The long advertised heat wave is set to kick in Thursday beginning a 3 day stretch of intensely steamy summer weather. Most of Iowa and parts of surrounding states are under an excessive heat warning through Saturday.
After some scattered morning storms Thursday, a hot and oppressively humid air mass will build across the region during the afternoon and persist into the weekend. This will lead to heat indices reaching 100 to 110 degrees during the afternoon and evening hours from Thursday through Saturday. In addition, very warm overnight temperatures will offer little in the way of relief. This graphic from the NWS shows some of the peak heat values (how it will feel) during the period.
We've been talking about this event for some time but the past couple of days my area has remained on the edge of the heat in an area known as the ring of fire. That has resulted in occasional clouds and even some storms which so far have kept the heat at bay. That is likely to change later Thursday as very warm air aloft builds into the region creating a formidable cap. That will end the thunderstorm threat until Saturday night. These are the temperature departures for the next 5 days. The heat centered over the heart of my area
Eventually a front is slated to pass through the region Saturday night bringing a chance of storms and a change to a cooler less humid brand of weather next week. The cool-down is well teleconnected by our 2 major models. The EPO (eastern Pacific Oscillation) is shown by both the EURO and GFS going from the warmth of the positive phase to the relative coolness of the negative version.
The EURO EPO forecast through August 1st.
The GFS EPO forecast.
Here's the temperature correlation for the negative EPO phase in the month of July. Cool rules over the upper Midwest.
Conversely, you can see how the positive phase (which is what we are in now) correlates to above normal readings.
All things considered I have high confidence that the Midwest is going into a pleasant mid-summer temperature pattern next week. Here's what the change to NW flow looks like at jet stream level next Wednesday.
These are the 5 day temperature departures for the coming week. A big change from the heat we'll be dealing with the next 3 days.
In summary, the roller coaster is on the way up through Saturday. Then we peak with storms Saturday night before plunging into a more seasonal pattern next week. Should be worth the price of admission! Even better, there's no lines for this ride. Roll weather...TS