I found it!

I think...
.
Even Fr. Z has asked where the quote comes from referring to souls falling into hell like snowflakes - or leaves falling from the trees in Fall.  Some have attributed it to St. Teresa of Avila (I never came across it), others to the messages of Our Lady of Fatima (I never found it in any of the writings), but now I think I may have found what appears to be the closest, most verifiable contemporary source. 
.
From a message given by the Blessed Virgin to Venerable Elena Aiello, an Italian nun and mystic, soon to be beatified:

“The Madonna then came closer, and with a sad expression, showed me the flames of Hell. She said:” ‘Satan reigns and triumphs on earth! See how the souls are falling into Hell. See how high the flames are, and the souls who fall into them like flakes of snow look like transparent embers! How many sparks! How many cries of hate, and of despair! How much pain!’" - Mystics of the Church

Soon after my conversion in 1972 I read many mystics and revelations regarding coming chastisements and so on.  I was impressed for a time with Mother Elena, due in part to her devotion to the Holy Face.  Over the years I tried to mortify my interest in private revelation and apparitions since many were in dispute and most seemed unfulfilled.  I also felt such things were novel distractions, somewhat like spiritual science fiction entertainment - not to mention that a lot of crazy people got themselves all worked up over such things.  The freaks often scared me away, but if I did get involved, the initial excitement and fervor gradually diminished and ended in disappointment that nothing 'big' ever happened. 
.
In the meantime, preachers and teachers kept saying things like, 'in every age there were doomsayers', 'back in such and such century even some of the saints believed the world would end', 'the end of the world comes to every person at death', yadda, yadda,yadda.  So I more or less ignored the increase of mystics and their private revelations, although always keeping in mind the 'warnings' I heard before from mystics such as Mother Aiello.  The earlier revelations became a sort of reference point by which to discern the plethora of new warnings - usually resulting in my wondering if the new mystics hadn't read the same stuff I had.  So here I am today - and the mystics are getting beatified - and I'm still my sinful, skeptical self -  "time will prove where wisdom lies." [Matt. 11:19]
.
One thing about M. Aiello's 'messages' is that today we can look back on what she wrote and kind of see more clearly what they referred to and how they were either fulfilled or perhaps mitigated.  We also can learn something regarding the nature of private revelations as well - that they are received according to the mode of understanding of the receiver.  In other words, some stuff can be mixed up in the translation, some stuff is symbolic, and so on.  Such communications and messages remain interesting to read and ponder however, and they can be useful to jump-start a tepid devotion, or to cast light upon one's state of soul and/or the troubled times we live in.  Hence they can be good insofar as they lead one to a deeper, more solid devotion and fidelity to the Church and the Gospel.
.
As Catholics we have the added consolation of knowing that holy persons are never canonized for their private revelations or the mystical phenomena and charisms they may have exhibited while on earth. 
.
Venerable Elena Aiello will be declared Blessed on September 14, 2011 -Feast of the Triumph of the Holy Cross.
.
Photo:  Flaky Bayside visionary, Veronica Lueken claimed to be 'miraculous photo'  of souls falling into hell.  Another reason I don't get involved in mystics and apparitions.