El Niño does not have one snow answer
Snow is a two-gate problem: you need precipitation and you need air cold enough for that precipitation to fall as snow. El Niño can increase one and reduce the other.
Where historical El Niño snow tends to increase
NOAA Climate.gov analyses show a broad tendency toward more snowfall across parts of the southern half of the United States, especially higher and colder western terrain. California, Nevada, Utah, Colorado, New Mexico and Arizona have all shown positive signals in historical composites, while the Mid-Atlantic and southern Appalachians can also be more favorable.
Where it often decreases
The Pacific Northwest, northern Rockies, Great Lakes, interior New England and much of Alaska have historically leaned toward less snowfall during El Niño winters. A warmer background can also push marginal events from snow toward rain.
Why strong El Niño still cannot promise snow
Even in the Mid-Atlantic, where El Niño can be favorable for seasonal snowfall, strong events have produced both very snowy and nearly snowless winters. A single blocking pattern or storm track can dominate the seasonal total.
Ski planning rule of thumb
Higher elevation gives a region more ability to convert a wetter storm track into snow. Lower elevation increases the risk that a warm El Niño storm arrives as rain. That is why the checker gives snow its own label instead of deriving it directly from precipitation.