We have already started to see garden-variety (non-severe) thunderstorms moving in from the southwest to northeast from Nebraska. Some brief downpours have been occurring with the strongest of these cells. Sioux Falls received up a quick few-tenths of an inch, along with a 58 mph wind gust at the airport. Limited sunshine earlier in the day helped destabilize the atmosphere, but these afternoon thundershowers have also helped to remove some of the available moisture at cloud level.
Tonight we will see a storm system moving through Nebraska move northeast into KELOLAND, producing a broad area of thunderstorms, some of which be strong or severe.
Much of KELOLAND has a severe weather risk overnight. Sioux Falls will have a brisk easterly wind tonight, with a low of 60 degrees. Lows will be in the 40s with a strong NE wind to the north and west.
Tomorrow – especially the early morning hours of tomorrow – we expect widespread rainfall, possibly heavy. Temperatures will remain warm, around 70, in Sioux Falls and SE KELOLAND. With a brisk northeasterly wind and cloud cover, northern and western South Dakota will mainly be in the 50s. Rapid City will be a little cooler.
How heavy will the rainfall be? Much of the eastern half of KELOLAND will see one to two inches of rain tonight and tomorrow.
Sunday also looks cloudy and rainy and cooler. Rainfall looks to be on the light to moderate side, but north winds will keep afternoon temperatures in the mid to upper 40s, which is more than ten degrees below normal. Rapid City can expect a mix of rain and snow.
Monday will be our “in-between” systems day. Temperatures will recover into the 50s. But more precipitation will occur, and Rapid City could even get a few inches of snowfall Monday night and Tuesday.
Eastern KELOLAND will have another breezy day on Tuesday as the next system comes in late in the day. Highs will be in the 50s. It could be a second round of widespread rain across KELOLAND Tuesday afternoon through Wednesday.
Thursday will give us another break from rainfall, with temperatures remaining in the upper 60s to low 70s. But Thursday night and Friday morning we expect another round of rainfall.
Unfortunately it appears this cool weather pattern will hang around, with colder than normal temperatures fairly likely through the end of May.