changes in altitude or attitude. Occasional bumps. No threat to occupants or equipment.
Moderate turbulence means more rapid and significant changes in altitude and attitude. Objects in the cabin may become unsecured. Occupants feel definite strain against their seatbelts. Walking in the cabin is difficult. Consistent moderate turbulence in a light aircraft warrants serious consideration of your options.
Severe turbulence means the aircraft is momentarily out of control. Altitude and attitude change abruptly by large amounts. Occupants are thrown violently against their seatbelts. Structural damage is possible.
Extreme turbulence means the aircraft is violently tossed about and practically impossible to control. Structural damage is not just possible - it is likely.
When you see SEV or EXTRM in a PIREP, treat it as an active hazard, not an interesting data point. Plan around it.
What Does Icing Type and Intensity Mean in a PIREP?
Icing intensity follows a similar scale: trace, light, moderate, severe. Reports will also describe the type.
Clear ice forms in conditions with large supercooled water droplets, typically inside cumuliform cloud. It builds quickly and accumulates as a smooth, heavy mass on leading edges - aerodynamically the most damaging type because it lacks the rough texture of rime ice.
Rime ice forms in stable cloud with smaller droplets, producing a rougher, more brittle accumulation on leading edges.
Mixed ice is both types occurring simultaneously.
None of these belong on an aircraft not equipped and certified for flight into known icing conditions. A PIREP reporting any icing along your route is a significant input into your go/no-go decision.
What Does It Mean When There Are No PIREPs on Your Route?
The absence of PIREPs does not mean clear skies and smooth air. It means no pilot has recently flown that route and filed a report.
That blank space on your map reflects a data gap, not a clean forecast. In marginal conditions or when flying through unfamiliar airspace, the absence of recent PIREPs is itself important information. Factor it into your risk assessment accordingly.
How Do You File a PIREP?
Most general aviation pilots never file a single PIREP in their flying career. The AIM is direct: pilots are encouraged to file whenever they encounter conditions useful to other pilots. Unexpected cloud layers, tops significantly different from the forecast, any icing, unforecast turbulence, winds aloft differing substantially from the published forecast - all of these warrant a report.
When you encounter icing or severe turbulence, the AIM says to file immediately, while still airborne.
Filing by radio through ATC is the simplest method in flight. Tell any Center or Approach controller you’d like to file a PIREP. They’ll take your report and relay it. The process takes roughly 60 seconds of radio time.
Flight Service accepts PIREPs by radio or by calling 1-800-WEATHER-BRIEF.
ForeFlight and Garmin Pilot both include built-in PIREP filing tools. ForeFlight pre-fills your position and altitude from your GPS fix. You log what you’re observing and submit. The report goes directly into the aviation weather system.
The format mirrors what you’ve already decoded:
- Location over a navaid or GPS fix
- Altitude
- Aircraft type
- Sky condition (cloud bases or tops if visible)
- Temperature
- Winds, if significantly different from forecast
- Turbulence intensity (continuous or intermittent)
- Icing intensity and type, if present
- Remarks for anything else
You don’t need to report every element. A negative PIREP - confirming clear skies and smooth air along a route - is just as valuable as a report of adverse conditions. It confirms the forecast is holding and tells the next pilot that someone flew that route recently and found nothing concerning.
How Do PIREPs Fit Into a Standard Weather Briefing?
A standard weather briefing follows a specific sequence. Adverse conditions come first: SIGMETs, convective SIGMETs, and AIRMETs affecting your route. Then the synopsis - the big-picture atmospheric overview. Then current conditions at departure, en route, and destination. Then forecast conditions (TAFs, area forecasts). Then winds and temperatures aloft. Then NOTAMs.
PIREPs integrate throughout this sequence, tied to the relevant section. They are not a separate step - they are the real-world verification layer running parallel to everything else.
When a TAF reports ceilings at 3,000 feet and a PIREP from 40 minutes ago shows tops at 5,000 feet with bases at 2,500 feet and light icing in the layer, those two pieces of information together tell you something neither one could alone. The layer is real. The icing is active. And you have a decision to make.
What Is the Difference Between a Routine and an Urgent PIREP?
A routine PIREP enters the database, appears on EFBs, and becomes available to weather forecasters and all pilots pulling subsequent briefings. It improves the picture for everyone who follows you.
An urgent PIREP is distributed immediately. It goes to the National Weather Service, Air Route Traffic Control Centers, and may trigger a SIGMET amendment or a special weather advisory for a large area of airspace. Filing an urgent PIREP doesn’t just inform the next pilot - it can update the official aviation weather picture for an entire region.
File an urgent PIREP while airborne any time you encounter severe icing in an aircraft not certified for it, or severe turbulence that was completely unforecast and unreported. Contact ATC, state that you need to file an urgent PIREP, and walk them through what you found.
Key Takeaways
- PIREPs are the only source of real-world, in-flight conditions - ground-based forecasts cannot see the airspace you actually fly through
- Always check PIREP age first: a 30-minute-old report from your route and altitude is far more valuable than a 4-hour-old report
- Calibrate turbulence and icing reports against the reporting aircraft type - a 172 and a 737 measure the same conditions very differently
- No PIREPs on your route does not mean clear conditions - it means you have no real-world data from that airspace
- You have a responsibility to file PIREPs; urgent reports (severe turbulence, any icing) go in while airborne, not after landing
- Negative PIREPs - confirming benign conditions - are as useful to other pilots as reports of adverse weather
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