What weather is ahead for harvest?
The next few days will generally be quiet with seasonably cool weather. Some showers are possible across Illinois Thursday. However, most of this will be light. The exception is northeast Illinois where 0.1 to 0.25 inch could fall.
Temperatures, compared to what we have experienced so far this October, will feel downright chilly with 50's across the western MIdwest through Saturday, closer to 60 farther east. A brief warmup may occur Sunday before more cool weather is possible next week as a large upper-level trough digs south through the region. No major rainfall events are anticipated in the long-term.
This is quite an abrupt change from the prolonged and often extraordinary warmth of the late summer/early fall. In fact, looking at this year's growing season, we had quite a remarkable and variable weather pattern.
From cool and wet weather in May and June to dry and hot weather in August and September, we really saw it all. What could possibly explain this volatility? For one, the ENSO has been consistent the past several months. We have seen weather both characteristic of typical El Nino and La Nina patterns, a possible result of the current Neutral ENSO stage.
However, the NAO, which typically has weak summer correlations with Midwestern climate, did offer some clues. The NAO was slightly negative July into early August, then went sharply positive in mid-August, nearly coincident with the arrival of our hot and dry pattern. Here it stayed positive until more recently, and now it has taken a negative dive, just as below-normal temperatures have arrived.
It sure has been a roller coaster of weather patterns with extreme heat across the Plains and Midwest August into September, followed by an early-season blizzard across the Black Hills of South Dakota, of which tens of thousands of cattle perished due to deep snow and remarkably strong winds. As we look forward, should we expect more extreme climate variability?
There are some long-term signs in the upper levels that ridging in the Eastern Pacific will maintain a trough across the central U.S. Another key indicator, known as the Madden-Julian Oscillation (MJO), is forecast to transition into Phases 8 and then eventually 1 over the next few weeks. This typically yields below-normal temperatures for the central U.S. Thus, it does appear a more stable climate regime is on its way for much of the central U.S, with below-normal temperatures to finish October and start November.