The rain machine has been up and running around the Midwest much of September. Below you can see the monthly totals and many spots roughly near and north of I-80 have seen a good 5-8 inches. 10-15 inch totals are showing up in NE Iowa, SW Wisconsin, and NW Illinois.
Departures of 2-4 inches are common with some locations exceeding the norms by an astounding 10 inches in far SW Wisconsin.
Too much of a good thing can be a problem and if the pattern gets established as models are suggesting, more heavy rain is in the future. Check this out, it's the 500mb jet forecast for Sunday.
A big heat dome has built into the southeast U.S. Strong subsidence will bring hot and dry conditions to that part of the nation. Meanwhile, the ring of fire on the periphery of the heat is aimed directly at the Midwest meaning rounds of showers and thunderstorms starting Friday and continuing on an occasional basis through next week. This is the GFS 16 day precipitation departures. It's very evident where the storm track exists by all the heavy rain shown over Iowa, northern Illinois, and southern Wisconsin.
PWAT's (water vapor) are again shown at mid summer levels well over 2 inches in my area
Below you can see the deep axis of moisture that extends from Mexico into Iowa and the Great Lakes. The model shows moisture levels up to 300% above normal. Note too how dry the air is over the NW third of the US and SW Canada where unseasonably cold air will deliver early season snows.
Over the next 10 days the EURO has this for snowfall. That is very impressive!
The temperature contrast across the nation is just as remarkable with departures that look like this October 2nd. Dramatic extremes on both ends of the spectrum.
Where the warmth and chill combat you can look for the establishment of a heavy rain breeding ground that I mentioned earlier. It's impossible to accurately lay out the axis of excessive rain but I can give you an idea of the potential that exists for some part of the central Midwest. This is what the GFS cranks out over the next 16 days. There's a max of 8.37" just southeast of Dubuque, Iowa. That's the region I showed you earlier that's already had 8-11" of rain this September.
The Climate Prediction Center is all in showing a broad area at risk of heavy rains to end September and start October.
Meantime, Wednesday and Thursday will be a pleasant days with sunshine and seasonal temperatures mainly in the low to mid 70s. However, return flow kicks in on a 50-60 kt 850 jet Thursday night ushering the next round of significant rains into the area. The potential exists for some spots to see more than an inch late Thursday night and Friday. Just the beginnings of what looks to be a very active 6-10 days of weather. Weird how similar this is to last year. Happy hump day and roll weather...TS