The PIREP, the Real-Time Pilot Weather Report That Ground-Based Forecasters Cannot See, and the Filing Habit That Makes Every Pilot Part of the Weather Network
PIREPs are real-time in-flight weather reports that reveal icing, turbulence, and cloud layers no ground-based forecast can capture - here's how to decode and file them.
A PIREP (pilot weather report) is a standardized weather observation filed by a pilot in flight, documenting actual conditions at altitude - cloud bases and tops, icing, turbulence, wind, and temperature. Unlike METARs, TAFs, or winds aloft forecasts, a PIREP reflects what the atmosphere is actually doing at a specific location and altitude. National Weather Service forecasters use PIREPs to calibrate their models and issue AIRMETs and SIGMETs; every report a pilot files improves the forecast for everyone who flies that route after them.
Why Do PIREPs Matter More Than Other Weather Products?
METARs are surface observations. TAFs are computer-generated forecasts. Neither one can tell you with certainty what is happening at eight thousand feet between two reporting stations. A PIREP can.
When forecasters see a cluster of icing PIREPs concentrated in a specific area, they update the forecast. When turbulence PIREPs come in from multiple aircraft along a route, that data feeds the Graphical Forecast for Aviation. PIREPs are not supplemental information - they are part of the weather data infrastructure, filed by pilots and used by forecasters, dispatchers, and every pilot flying that route after you.
What Are the Two Types of PIREPs?
Every PIREP begins with a type identifier. A routine report starts with UA. An urgent PIREP starts with UUA and is reserved for conditions that pose an immediate danger to other aircraft: severe turbulence, severe icing, low-level wind shear, tornadoes, or similar hazards. When UUA appears at the front of a report, read the entire thing before continuing.
How Do You Decode a PIREP?
Every PIREP follows a standardized field structure. Once you know the codes, decoding takes about ten seconds. Here is each element in sequence:
OV - Location. Uses a three- or four-letter station identifier (the nearest VOR or airport), sometimes with a direction and distance appended. OV KIND means over Indianapolis. OV MKE030040 means the report was taken 40 miles northeast of Milwaukee’s Mitchell Field.
TM - Time. Always in Zulu, always four digits. TM1430 is 1430 UTC.
FL - Flight level. Altitude in hundreds of feet. FL060 is 6,000 feet. FL250 is flight level two-fifty. If altitude is unknown, the field reads FL UNKNWN.
TP - Aircraft type. This context matters. A Cessna 172 and a Boeing 767 do not experience turbulence the same way. Moderate turbulence in a heavy jet may equate to severe in a light aircraft. If you see moderate turbulence reported from a 767, treat that intensity as severe in your Piper Warrior.
SK - Sky condition. Cloud layer bases and tops, when the pilot can observe them. SK OVC030 means an overcast with a base around 3,000 feet. A pilot who climbed through a layer can report both the base and the tops from direct observation - your TAF and NEXRAD cannot do that.
WX - Weather and obstructions. Rain, snow, mist, or other precipitation and visibility-reducing conditions.
TA - Temperature. Reported in Celsius at altitude.
WV - Wind. Direction and speed at altitude. If the reported wind contradicts your winds aloft forecast at your planned cruise altitude, that is worth knowing before you commit to a fuel plan.
IC - Icing. Intensity codes: TR (trace), LGT (light), MOD (moderate), SVR (severe). Ice type: ICE (clear ice), RIME (rime ice), MIXED (mixed). So IC LGT MOD ICE means light to moderate clear icing.
TB - Turbulence. Same intensity scale - trace, light, moderate, severe, EXTRM (extreme). Extreme turbulence means the aircraft is momentarily out of control; take that code literally. CHOP indicates lighter, intermittent turbulence. CAT means clear air turbulence.
RMK - Remarks. Plain language added by the pilot. Tops at niner thousand. Smooth above one two thousand. Recommend avoiding. Read the remarks - they often contain the most operationally useful sentence in the entire report.
