The PIREP, the Pilot Weather Report Filed From Cockpits Across the System, and Why the Best Real-Time Weather Data in Your Briefing Comes From Other Pilots

Of every product in a standard weather briefing, the PIREP - the Pilot Weather Report, encoded as UA (routine) or UUA (urgent) - is arguably the most valuable. Every other product is either ground-based, forecast-based, or both. The PIREP comes from someone who was just up there.

What Makes a PIREP Different From Every Other Briefing Product?

The METAR is a sensor reading from a fixed ground station. It tells you what conditions are at that airport at that moment - nothing about altitude, nothing about conditions fifteen miles away. The TAF is a trained forecaster’s prediction about the future. The AIRMET is a broad advisory covering a large geographic region over several hours.

All of those products are valuable. None of them tell you what a pilot observed at 8,500 feet over a specific navaid thirty minutes ago.

A routine PIREP is labeled UA. An urgent PIREP - reporting severe or extreme turbulence, severe icing, or other immediately hazardous conditions - is labeled UUA. If you see UUA anywhere in your briefing, read it first. It is the highest-priority item on the page.

How Do I Read a PIREP? A Field-by-Field Breakdown

Location is given as a reference to a navaid or airport identifier, plus a bearing and distance - for example, twenty miles northeast of Oakland. PIREPs are point observations. They describe a specific place in the sky, not conditions along an entire route.

Time is reported in Zulu. The age of the report matters enormously. A PIREP filed fifteen minutes ago is an extremely current data point. A PIREP filed four hours ago is historical context. Fronts move. Layers rise and fall. Always note the timestamp before drawing conclusions.

Altitude tells you where in the vertical column the observation was made. If altitude is marked unknown, the report’s usefulness drops significantly - you have no way to place the observed conditions within the atmosphere.

Aircraft type is more important than most pilots give it credit for. A Boeing 737 reporting light turbulence at FL230 and a Cessna 172 reporting light turbulence at 8,000 feet are not describing the same experience. The airliner is large, heavy, fast, and mechanically damped. What a heavy jet calls light, a light single may experience as moderate. When a heavy jet reports smooth, that’s good news. When a light piston aircraft reports smooth, that’s even better news if you’re flying something similar.

Sky condition gives you cloud layers in real time - often more precise than the surface METAR for layers above the reporting station. Visibility and precipitation in the weather field, combined with the ceiling report, give you a live composite picture of what conditions in that area actually look like.

Temperature is reported in Celsius and connects directly to icing risk. Wind direction and speed let you check forecast winds against reality. If the winds aloft forecast showed a 22-knot tailwind at 8,000 feet and a recent PIREP along your route shows winds out of the northwest at 48 knots, go back and revisit your fuel burn. The model was wrong.

How Do I Interpret Turbulence Intensities in a PIREP?

Turbulence intensity is standardized across four levels.

Light turbulence means slight, erratic changes in altitude and attitude. Passengers feel some strain against their seat belts. You remain in full control without significant effort. It is an annoyance for most pilots in most aircraft, not a hazard.

Moderate turbulence produces more significant changes in attitude and altitude. The aircraft remains controllable but demands your attention. Passengers are uncomfortable. For a student pilot in a training aircraft, moderate turbulence is a signal to evaluate whether to continue.

Severe turbulence causes large, abrupt changes. The aircraft may momentarily be out of positive control. Unsecured items become projectiles. Do not intentionally fly a training aircraft into severe turbulence.

Extreme turbulence renders the aircraft essentially uncontrollable. Avoid it entirely.

You may also see turbulence described as continuous, intermittent, or occasional. Chop refers to rapid bumps without significant changes in altitude. Clear air turbulence (CAT) is turbulence unassociated with visible clouds or convection - particularly significant because there is nothing visible to steer around.

What Do PIREP Icing Intensities Mean for My Flight?

For general aviation pilots flying aircraft without deicing equipment, icing is the most consequential hazard category in the entire briefing. The intensities are trace, light, moderate, and severe.

Trace icing means very slight accumulation - greater than sublimation but not significant unless you remain in it for an extended period. Light icing accumulates at a rate that could become problematic over time.

Moderate icing accumulates fast enough that even brief encounters are potentially hazardous. On an aircraft with deicing equipment, you would run it continuously. On an aircraft without deicing, you should not be in it.

Severe icing accumulates at a rate that would overwhelm deicing equipment even if you had it. Exit immediately.

If you are flying a standard training aircraft - a Cessna 172, a Piper Cherokee, a Diamond DA20, or anything without a deicing system - there is no category of icing acceptable for intentional entry. You are not certificated for flight into known icing conditions. A brief, unintended encounter with trace icing during a climb may be manageable. Planning to fly through icing is not.

