Before every flight, a smart pilot checks more than just surface conditions. The Winds and Temperatures Aloft Forecast—officially designated the FB winds forecast by the National Weather Service—predicts wind direction, wind speed, and air temperature at a series of altitude levels above the surface. For sport pilots operating light-sport aircraft (LSA) typically below 10,000 feet MSL, the lower altitude levels of this forecast are directly and immediately relevant to every cross-country flight. Knowing how to decode the product, apply its data to flight planning, and avoid its common pitfalls separates a well-prepared pilot from one who is guessing at groundspeed and fuel burn.
What the FB Winds Forecast Is and Where It Comes From
The FB winds forecast is a computer-generated numerical weather product issued by the National Weather Service four times daily, based on upper-air observations and atmospheric modeling. Each issuance covers forecast periods of 6, 12, and 24 hours, giving pilots near-term and longer-range planning tools. The forecast is produced for a network of fixed reporting stations across the contiguous United States, Alaska, and Hawaii, so the data applies to a general geographic area rather than a pinpoint location—interpolation between stations is sometimes needed for routes that fall between reporting points.
The product is available through standard FAA weather resources, including aviationweather.gov, the standard preflight briefing from a Flight Service specialist, and many electronic flight bag applications. Because the Aviation Weather Services handbook (FAA-H-8083-28) identifies FB winds as a primary upper-air planning tool, it is tested on both the Sport Pilot and Private Pilot knowledge examinations.
Altitude Coverage and the 3,000-Foot Rule
FB winds forecasts cover a standard set of altitude levels that typically begins at 3,000 feet MSL and steps upward through 6,000, 9,000, 12,000, 18,000, 24,000, 30,000, 34,000, and 39,000 feet MSL. No forecast is issued for the surface or for altitudes below 3,000 feet MSL. The FAA's reasoning is straightforward: surface friction, terrain, and localized heating create wind variability near the ground that cannot be reliably predicted in a tabular, area-wide format. For surface and low-level wind information, a pilot must rely on the Terminal Aerodrome Forecast (TAF), the Aviation Routine Weather Report (METAR), or the Area Forecast Discussion—not the FB winds product.
An important subtlety involves temperature data. At 3,000 feet MSL the forecast includes only wind direction and speed—no temperature is provided at that level. Temperature forecasts begin at 6,000 feet MSL and continue through the higher levels. Sport pilots planning to cruise at 3,000 feet who need a temperature estimate for density altitude calculations must extrapolate from the 6,000-foot value or use other sources such as the standard lapse rate (approximately 2°C per 1,000 feet) as a rough guide.
Decoding the Four-Digit Wind Group
Each winds aloft entry presents data in a compact coded format. Understanding the encoding rules is essential for both flight planning and the FAA knowledge examination.
Standard encoding
The wind data appears as a four-digit group, sometimes followed by a temperature. The first two digits encode wind direction in tens of degrees true—the direction the wind is coming from. The second two digits encode wind speed in knots. Temperature in degrees Celsius follows, preceded by a plus or minus sign. For example, the entry 2732+08 decodes as: winds from 270° true at 32 knots, temperature +8°C. A wind from 090° at 15 knots with a temperature of −5°C would appear as 0915−05.
Light and variable winds: the 9900 code
When forecast winds are less than 5 knots—too light and variable to assign a meaningful direction—the entry is shown as 9900, with no temperature suffix at the lower levels. Treat 9900 as a signal for light and variable conditions. Do not attempt to decode it as a direction of 990° or a speed derived from those digits; it is a placeholder, not a numeric value.
High-speed wind encoding
When forecast winds exceed 100 knots, a special encoding convention prevents the speed from overflowing the two-digit speed field. The encoder adds 50 to the direction group and subtracts 100 from the speed. A pilot who sees a direction group greater than 36—say, 73—knows to subtract 50 (giving true direction 230°) and add 100 to the stated speed to recover the actual knot value. For instance, an entry of 731545 decodes as: direction 230° true (73 − 50 = 23, ×10 = 230°), speed 115 knots (15 + 100), temperature −45°C. This situation is rare at sport pilot altitudes but is a favorite FAA knowledge-test question precisely because the unwary pilot will misread an encoded direction of 73 as 730°, which is meaningless.