How Do You Decode a Complete PIREP? (Worked Example)
UA/OV ABR/TM1745/FL060/TP CESNA172/SK BKN040 TPS080/TA -04/IC LGT RIME/RMK SMOOTH ABV 9 THOUSAND
- Type: Routine PIREP
- Location: Over Abilene, Texas
- Time: 1745 Zulu
- Altitude: 6,000 feet
- Aircraft: Cessna 172
- Sky: Broken layer, base 4,000 feet, tops 8,000 feet
- Temperature: -4°C
- Icing: Light rime icing
- Remarks: Smooth above 9,000 feet
The operational picture from that single report: the icing layer runs from 4,000 to 8,000 feet. Climbing above 9,000 feet clears both the layer and the icing. If your aircraft cannot reach 9,000 feet, this route requires serious reconsideration. That is actionable information no model produced.
How Do You File a PIREP?
The easiest method is through Leidos Flight Service, either by phone at 1-800-WXBRIEF or through the online portal at 1800wxbrief.com. ForeFlight users can file directly in the app under the Pilot Reports section; Garmin Pilot has the same capability. In the air, call Flight Service on 122.2 or a Remote Communications Outlet (RCO) frequency listed on your sectional charts.
The format mirrors what you just decoded: give your location, time, altitude, and aircraft type, then report what you observed - sky conditions with cloud bases and tops if known, temperature, any precipitation, icing with intensity and type, and turbulence with intensity and character (continuous or intermittent).
A PIREP does not have to be complete to be useful. A report with only icing information is valuable. A report that says smooth at eight thousand on a day forecast for bumps is valuable. An incomplete PIREP is better than no PIREP.
When Are You Required to File a PIREP?
Most PIREP filing is voluntary, but certain conditions carry a mandatory reporting requirement under FAA guidance:
- Severe or extreme turbulence
- Severe icing
- Tornadoes, funnel clouds, or waterspouts
- Low-level wind shear within 2,000 feet of the surface
- Hail at cruise altitude
Everything else is voluntary - but file anyway. Every report makes the system more accurate for the pilot flying your route next.
How Do PIREPs Fit Into a Preflight Weather Briefing?
PIREPs function as the reality check on everything else in your briefing. A useful sequence for cross-country planning:
- Prog charts - the big-picture weather system, frontal position and movement
- METARs - current conditions at departure, destination, and alternates
- TAFs - forecast conditions across your routing timeframe
- AIRMETs and SIGMETs - already-issued official hazard products (mandatory checks)
- PIREPs - real conditions reported by pilots who were just there
Once you have the official products, PIREPs either confirm or contradict them. A TAF calling for ceiling lift by noon, combined with a recent PIREP showing smooth conditions and high tops, supports your plan. A PIREP showing icing exactly where the forecast said tops would be above your altitude tells you to reconsider the whole route.
The absence of PIREPs on a route is not a green light. It may mean conditions are fine. It may mean no aircraft have flown the route recently enough to report. It may mean conditions kept everyone on the ground. Treat no PIREPs as neutral information, not reassurance.
How Do PIREPs Show Up on the Checkride?
Private pilot ACS: The examiner expects you to obtain and interpret weather information, and PIREPs are part of that evaluation. You need to demonstrate you understand what a PIREP is, where it comes from, and how it informs a go/no-go decision. You do not need the format codes memorized - you need to explain what the report is telling you and whether it changes your plan.
Instrument rating ACS: PIREPs carry significantly more weight here. Icing and turbulence PIREPs along your route are not optional reading on an IFR flight - they are part of your dispatch decision. Instrument practical tests routinely include scenario-based weather decision-making, and being able to pull a PIREP off the screen, decode it, and explain its implication for a specific route at a specific altitude is exactly the competency examiners are watching for.
The full PIREP format is documented in AIM Chapter 7. The FAA Aviation Weather Services handbook covers how PIREPs feed the forecast cycle in detail if you want the complete picture.
Key Takeaways
- A PIREP is the only real-time weather observation from inside an actual cloud layer - METARs and TAFs cannot replace it.
- UA indicates a routine PIREP; UUA indicates an urgent one requiring immediate attention.
- Aircraft type (TP) is critical context: moderate turbulence in a heavy jet often means severe in a light aircraft.
- Mandatory PIREP filing applies for severe or extreme turbulence, severe icing, tornadoes or funnel clouds, low-level wind shear within 2,000 feet AGL, and hail at cruise altitude.
- The absence of PIREPs on a route is not confirmation of good conditions - it is simply the absence of data.
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