Most structural icing occurs when temperatures are between 0°C and −20°C. The most severe icing tends to occur between 0°C and −10°C, where supercooled large water droplets create conditions favorable for clear ice formation. Clear ice is dense, heavy, and conforms closely to the airfoil - harder to detect visually than rime ice and harder to remove. Rime ice is rough, milky, and opaque, forming when small droplets freeze rapidly on contact. Both degrade aircraft performance. If a PIREP shows a cloud layer at −6°C and you need to climb through it, the icing risk is real regardless of what the forecast says.

What Should I Look for in the Remarks Section?

The remarks field is plain-language narrative from the pilot - and it is frequently the most useful part of the entire report.

This is where you find notes like tops were above my altitude during climb, unable to get on top, or first smooth air started at FL180, or layer was broken on the way out, solid overcast on the return. Remarks capture what pilots actually experienced in words the code fields can’t convey. Read that section every time.

Why Are There Sometimes No PIREPs Along My Route?

PIREPs only exist where pilots are flying and filing. On a busy airway corridor during a weekday morning, you may have a dense, recent network of reports giving you an excellent real-time picture. On a Sunday afternoon over the interior of a lightly traveled state, you might have zero PIREPs along a 250-mile route.

The absence of PIREPs does not mean conditions are good. It means nobody was there to report.

This is a known structural limitation of the system. The FAA and the National Weather Service have worked for years to encourage more PIREP filing, because the gap between what forecasters can model and what is actually happening in the atmosphere is filled almost entirely by pilot observations. When that data is absent, forecasters are working with less.

How Do I File a PIREP?

Filing takes roughly sixty seconds on the radio with Flight Service. Most major EFB platforms also allow direct in-app filing.

The format follows the same fields you’ve been reading: your location relative to a navaid, time, altitude, aircraft type, sky condition, weather, temperature, wind, turbulence, icing, and any remarks. Flight Service will guide you through it if you’re new to the process.

You don’t need dramatic conditions to make the call. A smooth ride at 8,000 feet with a broken layer at 4,000 feet and a temperature of +2°C is useful information - you are confirming what the forecast suggested, and that confirmation matters to the next pilot building a decision from that same briefing.

When you file, you’re also feeding data to meteorologists who update advisories in near real time. Your observation improves the product for everyone who pulls a briefing in the next two to three hours.

How Do I Use PIREPs to Make a Go/No-Go Decision?

Consider this scenario. You’re planning a VFR cross-country of 250 miles at 7,500 feet. The area forecast shows broken to overcast ceilings at 5,000 feet, tops unknown. An AIRMET Sierra is in effect for IFR conditions along your route. The TAF at your destination shows a temporary group with possible ceilings down to 300 feet within two hours of your ETA.

That briefing is uncomfortable. Then you find a PIREP: a Mooney at 7,500 feet, filed 40 minutes ago, 60 miles north of your route. The pilot reported an overcast layer with tops at 4,800 feet. Smooth on top. Temperature −2°C. Visibility unrestricted above the layer.

That PIREP just told you something the forecast couldn’t. The layer tops under 5,000 feet. The temperature at cloud level is just below freezing, so get through that climb without dawdling - but the overall picture is better than the forecast alone suggested.

Now run the same briefing with a different PIREP: the layer had tops above the pilot’s altitude during climb, unable to get on top, temperature −8°C, and moderate rime icing reported throughout the climb.

Same AIRMET. Same TAF. Different PIREP. Completely different decision.

That is weather briefing synthesis. The METAR gives you the surface. The TAF gives you the forecast. The AIRMET gives you the advisory picture. The PIREP ties the model to reality. When an examiner asks about your weather decision-making during a checkride, walk them through what the PIREP said, how it fit with the forecast, and what you would have done if it had said something different. That is the difference between a pilot who checked the weather and a pilot who briefed it.

Source material: FAA Pilot’s Handbook of Aeronautical Knowledge, Aviation Weather Services advisory circular (AC 00-45), and the National Weather Service Aviation Weather Center at aviationweather.gov.

Key Takeaways

• A routine PIREP (UA) is a real-time cockpit observation; an urgent PIREP (UUA) reports immediately hazardous conditions and is your first read in any briefing.
• The aircraft type field is critical context - a heavy jet’s “light turbulence” and a light single’s “light turbulence” do not describe the same ride.
• Moderate icing or worse is a no-go condition in any aircraft without a certificated deicing system; most structural icing occurs between 0°C and −20°C.
• The absence of PIREPs on a route means no one filed, not that conditions are acceptable - always note coverage gaps.
• Filing your own PIREPs takes about 60 seconds and directly improves weather products for every pilot briefing that area for the next two to three hours.