Aviation Weather
Understand weather theory, METAR/TAF reports, fronts, thunderstorms, icing, and how weather impacts flight safety.
Overview
Aviation weather is one of the most heavily tested areas on the FAA knowledge test. This area covers the atmospheric processes that create weather, how to read and interpret weather reports and forecasts, and the specific hazards that weather poses to safe flight operations. You'll need to understand both the theory (why weather happens) and the practical application (what to do about it).
Why This Matters
Weather is the single biggest factor in aviation accidents. Understanding weather theory helps you make go/no-go decisions, plan diversions, and recognize developing hazards before they become dangerous. The FAA tests this area heavily because it's directly tied to pilot safety.
Exam Weight
Expected Questions
8-12 questions
Difficulty
High
Notes
Expect METAR/TAF decoding questions, weather chart interpretation, and scenario-based hazard recognition. This is often the largest single topic on the PPL exam.
Key Concepts
The 6 essential concepts you need to understand for this topic.
Atmospheric Pressure and Wind
Air flows from high pressure to low pressure, deflected by the Coriolis effect. In the Northern Hemisphere, wind flows clockwise around highs and counterclockwise around lows. Surface friction causes wind to cross isobars toward low pressure.
Air Masses and Fronts
When different air masses meet, they form fronts. Cold fronts bring rapid weather changes with cumuliform clouds and possible thunderstorms. Warm fronts bring gradual changes with stratiform clouds and steady precipitation. Stationary fronts persist and can produce extended periods of poor weather.
Thunderstorms
Thunderstorms require moisture, an unstable atmosphere, and a lifting action. They develop in three stages: cumulus (updrafts), mature (up and downdrafts, heaviest precipitation), and dissipating (downdrafts only). Never fly within 20 nautical miles of a severe thunderstorm.
Fog Formation
Fog forms when the temperature-dewpoint spread narrows to within 2°C. Radiation fog forms on clear, calm nights. Advection fog forms when warm, moist air moves over a cold surface. Upslope fog forms as air rises along terrain. Each type has distinct formation and dissipation characteristics.
METAR and TAF Interpretation
METARs report current conditions (wind, visibility, weather, clouds, temp/dewpoint, altimeter). TAFs forecast conditions over 24-30 hours using BECMG, TEMPO, and FM groups. Being able to quickly decode these reports is essential for both the exam and real flying.
Icing Conditions
Structural icing occurs when visible moisture exists at temperatures between 0°C and -20°C. Clear ice forms in large supercooled droplets (most dangerous), rime ice forms in small droplets. Carburetor icing can occur even in warm temperatures with moderate humidity.
Common Mistakes
Confusing cloud types associated with cold fronts (cumuliform) versus warm fronts (stratiform).
Forgetting that carburetor icing can occur at temperatures well above freezing — even up to 70°F with high humidity.
Misreading METAR visibility — it's reported in statute miles, not nautical miles.
Not recognizing that fog forms when the temperature-dewpoint spread is narrowing, not just when it's already small.
Thinking all thunderstorms are visible — embedded thunderstorms in stratiform layers are a major hidden hazard.
Study Tips
Practice decoding real METARs daily — use AviaSkill's free METAR decoder to check your work.
Create flashcards for fog types — each has a distinct trigger and dissipation pattern.
Learn the thunderstorm lifecycle stages and associated hazards for each stage.
Study weather charts alongside METAR/TAF data to see how they relate to real conditions.
Pay special attention to temperature-dewpoint relationships — they appear in many question types.
FAA References
Pilot's Handbook of Aeronautical Knowledge (PHAK)
Chapter 12 — Weather Theory
Pilot's Handbook of Aeronautical Knowledge (PHAK)
Chapter 13 — Aviation Weather Services
Aviation Weather (AC 00-6B)
Complete reference
Related Free Tools
Sample Questions
Test your knowledge with these representative questions from the FAA exam.
1. What type of fog forms when warm, moist air moves over a colder surface?
Explanation: Advection fog forms when warm, moist air moves horizontally over a cold surface. Unlike radiation fog, it can form in windy conditions and at any time of day.
2. Which stage of a thunderstorm is characterized by both updrafts and downdrafts?
Explanation: The mature stage has both strong updrafts and downdrafts, producing the heaviest rain, strongest winds, and most severe turbulence. This is the most dangerous stage.
3. In a METAR, what does "BKN025" indicate?
Explanation: Cloud heights in METARs are reported in hundreds of feet AGL. "025" means 2,500 feet AGL. "BKN" means broken (5/8 to 7/8 cloud coverage).
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