What is the winds aloft forecast and where do I find it?

The winds aloft forecast (product code FB) is published by the Aviation Weather Center four times daily and provides forecast wind direction, speed, and temperature at standard altitudes from 3,000 to 30,000 feet MSL. It's available through Leidos Flight Service in a standard weather briefing or directly on the Aviation Weather Center website.

How do I decode a winds aloft four-digit code?

The first two digits are wind direction in tens of degrees true, and the second two digits are wind speed in knots. For example, 2130 means wind from 210 degrees at 30 knots. When wind speed exceeds 100 knots, 50 is added to the direction code and 100 is subtracted from the speed - a code of 7715 decodes to 227 degrees at 115 knots.

How do I know which altitude will give me the best groundspeed?

Pull up the six-hour winds aloft forecast and read the wind data at every legal altitude option for your magnetic course. Work the wind correction angle at each level, estimate your groundspeed, and compare. Factor in climb cost relative to your leg length - the higher altitude usually pays back on legs over 150 nautical miles.

Why does temperature matter in the winds aloft forecast?

Outside air temperature affects your density altitude at cruise, which in turn affects true airspeed and fuel burn. Standard cruise performance charts assume standard atmosphere conditions; when actual temperatures differ significantly - especially in cold winter conditions - using the temperatures aloft data gives you a more accurate performance and fuel picture.

What is the MEF and how does it affect my altitude choice?

The Maximum Elevation Figure (MEF) is the blue number printed in each grid square on a sectional chart. It represents the highest terrain or obstacle in that area with a clearance buffer included. Before finalizing your cruise altitude, trace your route on the sectional and confirm your planned altitude provides adequate clearance over every MEF along the way.

Altitude Selection on a Cross-Country, the Winds and Temperatures Aloft Forecast Most Pilots Scan Instead of Read, and the Five-Minute Process That Can Add Twenty Knots to Your Groundspeed

Most pilots pick a legal cruise altitude and write down the wind at that one level. That habit leaves significant groundspeed - sometimes 20 knots or more - on the table. The fix is a five-minute comparison of two or three altitude options using the winds and temperatures aloft forecast before you ever leave the planning table.

Why Altitude Selection Is More Than a Legal Requirement

FAR 91.159 establishes the hemispheric rule for cruise altitudes: on a magnetic course between 0 and 179 degrees (roughly eastbound), fly at odd thousands plus 500 feet - 3,500, 5,500, 7,500, and so on. On a magnetic course between 180 and 359 degrees (roughly westbound), fly at even thousands plus 500 feet - 4,500, 6,500, 8,500.

That rule eliminates some choices. It doesn’t make the remaining choice for you. At any given magnetic course, you typically have three to five legal options depending on your aircraft, terrain, and airspace. The regulation defines the structure; you still have to select the altitude within it.

The tool designed to help you make that selection is the winds and temperatures aloft forecast.

How to Read the Winds Aloft Forecast

The Aviation Weather Center publishes the winds and temperatures aloft forecast four times a day. The legacy product code is FB, and most aviation weather software still uses that label. The forecast covers a grid of reporting stations and provides wind direction, wind speed, and outside air temperature at standard altitudes: 3,000, 6,000, 9,000, 12,000, 18,000, 24,000, and 30,000 feet MSL, with higher levels available above that.

Three time ranges are available: a 6-hour forecast, a 12-hour forecast, and a 24-hour forecast. For a flight departing within the next few hours, use the 6-hour product - it’s the most accurate. If you’re briefing the night before for an early morning departure, start with the 12-hour to get the general picture, then verify with the 6-hour product as your departure approaches. A 24-hour forecast of jet stream position can be off by hundreds of miles; by six hours out, the meteorologists have a much tighter read on actual conditions aloft.

Leidos Flight Service automatically selects the appropriate time range in a standard weather briefing based on your proposed departure time. If you’re self-briefing on the Aviation Weather Center website, the graphical winds aloft products are worth learning - they let you visualize wind speed and direction overlaid on a map rather than hunting through encoded text tables.

How to Decode the Winds Aloft Encoding

Wind direction and speed appear as a four-digit group in the text product. The first two digits are wind direction in tens of degrees true. The second two digits are wind speed in knots.

A code of 1825 means the wind is from 180 degrees (due south) at 25 knots. A code of 3040 means the wind is from 300 degrees (west-northwest) at 40 knots.

One special case trips up students: when wind speed exceeds 100 knots, the encoding adds 50 to the direction code and subtracts 100 from the speed. A code of 7715 decodes to 227 degrees at 115 knots - subtract 50 from 77 to get 27, multiply by 10 for the direction, then add 100 to the speed. You’ll encounter this near the jet stream at high altitudes, not at typical light aircraft cruise levels, but knowing the convention means those numbers won’t confuse you if you spot them.

When wind is calm or light and variable, the product shows 9900 at that position.

Temperatures follow the wind group in degrees Celsius. At higher altitude levels, the negative sign is sometimes dropped since subzero values are assumed. Briefing software typically handles that formatting automatically.

