Seven states saw record snowfall yesterday from Texas to Illinois. Records were set for snowfall at both O’Hare and Midway on Tuesday. 3.6″ of snow fell at Midway, a new record for February 26th. O’Hare’s 4.8″ was also a record for the date.
So far this month we have seen 14.9″ of snow at O’Hare or 81% of our entire snowfall for the season. The weather pattern has been more active this month and now there are indications it could remain active into March. The North Atlantic Oscillation Index is one of the forecast indicators that we look at to give us a hint of what is to come. The index forecasts the fluctuations in pressure fields between the Icelandic Low and the Azores High. Bottom line is a positive index caused by greater pressure differences tends to result in relatively milder and dry conditions here. A negative index means a weaker Icelandic Low and Azores High which allows for more frequent intrusions of colder air and a more active storm track.
The image below shows a forecast for a negative index forecast for the next 10 days leading me to believe we can expect colder than average temperatures and a greater frequency of storms compared to average.
The Climate Prediction Center’s 6 to 10 day outlook seems to support the colder than average part of the forecast. We have a 50% or greater probability of seeing below average temperatures for the forecast period of March 4th through March 8th (see graphic below).