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WEATHER CHARTS



Weather charts are used to show the overall view of the U.S. current or forecast weather. These charts typically show fronts and major weather systems as the move across the country and are a good source of current weather information. There are three types of charts used, they are:

  • Surface Analysis Chart

  • Weather Depiction Chart

  • Significant Weather Prognostic Chart

Surface Analysis Charts:

These charts show the current surface weather such as high and low pressure, fronts, temperature, dew point, wind direction and speed, etc. These three charts are issued every 3 hours and cover the lower 48 states.




Weather Depiction Charts:

They show the surface conditions derived from the METARs and other surface observations. These charts are computerized, issued every 3 hours starting at 0100Z. Weather depiction charts also shows areas of IFR, VFR, and MVFR (Marginal VFR) along with fronts, troughs, and squall lines.

  • IFR – Ceiling less than 1,000 feet with visibility less than 3 miles.

  • VFR – Ceiling greater than 3,000 feet or clear skies with visibility more than 5 miles.

  • MVFR – Ceilings 1,000 – 3,000 feet with visibility 3 – 5 miles.


Significant Weather Prognostic Charts:

Significant Weather Prognostic (SIGWX) Charts can be seen in two different ways; one is low-level form the surface up to FL240 (24,000 feet) and the other is high-level from FL250 – FL630 (25,000 - 63,000 feet). The low-level Prognostic chart is the primary chart to help brief the VFR pilots.

They are issued four times a day 0000Z, 0600Z, 1200Z and 1800Z. The Prognostic Charts are used to show freezing levels, turbulence, and low cloud ceilings or restricted visibly by area of MVFR and or IFR conditions.



References:

Aviation Weather Handbook FAA-H-8083-28 (NEW Publication Dec. 22, 2022)




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