The Winds Aloft Forecast, the FB14 Grid That Most Student Pilots Skip in the Briefing, and the Altitude Decision That Can Turn a Two-Hour Leg Into a Three-Hour Headwind

The winds aloft forecast is one of the most underused tools in a VFR preflight briefing. Learning to decode the Forecast Winds and Temperatures Aloft - known as the FB forecast - turns altitude selection from a habit into a data-driven decision. The difference between a favorable and unfavorable altitude can cost 15 minutes or more on a 90-mile leg, and the forecast had the answer the whole time.

Why Checking the METAR Isn’t Enough for a Cross-Country

General aviation cross-country flights operate between roughly 3,000 and 12,000 feet MSL. The wind at those altitudes can differ dramatically from the surface wind - not just in speed, but in direction.

Surface winds are shaped by terrain friction, differential heating, and local circulations. Mountains channel airflow into valleys. The bottom few thousand feet of the atmosphere is where the ground drags on the air and slows it down. Above that layer, winds smooth out and align with the large-scale pressure pattern driving the overall weather system.

On the same day and location, you might see calm surface winds while 6,000 feet shows 25 knots from the southwest. Treating the AWOS readout as representative of your cruise altitude is a fundamental planning error. They are measuring two different things in two different regimes of the atmosphere.

What the Winds Aloft Forecast Is and Where to Find It

The Forecast Winds and Temperatures Aloft is issued by the National Weather Service. It covers altitudes from 3,000 feet up to 39,000 feet. For VFR general aviation training, the four most useful altitudes are 3,000, 6,000, 9,000, and 12,000 feet MSL.

You’ll find it in any standard weather briefing: 1-800-WX-BRIEF, ForeFlight, Garmin Pilot, and the Aviation Weather Center at aviationweather.gov. It’s available both as a decoded table tied to geographic station codes and as a graphical map layer you can step through by altitude.

The product is labeled with an issuance time and a valid time in Coordinated Universal Time (Zulu). Always confirm the forecast covers your actual flight window before using it.

How Do You Decode the Winds Aloft Table?

The Airman Certification Standards for the private pilot practical test require you to decode the table format. Each station entry is a compact code with three components.

Wind direction - The first two digits represent wind direction in tens of degrees. The code 24 means the wind is from 240°. The code 18 means from 180° (due south).

Wind speed - The next two digits are speed in knots. Combined with the direction example above, 2435 means wind from 240° at 35 knots.

Temperature - The remaining digits are temperature in degrees Celsius with a sign. +05 is +5°C. -12 is −12°C.

A complete entry of 2435-04 decodes to: wind from 240° at 35 knots, temperature −4°C. Three pieces of information in one short code.

What Do the Special Codes in the Winds Aloft Table Mean?

Two special encoding cases appear regularly and need to be recognized immediately.

Light and variable - 9900: When you see 9900 in the wind position, the wind speed is less than 5 knots and direction is not meaningful. Light and variable at cruise altitude is generally favorable news for a cross-country flight.

High wind encoding: When wind speeds reach 100 knots or more, the format changes. 50 is added to the two-digit direction code, and 100 is subtracted from the speed. A direction code of 73 means subtract 50 → the true direction is 230°. A speed code of 27 means add 100 → the actual speed is 127 knots.

Any direction code of 50 or higher in the winds aloft table signals extremely high winds. A general aviation training airplane won’t be flying in those conditions, but recognizing the encoding prevents the numbers from confusing you on a briefing printout.

How Do You Use Winds Aloft to Choose the Right Cruise Altitude?

The FB forecast is fundamentally an altitude selector. On any cross-country where you have a choice of altitudes, identify the level where the wind component along your route is most favorable.

Consider a flight from Denver to Pueblo - roughly 90 miles on a southbound course. Under the hemispheric rule, 9,500 feet is an appropriate VFR altitude for that heading. (The hemispheric rule: odd thousands + 500 feet for magnetic courses 000° through 179°; even thousands + 500 feet for courses 180° through 359°.) But appropriate doesn’t mean optimal for the wind.

If the winds aloft show 180° at 25 knots at 9,000 feet, that’s a direct headwind on a southbound leg. At 6,000 feet, a 270° at 12 knots wind is a direct crosswind - no meaningful headwind component at all.

