The Winds Aloft Forecast and the cruise altitude decision that changes everything about your cross-country

The winds aloft forecast is one of the most useful tools in your entire weather briefing - and one of the most overlooked by student pilots. Once you understand its format, that table of numbers becomes the foundation for every cruise altitude decision you make on a cross-country flight.

What Is the Winds Aloft Forecast?

Officially called the Forecast Winds and Temperatures Aloft - sometimes labeled FD winds or FB winds depending on your tool - this product gives you predicted wind direction, wind speed, and temperature at a series of altitude levels. Standard reporting levels are 3,000 through 39,000 feet MSL, in increments of 3,000 to 6,000 feet.

For most general aviation pilots, the relevant range is 3,000 through 12,000 or 18,000 feet.

The product is issued four times daily and carries both an issuance time and a valid time. Always confirm you’re reading the forecast valid for your planned flight time, not one issued earlier in the day.

The authoritative sources are 1800wxbrief.com (included in your standard briefing) and the Aviation Weather Center at aviationweather.gov. Both draw from the same underlying data.

How to Decode the Format

Each altitude entry looks like this: 0415+03

Read it in three parts:

• First two digits - wind direction in tens of degrees magnetic. 04 means 040 degrees. The wind is from the northeast.
• Next two digits - wind speed in knots. 15 means 15 knots.
• Number after the space - temperature in degrees Celsius. +03 means positive 3°C at that altitude.

Full translation: winds from 040 at 15 knots, temperature +3°C.

Here’s a full example table to work through:

In this picture, winds are veering clockwise (shifting from northeast toward east) and accelerating with altitude. That’s a coherent, readable weather story.

What Do the Special Codes Mean?

9900 - Calm or light and variable. No significant directional flow was forecast at that altitude. Common at the 3,000-foot level on mild days. Not a concern - just nothing to report.

Direction digits between 51 and 86 - Wind speed exceeds 100 knots. Forecasters add 50 to the direction digits and subtract 100 from the speed digits to fit the format. Example: 0835 decodes as direction 030° (08 minus 5 = 03, times 10) and speed 135 knots (35 plus 100). You’ll see this in jetstream data at high altitudes, not on typical training flights - but recognize it when it appears.

9999 - No forecast available for that station at that altitude. The site may be below terrain, or the data simply isn’t there. Move to the next station along your route.

How Do You Choose a Cruise Altitude Using This Data?

The hemispheric rule defines your legal options: odd thousands plus 500 feet eastbound (VFR), even thousands plus 500 feet westbound. For an eastbound flight, that gives you 3,500, 5,500, 7,500, 9,500, or 11,500 feet to choose from.

The winds aloft forecast is how you pick the best one.

Pull up data for multiple stations along your route - not just departure and destination, but intermediate stations as well. For each candidate altitude, note the wind direction, speed, and temperature, then estimate your headwind or tailwind component against your planned track.

A 15-knot tailwind in a Cessna 172 is not a minor detail. That’s real time saved, real fuel conserved, and real margin added to your reserves. Conversely, a 20-knot direct headwind at your planned altitude can stretch flight time and tighten your fuel picture significantly.

Winds can also change along a 200-mile route. A tailwind in the first half at the same altitude may become a headwind in the second half. Looking at multiple stations gives you a longitudinal view of what the airmass is doing across the full route.

Why Does the Temperature Column Matter?

Temperature is where the winds aloft forecast becomes a safety tool, not just a planning tool.

At or below 0°C, in or near clouds, you have potential icing conditions. Most training aircraft are not approved for flight into known icing - that’s a hard limit in the Pilot’s Operating Handbook.

The temperature data lets you assess icing risk before you leave the ground. If you must transition through a cloud layer, you can check whether the temperature at that altitude is above or below freezing and look for an altitude that keeps you clear.

You can also estimate the freezing level directly from the data. If 6,000 feet shows +4°C and 9,000 feet shows −3°C, the freezing level is somewhere around 7,500 feet, depending on the lapse rate. Cross that against cloud tops and bases, and you have a real picture of where the icing environment begins.

Continued flight into icing conditions in an unprepared aircraft is exactly the kind of scenario that ends badly. The temperature column is one of your earliest warning systems.

What Doesn’t the Winds Aloft Forecast Cover?

Surface winds are a separate product. For current surface conditions, use METARs. For expected surface winds at your destination, use the TAF (Terminal Aerodrome Forecast). Winds aloft starts at 3,000 feet MSL and goes up.

Local terrain effects are not captured. A 20-knot westerly at 9,000 feet over the Rockies behaves very differently than the same forecast over flat terrain. Mountain terrain can produce mechanical turbulence, rotor, or mountain wave that the winds aloft product won’t call out. When flying near significant terrain, pair this data with AIRMETs for turbulence and any available PIREPs.

Where Does the Winds Aloft Fit in a Standard Briefing?

A standard briefing follows a defined sequence: adverse conditions, synopsis, current conditions (METARs and PIREPs), en route forecast, destination forecast and TAF, winds and temperatures aloft, NOTAMs, and ATC delays.

Winds aloft appears near the end of that sequence - but don’t treat it as an afterthought. Your altitude decision determines your fuel burn, flight time, icing exposure, turbulence exposure, and alternates. It’s the single decision with the most downstream consequences in your planning.

On a private pilot checkride, the examiner may hand you a weather briefing packet and ask you to justify your altitude selection. A complete answer sounds like: “I chose 7,500 feet because at that altitude I have a tailwind component of 10 knots, the temperature is −2°C which is above freezing at that altitude given the VFR conditions, and this altitude complies with the hemispheric rule for my eastbound direction of flight.”

That’s what the Airman Certification Standards expect. The data to build that answer lives in the winds aloft table.

How Do PIREPs Fit In?

The winds aloft forecast is a prediction. Actual winds at altitude can differ from the forecast, sometimes significantly, especially in rapidly changing conditions or areas with limited model data.

PIREPs - pilot reports - provide real-world data from someone who flew the route recently. A PIREP reporting actual winds at altitude two hours before your flight is ground truth the forecast cannot match. Check for PIREPs along your route when available. They’re not always there, especially on low-traffic days and rural routes - but when they exist, read them.

Key Takeaways

• The winds aloft forecast provides predicted wind direction, wind speed, and temperature at altitudes from 3,000 to 39,000 feet MSL, issued four times daily.
• The format reads as: direction (tens of degrees) + speed (knots) + temperature (°C). Code 9900 means calm/variable; direction digits 51–86 signal speeds over 100 knots.
• Use data from multiple stations along your route to identify the altitude with the best headwind/tailwind component for your track.
• The temperature column is a safety check: at or below 0°C in or near clouds means potential icing. Most training aircraft are not approved for known icing.
• No single product tells the whole story - combine winds aloft with METARs, TAFs, AIRMETs, and PIREPs to build a complete pre-flight picture.