Aviation Routine Weather Report (METAR)
Terminal Aerodrome Forecast (TAF)
Graphical Forecasts for Aviation (GFA)
Winds and Temperatures Aloft Forecast (FB)
Inflight Weather Advisories (WA, WS, WST)
Significant Weather (SIGWX) Forecast Charts
An international weather reporting code is used for weather reports (METAR) and forecasts (TAFs) worldwide. The reports follow the format shown in Figure 2-1.
For aviation purposes, the ceiling is the lowest broken or overcast layer, or vertical visibility into an obscuration.

Figure 2-1. TAF/METAR weather card
A TAF is a concise statement of the expected meteorological conditions at an airport during a specified period (usually 24 hours). TAFs use the same code used in the METAR weather reports (See Figure 2-1).
TAFs are issued in the following format:
TYPE / LOCATION / ISSUANCE TIME / VALID TIME / FORECAST
Note: the “/” above are for separation purposes and do not appear in the actual TAFs.
The GFA is an online interactive map of observed and forecast weather information over the continental United States (CONUS), and can be accessed at aviationweather.gov/gfa. It is intended to give users a complete picture of weather critical to aviation safety. The GFA display shows user-selected weather categories each containing multiple fields of interest at altitudes from the surface up to FL480. Depending on the field of interest chosen, weather information is available from -6 hours in the past (observed) to +15 hours in the future (forecast).
The GFA is an aggregate of several existing weather products. The information and data from the various weather products are overlaid on a high-resolution basemap of the United States. The user selects flight levels and current time period for either observed or forecast weather information. Mouse-clicking or hovering over the map provides additional information in textual format, such as current METAR or TAF for a selected airport. The GFA replaces the textual area forecast (FA) for the CONUS and Hawaii with a more modern digital solution for obtaining weather information. The Aviation Surface Forecast and Aviation Cloud Forecast graphics are snapshot images derived from a subset of the aviation weather forecasts.
The Aviation Surface Forecast displays surface visibility with overlays of wind and gusts, predominant precipitation type (i.e., rain, snow, mix, ice, or thunderstorm) coincident with any cloud and predominant weather type (i.e., haze, fog, smoke, blowing dust/sand). The graphical AIRMETs for IFR and strong surface wind are overlaid. See FAA Figure 260. Forecast surface visibility is contoured for Low IFR (0–1 statute miles), IFR (1–3 statute miles), and Marginal VFR (MVFR; 3–5 statute miles) conditions. Visibilities in excess of 5 statute miles are not shown. Winds are depicted with a standard wind barb, in red when indicating gusts. See Figure 2-2.

Figure 2-2. Weather symbols
The Aviation Cloud Forecast displays a cloud coverage fraction (few/scattered, broken, overcast) for clouds with bases below FL180 (18,000 feet MSL). Text overlays indicate cloud coverage and height in feet above MSL at that particular location. See FAA Figure 263. The fill fraction of the circle at each forecasted point depicts sky cloud coverage. Clear skies are annotated as SKC. Clouds above FL180 are indicated as cirrus or CI. The bases below FL180 of FEW/SCT, BKN, and OVC clouds are labeled. The tops of the highest BKN or OVC layer with bases below FL180 are labeled. When multiple layers of BKN or OVC clouds exist, the top of the highest layer will be given preceded by LYRD. Cirrus clouds above clouds with bases below FL180 are labeled as CI ABV. The graphical AIRMETs for icing and mountain obscuration are also overlaid.
Aircraft in flight are the only means of directly observing cloud tops, icing, and turbulence; therefore, no observation is more timely than one made from the flight deck. While the FAA encourages pilots to report inflight weather, a report of any unforecast weather is required by regulation. A PIREP (UA) is usually transmitted in a prescribed format. See Figure 2-3.
Pilots seeking weather avoidance assistance should keep in mind that ATC radar limitations and frequency congestion may limit the controller’s capability to provide this service.

