The FB Winds and Temperatures Aloft Forecast, the Two-Digit Code That Hides a Forty-Knot Tailwind in Plain Sight, and the Altitude Choice That Changes Your Entire Fuel Plan

The FB Winds and Temperatures Aloft Forecast is one of the most useful pre-flight planning tools available, yet it’s routinely skipped by pilots preparing for cross-country flights. Ignoring it means planning with true airspeed as your ground speed - an error that can put you 30 to 50 knots off on a windy day. Five minutes with this chart before departure closes that gap.

What Is the FB Winds and Temperatures Aloft Forecast?

The FB chart is issued by the National Weather Service four times daily. It provides predicted wind direction, wind speed, and temperature at specific altitudes: 3,000; 6,000; 9,000; 12,000; 18,000; 24,000; 30,000; 34,000; and 39,000 feet MSL. For VFR cross-countries, the relevant range is 3,000 through 12,000 feet.

The forecast is issued for specific points scattered around the country - not for individual airports. Each point covers a broad area. For a flight crossing multiple regions, check two or three points along your route. The valid time is printed at the top of the chart. Always confirm you are using the version that covers your departure window, not a stale morning forecast for an afternoon flight.

Where to Find the FB Chart

On the web, find it at aviationweather.gov under Products > Winds and Temperatures Aloft. In ForeFlight and most electronic flight bags, it appears under the Winds layer or in the weather products section.

A graphical winds display is available and is fast to interpret - color-coded by speed, easy to scan. Use it. But learn the text version too. The graphical display is only as reliable as your ability to sanity-check it. When something looks off, go back to the raw data.

How to Decode the FB Forecast Code

The text code looks strange at first. A typical entry reads: 2714+08. Here is how to parse it:

• First two digits - wind direction in tens of degrees. Add a zero to get the actual direction. “27” = 270° (wind from the west). “09” = 090° (wind from the east). “18” = 180° (wind from the south).
• Second two digits - wind speed in knots. “14” = 14 knots.
• Temperature suffix - in Celsius at that altitude. “+08” = +8°C. “−23” = −23°C.

So 2714+08 means: wind from 270° at 14 knots, temperature +8°C.

One special case: 9900 means winds are calm or light and variable - speed below 5 knots, direction too variable to specify. This appears most often at lower altitudes on still days.

At the 3,000-foot level, no temperature is listed. The National Weather Service does not issue temperature forecasts at that altitude. Everything from 6,000 feet up includes both wind and temperature data.

What Happens When Wind Speeds Exceed 99 Knots

When forecast winds exceed 99 knots, the National Weather Service adds 50 to the direction digits and subtracts 100 from the speed. If you see 7232, the “72” is the flag - no wind comes from 720°. Subtract 50: 72 − 50 = 22, meaning 220°. Add 100 to the speed: 32 + 100 = 132 knots.

This is jet stream territory. You will almost never encounter it on a VFR cross-country below 12,000 feet. But recognizing the code means you won’t stare at it confused when it appears.

True Versus Magnetic: The Direction Trap

Wind direction in the FB forecast is true, not magnetic. Your compass reads magnetic. Your flight plan headings are magnetic. When you feed FB wind data into your planning, you must account for magnetic variation.

The isogonic lines on your sectional chart show the variation for your area. In the eastern United States, variation is generally westerly - add it when converting from true to magnetic. In the western United States, variation is easterly - subtract it. The memory phrase: “East is least, west is best.” Least means subtract. Best means add.

Your flight planning software handles this automatically. On a checkride, your examiner may ask you to walk through it by hand. Understand the concept, not just the app.

How Winds Aloft Should Drive Your Altitude Choice

Here is a practical example. You are flying eastbound in a Cessna 172, cruise true airspeed 115 knots, covering 250 nautical miles.

The FB chart shows:

• 3,000 feet: 2720 - wind from the west at 20 knots. Direct tailwind on an eastbound flight. Estimated ground speed: 135 knots.
• 6,000 feet: 3018 - wind from the northwest at 18 knots. Partial tailwind component, lower ground speed.
• 9,000 feet: 3125 - wind from the northwest at 25 knots. Less tailwind component still.

On wind numbers alone, 3,000 feet wins. But altitude choice is not purely a math problem.

