To add april to the snow months modify one line in ws_snow/ws_snow.php:
Line approx. 284-286 # J F M A M J J A S O N D
$arr_snow_months= array (0,0,0,0,4,5,6,7,8,9,0,0,0);
$arr_snow_nh = array (0,7,8,9,0,0,0,0,0,0,4,5,6);
to# J F M A M J J A S O N D
$arr_snow_months= array (0,0,0,0,4,5,6,7,8,9,0,0,0);
$arr_snow_nh = array (0,7,8,9,10,0,0,0,0,0,4,5,6);
So the only change is in the NH line, the 0 for april goes to 10.
Wim