In a Cessna 172 at approximately 110 knots true airspeed:

• At 9,000 ft with a 25-knot direct headwind → ~85 knots groundspeed → ~64 minutes for the leg
• At 6,000 ft with a 12-knot crosswind → ~110 knots groundspeed → ~49 minutes for the leg

That’s 15 minutes saved on a 90-mile leg purely by choosing the lower altitude. Terrain considerations near Denver add a layer of judgment, but the core principle holds: let the data drive the altitude choice, not habit.

These wind values feed directly into your navigation log. The forecast wind at cruise altitude determines your wind correction angle, your estimated groundspeed at each checkpoint, and your fuel burn figures. If your nav log shows a groundspeed equal to true airspeed on a day with a 30-knot headwind at your filed altitude, the examiner sees either that you didn’t check the winds aloft or didn’t know what to do with them.

What Does the Temperature Column Tell You?

Every winds aloft entry includes temperature at that altitude in Celsius. This gives you two pieces of useful information.

Density altitude at cruise: Colder temperatures at altitude mean denser air - better engine performance and aerodynamic efficiency. If an airplane has been underperforming its charts on hot summer afternoons, the temperature values at cruise altitude are part of that story.

Proximity to the freezing level: 0°C is the threshold where visible moisture can begin forming structural ice. As a VFR pilot in an airplane not certified for known icing, knowing where the freezing level sits relative to your route and any cloud layers is a safety-critical check.

The temperature column isn’t a complete icing picture on its own. Combine it with the AIRMET Zulu for icing and the area forecast to understand moisture content. But if temperatures are well above freezing at all your usable altitudes, that concern is quickly set aside.

When Is the Winds Aloft Forecast Valid, and Why Does It Matter?

The forecast is issued several times daily, and each product has a specific valid time stated in Zulu. Confirming the valid time is a basic part of using the product correctly - and it’s a routine question on checkrides.

If you’re departing at 1300Z and arriving at 1500Z, you need a forecast valid for that window. A forecast issued early in the morning and valid through noon Zulu may be substantially out of date for an afternoon flight.

Every weather product in your briefing is a snapshot. METARs have an observation time. TAFs have a validity window. Area Forecasts have a valid period. Understanding when each product was issued and what it covers is part of interpreting it correctly. “I’m not sure” is not an acceptable answer when an examiner asks when your winds aloft forecast is valid.

Where Does the Winds Aloft Forecast Fit in Your Preflight Briefing?

A standard VFR weather briefing follows a logical sequence: synopsis and prog charts, adverse conditions (AIRMETs, SIGMETs), current conditions (METARs), forecasts (TAFs), and then the winds aloft.

The winds aloft section is where you optimize, not where you decide. The go/no-go decision comes from the adverse conditions and current/forecast sections earlier in the briefing. The winds aloft tell you how to go - at what altitude, with what groundspeed and fuel expectations in your plan.

Don’t stop at the TAF. Getting a go and tuning out is exactly how you end up landing 40 minutes late with lower fuel than expected on a day when the weather cooperated completely.

The graphical winds aloft display in ForeFlight and similar apps is a genuinely useful visualization - you can scroll through altitude layers and see where winds are working for or against you along the whole route. But glancing at color-coded arrows is different from engaging with actual numbers. Learning to read the table at least once in training forces you to process direction, speed, and temperature as values you can calculate with, which makes the graphical display a tool you understand rather than a picture you looked at.

Key Takeaways

• The FB forecast covers altitudes from 3,000 to 39,000 feet and is your primary tool for selecting cruise altitude - treat it as an altitude selector, not a checkbox
• Surface winds and cruise-altitude winds can differ significantly in both speed and direction; the METAR does not tell you what you’ll find at 9,000 feet
• The table encodes wind direction (tens of degrees), speed (knots), and temperature (°C); 9900 means light and variable; any direction code 50 or higher signals winds at or above 100 knots
• On a 90-mile leg, choosing the right altitude based on wind can save 15 minutes - and the same wind data drives every groundspeed figure in your navigation log
• Always confirm the Zulu valid time of any winds aloft forecast before using it; examiners ask this routinely