Weather
Fronts and pressure systems for Part 107 pilots
Highs bring descending air and generally good weather, and lows bring rising air, cloud and precipitation. A front is the boundary between air masses, and its passage shows up as a wind shift together with changes in temperature and pressure, with cold fronts bringing sudden storms and warm fronts bringing low ceilings and widespread rain.
How do high and low pressure systems differ?
In the Northern Hemisphere, air flowing from high to low pressure is deflected to the right by the Coriolis force. That gives a clockwise, outward spiral around a high (anticyclonic) and a counterclockwise, inward spiral around a low (cyclonic). Near the ground friction turns the wind across the isobars toward lower pressure, by about 10 degrees over water and up to 45 degrees over rugged terrain (AWH Chapter 10).
| High pressure | Low pressure | |
|---|---|---|
| Air motion | Descending, dry | Rising to replace air that has left |
| Typical weather | Good, generally clear | Increasing cloud, precipitation, "bad weather" |
| Winds around it | Clockwise, spiral outward | Counterclockwise, spiral inward |
| Trend that tells you | Rising pressure suggests fair weather coming | Falling or rapidly falling pressure suggests bad weather and possibly severe storms |
The Pilot's Handbook says high-pressure systems are generally areas of dry, descending air, and low-pressure areas draw air in to replace rising air, which usually brings increasing cloudiness and precipitation. A free question in the app asks what to expect when a low moves over the site: rising air, more clouds and likely precipitation.
Sources (checked 2026-11-14): FAA Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C); FAA Aviation Weather Handbook (FAA-H-8083-28B, 2026).
Why does pressure matter beyond the forecast?
Pressure sets the altimeter setting and feeds density altitude. Low pressure means higher density altitude and thinner air, which cuts lift and thrust. Weather stations convert station pressure to sea level pressure by adding about 1 inHg per 1,000 ft of elevation, so pressure reports can be compared across stations. See density altitude.
Sources (checked 2026-11-14): FAA Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C).
What is an air mass?
An air mass is a large body of air that takes on the temperature and moisture of its source region, an area where the air stays stagnant for days or longer. The Pilot's Handbook names source regions in polar areas, over tropical oceans and over dry deserts. Air masses are identified as polar or tropical by temperature and maritime or continental by moisture, so a continental polar air mass is cool and dry and a maritime tropical one is warm and moist.
As an air mass moves, the surface under it modifies it. Moving over a warmer surface it warms from below, becomes unstable and produces cumulus, showers and turbulence with good surface visibility. Moving over a colder surface it becomes stable, traps smoke and dust near the ground, and can produce low stratus and fog. See stability and clouds.
Sources (checked 2026-11-14): FAA Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C).
What is a front?
An air mass takes on the temperature and moisture of its source region. Where two different air masses meet, the boundary is a front. The Pilot's Handbook lists four types named by the temperature of the advancing air relative to the air it replaces: warm, cold, stationary and occluded. It adds that an approaching front of any type always means changes to the weather are imminent. The study guide says that across a frontal zone, temperature, humidity and wind often change rapidly over short distances.
Sources (checked 2026-11-14): FAA Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C); FAA Remote Pilot sUAS Study Guide (FAA-G-8082-22).
What do warm and cold fronts bring?
| Warm front | Cold front | |
|---|---|---|
| What advances | Warm air replaces colder air | Cold, dense, stable air replaces warmer air |
| Speed (PHAK) | Slow, typically 10 to 25 mph | Typically 25 to 30 mph, extreme cases up to 60 mph |
| Slope | Gradual; warm air slides over the cool air | Steep; acts like a snowplow under warm air |
| Before it arrives | Cirriform then stratiform clouds, fog, light to moderate rain, drizzle, poor visibility; pressure keeps falling | Cirriform or towering cumulus, possibly cumulonimbus; high dew point, falling pressure |
| During passage | Stratiform clouds, drizzle, poor visibility improving, variable winds, temperature rising, pressure levels off | Cumulonimbus, heavy showers, lightning, hail, gusty variable winds, temperature and dew point drop rapidly, pressure bottoms out |
| After it passes | Stratocumulus, showers possible, haze, wind from south-southwest | Clearing, good visibility, cooler, wind from west-northwest, pressure rising |
| Warning time | Advance warning; can take days to pass | Little or no warning, weather changes in a few hours |
The Pilot's Handbook sums up the contrast this way: warm fronts bring low ceilings, poor visibility and rain, and cold fronts bring sudden storms, gusty winds, turbulence and sometimes hail or tornadoes. Violent weather with a cold front usually sits along the boundary, not ahead of it, although summer squall lines can form up to 200 miles in advance of a strong one.
Sources (checked 2026-11-14): FAA Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C).
What about stationary and occluded fronts?
A stationary front is a boundary between air masses of about equal strength that does not move, and it can influence the weather for days, with a mix of warm and cold front conditions. An occluded front forms when a fast-moving cold front catches a slow warm front. As it approaches, warm front weather arrives first and is followed immediately by cold front weather. Embedded thunderstorms, rain and fog are likely with a warm front occlusion if the air forced aloft is unstable. After passage nimbostratus and altostratus remain, precipitation decreases and visibility improves.
Sources (checked 2026-11-14): FAA Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C).
How do I recognize a frontal passage?
The test answer is a shift in wind direction together with changes in temperature and pressure. A rise in visibility alone does not prove a front, and neither does rising humidity alone. In a METAR you can see it as a veering wind, a temperature and dew point drop, and a pressure trend. At observing stations a WSHFT remark with FROPA flags a wind shift that the observer believes was a frontal passage.
