The Ohio Valley and Great Lakes areas can expect temperatures to average cooler than normal over the next three months, while the rest of the country will have a warmer-than-normal summer, according to forecasters at Andover, MA-based WSI Corp.

“May has been a rather chilly month across most of the U.S. so far as the atmospheric pattern has changed to allow cooler weather to temporarily return to the southern U.S. This change in the pattern towards increased high-latitude blocking, or a more amplified jet stream, will likely persist and evolve into June,” said WSI Chief Meteorologist Todd Crawford. “Because of this, we expect the coolest part of summer (relative to normal) to be early, especially across the north-central and Great Lakes states. During the last half of summer, we think that the pattern will reverse with the potential for some significant heat to return to the northern U.S. by August.”

The Northeast (except western New York, Pennsylvania and Vermont), Southeast, South Central and Southwest areas will see warmer-than-normal temperatures in June, while the North Central and Northwest will average cooler than normal, WSI said in a forecast issued Monday. The warmer-than-normal temperatures in New England and the Atlantic and Gulf Coast regions “will provide a bullish underpinning for power prices,” Paul Flemming, Energy Security Analysis Inc. (ESAI) director of power and gas, said in a statement issued in conjunction with WSI’s outlook.

“However, cooler-than-normal temperatures will prevail in most areas of New York and PJM moderating prices overall in those pools. The cooler-than-normal temperatures in California and the Northwest, as well as ample hydro, will be bearish for power prices in those markets. Given the expected weather patterns and the return of most generation from maintenance, gas demand should be near normal for June,” Flemming said.

By July WSI sees cooler-than-normal temperatures moving into the East and South Central (except western Texas) United States, while temperatures are expected to average warmer than normal in the North Central area and in the inland portion of the Northwest. The relatively lower temperatures in key demand centers should result in lower-than-normal natural gas demand, Flemming said.

“The cooler-than-normal temperatures in the eastern regions will also result in lower power prices and less price volatility in the PJM, New York and New England control areas during July. Cooler temperatures will also translate into lower probabilities of heat events during July,” he said.

As WSI forecasters had hinted in their previous outlook (see Daily GPI, April 26), August promises to be warmer than normal nationwide (with the exception of the Mississippi and Ohio river valleys).

“Much warmer-than-normal temperatures in the key eastern and western markets will result in greater natural gas demand to meet power sector demand for cooling,” Flemming said. “The warmer outlook increases the chances of heat events in August that could result in price spikes in the Northeast and California markets.”

WSI is scheduled to issue its next seasonal outlook on June 21.

MDA EarthSat Weather has said a faster-than-expected transition to El Nino/Southern Oscillation-neutral conditions this spring suggests that the summer “will be approximately 14.5% cooler than last summer” (see Daily GPI, May 18).

WSI is one of a number of forecasters who have said they expect the 2011 Atlantic hurricane season to be more active than normal (see Daily GPI, May 20). WSI, which has predicted 15 named storms, including eight hurricanes, four of them intense, is scheduled to release an updated tropical storm forecast this week (see Daily GPI, April 27). The 2011 Atlantic hurricane season officially begins June 1.

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