A Flash Flood WATCH has been issued for the entire Quad Cities region through 1am Monday. Additional heavy rainfall in the next 24-hours is likely going to increase the amount of flooding that we see in our hometowns, especially in fields.
In just the last 48 hours alone several locations have picked up more than three to as much as six inches of rainfall stretching in a line from Iowa City to Muscatine to just north of Galesburg. It will be these same areas that see the threat for additional heavy rainfall through Sunday evening.
The current setup involves two potent sources for moisture, the Pacific courtesy of Tropical Storms Mario and Lorena, along with the leftover moisture from Imelda that developed in the Gulf of Mexico. Both of these sources are streaming in our direction and will actually combine forces to drive a very unusual amount of moisture that showers and storms will utilize to lay down locally heavy rainfall.
The amount of available moisture looks to be maximized early Sunday morning. That’s when precipitable water (a value we use to measure how much rain could fall in just one single thunderstorm) reaches above the two-inch mark. This is represented by the darker green shading on the map above. Much of the Quad Cities remains in this extremely high moisture content air mass for a good chunk of Sunday. Unfortunately, the highest values are concentrated right overtop areas that have already seen extremely heavy rainfall in the last week. It’s these areas, especially along and south of I-80, that will be vulnerable to Flash Flooding through Sunday evening.
Showers and storms will come in waves, the heaviest in the morning, with moderate to locally heavy rainfall continuing in the afternoon. In all, many locations will exceed two inches of more stretching from Mount Pleasant Iowa up through Geneseo and Sterling/Rock Falls. Isolated higher amounts of more than four inches are likely in isolated locations. Because the ground is saturated and the rate of rainfall will be quite high, flash flooding is likely.
The threat of severe weather is extremely low because our atmosphere is so saturated with moisture. A few lightning strikes will be possible at times.
The heavy rainfall threat will quickly diminish after dark Sunday evening. Thankfully we’ll get a couple of days to dry out before the next batch of rain arrives midweek.
All of this heavy rain will eventually impact rivers next week. We’ll have a better grip on how significant those impacts will be once we get a feel for how much rain has fallen during this event. Stay tuned!
Meteorologist Andrew Stutzke
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