Heavy Rain Potential

After a hot and humid weekend with several days in the 90's, the pattern is finally beginning to change. However, we have one more day of heat and humidity. Highs today are forecast to climb into the upper 80's and low 90's with heat index values again approaching 100°. But the upper level pattern begins to break down today and tonight, and as that happens a cold front will start to sink south into southern Wisconsin and northern Illinois. Ahead of this front, showers and storms will develop and sink south into the area.  Instability grows with increasing moisture ahead of the front, which will support heavy rain producing storms today and tonight.

Models differ on timing of when exactly the storms initiate, some develop convection around 2/3pm while others wait until about 6pm. I do think a few scattered storms will be possible by the mid to late afternoon, with then increasing coverage of storms this evening and overnight as the front sinks south.

By Tuesday the front will be positioned just south of the Stateline, but with another disturbance passing through the mid level flow, another round of showers and storms will be possible Tuesday. While its possible for a couple gusty storms today and tomorrow, heavy rain will be a bigger threat.

Some models bring rain totals up near 1-1.75" of rain, with totals near 2-4" across portions of Iowa! While the threat for rain lingers through the week and into the weekend, there does appear to be a mostly dry forecast for Wednesday and Thursday.