Whiter than snow?

Psalms 50 and 51. Yesterday in class we discussed social location and how readers from various parts of the world bring different lenses to the Psalms. Today I'm wondering about the social location of the psalmist and Psalm 51. This is a familiar lament that is much sung and recited in worship, where the psalmist asks for God's cleansing in the light of sin.  I'm not exactly sure what hyssop is, and the notes in my Bible refer to a hyssop bush, which I'm fairly certain doesn't grow in the northern hemisphere. But I'm wondering if the psalmist does indeed know about snow the way I know about snow -- how it is many shades of white/grey/yellow and cold and crunchy or wet and sloppy. Does it really snow enough in the Middle East for it to be a common images, as in in 51:7 "Purge me with hyssop, and I shall be clean; wash me, and I shall be whiter than snow." It's snowing here in Winnipeg -- big wet clumpy flakes that doesn't make for pleasant start to winter, especially on Oct. 9. Right now, I'd rather read about the psalmists longing for green pastures than white snow.