Aviation weather has gotten complicated — not because the atmosphere changed, but because the information available to pilots has multiplied dramatically. As someone who has flown through every variety of forecast that turned out to be wrong, I learned what the products actually mean and how to use them in the real world. Today, I will share it all with you.
The fundamental difference between a phone weather app and aviation weather is consequence. A 30 percent chance of afternoon thunderstorms is a minor inconvenience for someone on the ground. For a VFR pilot in a light aircraft, it might mean a divert, a go-around, or something worse if the decision process was wrong. Aviation weather products are designed for pilots who need precise, actionable information — not general guidance about whether to bring an umbrella.
METARs — What’s Happening Right Now
A METAR is an observation of current conditions at a specific airport, issued every hour. It contains wind direction and speed, visibility in statute miles, sky condition with cloud layers in feet AGL, temperature and dewpoint in Celsius, and the altimeter setting.
The temperature-dewpoint spread is worth watching. When those two numbers get within two or three degrees of each other, relative humidity is high — and the likelihood of fog, mist, or precipitation rises fast. A spread of 2°C or less an hour before your planned departure is worth a phone call to flight service.
Special METARs (SPECIs) are issued when conditions change significantly between scheduled observations — a sudden visibility drop, a wind shift, or new precipitation. If a SPECI drops while you’re en route, it’s worth a radio call to check it.
TAFs — What to Expect at Your Destination
A TAF (Terminal Aerodrome Forecast) covers conditions at a specific airport over a 24 or 30-hour window in a format similar to METARs. A few terms worth knowing:
- FM (From) marks the start of a new forecast period
- TEMPO means temporary — conditions expected to last less than an hour at a time
- BECMG (Becoming) indicates a gradual change over a defined period
- PROB followed by a percentage means probability — PROB30 is a 30 percent chance
A TAF showing PROB40 TS at your destination during your estimated arrival window isn’t automatically a no-go. But it demands a solid alternate plan and a serious look at the area forecast before you depart.
PIREPs — What Other Pilots Are Actually Seeing
Pilot Reports are firsthand observations filed by pilots in flight. They’re one of the most valuable weather products available because they reflect actual in-flight conditions rather than model forecasts. A PIREP might report turbulence at a specific altitude, icing with the aircraft type, cloud tops and bases, or thunderstorm locations.
Check PIREPs along your route before departing. Three pilots reporting moderate icing at 8,000 feet in the last two hours while your route takes you through 8,000 feet without de-icing equipment is a straightforward answer to the go/no-go question.
AIRMETs and SIGMETs
AIRMETs (Airmen’s Meteorological Information) cover three categories of hazardous weather: Sierra for IFR conditions and mountain obscuration, Tango for moderate turbulence and low-level wind shear, and Zulu for icing and freezing levels. AIRMETs are significant for lighter aircraft and VFR operations — not emergencies, but not background noise either.
SIGMETs cover severe or extreme weather: significant turbulence, severe icing, volcanic ash, sandstorms. Convective SIGMETs cover thunderstorms and are issued when conditions warrant immediate pilot attention.
If a convective SIGMET covers your route, you plan around it. Thunderstorms are non-negotiable.
Winds Aloft Forecasts
Winds Aloft forecasts give predicted wind direction and speed at altitudes from 3,000 to 45,000 feet. They’re essential for calculating groundspeed and fuel burn, picking the best cruise altitude, understanding turbulence potential, and identifying icing levels. The forecast shows up as a four-digit group — the first two digits are direction in tens of degrees, the last two are speed in knots. Temperatures are included at most levels.
The Preflight Weather Brief
A complete preflight brief covers adverse conditions, the synoptic weather pattern, the en route forecast, winds and temperatures aloft, destination weather, and NOTAMs. You can get a standard briefing from 1800wxbrief.com through Leidos Flight Service, or through ForeFlight, Garmin Pilot, or similar applications.
Go/No-Go Decision Making
The best pilots don’t make binary decisions. They build decision trees. “If conditions at my destination are below minimums when I arrive, where will I divert, and do I have the fuel to get there?” Every flight plan should have that answer before you start the engine.
That’s what makes weather judgment something that develops over time — it’s not about memorizing products, it’s about knowing what they tell you and, just as importantly, what they don’t. A forecast is a probability. Always leave yourself an out.
