Sometimes the sensors get ice rhyme and say there is more then there is. If it looks wrong, it probably is. You can look at the past history(10 day), and then take a guess how much by how much precip and how cold it's been.
The RH% is relative humidity.
I think the general rule of thumb is -3.5 degrees for evey 1,000'? so if it's 46 degrees at sea level, it should be about freezing at 4,000'. but not always.