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FM210100 14010KT P6SM SKC 

− “after 0100Z on the

21st, wind one four zero at one zero, visibility more than six,
sky clear.”


Becoming (BECMG) group. The BECMG

group is used when a gradual change in conditions is
expected over a longer time period, usually two
hours. The time period when the change is expected
is two four

−digit groups separated by a “/”, with the

beginning date and hour, and ending date and hour of
the change period which follows the BECMG
indicator. The gradual change will occur at an
unspecified time within this time period. Only the
changing forecast meteorological conditions are
included in BECMG groups. The omitted conditions
are carried over from the previous time group.


The NWS does not use BECMG in the TAF.

OVC012 BECMG 0114/0116 BKN020 

− “ceiling one

thousand two hundred overcast. Then a gradual change
to ceiling two thousand broken between 1400Z on the 1st
and 1600Z on the 1st.”


Temporary (TEMPO) group. The TEMPO

group is used for any conditions in wind, visibility,
weather, or sky condition which are expected to last
for generally less than an hour at a time (occasional),
and are expected to occur during less than half the
time period. The TEMPO indicator is followed by
two four

−digit groups separated by a “/”. The first

four digit group gives the beginning date and hour,
and the second four digit group gives the ending date
and hour of the time period during which the
temporary conditions are expected. Only the
changing forecast meteorological conditions are
included in TEMPO groups. The omitted conditions
are carried over from the previous time group.


1. SCT030 TEMPO 0519/0523 BKN030 

− “three

thousand scattered with occasional ceilings three thousand
broken between 1900Z on the 5th and 2300Z on the 5th.”

2. 4SM HZ TEMPO 1900/1906 2SM BR HZ 

− “visibility

four in haze with occasional visibility two in mist and haze
between 0000Z on the 19th and 0600Z on the 19th.”