The folks at NOAA have some news for Montana: a 70% chance of an El Niño conditions for January, February and March. 

NOAA
NOAA
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At this point, we're dealing with predictions but NOAA has decades of trends to make these predictions.

How many cycles have we seen in recent years? Here's the ONI chart used by NOAA to determine official El Niño years and their intensity:

El Nino history chart
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So, it hasn't been that long since we've see an El Niño year, but being given a 70% chance of one occurring this upcoming winter season is an interesting thought.

NWS/NOAA
NWS/NOAA
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What does this mean for Montana? Here's what NOAA says EXACTLY:

During an El Niño, snowfall is greater than average across the southern Rockies and Sierra Nevada mountain range, and is well-below normal across the Upper Midwest and Great Lakes states.

US Climate Data
US Climate Data
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This quick video explains El Niño conditions and trends: