OK, so I don't know if this requires a brain transplant or not...but WI starting on about May 15th or so in 1941, Stalin believes all the reports that are coming in, and realizes the Germans really, really are coming for the USSR.
Hoping against hope, Stalin does not authorize a spoling attack, but the Red Army prepares for war. There is not enough time to make and doctrinal changes, and all the weaknesses the Red Army had IOTL exist here as well. But, as June 21 draws nearer, the Soviets get more prepared. Front commanders are authorized to be sensible in their defense. The Red Air Force agressively patrols the borders, and the reserves are called up.
When the British (and others) get the exact date of the war to Stalin, the Red Army prepares. The Germans attack, and the Soviet military is expecting them.
What now?
Mike Turcotte