Figure 2-3
The winds and temperatures aloft forecast is displayed in a 6-digit format (DDffTT). It shows wind direction (DD), wind velocity (ff), and temperature (TT) that is forecast to exist at specified levels. For example, “234502” decodes as: winds from 230° true north, at 45 knots, temperature 2°C.
When the wind speed (ff) is between 100 and 199 knots, the wind direction (DD) portion of the code will be greater than 50. In cases such as this, you will need to subtract 50 from the coded wind direction, and add 100 to the coded wind speed in order to decipher the code. For example, “734502” decodes as: winds from 230° true north, at 145 knots, temperature 2°C. When the wind speed is 200 knots or greater, the speed will be indicated by 99. In this case, you will again need to subtract 50 from the coded wind direction and translate the 99 to “greater than 200 knots.” For example, “739902” decodes as winds 230°, greater than 200 knots, temperature 2°C.
Temperatures with a negative symbol in front of them (DDff-37) are negative. For altitudes above 24,000 feet MSL, temperatures are always negative and will not have a negative symbol. Light and variable winds or wind speeds below 5 knots are indicated by 9900, followed by the forecast temperature. For example, the coded winds aloft forecast for FL270 is “990017” and decodes as: winds are light and variable, temperature -17°C.
Previously called Severe Weather Watch Bulletins (WW), the National Weather Service releases the Aviation Notification Watch Message (SAW) as needed. The SAW provides an area threat alert for the aviation meteorology community to forecast organized severe thunderstorms that may produce tornadoes, large hail, and/or convective damaging winds.
Inflight Weather Advisories advise pilots en route of the possibility of encountering hazardous flying conditions that may not have been forecast at the time of the preflight weather briefing.
AIRMETs (WA) contain information on weather that may be hazardous to single engine, other light aircraft, and VFR pilots. The items covered are moderate icing or turbulence, sustained winds of 30 knots or more at the surface, widespread areas of IFR conditions, and extensive mountain obscurement.
SIGMETs (WS) advise of weather potentially hazardous to all aircraft. A SIGMET may be issued when any of the following conditions occur or is expected to occur in an area affecting at least 3,000 square miles or an area deemed to have a significant effect on the safety of aircraft operations: thunderstorms (except for the contiguous U.S. where Convective SIGMETs are used instead), severe or greater turbulence, severe icing, widespread duststorm, widespread sandstorm, volcanic ash, or tropical cyclone.
SIGMETs and AIRMETs are broadcast upon receipt and at 30-minute intervals (H + 15 and H + 45) during the first hour. If the advisory is still in effect after the first hour, an alert notice will be broadcast. Pilots may contact the nearest FSS to ascertain whether the advisory is pertinent to their flights.
Convective SIGMETs (WST) cover weather developments such as tornadoes, lines of thunderstorms, and embedded thunderstorms, and they also imply severe or greater turbulence, severe icing, and low-level wind shear. Convective SIGMET Bulletins are issued hourly at H+55. Unscheduled Convective SIGMETs are broadcast upon receipt and at 15-minute intervals for the first hour (H + 15, H + 30, H + 45).
A Convective Outlook (AC) describes the prospects for general thunderstorm activity during the following 24 hours. Areas in which there is a high, moderate, or slight risk of severe thunderstorms are included as well as areas where thunderstorms may approach severe limits. Convective Outlooks are produced at the Storm Prediction Center (SPC) in Norman, Oklahoma. Pilots should use an AC primarily for planning flights later in the day.
The Surface Analysis Chart depicts frontal positions, pressure patterns, temperature, dew point, wind, weather, and obstructions to vision as of the valid time of the chart.
A Constant Pressure Analysis Chart is an upper air weather map where all the information depicted is at the specified pressure of the chart. Each of the Constant Pressure Analysis Charts (850 MB, 700 MB, 500 MB, 300 MB, 250 MB, and 200 MB) can provide observed temperature, temperature/dew point spread, wind, height of the pressure surface, and the height changes over the previous 12-hour period.
The Low-Level Significant Weather Prognostic Chart (FL240 and below) portrays forecast weather hazards that may influence flight planning, including those areas or activities of most significant turbulence and icing. It is a two-panel display representing a 12-hour forecast interval (left) and 24-hour forecast interval (right). Turbulence intensities are identified by standard symbols as shown in Figure 2-4. The vertical extent of turbulence layers is depicted by top and base heights separated by a slant and shown in hundreds of feet MSL (180/100 = 18,000 feet MSL to 10,000 feet MSL). Freezing levels above the surface will correspond with a given altitude in hundreds of feet MSL (080 = 8,000 feet MSL). Low-level SIGWX charts are issued four times daily, and valid time, date, and chart type are depicted in the lower left corner of each panel.

Figure 2-4
The High-Level Significant Weather Prognostic Chart (FL250 to FL630) outlines areas of forecast turbulence and cumulonimbus clouds, shows the expected height of the tropopause, and predicts jet stream location and velocity. The chart depicts clouds and turbulence as shown in Figure 2-5.

Figure 2-5
Cumulonimbus cloud (CB) areas are enclosed by a red scalloped line. The height of the tropopause is shown in hundreds of feet MSL and enclosed in a rectangular box; centers of high (H) and low (L) heights are enclosed in polygons. Areas of turbulence are enclosed in yellow dashed lines and labeled with the appropriate severity symbol and top and base altitudes. A jet stream axis containing a wind speed of 80 knots or greater is identified by a bold green line and directional arrowhead. A standard wind symbol is placed on the jet stream to identify velocity and an associated flight level is placed adjacent to it. An omission of a base altitude (XXX) identifies that the weather phenomena exceeds the lower limit of the high-level SIGWX chart (FL250). See also FAA Figures 5, 7, and 18.
[10-2024]