PIREPs, the Real-Time Report From Inside the Air Mass, and the Filing Responsibility That Turns Every Pilot Into a Weather Observer

A PIREP (Pilot Weather Report) delivers something no forecast or surface observation can: a report from a pilot who was actually inside the air mass you’re about to enter. Understanding how to decode, weight, and file these reports is one of the most practical weather skills any pilot can develop.

What Makes a PIREP Different From Other Weather Products?

The TAF is a forecast. The METAR is a surface observation, usually automated, from the ground. The Area Forecast Discussion is a meteorologist interpreting numerical model output. All of these are valuable - but they’re all constructed from some distance from the actual air mass you’re flying into.

A PIREP is from a pilot who was inside it. They reported what their aircraft actually encountered at a specific altitude, over a specific location, at a specific time. The icing that wasn’t in the forecast. The smooth air above the broken layer. The wind shear on final that caught them by surprise. That’s a data point no forecast model can generate.

The formal designation in raw data is UA for a routine report, or UUA for an urgent one.

How Do You Decode a PIREP?

PIREPs use a standard set of field headers:

• OV - Location
• TM - Time in Zulu
• FL - Altitude
• TP - Aircraft type
• SK - Sky conditions
• TA - Temperature in Celsius
• WV - Wind
• TB - Turbulence
• IC - Icing
• RM - Remarks

Not every field appears in every report. A pilot who called in a quick turbulence report may not have included sky conditions. What you get is what they observed and chose to include.

Here’s a real example:

UA /OV MKC090040 /TM 1522 /FL085 /TP C172 /SK SCT 040 BKN 075 OVC 090 /TA M06 /TB MDT /RM LLWS B LO ALT

Breaking it down:

UA - Routine PIREP.

OV MKC090040 - MKC is Kansas City Muni. The numbers represent radial and distance: 40 nautical miles on the 090-degree radial from the airport, putting this observation roughly east of Kansas City.

TM 1522 - Observed at 1522 Zulu.

FL085 - 8,500 feet MSL.

TP C172 - A Cessna 172. Aircraft type matters significantly - more on this below.

SK SCT 040 BKN 075 OVC 090 - Scattered clouds at 4,000 feet, broken at 7,500 feet, overcast at 9,000 feet. A VFR flight in this area needs to remain below 4,000 feet with required visibility.

TA M06 - Temperature at altitude is minus 6°C - well within the icing envelope, particularly inside those cloud layers.

TB MDT - Moderate turbulence.

RM LLWS B LO ALT - Remarks indicate low-level wind shear below standard altitude. A hazard advisory in the final approach environment.

From a single string of characters, you’ve extracted cloud bases, cloud tops, temperature, turbulence intensity, a wind shear advisory, location, time, and aircraft type. That’s a complete snapshot of one corridor of airspace at one specific moment.

Why Does Aircraft Type Matter When Reading a PIREP?

A Cessna 172 reporting moderate turbulence is not the same data point as a Boeing 757 reporting moderate turbulence.

A heavy aircraft has significantly more inertia. It doesn’t feel light chop the way a light single does. A large transport crew may describe conditions as “light” while a Cessna 172 crew would describe the same air as “moderate” or worse. When reading a PIREP from a heavy jet, expect to feel it more than they did.

The inverse is equally useful. When a Cessna 172 crew reports light turbulence, that’s probably an accurate read. When that same crew reports severe, believe them completely.

What Do the Turbulence Intensity Levels Mean?

The turbulence intensity scale runs: smooth, light, moderate, severe, extreme.

Smooth - No turbulence. No altitude or attitude deviation.

Light - Slight, erratic changes in altitude or attitude. Passengers feel a slight strain against their seatbelts. Unsecured objects may shift. Uncomfortable for some but entirely manageable.

Moderate - Similar in character to light but significantly greater in intensity. The aircraft remains in positive control at all times. Changes in altitude and attitude are definite and notable. Passengers feel a real strain against their seatbelts. Unsecured objects get moved around or knocked over.

Severe - Large, abrupt changes in altitude or attitude. The aircraft may momentarily be out of controlled flight. Passengers are forced violently into their restraints. This is where in-flight injuries occur.

Extreme - The aircraft is essentially uncontrollable. Structural damage is possible.

For flight planning in light singles, the transition from light to moderate is where serious route adjustments are warranted. Severe and extreme are not flying conditions for light aircraft.

What Do the Icing Intensity Levels Mean?

The icing intensity scale runs: trace, light, moderate, severe.

Trace - Perceptible but accumulation is slight. Brief exposure is manageable in most aircraft.

Light - Accumulates slowly enough that short exposure isn’t immediately dangerous, but extended time in it becomes a problem.

Moderate - Accumulates quickly enough to be a hazard within a short time, even with deice equipment operating.

Severe - Cannot be handled even by aircraft certified for flight in known icing conditions.

For non-icing-certified aircraft - which includes most trainers - the threshold is far lower. Any significant icing means getting out of it immediately. A PIREP showing moderate icing at 9,000 feet is a direct signal to find a different altitude or file a different route before you depart.

