Friday, November 24, 2017, 16:29 - An abundance of winter weather is expected across the northern half of the country during the upcoming winter season. However, across the South temperatures are expected be warmer than normal with below normal precipitation.
The contrasting temperatures patterns across the country during winter are one of the signatures of La Niña, which is currently developing. La Niña features cooler than normal ocean water temperatures near the Equator in the Pacific Ocean, in contrast to El Niño which features warmer than normal ocean water temperatures in this region.
There are many other factors that are considered when developing a winter forecast, but this year the overwhelming majority of these considerations are pointing to the same pattern. The contrast in temperatures and an active storm track into the Pacific Northwest will help to fuel an active winter across the northern half of the country, including the Great Lakes and the Northeast.
This winter is also expected to feature changeable temperature patterns. At times the focus of the coldest weather will be across the eastern half of the country (especially early in the season), but at other times the focus of the coldest weather will shift to the Pacific Northwest, resulting in periods of milder weather in the east. Under both patterns, the Northern Plains will have the potential to be colder than normal, but even this region should experience a period of milder weather.
Here is a look at what the changeable and contrasting weather patterns will mean for each region of the country this winter.
Southwest
Milder and drier weather is expected dominate the winter season across this region, especially in contrast to last year which brought record breaking rain and snow to much of California. However, there is still the potential for a few periods of stormy weather. An active storm track is expected for northern California and at times this could track further to the south into central and even southern California. With warmer than normal sea surface temperatures across the subtropical Pacific ready to contribute abundant moisture to Pacific systems, the potential is still there for a couple higher impact rain (and mountain snow) events.
Northwest
A stormy winter with above normal precipitation and near normal temperatures is expected for most of the region, but trending colder than normal to the northeast. This winter will not be as severe as last winter but an abundance of snow is expected for ski areas. While winter weather started early in November, it looks like extended periods of cold weather will be more likely during the second half of the winter season with a tendency towards milder conditions during December.
Northeast, Midwest & Eastern Great Lakes
This region is expected to see periods of high impact winter weather with colder than normal temperatures and an active storm track which should bring above average snowfall to much of the region. There is also a heightened threat for freezing rain, especially across interior New England.
However, the Northeast also has the potential to see extended periods of mild temperatures (an extended thaw) during the winter, helping to offset the periods of cold weather. Winter temperatures are expected to tip to the warm side of normal close to the Eastern Seaboard due to warmer than normal ocean temperatures in the Atlantic and a more inland storm track should which will often draw milder air into this region.
South
A warmer and drier than normal winter is expected to dominate the winter season across this region. However, we still expect a few shots of arctic air with the threat for couple of freezes along the Gulf Coast. Despite the drier pattern the region also has the threat for a couple of severe weather events.
Northern Plains, Upper Midwest, & Western Great Lakes
A cold winter is in the forecast across this region, though a significant mid-winter thaw is expected. Above average precipitation is expected for much of the region, which should help replenish soil moisture in the regions that experienced a drought last summer.
Early Spring?
While it is too early to have very much confidence in weather patterns for the spring, when we look back at years in the past that had global patterns similar to what we are currently seeing (such as a developing La Niña) there is a remarkable consistency - spring does not come early across the northern half of the country.
Of course a lot can change between now and then, but our preliminary thought it that the regions that experience the coldest and snowiest weather this weekend will see those conditions persist for much of March.
However, across the South, the very region that gets off the easiest this winter should also see an extra early arrival of spring weather. But, this is not all good news as a mild winter and an early start to warm spring weather elevates the concern that blossoms could bloom before the threat for a freeze has ended for the season.
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