I’ve been getting this question a lot from my Meteorology students. The culprit for the arctic blast is our very warm March . Whenever a large portion of the U.S. has such warm temperature anomalies, it means that Canada was equally as cold. The zonal pattern that led to the anomalous warmth broke down since a zonal pattern is baroclinically unstable over time. The East Pacific Oscillation (EPO) and North Atlantic Oscillation (NAO) have also been somewhat well correlated since December.
When the EPO and NAO have both been positive (Dec 1- Jan 15 & Feb 21-Mar 31) the eastern U.S. has been very warm. When the EPO and NAO have both been negative (Jan 15-Feb 20 & April 1-current) the eastern U.S. has been very cold. Since the pattern has been well established since the fall, I would expect this recent cold snap to last about three weeks. The arctic blast will continue through the weekend, but a surface low will develop on Tuesday in response to the return flow from the Gulf of Mexico as the Arctic high departs to the east. This will be a short-lived warm-up (still below normal) as another cold high will push through mid-week. This mid-week high could produce some severe weather across the central plains and the mid-south and could be a snow producer in interior New England.
Beyond that, the ensembles suggest an unsettled pattern and cooler than normal pattern through at least April 20th. One of the WKU graduate students pointed out to me that the 312hr run of the GFS suggests snow for KY. While it is climatologically unlikely, as Shane Holinde, Chief Meteorologist of WBKO pointed out in response to my “April Snow in Kentucky” post, stranger things have happened.