Routine forecast (TAF)

The regularly scheduled routine forecast that is released at the standard issue time is referred to simply as a “TAF.” Routine TAFs are issued four times a day at a frequency of every six hours. Pilots will receive new TAFs at 0000, 0600, 1200, and 1800 Zulu time each day. Most TAFs are generated for a time period of the upcoming 24 hours and in some locations TAFs can be issued for predicted weather up to 30 hours in advance.

Amended forecast (TAF AMD)

If a change or correction needs to be made to the previously issued standard TAF, the update will be coded as “TAF AMD.” The “AMD” signifies that the original TAF has been amended and that the new TAF AMD supersedes the original. Amended TAFs are issued whenever the currently active TAF no longer accurately represents the expected weather conditions.

While routine forecast TAFs are issued for a time period of 24 or 30 hours, an amended TAF may have a much shorter forecast period. A TAF that is issued at a nonstandard time is an amended forecast.

Corrected (COR) or Delayed (RTD)

If the TAF being issued has been corrected for an error or was delayed in being issued, this will be indicated by “COR” or “RTD”. Look for these abbreviations in the communications header preceding the text of the TAF.

Delayed TAFs are most common at locations that operate on a part-time basis. When the observer returns, they complete two observation cycles prior to issuing a TAF. The first TAF issued during their shift is coded as delayed (RTD).

Qualifiers of Intensity or Proximity

• - Light

• Moderate (no qualifier)

• + Heavy or well-developed

• VC in the Vicinity

Qualifier Descriptor

• MI Shallow

• BC Patches

• DR Low Drifting

• BL Blowing

• SH Showers

• TS Thunderstorm

• FZ Freezing

• PR Partial

Precipitation

• DZ Drizzle

• RA Rain

• SN Snow

• SG Snow Grains

• IC Ice Crystals

• PL Ice Pellets

• GR Hail

• GS Small Hail or Snow Pellets (less than 1/4 inch in diameter)

• UP Unknown precipitation (automated stations only)

Obscuration

• BR Mist (Foggy conditions with visibilities greater than 5/8 statute mile)

• FG Fog (visibility 5/8 statute mile or less)

• FU Smoke

• DU Dust

• SA Sand

• HZ Haze

• PY Spray

• VA Volcanic Ash

​Other

• PO Well-Developed Dust/Sand Whirls

• SQ Squalls

• FC Funnel Cloud

• +FC Well-Developed Funnel Cloud, Tornado or Waterspout

• SS Sandstorm

• DS Duststorm

The code “NSW” or No Significant Weather is used to denote a period of no significant weather following a period where significant weather was predicted.

​1: ICAO Station Identifier

2: Date and Time Origin or when the forecast was updated
3: Valid Time Period

4. Forecast Meteorological Conditions 
5. Forecast Change Indicators