https://grist.org/energy/railroad-strike-coal-power-shortage/

From the article:

"The industry’s reliance on rail has proven to be a constraint even before the recent union disputes. A railroad industry labor shortage has already led to thinner and less reliable rail service, hampering coal producers’ ability to move their products aroundand reducing coal stockpiles at power plants around the country. A survey from the National Coal Transportation Association earlier this year found that around 80 percent of utilities said they’d missed coal shipments thanks to faulty rail service. A prolonged rail shutdown would supercharge that dynamic, forcing coal miners to hold on to more of their product. 

“Coal stockpiles are already at historic lows in the United States,” said Ward. “Any further interruptions could be disastrous for power generation. In the good old days, it wasn’t uncommon for utilities to have a 60- or 90-day supply of fuel, but I don’t know anybody who has that luxury now. If it became an extended strike, the consequences could be dire.” Should utilities burn through their stockpiles, they’ll have to slow down generation to save supply, which could lead to power shortages during times of peak demand. Prices would jump for as long as the supply backlog lasted.

The worst-affected places would be states like West Virginia and Missouri, which generate around 90 percent of their electricityfrom coal and don’t have the opportunity to switch to natural gas on short notice. Even states with large gas supplies will struggle, though, since gas markets are also tight as producers export large quantities of gas to Europe."