How can I modify the 30/60 days forcast alert

Make a copy of the original alert and add the last line, like that :

SELECT VolumesForecastCapacity.Uri, VolumesForecastCapacity.DisplayName 
FROM Orion.VolumesForecastCapacity AS VolumesForecastCapacity
 LEFT JOIN Orion.Nodes nodes on nodes.NodeID = VolumesForecastCapacity.NodeID
 LEFT JOIN Orion.Settings s ON s.SettingID = 'ForecastMinDays' 
WHERE 
  VolumesForecastCapacity.DaysToCapacityAvg <= 60
  AND VolumesForecastCapacity.MetricName = 'Forecast.Metric.PercentDiskUsed'
  AND DayDiff(VolumesForecastCapacity.MinDateTime, VolumesForecastCapacity.MaxDateTime) >= ISNULL(s.CurrentValue, 7)
  AND nodes.Unmanaged = false
  AND VolumesForecastCapacity.Volume.Type = 'Fixed Disk'

Great, I'll try that and let you know.

Great, I'll try that and let you know.