Applying Winds Aloft Data to Sport Pilot Flight Planning
Altitude selection for efficiency
One of the most practical uses of the FB winds forecast is comparing winds at different altitude levels to select the most favorable cruise altitude. A headwind of 20 knots at 6,000 feet but only 8 knots at 3,000 feet is a compelling argument for staying lower, despite the temptation to use a higher altitude for terrain clearance. Conversely, a strong tailwind at 6,000 feet may more than compensate for the slight fuel penalty of climbing. For sport pilots flying LSA with modest climb rates and fuel capacities, shaving even 5 knots off a headwind across a 150-nautical-mile cross-country meaningfully reduces both flight time and fuel burn.
Groundspeed and fuel planning
Once the headwind or tailwind component is determined from the winds aloft forecast, the pilot can compute estimated groundspeed by adding a tailwind or subtracting a headwind from true airspeed. That groundspeed feeds directly into fuel burn calculations: time en route equals distance divided by groundspeed, and fuel required equals time multiplied by fuel consumption rate. Accurate winds aloft data therefore closes the loop between weather awareness and fuel reserve planning—both of which are risk management fundamentals identified in the FAA Risk Management Handbook (FAA-H-8083-2).
True versus magnetic: the conversion you cannot skip
FB winds forecasts encode direction in true degrees, matching the way upper-air meteorology is universally reported. Aircraft compasses and VOR radials, however, reference magnetic north. Before using a winds aloft direction to compute a wind correction angle or to compare against a magnetic course, the pilot must apply the local magnetic variation—adding easterly variation or subtracting westerly variation to convert true to magnetic. Omitting this step produces a wind correction angle error equal to the local variation, which in parts of the eastern or western United States can be 15° or more.
Temperature data and density altitude
The forecast temperatures at altitude allow the pilot to assess density altitude before departure. If the forecast temperature at 6,000 feet is significantly above the International Standard Atmosphere (ISA) value of +3°C at that level, the air is less dense than standard, and aircraft performance will be degraded accordingly. The PHAK (FAA-H-8083-25) emphasizes that density altitude is performance altitude—high density altitude means longer takeoff rolls, reduced climb rates, and higher true airspeed for a given indicated airspeed. Catching an above-standard temperature aloft during preflight planning allows the pilot to adjust cruise altitude, fuel load, or departure timing rather than discovering the performance penalty airborne.
Wind shear and turbulence awareness
A large change in wind speed or direction between two adjacent altitude levels signals the presence of wind shear. Even on a clear, cloudless day, significant wind shear between 3,000 and 6,000 feet can produce light-to-moderate turbulence. While the FB winds forecast does not explicitly forecast turbulence, an alert pilot who notices a 30-knot speed difference or a 60° direction shift between adjacent levels should anticipate an unsettled ride through the shear layer and may want to cruise above or below it when practical.
Key Numbers and Rules to Remember
- Issued 4 times daily with 6-, 12-, and 24-hour forecast periods.
- Lowest forecast level: 3,000 feet MSL—no winds aloft data below that altitude.
- Temperature data starts at 6,000 feet MSL—not provided at 3,000 feet.
- Directions are in true degrees—always apply magnetic variation before navigation use.
- 9900 = light and variable, less than 5 knots—not a decodable number.
- High-speed encoding: direction group > 36 means subtract 50 from direction, add 100 to speed.
- Standard ISA lapse rate: approximately 2°C per 1,000 feet—useful for extrapolating temperature to unlisted altitudes.
Common Test Traps
- Forgetting true-to-magnetic conversion: The FAA knowledge examination frequently presents a winds aloft entry and asks for the wind correction angle or magnetic heading. Students who skip the variation step get the wrong answer.
- Expecting winds below 3,000 feet MSL: The FB winds product provides no data at or below this level. A question asking which product to use for surface wind information calls for METAR or TAF, not FB winds.
- Misreading 9900: Some students try to divide 9900 into a direction of 990°—an impossible heading—and a speed of 00. Recognize it immediately as the light-and-variable placeholder.
- Missing high-speed encoding: A direction code of 51 through 86 does not represent a direction between 510° and 860°. Subtract 50 and add 100 knots. Failing to apply this rule produces dramatically wrong answers on the knowledge exam.
- Assuming the forecast is site-specific: FB winds are forecast for named stations and represent broad areas. Microclimatic effects, valley winds, and mountain wave activity near terrain are not captured in this product.