How Should You Use PIREPs in Your Preflight Briefing?

PIREPs are most valuable when read as part of a developing picture, not as isolated data points.

Consider this scenario: you’re planning a cross-country over a ridge line. The TAF is showing VFR at both ends. Winds aloft look favorable. But the Area Forecast Discussion mentions wave activity over the terrain, and there’s a low-probability icing AIRMET (Airmen’s Meteorological Information) covering the mountains.

You pull up PIREPs for your route and find two reports. The first is from three hours ago - a Piper Cherokee, light turbulence at 8,000 feet over the ridge, smooth below 6,000 feet. The second is from 45 minutes ago - a Cessna 172, moderate turbulence at 7,000 feet on the same radial, trace icing in the tops.

Conditions deteriorated between those two reports. The more recent one comes from an aircraft similar to yours. It found turbulence at your planned altitude and picked up trace icing in the cloud tops.

That’s not a go/no-go decision by itself. But it’s a signal - one that tells you to call the briefer, ask specifically about conditions over that ridge for the next two to three hours, and have a contingency plan ready.

Two hours is a reasonable threshold for treating a PIREP as current. Older reports provide useful context about what the atmosphere has been doing, but shouldn’t be treated as a reliable picture of present conditions.

One critical point on PIREP gaps: if there’s a long stretch of your route with no PIREPs on it, that is not a green light. It may simply mean no one has flown that corridor recently enough to file. Absence of PIREPs does not mean conditions are good - it means you don’t have information.

Where Do You Find PIREPs?

1-800-WX-BRIEF - A standard weather briefing will include relevant PIREPs. Ask specifically if they don’t come up, and you can request them filtered to a corridor or altitude band.

ForeFlight - PIREPs appear on the map layer. Filter by altitude range and recency. Blue markers indicate icing reports; yellow and red indicate turbulence. Tap any marker for the full decoded report.

Aviation Weather Center website - Query PIREPs by region and altitude band. For a cross-country briefing, pull the full route corridor filtered to the last two hours.

How Do You File a PIREP?

Every pilot has a responsibility to file PIREPs. The entire system runs on pilots reporting what they actually encountered. When you fly through smooth air at 9,000 feet and say nothing, the pilot departing two hours behind you has a question mark over that corridor.

While airborne: Contact approach control or center and say: “Denver Center, Skyhawk four six seven sierra, PIREP.” They’ll acknowledge and ask you to go ahead. Give them your location referenced to a nearby fix or navaid, your altitude, your aircraft type, and what you observed.

You don’t need the full format memorized to file verbally. Controllers are accustomed to these calls. Give them the intensity, the altitude, the location, and the aircraft type, and you’ve done the essential job.

After landing: File through the Aviation Weather Center website, ForeFlight’s PIREP filing tool, or Garmin Pilot. It takes under two minutes while your memory is fresh on the ramp.

Use standard intensity vocabulary when filing. “It was a little bumpy” is not a PIREP. “Light turbulence, continuous, from 9,000 to 11,000 feet, over the Victor 12 corridor” is a PIREP. The specificity matters because other pilots will use your report to make decisions.

File when conditions are good too. A report of smooth air at 10,000 feet, no icing in the tops, and clear visibilities above the broken layer is valuable information. Pilots need to know when conditions are benign as much as when they’re adverse.

What Is a UUA (Urgent PIREP)?

The UUA designation applies to specific hazardous conditions:

• Tornadoes or funnel clouds
• Severe or extreme turbulence
• Severe icing
• Hail
• Low-level wind shear within 2,000 feet of the surface
• Volcanic ash
• Any other condition representing an immediate hazard to flight

If you encounter any of these, file urgently and use the word urgent when you call it in. That triggers immediate dissemination to other aircraft and to facilities throughout your region. Don’t hesitate - that’s exactly what the system is built for.

What Should You Know About PIREPs for Your Oral Exam?

The Airman Certification Standards expect you to interpret a PIREP on your oral exam. When the examiner asks how you used weather products to plan your cross-country flight, PIREPs need to be part of your answer.

The examiner wants to see that you built a complete picture - not just checked boxes. That means understanding who gave you the information, what aircraft they were flying, how recent the report was, and what it means for your specific airplane at your specific altitude.

That’s what separates sound weather judgment from simply getting through the oral.

Key Takeaways

• A PIREP delivers real-time weather intelligence from inside the actual air mass - something no forecast or surface observation can provide.
• Aircraft type context is essential: a heavy jet reporting light turbulence will likely feel moderate or worse in a light single.
• Two hours is a practical threshold for treating a PIREP as current; gaps in PIREP coverage don’t indicate good conditions - they indicate missing information.
• For non-icing-certified aircraft, any significant icing in a PIREP means finding a different altitude or route before departure.
• Filing PIREPs - including reports of smooth, benign conditions - is a responsibility every pilot carries on every flight.