Pilot reports and the weather picture no forecast can give you until someone actually flies through it

PIREPs (pilot reports) are the only source of real-time, in-flight weather observations in the entire aviation briefing system. Every other weather product — METARs, TAFs, winds aloft, prog charts — is either a ground-based observation or a computer-generated forecast. PIREPs tell you what conditions are actually like between the surface and cruising altitude right now, reported by pilots who just flew through that airspace.

If you’re not reviewing PIREPs before every flight, you’re making go/no-go decisions with an incomplete picture.

Why Can’t METARs and TAFs Replace PIREPs?

METARs report surface conditions at a specific airport. TAFs forecast what a meteorologist expects over the next 24 to 30 hours. Winds and temperatures aloft are modeled conditions at set altitudes. Prog charts paint the big picture.

None of these products can tell you whether a thin layer of rime ice is building at 6,500 feet over central Pennsylvania right now. None can confirm whether that forecast moderate turbulence actually materialized. PIREPs fill that gap with real observations from real cockpits.

How Do You Read a PIREP?

A pilot report follows a standard format with fields separated by slashes, always in the same order. Once you’ve seen a few, decoding becomes second nature.

Location (OV): Where the pilot was when they made the report. Could be a three-letter identifier like ABE (Allentown) or a relative position like “20 NW of ABE.”

Time: Reported in Zulu. This field matters more than most pilots realize. A PIREP from 45 minutes ago is actionable. A PIREP from three hours ago is interesting. A PIREP from six hours ago may be irrelevant — the weather has moved on.

Flight Level/Altitude (FL): FL065 means 6,500 feet MSL. This is critical because weather lives in layers. Turbulence at 8,000 feet doesn’t mean turbulence at 4,000 feet.

Aircraft Type: Often overlooked, but important for calibration. If a Boeing 757 reports light turbulence, that same air might throw a Cessna 172 around violently. A heavy aircraft’s light chop could be your moderate turbulence.

Weather Conditions: The core of the report — sky conditions, visibility, temperature, wind, turbulence, and icing.

How Is Turbulence Reported in PIREPs?

Turbulence uses a four-level scale:

• Light — minor altitude deviations, slight bumpiness
• Moderate — difficulty holding altitude, passengers getting uncomfortable
• Severe — temporary loss of aircraft control possible
• Extreme — structural damage territory

Light and moderate are judgment calls and are relative to the airplane filing the report. That’s why the aircraft type field matters so much. You will never intentionally fly into severe or extreme turbulence.

How Is Icing Reported in PIREPs?

Icing is reported by intensity — trace, light, moderate, and severe — along with type:

• Rime ice: rough, milky white; forms when small supercooled droplets freeze on contact
• Clear ice: smooth, hard to see, and dangerous; forms when larger droplets run back along the surface before freezing
• Mixed: both rime and clear

How Should PIREPs Change Your Go/No-Go Decision?

Consider this scenario. You’re planning a cross-country from Lancaster, Pennsylvania to Frederick, Maryland in late November. METARs at both airports look fine — visibility 10 miles, ceiling broken at 5,000 feet. The TAF doesn’t mention icing. Winds aloft at 6,000 feet show 290 at 20 knots, temperature minus 4°C.

That temperature should get your attention. You’ll be flying near the freezing level with clouds in the area.

You pull up PIREPs along your route and find this: a Piper Cherokee reported light rime icing between 4,500 and 5,800 feet, 15 nautical miles south of Harrisburg, filed 40 minutes ago.

You’re in a Cessna 172 with no deicing equipment. That single PIREP just gave you information no METAR, TAF, or prog chart was going to provide. It confirmed that right now, in that specific slice of sky, ice is forming on airplanes.

If you can fly the route at 3,500 feet and stay below the icing layer — and terrain, airspace, and cloud bases allow it — you might still go. But you need an out. What if the bases lower en route? What if the freezing level drops? This is the difference between a pilot who checks the weather and a pilot who actually uses it.

What Does “No PIREPs” Actually Mean?

No PIREPs doesn’t mean no weather. It might mean nobody has been up there yet, or it might mean the pilots who flew didn’t bother to report.

This absence of information is itself information. If your route crosses a mountain pass, the TAF calls for winds at 25 knots gusting 30 at ridge level, and there are zero PIREPs along that route — consider why. Mountain wave turbulence and severe downdrafts are possible. If experienced local pilots aren’t flying that route in those conditions, that silence should factor into your decision.

The Airman Certification Standards expect you to evaluate weather information and make a competent go/no-go decision. Knowing what to do when PIREPs are absent is just as important as knowing how to read them.

Where Do You Find PIREPs During a Preflight Briefing?

Flight Service (1-800-WX-BRIEF): Briefers include relevant PIREPs in your standard briefing. If they don’t mention any, ask directly: “Do you have any PIREPs along my route of flight?” Sometimes reports exist but weren’t flagged because they seemed routine.

Electronic flight bag apps: ForeFlight, Garmin Pilot, and similar apps display PIREPs as icons on the map. Tap them for the full decoded report. Most apps let you filter by type — icing only, turbulence only.

Aviation Weather Center website: The National Weather Service site offers a map view of all current PIREPs, filterable by type, altitude, and age.

What’s the Difference Between UA and UUA PIREPs?

There are two types of pilot reports:

Routine PIREPs (UA): Noteworthy but not immediately dangerous conditions — light to moderate turbulence, light icing, sky conditions, visibility.

Urgent PIREPs (UUA): Severe or extreme turbulence, severe icing, low-level wind shear, or any condition representing an immediate hazard. UUAs get distributed to air traffic control and Flight Service immediately, and controllers relay them to other aircraft in the area.

If you encounter severe turbulence or severe icing, filing a UUA isn’t just good practice — it could save someone’s life.

How Do You File a PIREP?

Filing is simple and takes under a minute:

• By radio: Call Flight Service on 122.0 (the universal frequency) or the published Flight Service frequency for your area
• By app: ForeFlight and other EFB apps now support electronic PIREP filing

You don’t need to have encountered anything dramatic. A negative PIREP — reporting smooth air, no icing, good visibility — is almost as valuable as one reporting hazards. It confirms that right now, in that corridor, at that altitude, conditions are pilot-friendly.

To make your PIREPs useful, be specific: report the altitude range (not just “turbulence”), give your location relative to a VOR or airport, include the time, and always mention your aircraft type so the next pilot can calibrate expectations.

Build PIREPs into your routine for every flight — not just cross-countries. Check them before you go, and file one when you land. Even a boring one. Especially a boring one. The more pilots contribute, the better the system works for everyone.

Key Takeaways

• PIREPs are the only real-time, in-flight weather observations in the briefing system — everything else is ground-based or forecast-modeled
• Always consider the aircraft type that filed the report; a heavy jet’s “light turbulence” may be your “moderate”
• No PIREPs doesn’t mean no weather — the absence of reports is itself a data point worth evaluating
• File PIREPs after every flight, including negative reports of smooth conditions — they help the next pilot make better decisions
• Urgent PIREPs (UUA) for severe conditions get immediate distribution to ATC and should always be filed when warranted

References: FAA Advisory Circular AC 00-45H (Aviation Weather Services) and the Pilot’s Handbook of Aeronautical Knowledge — both free from the FAA.