What is causing the heatwave in Russia?

Everyone is talking about the high temperatures, fire, and drought that is hurting Russia's grain crop, but what is causing this extreme weather situation? The New Scientist has a great article picking apart the meteorological data that is attributing to the severe climate. They describe a stuck or "static" jet stream, and how it is affecting the area:

Similarly, as the static jet stream snaked north over Russia, it pulled in a constant stream of hot air from Africa. The resulting heatwave is responsible for extensive drought and nearly 800 wildfires at the latest count. The same effect is probably responsible for the heatwave in Japan, which killed over 60 people in late July. At the same time, the blocking event put an end to unusually warm weather in western Europe.

You can also read more via Wunderblog, where they have satellite photos of the jet stream.