Winter -- better late than never...? | Environment
Here is one metric provided by the National Weather Service relative to the snow drought in Rochester, which I think is symptomatic of much of the country: In a normal winter, there are 76 days where the ground is covered be at least one inch of snow. The record for the least amount of such days is 35. So far this year there have been just 9 such days! (BTW, the record for the least amount of snowfall is 11 inches which was set in the winter of 1932-33. That record is safe.)
The other city we included in our analogue forecast for the Great Lakes was Chicago. And there certainly has been a snow drought there, as well. The total seasonal snowfall to date in Chicago stands at 13.9 inches. The normal snowfall to date is 22.9 inches and by this time last year there had been 50.1 inches of snow.
The numbers in Rochester and Chicago are consistent with what our analogue forecast suggested. So far, so good.
Now the question is will the month of February also verify? (Recall we have suggested, since December, that IF the winter season were to turn truly cold and snowy it would be late, focusing on February and even March.)
And we think that is still possible.
Let’s see where we stand (please refer to our first post in early December to refresh your memory, as needed, relative to the terms referred to below):
The AO and the NAO while trending negative in the short term go toward neutral mid and late month.
The MJO from most modeling moves into a very favorable phase for eastern chill.
The PNA is generally positive but will be trending neutral or negative later in the month.
Recent activity on the sun appears to be passed and right now the sun is looking virtually spotless.
The PDO remains negative.
The ensembles are generally suggesting that after a deep eastern trough delivers very cold air to the Northeast this weekend, the average trough position for the remainder of the month will retrograde westward and align along the Mississippi River while still keeping a moderately cold source region in play from time to time.
So, the lack of major high latitude blocking (as indicated by the lack of a strongly negative AO and NAO) moving deeper into February is a forecast concern and casts doubt on the staying power of any cold incursions. (For example, it is clear that the cold coming this weekend will not have staying power.)
But I feel that the idea of bigger, wetter and snowier storms in the central and eastern states along with an over all colder (but not extreme) national look is still on track for the remainder of this month based on the projected average position of the trough.
Thus it appears, in the absence of strong blocking but in the presence of the other factors, that there is some very cold air yet to come this winter, but that it may not be the kind of cold that can resist some moderation. But also note that these moderating conditions won’t be like those of the winter to date, which have largely been pleasant and free of major precipitation (recall not only are we in a snow drought, but there has been little in the way of sleet and freezing rain). I think the moderating conditions between cold shots will have storms with the full range of precipitation from rain to ice to snow. Finally, if cold air were to lock in for more than 2 or 3 days, it appears the best chance of that would be later February and March, likely after a major storm eastern storm.
So, in summary, from this upcoming weekend on well into March, there will be potent cold shots here, but some will be followed by quick and substantial reversals; there will be a more active storm pattern; and, the risk of significant snow and icing events will be greatly increased over what we have seen so far this winter. So let the fun begin!
One more point, as to whether or not Rochester is going to avoid setting a new record for the fewest days with snow cover, it will take maximizing the coming active pattern before the sun gets too high in the sky. And that may take quite a snowy March (and April?) I know there are some winter weather fans who are counting on it.