Green’s Dictionary of Slang

snowstorm n.

also snowfall
[snow n.1 (2)]

(US drugs) the using of cocaine or morphine.

[US]S.F. Call 27 Nov. 3/1: A cocaine fiend, referring to his practice [...] is always ‘taking a show ride’, or having a ‘snow storm’.
[US]E. Caldwell Bastard (1963) 49: John found some cocaine and Sook soon quieted down a little. And later, after two or three snow-storms, she wouldn’t let anyone else touch Sheriff Jim.
[US]C. Martinez ‘Gats in the Hat’ in Gun Molls Sept. [Internet] She [...] threw him a small folded paper. ‘Treat yourself to a snowstorm and see if you can stop that damn jerking!’ [...] he rubbed the fine white powder on the back of his left hand and sniffed eagerly.
[US]Anslinger & Tompkins Traffic In Narcotics 315: snow fall. A bout of cocaine- or morphine-using.

In phrases

caught in a snowstorm (adj.)

1. (US drugs) under the influence of cocaine, esp. when experiencing extreme effects.

[US]C.S. Montanye ‘Perfect Crime’ in Penzler Pulp Fiction (2007) 351: ‘Walk in a snow storm, brother?’ ‘It’s dope, isn’t it?’ [...] ‘Happy dust. Have some?’.
[US]San Quentin Bulletin in L.A. Times 6 May 7: CAUGHT IN A SNOWSTORM, drugged with cocaine.
[US]Monteleone Criminal Sl. (rev. edn).
[US]Anslinger & Tompkins Traffic In Narcotics 306: caught in a snowstorm. To be under the influence of drugs, especially of heroin, morphine, or cocaine.
[UK]J. Colebrook Cross of Lassitude 239: He can understand very little, most of it seeming to be about someone who was ‘caught in a snowstorm,’ and ‘riding the wave’.
[US]Bentley & Corbett Prison Sl. 80: Wired for Sound To be extremely high on amphetamines or cocaine. (Archaic: caught in a snow storm).

2. experiencing the hallucinations which accompany an overdose of morphine.

[US]Howsley Argot: Dict. of Und. Sl. 47: snow storm – hallucinations caused by an overdose of morphine.