It was 90 degrees in Minneapolis today, which is certainly a pretty warm start to June, and tomorrow and the weekend will only get hotter. Heat waves are certainly newsmakers, and in particular, they are big news when they arrive in the northern US. All this is true, and really, it’s not the most interesting part of this particular heat wave. Take a look at the forecast highs for Friday.

There is the typical hot spot in the Mojave, but otherwise, the warmest part of the country will be…. North Dakota? The interesting part of this heat wave, to me, is that it completely bypasses places to the south. The forecast high in Bismarck tomorrow is 101! Unintuitively, the forecast high in Austin tomorrow is 80, a full 20 degrees cooler. I don’t have to tell you this, but that’s not how it usually works!

Why is this going on? The answer is told in the upper air forecast. Take a look at the flow pattern forecast during the day tomorrow. I have added some arrows for your benefit.

The pattern over the US is tilted. The upper level trough over the eastern part of the US takes a westward turn and heads through the southern Plains. Forgive me, because the axis of the trough in the south is a little further north than I drew it, but the result is the same. Moisture is being drawn to the Red River Valley, and then it streams into the eastern Great Lakes, keeping the entire tract covered in clouds and rain.

Meanwhile, a ridge axis runs from the southwest towards the Upper Mississippi Valley. Remember how I noted how hot it was in the southwest? Well, that is where the air moving into the Dakotas is coming from. Combined with the scouring effect of the Rockies, the dry air can warm even more during full daylight.

When this pattern sorts itself out, the hot air won’t go anywhere, but instead of shipping off to the northeast, the moisture entering through Texas will find a route north. Until a cold front comes late next week, the heat of this weekend will become hot and humid.

It’s only June 3rd. and the summer is off to a hot, hot start in the Northern Plains.