On mornings like this one, a certain stillness descends upon the Big Sioux River corridor; the air is cloudy, dense with humidity approaching 93%, and seems to have been taken from somewhere much wetter. Right now, if you were standing anywhere close to downtown Sioux Falls, you would notice that the sky is low and gray, that the wind is coming from the southeast, and that the day seems to be building toward something. Yes, it is. By noon, thunderstorms and showers are predicted, and they won’t be mild. Before tonight ends, AccuWeather is warning that hail and damaging winds could occur.
It’s important to be aware of that combination, which is hail risk concealed within what might otherwise appear to be a typical spring thunderstorm. When warm Gulf moisture collides with whatever the northern plains decide to push south, the weather in Sioux Falls has a tendency to intensify rapidly in late May and early June. That collision appears to be especially fruitful this week. There is a 93% chance of precipitation on Wednesday alone, with strong thunderstorms predicted for the day and early morning. There’s more on Thursday. Storms Tuesday, Wednesday, Thursday, Friday, and more storms over the weekend make up the ten-day outlook, which reads more like a schedule of inconveniences than a weather forecast.
June is showing up with something to prove, and it’s difficult to ignore this. The atmosphere closes back up and the rain returns after Monday’s short window, which is the only truly calm day on the horizon with sunshine and temperatures approaching 30°C. This period of weather seems to be more established in the area rather than merely a passing system; meteorologists sometimes refer to this type of pattern as the atmosphere becoming “stuck.” Those who have experienced enough springs here in South Dakota will know it right away.
This week’s setup is especially intriguing because of the extreme temperature swing it contains. While afternoons are pushing toward 25°C and beyond under clouds that can turn dangerous in an hour, early mornings are dropping to about 16°C, damp and cold enough to warrant a jacket near the Falls Park walking paths. On paper, that range doesn’t seem dramatic, but when experienced over the course of a full day, particularly outside, it can take people by surprise. The perceived temperature is dropping toward 17°C in the morning wind, which carries a sharpness that doesn’t quite match the calendar, as the RealFeel temperatures are running lower than the actual.
As is typical for this region of the Great Plains, which is located within one of the nation’s more active severe weather corridors in the spring and early summer, the National Weather Service office in Sioux Falls is keeping a careful eye on the situation. Sioux Falls is directly in the area of concern for severe thunderstorms and additional downpours this weekend, which have already been noted in more general national forecasts for the Central States. The components are present: moisture, instability, and a forecast that consistently finds reasons to remain uneasy, but it’s still unclear whether any of this week’s systems will organize into something more serious.
This week, it’s important to remember that tree pollen is currently rated extremely highly throughout the region. The combination of high pollen and heavy moisture creates truly miserable conditions for anyone spending time outdoors between rain bands, such as at Terrace Park, along the bike trails near the river, or at any of the outdoor events that Sioux Falls summers typically fill up with. However, this detail is lost whenever storm coverage takes over. As of right now, the air quality is rated as excellent; however, this could change when storms start to kick up soil and debris.
If there is one bright spot in this ten-day period, it may be Saturday, June 6th, which is predicted to be partly sunny with temperatures close to 31°C, the first true hint of summer in a long time. It’s another matter entirely if it delivers. The weather in the plains has a tendency to change its plans at short notice.