How Do I Compare Altitudes to Find the Best Groundspeed?

This is the step most pilots skip - and it’s where the real planning happens. After decoding the forecast, read the wind data at every legal altitude option for your heading, not just the one you’ve already penciled in.

Consider a flight from Springfield, Missouri to Nashville, Tennessee - roughly 170 nautical miles on an east-northeast magnetic course. A Cessna 172 with a cruise true airspeed of about 105 knots has four legal altitude options on this eastbound heading: 3,500, 5,500, 7,500, and 9,500 feet.

Here’s what the six-hour winds aloft forecast might show along that route:

3,000 feet: wind from 190° at 12 knots - a mild tailwind component
6,000 feet: wind from 210° at 26 knots - a stronger push from behind
9,000 feet: wind from 230° at 42 knots - a substantial quartering tailwind

After working the wind correction angle, groundspeed at 9,500 feet could come out around 120 to 125 knots, compared to roughly 110 knots at 3,500 feet. On a 170-nautical-mile leg, that difference saves approximately 12 to 15 minutes in the air and reduces total fuel burn. If fuel planning was tight, those savings can change whether a fuel stop is necessary.

Does the Altitude Advantage Always Outweigh the Climb Cost?

Not always. Climbing to a higher altitude costs time and fuel on the way up, and on a short leg, that overhead can erase any groundspeed benefit before you even level off.

A useful rule of thumb:

On legs under about 100 nautical miles, the altitude premium rarely pays back the climb cost.
On legs over 150 nautical miles, it often does.
On anything over 200 nautical miles, the math almost always favors the higher altitude if the tailwind component is there.

The habit to build is running the comparison on every leg. Look at two or three altitude options, estimate your groundspeed at each one, factor in the climb penalty relative to your leg length, and then decide. Once practiced, that process takes about five minutes at the planning table.

How Does Temperature Affect Cruise Performance?

Most students treat the temperature column in the winds aloft forecast as an icing-assessment tool and nothing more. It’s also a performance tool.

At 9,500 feet in January over Missouri, the outside air temperature might be minus 10 to minus 15 degrees Celsius. Your density altitude at cruise could actually be lower than your physical altitude, meaning your normally aspirated engine is breathing denser air than a standard atmosphere calculation would predict. Your true airspeed, fuel burn, and climb performance are all affected.

Use the temperatures aloft to calculate density altitude at cruise, not just at your departure airport. Cruise performance charts assume a standard atmosphere by default. When actual conditions differ meaningfully from standard, the pilot who accounts for the temperature data is more accurate on fuel planning than the pilot who doesn’t.

How Do I Check Terrain Clearance When Selecting an Altitude?

Altitude selection isn’t only about winds. What’s underneath you matters too.

On your sectional chart, find the Maximum Elevation Figure (MEF) - the blue number printed in each latitude/longitude grid square along your route. The MEF represents the highest terrain or obstacle in that grid with a clearance buffer built in. It’s your floor during the planning phase.

Before finalizing your altitude, trace your planned route on the sectional and note the MEF in each grid section. If your planned cruise altitude of 5,500 feet passes over a grid with an MEF of 5,050 feet, you need to go higher or reconsider the route.

This check takes about two minutes and is especially important in areas that appear flat. The plains of Oklahoma, Kansas, and Missouri contain communication towers that exceed 2,000 feet above ground level. Those towers are charted and the MEF accounts for them - but only if you’re looking at it.

What Does an Examiner Expect About Altitude Selection?

The FAA Airman Certification Standards for the private pilot cross-country task are explicit: your altitude selection must demonstrate appropriate consideration for terrain, obstacles, and airspace. An examiner will ask about your altitude choice. The right answer is not just the legal designation - it’s why you chose that altitude over the other options available to you.

A practical habit to build before your checkride: on your planning log, next to your altitude entry, write one sentence explaining your decision. Something like: selected 7,500 feet based on winds aloft comparison showing best groundspeed at this level and comfortable MEF clearance throughout the route. That sentence forces you to confirm that you actually made a decision rather than filling in a number.

Can I Get Updated Winds Aloft Once Airborne?

Yes. If the winds don’t match the forecast, or you want an updated picture before reaching a checkpoint, contact Flight Service on 122.2. Flight Service specialists can provide updated winds aloft and current Pilot Reports (PIREPs) from aircraft along your route.

This matters on longer cross-countries. A forecast issued three hours ago and one issued thirty minutes ago can tell meaningfully different stories, particularly during changing weather.

Key Takeaways

FAR 91.159 defines the structure for cruise altitude selection; it doesn’t make the final choice for you - that’s your job.
The winds and temperatures aloft forecast (product code FB) is published four times daily; use the 6-hour product for flights departing within a few hours.
Compare two or three legal altitude options for your heading before committing - groundspeed differences of 15–20 knots between levels are common.
The climb cost rarely pays back on legs under 100 NM; it almost always pays on legs over 200 NM when a tailwind component is present.
Always check the MEF on your sectional along the full route, and use temperatures aloft to refine density altitude at cruise for accurate performance planning.