Military TAF Icing Codes: The 6-Group Decoded

Military TAF icing codes use the same six-digit shell as the turbulence group, with a different leading digit and a different meaning for the one that follows.

If you can read 520005 you can already read 620105. The frame is identical. Only the table behind the second digit changes.

How the 6-group is built

The group always opens with the digit 6, which marks it as icing.

• Digit 1: always 6, marking the icing group
• Digit 2: type and intensity together, from the table below
• Digits 3 to 5: base of the icing layer, in hundreds of feet
• Digit 6: thickness of the layer, in thousands of feet

620105 splits as 6, 2, 010, 5. Icing group, light rime icing in cloud, based at 1000 feet, 5000 feet thick. The layer runs from 1000 to 6000 feet.

As with turbulence, the base is in hundreds and the thickness is in thousands. Mixing those two up is the most common error with either group.

The icing codes

From AFMAN 15-124, Table 1.5, read by the wxdecoder parser as written.

The pattern behind the digits

The table has a rhythm, and once you see it the ten values collapse into two questions.

After the trace at zero, the codes run in blocks of three. Codes 1 to 3 are light. Codes 4 to 6 are moderate. Codes 7 to 9 are severe.

Inside each block the order is always the same: mixed, then rime in cloud, then clear in precipitation.

So the block tells you the intensity and the position inside the block tells you the type. Code 8 is in the severe block, second position, so it is severe rime in cloud. Code 3 is in the light block, third position, so it is light clear in precipitation.

Why the type matters as much as the intensity

The digit gives you both facts for a reason. They are not interchangeable.

Rime forms from small droplets that freeze on impact. It is opaque and brittle, it builds on leading edges, and boots shed it reasonably well.

Clear ice forms from large droplets that spread before freezing. It is dense and transparent, it bonds hard, and it runs back behind the protected surfaces where no equipment can reach it.

That is why the codes tie clear ice to precipitation. Large droplets mean liquid water falling, usually freezing rain or drizzle, and that is the worst airframe icing there is.

A code 6, moderate clear in precipitation, deserves more caution than a code 5, moderate rime in cloud, even though both say moderate.

Reading it alongside the other groups

The icing group sits in the TAF trailer with the turbulence group and the altimeter setting.

A trailer reading 510005 620105 QNH2992INS gives you three facts in a row: light turbulence from the surface to 5000, light rime icing from 1000 to 6000, and an altimeter setting of 29.92 inches.

Note the two hazard layers overlap without matching. Turbulence runs surface to 5000 and icing runs 1000 to 6000. They are forecast separately, so read each band on its own rather than assuming one describes the other.

Where a TEMPO or FM period carries its own groups, those apply for that period only.

A worked example

Take 680209 and cut it after digits one, two and five.

The 6 marks icing. The 8 sits in the severe block, second position, so it is severe rime icing in cloud. The 020 is the base, 2000 feet. The final 9 is the thickness, 9000 feet.

So the forecast is severe rime icing in cloud from 2000 to 11,000 feet. Severe means the build rate beats the ice protection, so that is a layer to stay out of rather than to transit.

Compare 600000. Icing group, code 0 for trace, base at the surface, thickness under a thousand feet. Same six digits, and nothing worth changing a plan for.

When there is no icing group at all

An absent group is not the same as a forecast of no ice, and the distinction catches people.

Code 0 means the forecaster expects trace icing. No group at all means the forecaster did not put one in, which usually means nothing significant was expected, but it can also mean the product was abbreviated.

Read a missing group alongside the rest of the forecast. A TAF with cloud from 1000 feet, temperatures near freezing and no icing group is worth a second thought, and worth checking AIRMET Zulu for the same area.

Verdict on military TAF icing codes

Split the group after digits one, two and five. Marker, type and intensity, base, thickness.

The second digit is the only thing to learn, and the blocks of three make it manageable. Light is 1 to 3, moderate is 4 to 6, severe is 7 to 9, and within each block the order runs mixed, rime, clear. Anything in the third position of its block means clear ice in precipitation, which is the one to respect most.

Last updated August 29, 2026