NOAA forecasts a warmer winter for much of U.S.

·3 min read

The National Oceanic and Atmospheric Administration is forecasting a cooler and wetter-than-average winter from the Pacific Northwest to the Great Lakes, with the Northeast and New England regions seeing warmer-than-average conditions but equal chances of above or below average precipitation, including rain and snow.

In its annual winter outlook released Thursday, the agency predicted a warmer-than-average and drier-than-average southern tier (from the Southwest to the Southeast).

A stormy northern half of the country with a warmer and drier southern half is a calling card of a La Niña weather pattern. When a La Niña pattern is in place, it starts with cooler-than-average water temperatures over the eastern tropical Atlantic. This is one of many factors in a recipe that ultimately causes the jet stream, the "highway" that steers storm systems, to surge to the north. The result is an active storm track stretching from Alaska down through the Northern Plains and the Great Lakes while warmer air surges across the South.

For snow lovers across the Northeast and New England, La Niña does not often favor a snowier-than-average winter. That's because the storm track normally tracks inland over the Appalachians (called inside-runners), as opposed to just off the East Coast like classic coastal storms and nor'easters. The inside track typically means more rain or wintry mix than pure snow.

This pattern often results in prolific rain and snow for the Pacific Northwest while the Southwest misses out on most of the rain. With more than 90 percent of the western region in drought, any place that can get rain will take it, but unfortunately areas experiencing the most exceptional drought could miss out.

Some good news from the winter outlook is that Northern California could get some of the expected rain and snow. It's already happening, in fact, with a series of storms set to impact the Pacific Northwest and much of California through the weekend.

Successive atmospheric rivers, defined as plumes of tropical moisture which feed storm systems, are set to combine with Pacific storm systems to produce up to 10 inches of rain and up to 8 feet of snow to parts of the Sierra through Tuesday.

The back-to-back storms could even be historic. The National Weather Service in Reno, Nevada, mentioned this could be the strongest October storm to impact the region on record (going back to 1979).

Meteorologists caution that while La Niña can have a strong influence in seasonal weather, it is just one of many atmospheric factors that ultimately determine the outcomes of winter weather. It's important to stress that while the outlook may predict warmer- or cooler-than-average conditions overall, there can still be extremes.

For example, last winter was also a La Niña winter, yet during the month of February, Texas experienced its worst cold outbreak in history. The event shattered both cold temperature records and snowfall records across Texas and other parts of the central and southern Plains.

Some notorious East Coast blizzards have also happened during La Niña years.

The big takeaway? NOAA's outlook is meant to provide a generalized 'big picture' of expected conditions for the months of December, January and February for planning purposes but it's important to stress the high uncertainty in the variability of day-to-day weather.

One wild card to watch out for will be any Arctic outbreaks associated with a weakening of the polar vortex that could send lobes of bitterly cold air south into the continental United States. Events like that are nearly impossible to predict on a seasonal scale, but can wreak havoc on short-term forecasts and sensible weather impacts such as cold outbreaks and major winter storms.

So, bundle up, get those winter survival kits ready, and stay tuned!

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