Longing for rain? There's some good news in the forecast, finally! Chances for showers and storms will be on the rise, especially Sunday and Monday.
A high level of moisture, the likes of which we haven't seen in weeks, will surge into the region by Sunday evening. This will come along with increasing amounts of humidity, especially by Monday. One of the products we look at to determine the threat for heavy rainfall is how much "precipitable water" is currently sitting above us. This value is essentially how much rainfall one single thunderstorm could produce if it were to sit in one spot and complete a life cycle, or rain itself out. Anytime this value approaches or exceeds two inches, that is considered an extreme rainfall rate. By Monday afternoon and evening, the value easily exceeds two inches meaning any storm complex that can organize and move through will produce localized heavy rainfall.
Monday evening will really be the only heavy rainfall producing time period. Any showers and storms that form through Sunday evening will contain brief downpours, but nothing that will cause any issues with flooding. With Monday evening's storms, those will be the ones that produce areas of heavy rainfall quite quickly. Some areas could pick up two inches or more by the time this is all said and done Tuesday morning. Favored locations will be south of I-80.
As a complex of showers and storms organizes along a warm front late Monday afternoon in southern Iowa and moves east Monday evening, the potential for damaging wind gusts will begin to emerge. A lot of this will depend on how much instability can build during the day and the exact location of the front. As it stands now, areas south of I-80 have the best chance at seeing some of the strong storm activity Monday evening.
We'll continue to track this system for the remainder of the weekend.
Meteorologist Andrew Stutzke