What is the winds aloft forecast and why is it different from the ATIS?

The Winds and Temperatures Aloft Forecast (FB) shows wind direction, speed, and temperature at altitudes from 3,000 to 39,000 feet. The ATIS reports surface conditions only - what's happening at ground level can be completely different from what you'll encounter at cruise altitude.

How do I decode a winds aloft forecast code like 2735?

Multiply the first two digits by 10 to get the wind direction in degrees (27 × 10 = 270°), and read the next two digits as the speed in knots (35 knots). If a slash and two more digits follow, that's the temperature in Celsius at that altitude.

Which FB reporting level should I use for a VFR altitude like 5,500 feet?

Use the nearest listed reporting level as a proxy. The FB reports at 3,000, 6,000, and 9,000 feet. For a planned cruise altitude of 5,500 feet, use the 6,000-foot data. The difference is small enough that it works for cross-country planning.

How does the winds aloft forecast affect my fuel planning?

A headwind reduces your groundspeed, which means more time in the air burning fuel to cover the same distance. In a Cessna 172 burning 8 gallons per hour, a 37-minute difference in flight time over a 250-mile leg can mean roughly 5 gallons more or less fuel consumed - a meaningful margin on a cross-country.

Which forecast window should I use for a flight departing this afternoon?

Use the 12-hour forecast rather than the 24-hour version when your flight is within a few hours of departure. All FB times are in Zulu (UTC), so convert your local departure time to Zulu and confirm you are using the valid window that covers your flight.

The Winds Aloft Forecast, the Altitude That Cuts Your Headwind in Half, and the Fuel Math That Changes the Moment You Open the FB Report

The Winds and Temperatures Aloft Forecast - called the FB - is one of the most consistently underused tools in student cross-country planning. Checking it before departure is how you avoid landing with less fuel than expected after fighting a 30-knot headwind you never saw coming. Used correctly, it changes your altitude choice, your groundspeed estimate, and your total fuel burn on every cross-country you fly.

What Is the Winds Aloft Forecast and Where Do You Get It?

The FB is issued by the National Weather Service and covers altitudes from 3,000 feet through 39,000 feet. It is not the same as checking surface winds at your departure airport. On a day when the ATIS reads winds light and variable, you might climb to 6,000 feet and find a 40-knot headwind - or a 20-knot tailwind that gets you to your destination early with fuel to spare.

You can access the forecast through the Aviation Weather Center, your electronic flight bag, or through a standard weather briefing with Flight Service. For cross-country training, you are primarily looking at the lower reporting levels: 3,000, 6,000, 9,000, and occasionally 12,000 feet.

How Do You Read the FB Forecast Code?

The forecast is organized in a grid - stations in rows, altitudes in columns. Each cell contains a six-digit code. The first four digits are the wind; the last two digits, following a slash, are the temperature in Celsius.

For a wind group like 2735: the first two digits (27) are the direction in tens of degrees - multiply by 10 to get 270°, wind from the west. The next two digits (35) are the speed in knots. This entry reads: wind from 270° at 35 knots.

When wind speed exceeds 99 knots, the encoding shifts. The National Weather Service adds 50 to the direction digits and subtracts 100 from the speed. A group of 7360 decodes as: 73 − 50 = 23, direction is 230°; 60 + 100 = 160 knots. That is jet-stream territory you will not fly as a VFR student, but you will see it in the data and knowing what it means prevents confusion.

The code 9900 means calm or light and variable - wind below 5 knots. No meaningful wind component to work with.

Why Does the Temperature Column Matter?

The two-digit Celsius value after the slash is more than background information. First, it feeds directly into density altitude awareness. If you are departing from a high-elevation airport on a warm day and temperatures aloft are above standard, your airplane performs as if it is at a higher altitude than the altimeter indicates - affecting climb rate and the true airspeed you are actually achieving at a given power setting.

Second, a temperature significantly warmer than standard at a given altitude can signal atmospheric instability, a capping inversion, or conditions worth cross-checking against AIRMETs and pilot reports. You are not doing a full meteorological analysis, but the temperature column gives you a more complete picture than wind alone.

How Do You Choose the Right Altitude Using the FB?

The correct approach is not simply looking up the winds at your planned altitude. The goal is to compare two or three legal altitudes and pick the one with the best outcome.

Under FAR 91.159, when flying VFR more than 3,000 feet AGL, you must maintain altitudes based on magnetic course:

Eastbound (0°–179° magnetic): odd thousands plus 500 - 3,500, 5,500, 7,500 feet
Westbound (180°–359° magnetic): even thousands plus 500 - 4,500, 6,500, 8,500 feet

The FB reports at 3,000, 6,000, and 9,000 feet - not the exact VFR altitudes. Use the nearest reporting level as your proxy: 3,000 for 3,500, 6,000 for 5,500, 9,000 for 7,500. The approximation is close enough for planning.

