The Airline Pilots Forum and Resource
The Airline Pilots Forum and Resource

SNOWTAM Decode

A SNOWTAM is a message describing the conditions of the runways, taxiways and apron at an aerodrome. During the winter season a SNOWTAM will be issued each day in the morning, before flying starts. A SNOWTAM is valid for 24 hours, but there are rules stating that a new SNOWTAM shall be issued sooner if significant changes occur.

The SNOWTAM consist of different fields, each with its own letter, and the information is almost entirely given in code. Below are two examples of SNOWTAM with the most used fields filled in.

Each aerodrome has its own SNOWTAM series, and they are numbered consecutively for the whole season, starting with 0001.

The SNOWTAM itself contains mostly codes, below are examples of SNOWTAM for aerodromes with one and two runways.

Single runway:

SWEN0393  ENHF  04200155
(SNOWTAM  0393  A) ENHF  B) 04200243  C) 05  F) 48/7/47  G) 02/XX/03  H) 60/58/53   GRT  N) 47 R) 47 T) RWY SANDED)

Two runways:

SWEN0497 ENGM 04200155
(SNOWTAM 0497 A) ENGM B) 04200155
C) 01L F) NIL/NIL/NIL G) XX/XX/XX H) 5/5/5 N) NIL
C) 01R F) NIL/NIL/NIL G) XX/XX/XX H) 5/5/5 N) NIL R) NIL)


SWEN is an international code for SNOWTAM originated in Norway, and the number indicates how many SNOWTAM has been issued for the aerodrome shown in the following field.

A) ENHF/ENGM is the ICAO 4-letter location indicator for the aerodrome.

B) 04200155 is the day-time group for when the SNOWTAM was issued. The format is month-day-hour-minute UTC.

C) 05/01L/01R is which runway the SNOWTAM is for. A SNOWTAM will always tell you the condtions of a runway seen from the end with the lower designator, for example if the runway orientation is 03/21, then the conditions for RWY 03 will be in the SNOWTAM.

F) This field show runway contamination (any deposits on the runway). The runway is divided into three equal parts, and the SNOWTAM will give the values for each third divided by a slash (/). The following codes are used to describe the type of contamination:

NIL:  Clear and dry
1:   Damp
2:   Wet or water patches
3:   Rime (normally less than 1 mm deep)
4:   Dry snow
5:   Wet snow
6:   Slush
7:   Ice
8:   Compact or rolled snow
9:   Frozen ruts or ridges.

As shown in the ENHF example, there may be more than one code used for each third of the RWY. If this is done, the codes will show the different layers of contamination from the top down. 48 thus indicates that there is dry snow on top of compact snow on the first third of the runway, the next third has ice (7), while the last third is covered with dry snow on ice (47).

G) This field in a SNOWTAM is the average depth of the contamination, again for each third of the runway. The depth is given in millimeters, but if the depth cannot be measured, as would be the case for ice, then the letters XX are used.

H) This field indicates the braking action, the friction on the runway. Again the runway is divided into three parts, and the numbers are the mean values for each third. The braking action may be determined by measuring equipment, or estimated. If measuring equipment have been used, the friction will always be given in two digits, and an abbreviation stating which equipment was used is also shown. If the friction have been estimated, a single digit will be used.

Measured fricton:

>40:        Good
39 36:   Medium/good
35 30:   Medium
29 26:   Medium/poor
<25:        Poor

Estimated friction:

5:   Good
4:   Medium/good
3:   Medium
2:   Medium/poor
1:   Poor
9:   Unreliable*

* If unreliable is used, it is because the contamination is outside the approved range of whatever equipment is used to measure the braking action. This could either be because the contamination is too deep, or of a type that the equipment is not approved for. For example, measured friction by Grip Tester (GRT) on wet ice is considered to be unreliable and the SNOWTAM will then have the value 9 in field H).

If the friction on the runway has been measured, the type of equipment used is indicated with the following abbreviations:

BRD:     Brakemeter-Dynometer
GRT:     Grip Tester
MUM:    Mu-meter
RFT:     Runway friction tester
SFH:     Surface friction tester (high pressure tires)
SFL:     Surface friction tester (low pressure tires)
SKH:     Skiddometer (high pressure tires)
SKL:     Skiddometer (low pressure tires)
TAP:    Tapleymeter

Any other type of equipment will be stated in clear text.

N) This field shows the conditions on the taxiways associated with the runway. The codes are the same as for the runway, but the taxiways are not divided into thirds.

R) This field tells you whats on the apron, again, the codes are the same as for the runway.

T) This field is a clear text-field. In this field information of significance will be entered. If there is no text in this field, the T) will not be shown on the SNOWTAM.


SNOWTAM Decode - METAR Format


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