Just like daily forecasts help the public plan for a given day, aviation forecasts assist aviation officials and pilots in making decisions on when to safely operate (or delay, detour, cancel) flights. The NOAA National Weather Service maintains a number of forecasts specifically for aviation use. Some of these forecasts are displayed as maps or images, while others appear as text.
Surface & Low Level:
Surface Weather Prognostic Charts
Surface prognostic charts display what the weather is expected to be at some future time; for aviation purposes, this time frame is the next 48 hours. They are an important resource for aviators because they show forecast conditions (including high and low pressure areas, fronts, and weather type and location) from the Earth's surface up to a height of 24,000 feet. (This distance is termed "low-level.")
Displayed as: Maps
Period of Issue: Prog charts are updated every hour. Each chart covers a 12-hour period.
View current prog charts
Meteorological Terminal Aviation Routine Weather Reports (METARs)
METARs give an overview of weather conditions observed at a specific airport location, at ground level. Reports are generated by automated airport weather stations, and generally consist of 1-2 lines of wrapped text.
The weather data contained in the report includes the following observations in this order: airport station identifier, date and time of report, wind speed and direction, < a href="http://weather.about.com/od/v/g/visibility.htm">visibility, observed weather, ceiling, sky conditions, temperature and dewpoint, and pressure. Additional data of interest can also be included in remarks, however, this is optional and usually is only done when hazardous weather is occurring.
Displayed as: Text
Period of Issue: METARs are issued every hour. If conditions change significantly, a "special" (SPECI) report may be issued sooner.
View current METARs
Terminal Aerodrome Forecasts (TAFs)
TAFs are very similar to METARs except they're produced by a human forecaster based on the ground, and consist of 4-5 lines of block text. They provide forecasts of cloud heights and ceilings, wind direction and speed, wind shear, visibility, and weather type all within a five statute mile radius from the center of an airport location.
Displayed as: Text
Period of Issue: TAFs are routinely issued every 6 hours. They're valid for 24 hours from time of issuance. (TAFs for major airports cover a 30-hour period.)
View current TAFs
Airman's Meteorological Advisory (AIRMET)
AIRMETs identify areas along air routes where ceilings, turbulence, and icing are expected to be of concern. In order for an AIRMET to be issued, the hazard must be considered widespread--meaning it affects an area of at least 3000 square miles.
The 3 AIRMET types:
- AIRMET Sierra: Issued for ceilings less than 1000 feet, visibility less than 3 miles (IFR conditions), or when mountains greatly obscure visibility
- AIRMET Tango: Issued for moderate turbulence, or sustained surface winds of 30+ knots
- AIRMET Zulu: Issued for moderate icing or freezing levels
Displayed as: Maps, text
Period of Issue: AIRMETs are issued every 6 hours, beginning at 0245 UTC time (Central Standard Time).
View current AIRMETs
View current turbulence forecasts
View current icing potential
Significant Meteorological Advisory (SIGMET)
SIGMETs are similar to AIRMETS, except they apply to severe weather hazards.
The 2 SIGMET types
- Non-convective SIGMETs: Issued for severe (or stronger) turbulence, severe icing, or for IFR conditions--each occurring over an area of 3000+ square miles
- Convective SIGMETs: Issued for areas of convective weather (i.e., thunderstorms) affecting an area of 3000+ square miles
Displayed as: Maps, text
Period of Issue: Non-convective SIGMETs are valid for up to 4 hours after issuance. During severe weather outbreaks, convective SIGMETs are issued/updated every 55 minutes and last for up to 2 hours.
View Current SIGMETs, convective hazards
Pilot Reports (PIREPs)
As the name implies, PIREPs are reports submitted by pilot or crew member. They detail actual weather conditions encountered during flight.
Reports include the following information (in this order): type (routine or urgent), location, flight level, sky conditions, weather type, icing levels, turbulence levels, and type of aircraft flown.
Displayed as: Text, but are also plotted on hazard maps
Period of Issue: PIREPs are issued every hour.
View Current PIREPs
The Use of Abbreviated Text
To help standardize and hasten the communication of weather data, all text aviation forecasts are written in encoded text. That is, instead of listing observations in plain English, these are given in a "raw" format and appear as a string of abbreviated text. (Links provided above give users the option to generate either format.)
To learn more about standard abbreviations used in aviation forecasts, visit the Federal Meteorological Handbook.