Aviation weather has gotten complicated with all the acronyms and coding systems flying around. As someone who spent years decoding METARs at 5 AM before dawn patrol flights, I learned everything there is to know about how pilots actually use these reports. Today, I will share it all with you.
Probably should have led with this section, honestly: weather kills more pilots than mechanical failures. Understanding what those cryptic strings of letters and numbers mean isn’t just academic—it’s survival.
Understanding METAR Reports
METAR stands for Meteorological Aerodrome Report. These standardized observations come from airports worldwide, and pilots need to decode them quickly. I still remember my first cross-country flight, staring at a METAR wondering what half the abbreviations meant.
Breaking Down the Components
Every METAR starts with a four-letter ICAO station identifier. US stations begin with K (like KJFK for Kennedy), Canadian stations with C. The timestamp follows in Zulu time—that’s UTC, not your local time zone. Get comfortable converting between local and Zulu because every weather product uses it.
Wind information comes next, and this is where things get practical. 27015G25KT means wind from 270 degrees at 15 knots, gusting to 25. Those gusts matter when you’re landing a light aircraft. I’ve turned around based on gust spreads alone. Variable winds show as VRB, and when direction varies significantly, you’ll see something like 240V310 after the main wind group.
Visibility shows in statute miles for US stations. Anything under three miles and you’re looking at special VFR or full IFR conditions. Runway visual range (RVR) supplements this when visibility drops low enough that it matters runway by runway. You’ll see it as R36L/2400VP6000FT, meaning Runway 36 Left has visibility between 2400 and more than 6000 feet.
Present weather uses abbreviations that become second nature: RA for rain, SN for snow, FG for fog, BR for mist, HZ for haze. The minus sign means light, no modifier means moderate, plus means heavy. TS before precipitation means thunderstorms—and that’s usually your cue to stay on the ground. Combining these, +TSRA means heavy thunderstorm with rain.
Sky condition tells you about clouds. FEW is 1-2 eighths coverage, SCT (scattered) is 3-4 eighths, BKN (broken) is 5-7 eighths, and OVC (overcast) means you can’t see sky. Heights are in hundreds of feet above ground level. BKN025 means broken clouds at 2,500 feet AGL. Multiple layers get reported in order of height.
Temperature and dewpoint appear as two-digit values separated by a slash. When they converge, expect fog or low clouds. A spread of 3 degrees or less usually means reduced visibility is coming. Altimeter setting follows, critical for accurate altitude readings. Missing this can put you hundreds of feet off from where you think you are. In the US it’s inches of mercury; internationally you’ll see hectopascals.
Terminal Aerodrome Forecasts
TAFs look ahead 24 to 30 hours for specific airports. That’s what makes them endearing to us planning types—you can see what’s coming before you commit to a flight. TAFs update every six hours at main stations, though amendments come out whenever conditions warrant.
Reading the Forecast Groups
The FM (from) group signals significant changes at specific times. FM181600 means from the 18th at 1600 Zulu, new conditions apply. TEMPO means temporary fluctuations you should expect, typically lasting less than an hour at a time. PROB indicates probability percentages for certain conditions—PROB40 means a 40% chance.
BECMG groups show gradual transitions, typically over two hours centered on the given time. Knowing when conditions will shift helps you time your departure. Leave too early and you fight headwinds; leave too late and you’re racing sunset or incoming weather.
Valid periods appear as date-time groups at the beginning. A TAF issued at 1800Z valid 1818/1918 covers 24 hours starting at 1800 Zulu. Understanding these windows helps you know how fresh your forecast information is. Older forecasts carry more uncertainty.
Weather Hazards That Ground Pilots
Thunderstorms
Thunderstorms pack multiple threats into one package: severe turbulence, lightning, hail, heavy rain, and microbursts. Mature cells can punch above 50,000 feet. The rule is simple—never fly through or under them. Period. Even the wake of a dissipating storm carries hazards.
Convective activity develops when unstable air rises rapidly. You’ll see it building on radar, watch it form visually on clear days. The tops of cumulonimbus clouds are where the real violence happens. Give them wide berth, at least 20 miles from severe cells. At night or in IMC when you can’t see them visually, that margin should increase.
Microbursts deserve their own warning. These intense downdrafts cause airspeed fluctuations that exceed what many aircraft can handle. A typical microburst might produce a 50-knot airspeed increase followed immediately by a 50-knot decrease—combine that with downdraft and you’ve got a recipe for a crash. When wind shear alerts pop up at an airport, delay your operations. No flight is worth tangling with a microburst.
Icing
Structural icing builds on wings and control surfaces when you fly through visible moisture below freezing. Clear ice forms in freezing rain (nasty stuff), rime ice develops in supercooled cloud droplets. Mixed icing combines both characteristics and can be particularly difficult to remove.
