"We don't expect a repeat of the record-breaking cold temperatures of November-December of last year, but this winter should be cooler than the warm winters of the late 1990s," said Scott Gudes, head of the National Oceanic and Atmospheric Administration.
In many parts of the country, the National Weather Service said Thursday, the weather will be similar to last winter. Sharp swings in temperature and rain or snowfall are likely with a threat of heavy lake-effect snows and Nor'easters.
This winter, better technologies will help National Weather Service forecasters pinpoint extreme weather, said National Weather Service director Jack Kelly.
He said the nation is likely to experience large temperature and precipitation swings during the winter.
Among the reasons for the expected variability, forecasters said, is the absence of the El Nino and La Nina phenomena. El Nino and La Nina involve either unusual warming or cooling of the water of the central Pacific Ocean. When they occur, it has a strong effect on climate in the United States and elsewhere. With neither of those acting strongly, winter weather becomes more variable.
In addition, the Arctic Oscillation is expected to influence the number of cold-air spurts in the South and Nor'easters on the East Coast.
The Arctic Oscillation varies during the season, affecting the circulation of air.
When it is in a positive phase, the mid-latitude jet stream shifts to the north and there is an increase in the number of warm days over much of the contiguous United States. In the negative phase, the high-latitude air flow is blocked near Greenland, resulting in an increase in the extreme cold days, especially from the Great Plains to the Southeast.
"Citizens should prepare for the full range of winter weather," Gudes said.
The regional outlook for this winter includes:
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