snow (television)

[Mullins, Bill]

>From OED:
    f. Spots that appear as a flickering mass filling a television or radar screen, caused by interference or a low signal-to-noise ratio. 

first OED cite 1946

TELEVISION COINS SLANG: BLIZZARD HEAD IS A BLONDE
Chicago Daily Tribune (1872-1963); Feb 5, 1939; pg. W10 col 4.
"Engineers have already compiled this brief list:  "Blizzard head" -- blondes of either sex, so-called because their hair reflects light, giving them the effect of a halo about the head; "snow" -- not crystallized weather, but small spots floating across the televised image; "ghost" -- a double image; "out of syn" -- bobbing and weaving of images due to the fact that receiving set and transmitter set are not operating in synchronization.

Also, "bloom" -- flare of light on the picture; "in the mud" -- not enough light on the images.  "In the mud" in radio means a voice so low or befogged that it can't be easily understood."