Hot day turns to heavy rain threat

Another scorcher today with high temperatures ranging from 87°-92°, but of course it's not the heat....it's the humidity. Dew point numbers already this morning are in the 70's (a very muggy air mass) and are expected to rise into the middle 70's by the afternoon.

With a ridge of high pressure in place over the Great Lakes, we've kept the southerly low level flow. With high dew points and lots of heating, the atmosphere over northern Illinois and southern Wisconsin is becoming unstable. This could support an isolated storm or two this afternoon, but it's the thunderstorms later this evening and overnight that we'll be watching.

Surface low pressure sliding east over the Northern Plains is beginning to flatten the ridge that is overhead turning it more zonal (from west to east). This is actually going to slow down the cold front, which could lead to heavy rain falling over the same area. There are high amounts of moisture available and heavy rain is likely tonight and into tomorrow morning. There is a
Flash Flood Watch already in place for eastern Iowa, where the heaviest rain is the most likely.

High pressure moves in this weekend, with drier air moving in. Temperatures fall then into the low 80's through next week!