This line will only create... one snowflake.
What you need is a loop that creates several.
But why not use Kegetys' snow script ? Here it is, as extracted from his winter Nogojev :
;
; Snowing script v1.0 by Kegetys <Kegetys@raketti.net>
; http://www.ofp.kege.cjb.net
;
; For Winter Nogojev
;
;
; Usage:
; [density] exec "\KEGnoecain_snow\script\snow.sqs"
;
; where density is the density of the snowing. If density is not specified a default of 5 is used.
; Note that the maximum working density is relative to the FPS.
;
_velocity = [0,0,-0.61]
_density = 5
? count _this > 0 : _density = _this select 0
#Begin
~0.001
_spawnDist = 35
_spawnHeight = 15
_foo = 0
#luup
_posDrop = [(getpos player select 0)-_spawnDist+(random (_spawnDist*2)), (getpos player select 1)-_spawnDist+(random (_spawnDist*2)), (getpos player select 2)+_spawnHeight]
_posDrop = [(_posDrop select 0)+((velocity vehicle player select 0)*5),(_posDrop select 1)+((velocity vehicle player select 1)*5),_posDrop select 2]
drop ["cl_water", "", "Billboard", 1, 7, _posDrop, _velocity, 1, 0.000001, 0.000, 1.4, [0.06,0.06], [[1,1,1,0], [1,1,1,1], [1,1,1,1], [1,1,1,1]], [0,1,0,1,0,1], 0.2, 1.2, "", "", ""]
_foo = _foo + 1
? _foo < _density : goto "luup"
goto "Begin"