The PIREP, the Real-Time Weather Report Nobody Files, and Why the Briefing You Got This Morning Is Missing the Most Important Data on Your Route

Pilot Weather Reports - PIREPs - are the only weather product in your briefing based on direct observation at altitude. A TAF is a forecast. An AIRMET covers thousands of square miles. A PIREP is a report from a real pilot who was physically in that airmass, often within the last hour. That distinction makes PIREPs the most honest data in your briefing, and the most underused.

What Is a PIREP and Why Does It Matter?

A PIREP is a weather observation filed by a pilot during or after flight. It captures what someone actually found at altitude - not what a model predicted, and not what a surface sensor measured from the ground. When your briefing shows benign conditions but a pilot an hour ahead of you filed a moderate icing report at your cruise altitude, that PIREP outranks the forecast.

There are two types. A routine PIREP is encoded as UA in raw data. These are filed voluntarily or during flight following coordination. An urgent PIREP is encoded as UUA and is required when a pilot encounters severe icing, severe turbulence, a tornado, a waterspout, or volcanic ash. A UUA in your briefing is a direct red flag for that route. Someone had a serious encounter and filed it so the next pilot wouldn’t have to discover it firsthand.

How Do You Read a PIREP?

PIREPs are structured in slash-separated fields. Once you know the key, they parse quickly.

Reporting station - The identifier at the start of the report (e.g., OKC) is the nearest navaid or airport to where the observation was made.

OV (Over) - The precise location. This may be a simple identifier (OV OKC) or a bearing and distance (OV OKC 030040, meaning 30 degrees and 40 miles from the Oklahoma City VORTAC). Location matters: a turbulence report over mountainous terrain reads differently than one over flat plains.

TM (Time) - Reported in Zulu time. A report timestamped TM 1730 was filed at 1730Z. Age matters enormously here. A 20-minute-old PIREP is highly actionable. A three-hour-old PIREP on a fast-moving front is nearly historical record.

FL (Flight Level/Altitude) - FL080 means 8,000 feet. FL UNK means the pilot didn’t report altitude, which reduces the report’s precision but doesn’t eliminate its value.

TP (Aircraft Type) - This field changes the meaning of everything that follows. A Piper Cherokee reporting light turbulence is a very different data point than a Boeing 757 reporting light turbulence. Certification standards and operating envelopes differ dramatically between light singles and heavy twins. When a heavy aircraft reports icing in a layer, a light unprotected single should treat that as a serious warning.

What Do the Weather Fields Mean?

SK (Sky Cover) - Cloud layers as observed by the pilot. SK BKN030 means a broken ceiling at 3,000 feet.

TA (Temperature) - Reported in degrees Celsius. Compare this to your winds aloft forecast. If the model projected -4°C at 8,000 feet and the pilot reports +2°C, the temperature profile is warmer than predicted - with direct implications for icing potential.

WV (Wind Velocity) - Direction and speed, in the same format as a winds aloft forecast.

TB (Turbulence) - The intensity scale has four levels:

• Light - Slight erratic changes in attitude or altitude. Occupants feel a slight strain against seatbelts.
• Moderate - Definite changes in attitude and altitude; aircraft remains in positive control. Walking is difficult. This is the level that rattles your kneeboard and makes you grateful for a secured cabin.
• Severe - Large, abrupt changes; aircraft may be temporarily out of control. Occupants are forced violently against seatbelts. This triggers a mandatory UUA filing.
• Extreme - Aircraft is tossed violently and may be uncontrollable. Structural damage is possible. If you see an extreme turbulence report on your route, reroute.

The TB field may also include CAT (clear air turbulence) or CHOP (rapid, repetitive bumps without significant altitude changes), along with an altitude range showing whether the turbulence was confined to a layer or continuous across a range.

IC (Icing) - Four intensity levels:

• Trace - Slight accumulation; deicing equipment, if installed, is not required.
• Light - Accumulation may become a problem if flight is prolonged.
• Moderate - Even short encounters can be hazardous for unprotected aircraft.
• Severe - Equipment cannot control the accumulation; immediate exit from conditions is required.