Worked example
A cold front crosses a job site
Say you are filming a construction site. At 1:00 pm the METAR shows 20012KT 6SM HZ BKN025 25/22 A2983 and towering cumulus is building to the west. At 3:00 pm it reads 31023G38KT 3SM +TSRA BKN015CB 18/16 A2970 RMK PRESFR. Later, 29015KT 10SM SCT035 12/03 A3002. Look at what changed: wind from the southwest then the northwest and gusty, temperature down 13 degrees, dew point down 19, pressure falling then rising, and heavy rain and thunderstorms in between. This is a classic cold front passage, and the safe window ends well before the storms arrive.
Sources (checked 2026-11-14): FAA Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C); FAA Aviation Weather Handbook (FAA-H-8083-28B, 2026); FAA Remote Pilot sUAS Study Guide (FAA-G-8082-22).
What is a squall line?
A squall line is a continuous line of thunderstorms that often forms on or ahead of a cold front, in moist unstable air. The Pilot's Handbook says squall lines are intense, move quickly and can extend 300 to 500 miles. The Handbook says new cells keep forming along the leading edge, with rain and sometimes hail behind. It calls them the thunderstorm type that is the most effective barrier to air traffic and says about 25 percent of tornadoes in the U.S. come from squall lines. The advice is simple: when you see a line on the radar or a forecast for one, do not plan a flight in its path. See thunderstorms and microbursts.
Sources (checked 2026-11-14): FAA Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C); FAA Aviation Weather Handbook (FAA-H-8083-28B, 2026).
How do I plan a drone job around a front?
- Find the front on the surface analysis and the forecast discussion, and note which direction it is moving.
- Decide whether it is a warm or cold front. For a warm front expect days of lowering ceilings, then widespread low cloud and rain. For a cold front expect a short, sharp window before it arrives and a gusty, cooler, clearing afternoon behind it.
- Check the TAF for FM, TEMPO and PROB30 groups near the time the front is forecast to pass, and for a wind shift in the forecast winds.
- Watch the local pressure trend and the wind. Falling pressure and rising dew point mean the front is close. After a cold front the wind is gusty from the west-northwest as the Pilot's Handbook describes, so do not assume clearing sky means calm air.
- Fly early on a cold-front day, and stay out of the squall line.
Sources (checked 2026-11-14): FAA Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C); FAA Aviation Weather Handbook (FAA-H-8083-28B, 2026).
How do I find fronts and pressure systems?
The Weather Prediction Center provides surface pressure and frontal analyses (AIM 7-1-1), and aviationweather.gov carries prog charts and forecast discussions. In the Pilot's Handbook's color code a warm front is red, a cold front is blue, a stationary front is red and blue, and an occluded front is purple, though charts may be black and white. Check the legend. The weather overview lists other sources.
Sources (checked 2026-11-14): AIM Chapter 7, Section 1: Meteorology; FAA Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C); Aviation Weather Center.
What does the test emphasize?
- A front passage means wind shift plus temperature and pressure changes.
- Low pressure goes with rising air, cloud and precipitation. High pressure goes with sinking air and clearing.
- Cold fronts move faster and bring sudden, violent weather; warm fronts are slower with low ceilings and widespread precipitation.
- Falling pressure signals deteriorating weather.
Sources (checked 2026-11-14): FAA Remote Pilot sUAS Study Guide (FAA-G-8082-22); FAA Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C).
Free practice questions on this topic
2 original questions from the Sectional Cue bank. Try each one, then open the answer.
Low pressure systems
1. Forecasts show a low-pressure area moving over a planned work site tomorrow. What weather should the remote pilot expect?
- Rising air, more clouds and likely precipitation
- Sinking air with clearing skies and good visibility
- Calm winds and unlimited visibility all day
Show answer and explanation
A. Rising air, more clouds and likely precipitation
Air converges and rises in a low, cooling to saturation, so lows bring clouds and precipitation. Sinking air and clearing skies are typical of a high. A passing low often brings stronger winds, not calm and unlimited visibility.
Source: PHAK (FAA-H-8083-25C), Chapter 12
Frontal passage
2. What set of changes marks the passage of a front over a site?
- A rise in visibility with no change in wind or temperature
- A steady increase in humidity with no change in wind
- A shift in wind direction along with changes in temperature and pressure
Show answer and explanation
C. A shift in wind direction along with changes in temperature and pressure
Fronts separate air masses, so crossing one brings a change in wind direction, temperature and pressure. Better visibility alone, with no change in wind or temperature, does not mark a front. Rising humidity alone can occur without any front.
Source: PHAK (FAA-H-8083-25C), Chapter 12
Related guides
- Weather for drone pilots: what the Part 107 test expects
- Thunderstorms and microbursts: what drone pilots need to know
- Wind shear and turbulence for drone pilots
- How to read a METAR for the Part 107 test
- All Part 107 guides
Study the charts on your phone
Sectional Cue has 1150+ original questions with explanations, 27 FAA figures you can tap to read, and timed 60-question rehearsals. About 152 questions and three chart lessons are free.
Sources
- FAA Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C), checked 2026-11-14
- FAA Aviation Weather Handbook (FAA-H-8083-28B, 2026), checked 2026-11-14
- FAA Remote Pilot sUAS Study Guide (FAA-G-8082-22), checked 2026-11-14
- AIM Chapter 7, Section 1: Meteorology, checked 2026-11-14
How this page was made: written by Certloom Learning from the sources above, with the rules checked against the current regulation text. Practice items are original questions from the app's reviewed bank. Spot an error? certloomlearning@gmail.com.