PoD#1: Hitler panics and orders AGC to retreat on January 1st
PoD#2: The weather continues to be bad in the second week of January
Result: AGC is effectively destroyed by the Soviet counteroffensive, as the Luftwaffe fails to help them whilst their lines break under the pressure, resulting in 2-3 pockets that are gradually worn down in the following weeks.
Fast forward 11 months, where Soviet forces reach Rostov, trapping all of AGS, as the overextended Germans were busy fighting in Stalingrad. Some make it out via the Kerch Strait and into Crimea, but most are killed or captured.
The Anglo-Americans try a landing in '43 in France, but it gets pushed back into the sea by the German strategic panzer reserve, which was supposed to have fought at Kursk. Eastern front meanwhile collapses on multiple points.
Even so, with such a massive Soviet-wank/German-screw, I don't see how the Soviets get to the Rhine before the Allies land in France once again and reach it first.