For pilots flying a certified single-engine piston with no de-ice or anti-ice equipment: if you are in conditions where icing is possible, you are in conditions that can kill you if you remain in them. Light icing in an unprotected aircraft changes your stall speed, degrades lift, and adds weight and drag - faster than textbooks convey. A PIREP showing IC LIGHT at your altitude and in your cloud layer is a go/no-go data point, not background noise.

WX (Weather) - Standard precipitation and obscuration abbreviations: RA (rain), SN (snow), FG (fog), and others.

RM (Remarks) - The free-text field. This is where pilots write what the codes cannot capture: “severe icing from 12,000 down to 8,000 on the east side of the front” or “broke out VFR at 5,500.” The remarks field often contains the most operationally useful detail in the entire report.

How Do You Use PIREPs in a Preflight Briefing?

Build your briefing from general to specific. Start with the big picture - surface analysis, prog charts, front positions, general flow. Then examine TAFs at departure and destination. Then review AIRMETs covering your route. Use PIREPs last, as your ground truth check against everything else.

If AIRMETs show no significant icing but three PIREPs in the last two hours report moderate icing at your cruise altitude, trust the PIREPs. They are more recent. They are more specific. They came from someone physically in that airmass.

If your briefing looks clean and there are no PIREPs at all for your route, recognize what that actually means: absence of reports, not absence of hazards. Routes with low traffic density - especially early morning or overnight - may simply have no one filing. A quiet PIREP section over terrain you’ve never flown is a data gap, not a green light.

Before every flight, ask two questions: Are there PIREPs on this route? If yes, what are they telling me? If no, why not - and what does that mean for my decision?

How Do You File a PIREP?

Filing a PIREP takes approximately 60 seconds and improves the system for every pilot who follows you on that route.

If you’re on flight following, report to approach control or center when you encounter turbulence, icing, or unexpected conditions. They will file it or ask you a few questions and file it on your behalf.

If you’re not on flight following, you can call Flight Service directly on 122.2 or through 1-800-WX-BRIEF. You can also file through ForeFlight and other apps that connect to the system.

The format does not need to be perfect. Reporting your altitude, aircraft type, and what you encountered is a valid submission - the briefer will fill in the remaining fields. “Cessna 172, 8,000 feet, picking up light icing” is enough to get a report into the system.

The FAA and the National Weather Service use pilot reports to calibrate and verify forecast models. The Current Icing Product (CIP), produced by the Aviation Weather Center, integrates radar, satellite, METARs, and PIREPs into a gridded, altitude-by-altitude icing probability map - and PIREPs are one of its primary validation inputs. When pilots file consistently, the CIP gains resolution. When pilots don’t, the model has blind spots. That is a direct line from pilot behavior to forecast quality to safety for everyone on that route. The full archive of current PIREPs is available in real time at aviationweather.gov.

What Should You Know for Your Practical Test?

The Airman Certification Standards require that you understand weather reports and forecasts, and PIREPs fall squarely within that category. Know the two types (UA and UUA), know the fields and their abbreviations, and know the turbulence and icing intensity scales.

More importantly, demonstrate that you actually use them. Examiners are looking for a genuine preflight habit - not a recitation of definitions.

A practical calibration exercise: for your next five training flights, write down every PIREP you find on your route before you fly - altitude, aircraft type, reported condition, and age of the report. After the flight, compare what the briefing showed to what you actually found in the air. That feedback loop permanently sharpens your ability to interpret the data, in a way no ground school lecture can replicate.

Key Takeaways

• PIREPs are eyewitness reports, not forecasts - they represent actual conditions observed at altitude, making them the most current and specific data in your briefing.
• A UUA (urgent PIREP) is a mandatory filing for severe icing, severe turbulence, tornadoes, waterspouts, or volcanic ash - treat any UUA on your route as a serious route hazard.
• Aircraft type determines context: light turbulence reported by a heavy twin is not the same as light turbulence reported by a light single.
• No PIREPs ≠ good weather - on low-traffic routes, absence of reports is a data gap that demands caution, not complacency.
• File your own PIREPs - every report you contribute directly improves forecast models, including the Current Icing Product (CIP), for every pilot who follows you.