Winter: The Coming Highs and Lows | Environment
The cold air coming to the Midwest and Northeast over the next 10 days will come in two or three surges with a spell of modestly milder air coming after each surge. This will result from the NAO going negative (please see our first blog in December for terminology explanations) during a developing +PNA pattern. This will allow Siberian air to cross over the North Pole, rush through Canada and then enter the United States via potent arctic fronts.
The –NAO appears likely to have resulted from the stratospheric warming event that we detailed several weeks ago. The result is going to be more typical winter conditions across the northern third of the country over the next one to two weeks, including air that is colder than normal more times than not and enhanced risks of accumulating snow. For Rochester and the Finger Lakes this means more snow and more cold than we have seen so far this winter, not that that is saying much.
But the various super computer model ensembles show that the “cross polar” flow is not going to be maintained much beyond the next ten to 14 days. After that the coldest air from atop the globe will be targeting Alaska once again and not the lower 48 States. This, in turn, will mean moderating conditions for areas that previously will have experienced the relatively harshest conditions of the season to date. In fact, there could be quite an eastern thaw during the last week of the month.
So, what then?
As you know, we have said for some time that IF winter is going to really roar for an extended time in the Rochester area it is most likely to do that in late January and February. We still believe that (for February, not so for late January). This is partly due to chatter in the meteorological community about another stratospheric warming event that is coming and partly due to the fact that so far, our analogue winter outlook is working out very well.
In the meantime, winter weather buffs around here will have to be satisfied with bursts of snow and cold that will be briefly intense but that will also alternate with spells of modest warmth.