PIREPs, AIRMETs, SIGMETs and TFRs
METARs and TAFs cover airports. These four cover everything in between — the part of the flight you actually spend the most time in.
Last updated August 2026
PIREPs — what pilots are actually finding
A pilot report is the only weather product generated by someone who was there. It is also the only one that can confirm what a forecast merely predicted, which makes it disproportionately valuable — particularly for icing, turbulence and cloud tops, none of which a ground observation can see.
UA /OV KSEA180010 /TM 1815 /FL055 /TP C172 /SK BKN035-TOP055 /TB LGT /IC NEG
| Field | Meaning |
|---|---|
UA / UUA | Routine report / urgent report |
/OV | Location — here, 010 nm on the 180 radial from KSEA |
/TM | Time in UTC |
/FL | Flight level — 5,500 feet |
/TP | Aircraft type — matters for interpreting turbulence and icing |
/SK | Sky — broken at 3,500, tops 5,500 |
/TB | Turbulence — light |
/IC | Icing — negative |
Aircraft type is not decoration. "Moderate turbulence" reported by a Cessna 172 and by a Boeing 737 describe very different air. Read the type before you read the intensity.
PIREPs are also sparse — they exist only where somebody filed one. An absence of icing reports along your route is not evidence there is no icing; it may only mean nobody has flown it in the last two hours. And file them yourself. The system only works because pilots contribute, and a negative report ("no icing, 6,000, smooth") is often more useful to the next pilot than a positive one.
AIRMETs — widespread, moderate
An AIRMET describes weather significant to light aircraft, affecting an area of at least 3,000 square miles. Three types:
- Sierra — IFR conditions or mountain obscuration.
- Tango — moderate turbulence, or sustained surface winds of 30 knots or more.
- Zulu — moderate icing and freezing level heights.
AIRMETs cover large areas and are issued every six hours with amendments. Because the areas are so big, an AIRMET Zulu over your whole route does not mean you will pick up ice everywhere in it — it means the conditions exist somewhere within it. Combine it with PIREPs and freezing levels to work out where.
SIGMETs — severe, and non-optional
A SIGMET is issued for weather hazardous to all aircraft: severe icing, severe or extreme turbulence, dust or sandstorms lowering visibility below three miles, and volcanic ash.
A Convective SIGMET is its own thing, issued hourly as needed for thunderstorm activity — embedded or line thunderstorms, or areas of thunderstorms with heavy precipitation. Any convective SIGMET implies severe turbulence, severe icing and low-level wind shear, whether or not they are spelled out.
There is no technique for penetrating a thunderstorm safely in a light aircraft. Convective SIGMETs are a routing problem to be solved on the ground, not a condition to be evaluated in flight.
TFRs — temporary flight restrictions
TFRs appear for VIP movements, sporting events, wildfires, disaster relief, space operations and security. They are the most common way a legal, well-planned flight becomes an enforcement action, because they can be published at short notice and they move.
Check them last, immediately before departure, and check them along the whole route rather than just at the ends. Stadium TFRs in particular catch people out — they are numerous, they activate around event times, and a 3-nautical-mile radius to 3,000 feet AGL sits exactly where a VFR transit would naturally go.
Seeing them in Flight Kneeboard
Turn on PIREPs, AIRMETs, SIGMETs and TFRs under Layers and they draw directly on the map, so you can see whether an advisory area actually intersects your route rather than inferring it from a text description. Any airport's Advisory tab shows the advisories relevant to it alongside its NOTAMs, grouped by type.
Bear in mind that advisory areas are approximations of a forecaster's judgement, drawn generously. Their edges are not fences.