What Does a Side-by-Side Altitude Comparison Look Like?

Consider an eastbound cross-country from the Midwest, 250 miles, magnetic course approximately 070°. Your legal altitude choices are 3,500, 5,500, and 7,500 feet. Here is what the FB shows for stations along the route:

3,000 feet: winds from 240° at 12 knots - mostly a crosswind, negligible headwind component
6,000 feet: winds from 270° at 22 knots - a partial tailwind component of roughly 8–10 knots
9,000 feet: winds from 310° at 35 knots - a partial tailwind component of roughly 15–18 knots

In a Cessna 172 at roughly 110 knots true airspeed, that translates to estimated groundspeeds of approximately 110, 119, and 126 knots at the three altitudes respectively.

Over a 250-mile leg:

250 miles at 80 knots (30-knot headwind scenario) = 3 hours 7 minutes
250 miles at 100 knots (10-knot headwind scenario) = 2 hours 30 minutes
That is 37 minutes off the total flight time

At a fuel burn of roughly 8 gallons per hour, 37 minutes is close to 5 gallons saved. On a cross-country where fuel margins matter, that is both real money and real safety buffer.

What Other Factors Go Into Altitude Selection?

Winds are not the only variable, and a checkride examiner will ask you to reason through all of them.

Terrain clearance comes first, always. Every leg of your flight plan begins with a minimum safe altitude. If the altitude with the best tailwind does not provide adequate clearance over terrain along the route, you move up to the next option.

ATC communication and radar coverage improve with altitude. Requesting flight-following becomes more reliable above roughly 4,000 feet AGL across most of the country. Lower altitudes in mountainous areas can create radio and radar dead zones.

Turbulence is not always worse at lower altitudes. On days with convective activity or a passing front, one altitude may be rough while another is smooth. A warm temperature reading aloft, combined with an unstable atmosphere, can indicate rough air below an inversion. Cross-check the FB with AIRMETs for turbulence and any available pilot reports along your route.

Aircraft practical ceiling matters too. A Cessna 172 has a published service ceiling of around 14,000 feet, but above 10,000 feet, climb rates slow and density altitude effects become meaningful. Most student cross-countries stay below 8,000 feet, and there is nothing wrong with that - flying lower with a thorough understanding of the wind profile is better than climbing without a good reason.

How Do You Use the Correct Forecast Window?

The FB is issued multiple times per day with 12-hour and 24-hour valid windows. All times are in Coordinated Universal Time (Zulu). If your flight departs at 3:00 PM local time, identify the corresponding Zulu time and use the forecast window that covers your departure. Pulling the 24-hour forecast for a flight two hours away gives you less accurate wind data than using the 12-hour version.

In your electronic flight bag, the graphical winds aloft layer is faster to read - wind barbs at different altitude levels give a quick visual read on flow along your route. But fluency in the text encoding also matters. The knowledge test will ask you to decode a printed FB group, and a checkride examiner may hand you raw forecast data to read. Both skills take roughly 20 minutes of practice to develop.

What Does the Preflight Workflow Look Like?

The practical sequence is straightforward:

Pull the FB during your preflight weather briefing
Identify two or three legal altitudes for your direction of flight
Look up the nearest FB reporting level for each
Note the wind direction, speed, and temperature at each level
Estimate the headwind or tailwind component along your magnetic course
Compare groundspeed results against terrain and communication requirements
Write the chosen altitude and your reasoning on your flight log

When the examiner asks why you selected a specific altitude, answer with your data: what the winds were at each level, what component that gave you, and how terrain clearance factored in. That kind of structured answer directly matches what the Airman Certification Standards are looking for in cross-country performance tasks.

Key Takeaways

The FB covers 3,000 to 39,000 feet and is entirely separate from surface wind conditions at your departure airport
Decode the six-digit wind group as: first two digits × 10 = direction in degrees, next two digits = speed in knots; last two digits after the slash = temperature in Celsius
FAR 91.159 requires specific VFR cruising altitudes based on magnetic course; use the nearest FB reporting level as a planning proxy for each legal option
On a 250-mile leg, a 20-knot groundspeed difference can mean 37 minutes of additional flight time and roughly 5 gallons of extra fuel burn
Always prioritize terrain clearance over wind optimization - then use the FB to pick the best option among altitudes that already clear the terrain
Use the forecast window that covers your departure time in Zulu; the 12-hour forecast is more accurate than the 24-hour for flights happening within a few hours