STORM CHANCES AND TEMPERATURES ON THE RISE

The five-day precipitation forecast from the Weather Prediction Center really says it all - widespread rainfall totals of 2-3" are likely across the Midwest as a series of thunderstorm events are forecast in the coming days. Several of these thunderstorm events are anticipated to be severe with damaging wind gusts and large hail a concern.

Latest Machine Learning forecasts Monday-Wednesday highlight the risk for severe weather in the region, with Tuesday and Wednesday the highest chances near the Quad Cities region. Additional chances are showing up Friday and Saturday as well, however confidence gets quite questionable at that range.

The official forecasts from the Storm Prediction Center have a Level 2 of 5 risk, a Slight Risk, in affect for portions of the region Monday through Wednesday. As confidence increases there is some likelihood the probabilities and levels could increase. Of note, that makes these severe weather forecasts challenging over an extended period of time is the fact one day will affect the next, and onward, as outflow boundaries shift the main focus for severe weather potential.

MONDAY - The NAM

The GFS

The Euro

For Monday the various models are forecasting some thunderstorm potential across the Upper Midwest. While placement is a bit all over the place, the general idea is storm formation in the late afternoon into the evening/overnight hours. Monday's threat likely stays away from the Q.C., whereas Tuesday and Wednesday are higher chances.

TUESDAY - The NAM

The GFS

The Euro

Tuesday model guidance shows more widespread thunderstorm activity across the Midwest and I think has the higher chance, as of now, of being a problem for the region.

Analogs have 70-80% probabilities of at least one severe weather report across Iowa into northern Illinois.

When looking at the probabilities of five severe wind reports, it's really honing in on the possibility of eastern Iowa and northwest Illinois. We can use these analogs as guidance, it's not a forecast. However when you see these percentages increasing with the models forming thunderstorms, it does give some elevated confidence in a forecast. I do believe we may see some movement of the risk area northward with time pending how storms evolve on Monday.

The European Ensemble has five-day precipitation average of the 50 members closing in on 2" across much of Iowa. This is quite a strong signal for some very heavy rain and could potentially lead to some flooding concerns, especially over areas that see multiple days of heavy rain consecutively.

A Slight Risk for flash flooding is already in place Tuesday and Tuesday night across much of Iowa and eastern Nebraska highlighting this likelihood of heavy rain.

Switching from the storms to the heat, it will certainly feel like summer in the days ahead. By Tuesday highs will likely reach 90 with more 90s likely looming heading into the weekend. This, combined with high humidity, will lead to some dangerous heat indices across the region.

Probabilities of above-normal temperatures are essentially maxed out across the Great Lakes region this weekend based on historical analogs.

Additionally, the percentage confidence of reaching at least 90° is 70-80% for the Quad Cities region. Those percentages increase to about 90% farther south towards St. Louis.

Temperatures at 850mb, roughly a mile above our heads, are forecast to be in the 99th percentile. This is a pretty strong signal for some rather intense heat looming this weekend.

Heat indices off the GFS are forecast to approach 100° this weekend for a large area. A word of warning, certain models likely to really inflate heat indices this time of year. Both the major global models the GFS and Euro have issues. The GFS tends to overmix air temperatures leading to inflated readings, while the Euro tends to undermix the boundary layer leading to really extreme heat indices. You might see some weather apps or Facebook weather enthusiast pages show some truly exaggerated values.

I'll end this post with a video recap of one of my storm chases from my storm chasing vacation. It features a few tornadoes, wild structure and some absolutely terrifying lightning. Fun day!

-Meteorologist Nick Stewart