The story in the upper Midwest over the next 24-48 hours will be torrential rain and flash flooding. Already this morning radar has estimated over 6″ of rain in the Council Bluffs area. As of 8 AM 4.06″ has fallen in Omaha, NE, making it the third wettest September day on record. As you can see by the video above, that is leading to some flooding in the region. Bad news – more rain is likely through the day.
Heavy Rain Set Up
There are a couple features at play over the next 24-48 hours in the upper Midwest that is leading to the heavy rain and flood threat. First, remnant tropical moisture from the Southwest has been transported into the upper Midwest (the same moisture that brought a flash flood threat there earlier this week). That has helped increase atmospheric moisture levels to near record levels for this time of year. The moisture, along with a stalled frontal boundary will help provide a favorable environment for storms to form that could produce heavy rain over the next couple days in these areas.
Flash Flood Watches In Effect
Rainfall amounts of 1-3″ are possible in some locations over the next three days across the upper Midwest, but amounts could be heavier if stuck in a thunderstorm that won’t move. The best chance of storms across the region will be today and tonight. Due to the potential of very heavy rainfall in a short amount of time – a weak steering flow aloft will allow very slow movement with storms – flash flooding will be possible at times. Rainfall amounts may be 2-3″ per hour in the heaviest of the storms. The system starts to fall apart a bit on Thursday, so while there will still be storms around, we don’t expect them as widespread as they will be today and tonight across the region.
Rain Is Needed
The good news with this rain is that it is coming to some areas that do need it. Some areas of western Minnesota, eastern Dakotas and down into Siouxland are a good 1-2″ below average for this time of September. The bad news – they don’t really need it all at once, like what is likely over the next couple days.
(CHECK OUT YOUR FORECAST: wx.aerisweather.com)
– Meteorologist D.J. Kayser