Ice kills aircraft performance. It adds weight, reduces lift, and increases drag simultaneously. The airfoil shape that generates lift gets distorted. Stall speeds increase while climb performance drops. In severe cases, aircraft have lost hundreds of feet per minute of climb capability. Anti-ice and de-ice systems help certified aircraft, but they have limits. Knowing those limits keeps you alive.
Freezing level information appears in AIRMETs and area forecasts. Plan your altitudes to stay above or below icing conditions when possible. If you pick up ice unexpectedly, change altitude immediately and report it via PIREP. Other pilots need to know what’s out there.
Low Visibility
Fog, haze, smoke, and precipitation all cut visibility. Radiation fog forms on clear nights when the ground cools enough to condense moisture—common after cold fronts pass through. Advection fog rolls in when warm moist air crosses cooler surfaces, particularly near coastlines and over cool water. Both can drop visibility below minimums faster than you’d expect.
Valley fog presents particular challenges in mountainous terrain. It can sit in low areas while peaks remain clear, creating deceptive conditions that trap pilots who descend into it. Sea fog along coastlines behaves similarly, pushed inland by afternoon breezes and retreating at night.
Getting Your Weather Briefing
Every flight deserves a thorough briefing. Standard briefings cover synopsis, current conditions, forecasts, winds aloft, NOTAMs, and potential ATC delays. Abbreviated briefings work for updates when you’re already familiar with the overall picture. Outlook briefings help when planning flights more than six hours ahead.
Where to Get Information
Flight Service provides official briefings by phone (1-800-WX-BRIEF) or online through platforms like 1800wxbrief.com. Aviation weather websites like AviationWeather.gov aggregate multiple sources into one view. Mobile apps like ForeFlight put everything in your pocket. Whatever source you use, responsibility for understanding the weather rests entirely with you.
Graphical forecasts show what’s happening visually. MOS (Model Output Statistics) data gives point forecasts for specific airports. Prog charts show frontal movement and expected conditions over time. Radar and satellite imagery reveal what’s happening right now. Use them all together to build a complete picture.
Making Go/No-Go Calls
Personal minimums help you make consistent decisions. Set these limits above regulatory requirements, especially while building experience. Consider ceiling, visibility, winds, crosswind components, and your own currency. A 500-foot ceiling might be legal but suicidal if you’ve only shot three approaches in the last six months.
When conditions look marginal, think about alternatives. Delay departure until afternoon when fog burns off. Pick a different route avoiding mountain weather. Plan alternate airports along your route. Cancel entirely if nothing works. Completing every flight safely matters infinitely more than completing every planned flight.
The 1-2-3 rule helps with destination weather: within one hour of ETA, the ceiling should be at least 2,000 feet and visibility at least 3 miles. Tighter conditions demand more experience and better equipment. Don’t push your luck.
Weather Changes En Route
Conditions shift while you’re airborne, requiring constant monitoring. Flight Watch frequencies (122.0) and Flight Service provide updates. ATC relays pilot reports and suggests routing around developing weather when workload permits. They’re not infallible, but they see the big picture.
Pilot reports—PIREPs—share real conditions encountered in flight. Filing them helps other pilots and improves forecasting accuracy. Report significant weather, turbulence, icing, anything that differs from what was forecast. Use standard format: location, time, altitude, aircraft type, conditions encountered. The system only works if pilots participate.
Onboard weather radar shows precipitation intensity but not cloud tops or turbulence directly. Datalink weather provides broader awareness but carries latency—the picture you see might be 10-15 minutes old. Neither replaces good judgment and conservative decision-making. Treat weather displays as advisory, not authoritative.
Seasonal Considerations
Winter brings icing, snow, low ceilings, and reduced daylight hours that compress your planning window. Summer means convective activity, density altitude concerns at high-elevation airports, and afternoon thunderstorms that build with clockwork regularity in many regions. Spring and fall feature rapidly changing conditions as air masses battle for dominance.
Regional patterns matter too. Coastal areas see marine layers and sea breezes that change character morning to evening. Mountain regions experience terrain-induced turbulence and rapid weather changes as air flows over ridges. The Gulf Coast deals with persistent moisture and tropical systems from June through November. Learning your local weather patterns makes planning easier and reveals which forecasts tend to verify.
The Bottom Line
Weather knowledge separates pilots who enjoy long careers from statistics. Keep learning, stay conservative, and respect what the atmosphere can do. The old saying holds: when in doubt, wait it out.
Certificates give you privileges. Judgment keeps you around to use them. Every pilot who flew into weather they couldn’t handle thought they could make it. Make decisions based on conditions, not hope. Your family will appreciate the conservatism even when you’re explaining why you didn’t fly that day.
