BECMG

• becoming (expected between 2 digit beginning hour and 2 digit ending hour)

  TAF

BECMG stands for “becoming (expected between 2 digit beginning hour and 2 digit ending hour)” (TAF usage). Got a NOTAM full of contractions? Paste it into the decoder.

Source: FAA Order JO 7340.2 Contractions. Not for operational use.