The Winds and Temperatures Aloft Forecast, the FB Product, and the Coded Numbers That Hide a Wind Too Strong to Print

The winds and temperatures aloft forecast, labeled FB on your briefing, is a National Weather Service product that predicts wind direction, wind speed, and temperature at specific altitudes above specific stations. A group like 213006 decodes to wind from 210 degrees true at 30 knots, temperature +6°C. Two coding tricks trip up new pilots: 9900 means light and variable, and any direction over 36 means you must subtract 50 and add 100 knots to the speed.

What Is the Winds and Temperatures Aloft Forecast (FB)?

The product is officially called the winds and temperatures aloft forecast. On briefings, legacy teletype codes, and most apps you’ll see it labeled FB. Many pilots still call it the “winds aloft,” and some say FD out of habit, because that was the old identifier for years. It’s the same thing.

It’s a forecast produced by the National Weather Service of what the wind and temperature are doing at specific altitudes above specific locations. Note the word forecast - these are predicted values, not observations.

Why the Winds Aloft Forecast Matters for Every Cross Country

Every cross country you fly lives or dies by the wind. Your flight plan says a leg takes 50 minutes, but the wind aloft decides whether it’s actually 40 minutes or an hour and 10. That’s the difference between landing with comfortable reserves and landing on fumes.

The winds aloft forecast is how you know before you go. It’s how you pick an altitude, how you decide whether today is a headwind day at 9,000 and a tailwind day at 6,000, and how you catch the freezing level sneaking down to where you actually want to fly.

How Is a Winds Aloft Forecast Organized?

The forecast is organized by station - each reporting point has its own line. Across the top runs a row of altitudes: 3,000, 6,000, 9,000, 12,000, 18,000, 24,000, 30,000, 34,000, and 39,000 feet.

Under each altitude, for each station, you get a small group of numbers. That group holds direction, speed, and temperature.

How Do You Decode a Winds Aloft Group?

Take a 6,000-foot column that reads 213006. Break it into three parts.

Direction (first two digits): 21 means 210 degrees. Critically, this direction is referenced to true north, not magnetic. The surface winds you get from the tower or ATIS are magnetic; the winds aloft are true. Mix them up and your wind correction angle will be off by however much magnetic variation exists in your area.

Speed (next two digits): 30 means 30 knots.

Temperature (final digits): +06 means +6°C. At and below 12,000 feet, the sign (plus or minus) is printed for you. Above 12,000 feet, the plus sign is dropped because it’s essentially always below freezing - a bare number up high is always negative. Above 24,000 feet, you can safely assume the temperature is minus.

So 213006 reads: wind from 210 degrees true at 30 knots, temperature +6°C. Say it that way out loud in the runup and it becomes second nature.

What Does 9900 Mean on a Winds Aloft Forecast?

9900 is the code for light and variable. When the forecast wind is less than 5 knots, the coders don’t assign a direction - they simply print 9900. It’s not a wind from 990 degrees (which is impossible); it means calm-ish air with no meaningful direction. When you see it, read it as “light and variable” and move on. That’s an easy leg.

How Do You Decode Winds of 100 Knots or More?

Wind direction only goes up to 360 degrees, so the first two digits can never exceed 36. The coders use that dead space to carry extra information. When the wind speed is 100 knots or more, they add 50 to the direction as a flag.

So if the first two digits are greater than 36, do two things: subtract 50 from the direction to get the real direction, and add 100 to the speed.

Here’s a real example from a 39,000-foot column: 731965.

• First pair 73 is impossible as a compass heading, so the fifty flag is on. Subtract 50: 73 − 50 = 23, meaning 230 degrees true.
• Next pair 19 - but the flag says add 100: 19 + 100 = 119 knots.
• Final pair 65 is the temperature: −65°C, because at 39,000 feet it’s always minus.

So 731965 decodes to wind from 230 degrees true at 119 knots, −65°C. That’s a jet stream core - the river of air the airlines surf across the country.

