A format for reporting weather forecast information.
Format specified by ICAO Doc 8896 manual of aeronautical meteorological practice.
https://skybrary.aero/bookshelf/books/2506.pdf
Example:
ENGM 051700Z 0518/0618 34010KT 9999 FEW050 BECMG 0518/0520 VRB05KT BECMG 0612/0614 18010KT=