CHICAGO – The March 2023 monthly temperature and precipitation trend forecasts are in from the National Weather Service’s Climate Prediction Center, and if the agency’s prediction verifies, the month could reverse the recent trend in which above-normal temperatures have dominated in recent months.

Despite Friday’s chill and the prospect of a below-average daytime temp, 38 of the past 48 days have finished above normal. Today is the first day of the past 14 likely to produce a below-average temperature.

But here’s what is interesting as we look toward what march may have in store. Long-range forecasters are interested in predictions of what may happen high above the north pole in the coming days & weeks.

Models are predicting what’s known as a sudden stratospheric warming event, which is often referred to as an “SSW”. This is when temps warm suddenly high above the North Pole in the stratosphere soar 4 to 12 miles above the North Pole.

SSW events can see stratosphere temps warm as much as 120 degrees in a matter of days. Such dramatic warming has been known to disrupt the polar vortex and split it in two. As this happens, chunks of cold air in the lower atmosphere can plunge southward into the mid-latitudes where we in Chicago are located.

This often leads to the buckling of the jet stream. “Wavy” jet streams can tap arctic air and tug it southward.

But here are the issues that long-range forecasters face: It’s not certain precisely where in the mid-latitudes the cold air might end up. It could crash down into the eastern rather than the western hemisphere. At the moment, models, while predicting a sudden stratospheric warming event, haven’t settled on the impact such high-altitude warming might have here in the lower portion of the atmosphere.

No two “SSW’s” are precisely alike as events like the ongoing La Nina can play a role in modifying any southward surges of cold air. So its safe to say there is uncertainty about where any cold surges may end up in the coming weeks. Long-range forecasters view the high certainty of a sudden warming of the stratosphere as a reason to pay close attention to more specific indications that cold air is on the move and will look for indications from weather forecast models that dramatic high altitude warming will impact events in the lower atmosphere, and if and when that happens, what is indicated in terms of where the cold air may end up.

Here’s what climate prediction center forecasters are saying in the discussion of their March 2023 projection (it’s a bit technical, but weather enthusiasts and students of sudden stratospheric warming events may find this interesting):

“The eventual impact of the SSW for the U.S. is considerably uncertain. The fact that short term forecasts are in very good agreement that a SSW will occur in the next few days is enough to a slight degree further elevate chances for below-normal temperatures on its own most likely later in the month. The SSW and so weakening of the stratospheric polar vortex and more variable/meridional jet stream makes the potential for arctic air outbreaks in the northern hemisphere more likely in March.

“However, there is high uncertainty with SSW events whether impacts will significantly affect the troposphere (i.e. AO index) to a sufficient degree to impact the eventual observed anomalous temperature. Currently the GFS and ECMWF guidance does not have the warming impacting the surface through the start of March, but this could happen later in March. Moreover, even if so, it is not a certainty that any arctic air outbreaks primary center of action will be in the western hemisphere, rather it is possible to more strongly impact Asia or Europe.”

Research shows sudden stratospheric warming events are hardly everyday events, occurring on average 6 times per decade in the northern hemisphere.

Read more about indications of the potential for sudden stratospheric warming in this NOAA release: