ByMike Stunson,

Forbes Staff.

Natural gas prices soared on Tuesday for the second straight day ahead of a major snowstorm expected to impact a large portion of the United States, suggesting the market is bracing for potential supply disruption at power plants.

Natural-gas futures — which react quickly to weather forecasts and supply risks — rose about 9% Tuesday and had a similar bump Wednesday morning, jumping to $3.53 after ending the previous week at $2.70.

Other markets showed 50% growth in two days, Bloomberg reported, signaling the makings of the “biggest weekly gain in over 35 years” for natural gas futures contracts, agreements that lock in today’s prices for natural gas to be used months later to heat homes.