After a frigid February, many folks across the Midwest are dying for some warmer weather. Thankfully, a recent shift in the pattern has led to mild temperatures during the second week of March. So the question is, are the milder conditions here to stay? Unfortunately, the answer appears to be no.
The main culprits of the recent cold across the region have been the Pacific North American Pattern (PNA) and the Eastern Pacific Oscillation (EPO). While the geographic positioning of these two teleconnections is over Western North America, they both have important implications for the Midwest. During the positive phase of the PNA and the negative phase of the EPO, a large ridge of high pressure is situated over the Pacific Northwest. This promotes a broad trough of low pressure across the eastern half of the country. As a result of this set-up, frigid air is able to usher south from the arctic region into the US, as seen below.
Our current pattern leading into mid-March has been a more zonal (west to east) flow, thus allowing more seasonable air to overspread Illinois, Indiana and Ohio. However, the aforementioned +PDO/-EPO regime is expected to redevelop just after St. Patrick’s Day. This in turn will favor below average temperatures to return. Luckily with higher sun angles and longer days on our side, the last two weeks of March will not feel nearly as cold as it did in February. But, we will likely still have a few wintry threats as the calendar approaches April.
So with the +PDO/-EPO in command, chilly conditions will be favored to linger through the early part of spring. At this point it appears likely that this pattern will stay entrenched at least through the next month and a half. Thus we won’t be ruling out any snowflakes even as we move in April. The best opportunity for a late season event will be for folks up in Chicago. But there will even be a threat for those in Indianapolis and Ohio.
As mention above, this redeveloping chilly pattern is expected to hold on through much of April. But don’t worry, there is a light at the end of the tunnel. Seasonable conditions are favored to return to the region by the time we head into May. This of course is welcomed news for those looking forward to spending some time outdoors; enjoying the beautiful weather that spring has to offer.
