| NWS Product Description Document (PDF) |
| NWS Directive (PDF) |
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| Package | Issue Time |
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| 24 hour forecast package valid at 00Z | 08Z |
| 24 hour forecast package valid at 06Z | 14Z |
| 24 hour forecast package valid at 12Z | 20Z |
| 24 hour forecast package valid at 18Z | 02Z |
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In accordance with the World Meteorological Organization (WMO) and the World Area Forecast System (WAFS) of the International Civil Aviation Organization (ICAO), high level significant weather (SIGWX) forecasts are provided for the en-route portion of international flights. The AWC provides a suite of SIGWX forecast products for the World Area Forecast Center (WAFC) in Washington, D.C. These products are used directly by airline dispatchers for flight planning and weather briefing before departure, and by flight crew members during flight.
High level SIGWX charts are valid at specific fixed times: 0000, 0600, 1200, and 1800 UTC. They show significant en-route weather phenomena over a range of flight levels from 250 to 630, and associated surface weather features. The significant weather elements are defined by WMO and ICAO, and include:
- thunderstorms and cumulonimbus clouds
- tropical cyclones
- moderate or severe turbulence
- tropopause heights
  
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- jetstreams (80kt and above depicted)
- volcanic eruptions
- Jet Depth *
- Hash Marks (each pair indicates successive 20kt wind speed changes referenced to Jet Max)
- Release of Radioactive Materials
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| * Jet Depth: The vertical depths to the 80 knot wind field above and below the jet steam using flight levels. Jet stream vertical depth forecasts are included when the maximum speed is 120 knots or more. More details ... |
WAFS Significant Weather (SIGWX) Data in BUFR |
ICAO WAFS SIGWX BUFR [pdf]
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| This document has been prepared by the World Area Forecast Centres (WAFCs) for the purpose of providing guidance to software developers who have the task of constructing WAFS SIGWX BUFR visualisation software. The document is designed to assist developers in the construction of compliant visualisation software that receives its data input from text files obtained from BUFR decoding software. |
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