Do you have a bathroom exhaust fan - is it anywhere near the area ?
Are you sure the the piping from a fan ( especially if it's flexible )
is not leaking or not connected at the fan properly , thus allowing
humid air to escape ? There could be a spot in the pipng that moisture
is puddling at and leaking ? Was the snow or ice sitting above where
it vents out the roof ? If so , this could cause the warm air to melt
any ice or snow above and arround the roof vent , and it is melting
back down in thru the vent into the house . Is your house humidified ?