Recent market tightness could herald “violent price upside” for U.S. natural gas this winter if temperatures are colder than average, according to analysts at Goldman Sachs Commodities Research.

In a recent note to clients, Goldman analysts led by Samantha Dart, Damien Courvalin and Huan Wei said bullish Energy Information Administration (EIA) storage data and strong power burns in August have added to “existing winter storage concerns, further increasing the winter risk premium priced in the market.”

Henry Hub prices “have broken out of the $3.85-$4.15/MMBtu trading range seen since late July,” rallying about 20% over the past week to $4.71 as of last Friday, they noted.

“The move was initially triggered by a large tight surprise in storage injections...