Arctic air returns but what about snow?
By any stretch of the imagination this has been a strange winter so far. We still have a long way to go, but December 2011 was 6.8° warmer than average with only 1.1″ of snow measured officially at Mitchell Int’l. (MKE) So far this January has also been mild, with highs in the 40s today (Thursday) and tomorrow (Friday, January 6, 2012). For the snow season of 2011-2012, only 1.7″ of snow has fallen at MKE. The least snowiest snow season was 11.3″ in 1884-85.
As I have written about previously and mentioned on my YouTube channel, the main reason for the warmth and lack of snow in much of the country is the positive phase of the NAO. Read more from one of my previous blogs HERE and watch my YouTube video on the NAO HERE.
It now appears that the NAO will trend towards zero or perhaps briefly dip into the negative phase beginning next Thursday, January 12, 2012. This trend may continue for 10 days. However, a major caveat here: this NAO forecast is based on the long range global computer model known to meteorologists as the GFS.
Figure 1: upper air pattern across North America so far this winter.
Figure 1 shows the upper air flow pattern for much of this winter. The positive NAO has kept the polar jet stream mainly north of Wisconsin, traveling west to east along the Canadian border. Weak storm systems starved of moisture travel along this path. We stay mild and dry while the arctic air remains in central Canada.
Figure 2: upper air pattern that would be favorable to a large snowstorm for Wisconsin.
Figure 2 shows the upper air flow pattern for winter storms in Wisconsin. We had this set-up several times last winter, including the incredible Ground Hog Day blizzard of 2011. Next week we could have a similar upper air situation with one major exception. The main subtropical jet stream will be positioned farther east, meaning the east coast and northeast U.S. see a large rain and snow event but we just received the cold air.
Figure 3 shows the GFS numerical prediction model solution for next Thursday, January 12, 2012, based on the 18z Thursday, January 5, 2012 model run.
Figure 3: GFS numerical model output for next Thursday, January 12, 2012, showing a dry day with cold and wind for Wisconsin, and a rain/snow event for the northeast U.S.
Cold air doesn’t always mean a lot of snow for us, and this could be the case late next week: cold and dry. However, as forecasters we need to be vigilant and watch for the eventual track of the southern storm. If it tracks farther north and west, Wisconsin could see a pretty good shot of snow. But that looks doubtful.