A polar vortex similar those that sent temperatures plummeting more than once last winter and again last month could send an early chill through the Northeast in September, according to forecasters at AccuWeather.com. It has the potential to alter natural gas demand in some of the nation’s most populous centers during the transitional month.

Autumn will begin with days of sunshine and temperatures above normal in New York, Philadelphia and other cities in the region, but the polar vortex is expected to make short, sporadic appearances, according to meteorologist Paul Pastelok.

“There could be a significant shot of chilly air that comes across the Great Lakes region and into the interior Northeast sometime in mid- to late-September,” Pastelok said. After that taste of the polar vortex, weather should turn a bit warmer in the Northeast in November, the forecaster said.

“Temperatures will not be as extreme in November when compared to last year, but October could be an extreme month,” Pastelok said. October could also bring snow and cold weather to the northern Plains and parts of the northeast Rockies, he said.

“December could get kind of wild due to the very active southern jet stream that is going to provide the moisture for bigger snowstorms. The Northeast could have a couple of big storms in December and early January.”

The winter of 2013-2014 was one of the coldest to hit the U.S. Northeast in years, with massive polar vortexes bringing freeze-offs, higher natural gas prices, and propane shortages (see Daily GPI, May 2; March 26; March 7). The season was responsible for the highest prices on record in NGI’s Daily Gas Price Index, with trading points such as Transco Zone 6 Non-NY hitting an all-time high of $140/MMBtu (see Daily GPI, Jan. 21), and total working gas in underground storage hit a five-year low of 822 Bcf for the week of March 28.

A summertime version of the vortex last month brought with it record low temperatures and tumbling physical natural gas prices (see Daily GPI, July 16).

Forecasters at Weather Services International (WSI) have said they expect temperatures in the Northeast will average cooler than normal this month, but the East and West can expect warmer-than-normal weather to dominate in September and October (see Daily GPI, July 21). For much of that time, below-normal temperatures are expected to be prevalent from the northern and central Rockies, eastward through the Great Lakes and Ohio Valley, WSI said.