Following the trend of the last few years, people in the northern and eastern United States might need to don their winter jackets a little earlier than normal if Weather Services International’s (WSI) fall forecast comes to fruition.

The Andover, MA-based weather forecasting service said Tuesday it expects the October-December period to average — referencing a standard 30-year norm (1981-2010) — cooler than normal in all of the northern and eastern United States, with above-normal temperatures confined to the Southwest.

“The primary ocean signals suggest the late fall and early winter period will resemble those of the last three years, with an early start to winter in the eastern U.S.,” said Todd Crawford, chief meteorologist at WSI. “While October should be relatively mild across much of the U.S., below-normal temperatures will become more common in the eastern U.S. in November and across all of the northern U.S. by December. The combination of the newly emerging La Nina event and the continued trend toward North Atlantic atmospheric blocking…both support this hypothesis.”

For October, WSI expects the Northeast, North Central, South Central and the Southwest — except coastal California — to experience warmer-than-normal temperatures, while the Southeast and Northwest see cooler-than-normal conditions. With October looking warmer than normal in some key energy demand regions, natural gas demand for power generation could remain stout.

Commenting on the October forecast, Paul Flemming, director of power and gas services at Energy Security Analysis Inc. (ESAI), said that while October is historically a shoulder month for electricity demand, generator maintenance during October results in a lower availability of coal and nuclear plant capacity. “This gap is filled by gas-fired generators and tends to increase the relative gas demand for power, despite lower overall demand for power,” he explained. “With warmer-than-normal temperatures expected in ERCOT, MISO, PJM, New York and New England during October, above-normal seasonal power demand early in the month and the continuation of the generation maintenance period should keep gas demand firm and gas prices from collapsing as the injection season nears its end.”

Due to slightly higher demand in October, Flemming said he expect gas inventory levels “to have trouble challenging last year’s record of 3,840 Bcf by the end of the injection season.” ESAI’s end-of-season storage forecast currently stands at 3,650 Bcf.

The arrival of November is expected to plunge the Southeast and Northeast — except Maine — into colder-than-normal conditions, with the rest of the country experiencing warmer-than-normal readings.

Flemming said the lower early-season gas demand, due to warmer-than-normal temperatures in the North Central and Northwest regions, will be offset by colder-than-normal temperatures in the Northeast and heating demand for gas will likely run slightly below normal in November. “Henry Hub natural gas prices can be expected to pick up slightly from October shoulder season levels as early-winter heating demand begins,” he said. “Gas inventory levels at the start of the withdrawal season should be slightly lower than last year.”

During the last month of the current forecast is when the real cold should begin, according to WSI. The entire country is expected to be colder than normal during December except for the Southwest, Florida and Texas, the forecasting service said.

“In December, much-colder-than-normal temperatures across the northern tier of the U.S. will result in much higher heating demand for gas,” Flemming said. “Typically, early-season cold weather indications are bullish for gas prices, as a long-term cold stretch starting in December could significantly reduce gas inventories. Power prices in the Northeast markets will be supported by colder weather, but warmer-than-normal temperatures in Texas and Florida will moderate power prices in those markets.”

WSI will release its first official 2011-2012 winter forecast covering December-February on Oct. 25.

©Copyright 2011Intelligence Press Inc. All rights reserved. The preceding news reportmay not be republished or redistributed, in whole or in part, in anyform, without prior written consent of Intelligence Press, Inc.