It's been no secret that the Winter of 2019-20 has been quite mild for many places. With the exception of areas near Chicago into northern New England, most have also had below normal snowfall season-to-date. The big question is, will any more snow fall before the end of winter? We'll answer this question later in the blog, but let's dive into the pattern a bit first.
Since January, the polar vortex has been very strong from the ground up into the stratosphere around the North Pole (an extremely positive arctic oscillation or AO). This has bottled up arctic air in the upper latitudes and hasn't let much cold air seep into areas east of the Mississippi. This pattern also keeps most of the Midwest and Northeast milder than normal with fast moving systems. Although enough cold air has met up with these systems to produce wintry weather in Chicago and northern New England, many further south have been dealing with mixed events that change quickly to plain rain. In this set-up, it's quite hard to get slow moving coastal storms to dump lots of snow throughout the Northeast.
However, we do see a little hope if you're looking for more snow this winter. There are two factors we are watching: The first is a pattern of thunderstorms in the deep tropics that influences the location and intensity of the jet stream. When these thunderstorms occur in the Western Hemisphere (much of the central and eastern Pacific, east through the Atlantic and Africa) it favors colder intrusions into the central and eastern United States; this is expected to occur late-February into early-March, which adds some colder and snowier "potential" into the outlook. How much this potential is realized likely hinges on the polar vortex. Every year, the polar vortex begins weakening quickly at some point in March; if this occurs early enough in the month, it may allow the pattern to respond better to the colder signals. If it remains strong well into March, we may see more of the same, which would mean a generally mild pattern with limited snow in the eastern U.S. for much of the month. Either way, we look to remain in an active pattern with frequent precipitation...whether or not there ends up being enough cold air for some of this precipitation to fall as snow remains to be seen. Overall, locations from the Midwest to the Great Lakes and New England appear most favored to see snow in late February and March, with a little bit more luck needed for substantial snow in the Ohio Valley and Mid-Atlantic.