On a summer afternoon over heated terrain, 3,000 feet may mean turbulence and reduced visibility in haze. On a clear winter morning with smooth air, that 20-knot tailwind is worth taking. On a bumpy summer afternoon, climbing to 6,000 for a smoother ride and better visibility may be worth the slightly reduced ground speed.

You weigh efficiency against terrain clearance, ride quality, and weather. That judgment call is exactly what the Airman Certification Standards expects you to demonstrate.

How to Calculate Fuel Requirements Using Winds Aloft Data

The calculation chain is straightforward:

1. True airspeed ± wind component = estimated ground speed
2. Distance ÷ ground speed = estimated time en route
3. Time en route × fuel burn (GPH) = fuel required
4. Add reserves

Here is what happens when you skip this step. On that same 250 nm flight in a Cessna 172 burning 9 GPH:

No wind correction (using TAS as ground speed, 115 knots): 250 ÷ 115 = 2.17 hours × 9 = ~19.5 gallons + 6.75 gallons reserve (45-minute VFR reserve at 9 GPH) = ~26.25 gallons total. A comfortable margin against the standard 172’s 56 gallons usable.

With a 25-knot headwind (ground speed 90 knots): 250 ÷ 90 = 2.78 hours × 9 = 25 gallons + 6.75 reserve = nearly 32 gallons total. You still make it. But if fuel burn has been running slightly high, routing was inefficient, or there were minor delays, you are eating into that cushion in ways the POH cruise-speed plan never revealed.

The FB chart tells you which situation you are in before you start the engine. That information determines whether you fly straight through or stop at the halfway point. Not checking it means that decision gets made for you by the fuel gauges.

What the Temperature Data Tells You

The temperature column gets scanned past, but it carries two important pieces of information.

First: density altitude. If temperature aloft is significantly warmer than the International Standard Atmosphere value for that altitude, your aircraft will not perform exactly as the POH describes. Hot days degrade performance; cold days improve it. The actual temperature at cruise altitude gives you a more accurate performance picture than the published tables assume.

Second: icing risk. If you are approaching 0°C at your planned cruise altitude and there is visible moisture in the area, you are near icing conditions. VFR pilots should not be in visible moisture - but knowing the temperature aloft helps you recognize when conditions ahead may push you toward that boundary.

Verifying Forecast Winds Once Airborne

The FB chart is a forecast. Forecasts are good. They are not perfect.

Before departure, check any PIREPs (pilot reports) filed along or near your route. If other pilots who flew your altitude in the last hour reported ground speeds significantly different from what the FB chart predicted, that is real-world data. Trust it over the forecast.

Once airborne, check your GPS ground speed early and compare it to what you planned. If you planned a 10-knot tailwind and you are seeing a 10-knot headwind, redo the fuel calculation immediately - while the decision of where to stop is still open. Not later, when your options have narrowed.

What Your Examiner Expects on the Checkride

The Private Pilot ACS requires you to gather, analyze, and apply weather information for cross-country flights. During the oral, your examiner wants to hear you walk through winds aloft by altitude, explain how that data influenced your altitude selection, and show the fuel calculation that followed.

“Winds aloft looked okay” is not enough. They want the numbers. They want the reasoning.

The pilots who do this well are not the ones who memorized the most. They are the ones who understand why the information matters. The examiner is not setting a trap - they are checking whether you actually use the tools that are there to keep you safe.

Check three altitudes, not just your planned one. Understand the tradeoff. Run the fuel numbers. It takes five extra minutes and is worth every one of them.

Key Takeaways

• The FB Winds and Temperatures Aloft Forecast is issued four times daily by the National Weather Service, covering altitudes from 3,000 to 39,000 feet MSL.
• Decode the four-digit code as direction (in tens of degrees) + speed (in knots). When direction digits exceed 50, subtract 50 for direction and add 100 for speed to get the true values.
• Wind direction in the FB forecast is true, not magnetic - account for variation when converting to magnetic flight plan headings.
• Altitude selection balances tailwind efficiency against terrain clearance, ride quality, and weather conditions - it is not a pure math problem.
• Always run the fuel calculation using winds-adjusted ground speed. On a windy day, the error from using TAS alone can exceed 30–50 knots and can quietly eliminate the margin between a comfortable flight and a fuel stop you didn’t plan for.