One edge case: a wind of exactly 200 knots is coded as direction-plus-50 with speed digits 99. So 7799 means wind from 270 degrees true at 200 knots. Two hundred knots is the ceiling; anything that strong or stronger gets pegged at 99. You’ll rarely meet this in a light airplane, but now it won’t surprise you.

Why Are Some Altitudes Blank on the Forecast?

The forecast will not publish a wind for any altitude within 1,500 feet of the station’s elevation. If a station sits around 5,000 feet on the high plains, you simply won’t get a 6,000-foot wind for it - the space is blank. That’s not an error; surface friction makes winds that low unreliable.

For the same reason, no temperature is published within 2,500 feet of the station elevation, and there’s no temperature at the 3,000-foot level at all. Temperatures start higher up, where they matter for icing and true airspeed corrections.

How Long Is a Winds Aloft Forecast Valid?

These are forecast winds, not observed. The FB is issued a few times a day, each valid for a block of hours. There’s a valid time and a “for use” window printed at the top of the product - check it. A forecast made for mid-afternoon may be stretched thin by evening. If the actual weather is diverging from the forecast, the winds aloft are diverging too.

How Do the Temperatures Reveal the Freezing Level?

Suppose you want to fly at 9,000 feet for smooth air and a tailwind, and the 9,000 column shows a healthy push. Beautiful - but look at the temperature in that same group. If it reads −2 or −3°C and there’s moisture in the sky, you’ve just found the freezing level, and you’re planning to fly right through it. That tailwind now comes with an icing question.

The temperature half of the forecast is your freezing-level flashlight. Most pilots read the wind and skip the temperature. Don’t. The temperature is telling you where the ice lives.

Examiners look for exactly this on a checkride. They don’t just want you to read the numbers - they want you to connect them: “I chose 7,000 instead of 9,000 because at 9,000 the temperature drops below freezing and there’s visible moisture, so I’m staying in warmer air.” That’s aeronautical decision making.

What’s the Practical Flow for Using Winds Aloft on Your Next Flight?

After you’ve reviewed the big picture - METAR, TAF, and charts - pull the winds aloft for the station nearest your route at the two or three altitudes you’re considering. Decode each one: direction (true), speed (knots), temperature (Celsius). Then do three things:

1. Compare altitudes for wind. Find the level with the best tailwind, or smallest headwind, that still keeps you high enough for terrain and glide. Sometimes an extra 2,000 feet buys you 15 knots of groundspeed; sometimes it costs you 15.
2. Read the temperatures for your freezing level. Ask the icing question at every altitude you’re considering, especially if there’s any moisture forecast.
3. Run your navigation log with the winds you picked. Calculate wind correction angle, groundspeed, time en route, and fuel burn - and convert the true wind direction against your true course before you chase your magnetic heading. Keep your references straight.

Learning this isn’t hard the way an engine failure is hard - it’s hard the way a foreign language is hard. It looks like gibberish until it doesn’t, and then you can never unsee it. The first ten times you’ll count on your fingers, subtracting 50 and adding 100. The eleventh time, you’ll look at 731965 and simply hear “230 true at 119.” That’s the whole game: reps. Nobody’s grading you on speed in the airplane, so take your time on the ground.

The decoding conventions are laid out in the FAA’s Aviation Weather Handbook, and the product itself comes from the National Weather Service and the Aviation Weather Center. Pull up a real winds aloft forecast tonight, pick a station, and decode a full column top to bottom.

Key Takeaways

• The FB (winds and temperatures aloft) forecast gives predicted direction (true north), speed (knots), and temperature (Celsius) at set altitudes by station.
• 9900 means light and variable - a forecast wind under 5 knots with no meaningful direction.
• When the first two direction digits exceed 36, the wind is 100+ knots: subtract 50 from the direction and add 100 to the speed. Exactly 200 knots is coded with speed digits 99.
• Below 12,000 feet the temperature sign is printed; above it, temperatures are always negative. No wind is published within 1,500 feet, and no temperature within 2,500 feet, of the station elevation.
• Read the temperature alongside the wind to spot the freezing level and answer the icing question before you launch.