/usr/share/eccodes/definitions/metar/weatherCodes-trend-template.txt is in libeccodes-data 2.6.0-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 | DZ
SN
PL
SS
FZDZ
FZRA
SHGR
SHGS
SHRA
SHSN
TSGR
TSGS
TSRA
TSSN
RA
SG
DS
-DZ
-SN
-PL
-SS
-FZDZ
-FZRA
-SHGR
-SHGS
-SHRA
-SHSN
-TSGR
-TSGS
-TSRA
-TSSN
-RA
-SG
-DS
+DZ
+SN
+PL
+SS
+FZDZ
+FZRA
+SHGR
+SHGS
+SHRA
+SHSN
+TSGR
+TSGS
+TSRA
+TSSN
+RA
+SG
+DS
IC
BR
SA
HZ
FU
SQ
PO
TS
BCFG
BLDU
BLSA
BLSN
DRDU
DRSA
DRSN
FZFG
MIFG
PRFG
FG
DU
HZ
VA
FC
|