Chapter 3
Overview of Aviation Weather Information
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3.4.2.14 Products with Surface-Based IFR Information
For most aviation weather products, IFR refers to ceilings less than 1,000 feet (ft) (i.e., above ground level (AGL)) and/or surface visibilities less than 3 statute miles (SM). But many aviation weather websites provide a graphical depiction of METARs or Aviation Selected Special Weather Reports (SPECI), and sometimes TAFs, using color-coded station plots for various Weather Flight Categories. These Weather Flight Categories and color codes serve as a means to help pilots visually assess ceilings and visibilities on a map of METARs. Most aviation weather websites use the following color codes and definitions for their display of METARs/SPECIs (and sometimes TAFs) on their website:
- Purple: LIFR = Low IFR, ceilings less than 500 ft and/or visibilities less than 1 SM.
- Red: IFR = Ceiling 500 ft to less than 1,000 ft and/or visibility 1 SM to less than 3 SM.
- Blue: MVFR = Ceiling 1,000 to 3,000 ft and/or visibility 3 to 5 SM.
- Green: VFR = Ceiling greater than 3,000 ft and visibility greater than 5 SM.
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3.4.2.15 Products with Surface-Based MVFR Information
MVFR is a Weather Flight Category. While the “R” in the acronym means “rules,” there are no 14 CFR part 91 MVFR weather minimums. The MVFR weather category is defined as ceilings from 1,000 ft to and including 3,000 ft (AGL), and/or surface visibilities from 3 SM to and including 5 SM.
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3.4.2.16 Products with Cloud Coverage Information
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3.4.2.17 Products with Cloud Base Information
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3.4.2.18 Products with Cloud Tops Information
