The first day with Mud. This has a number of effects.
First, Local Supply Values away from the road network are abysmal. A Forest hex right next to a secondary road might still see a drop of 8 points compared to the hex on the road. I took care to pick locations where my units are reasonably close to the primary road network, as weather has no effect on primary road movement (and thus supply tracing).
Only a part of 38. ID and some cavalry units in the south are some distance away from the road network, but the cavalry are withdrawing and 38. ID is just screening the flank of 22. ID and protecting the north-south road from Sieradz to the north on the western side of the Warta.
For the Russians, this complicates logistics even more as my units are sitting on the east-west road primary from Warsaw and supply tracing now needs to trace a path through Lodz and/or Orzokow as the route with the lowest MP costs. Local supply values might very well be around 10 for some Russian units. For the units in my bridgeheads, local supply is 25-30 or so, though it might worsen for a short while when the Russians can ZOC-block the supply trace at Leczyca.
Second, non-Jaeger infantry units can only move 2 hexes at best when not in T-mode on a road. This is an issue mostly for the Russians, due to the third effect.
Third, only A and B quality regular infantry units and Jaeger units can move and assault in Clear/Field terrain. Mounted cavalry can move and assault as well. My opponent now faces the issue that he has D quality units in between my bridgeheads that can move 1-2 hexes per turn due to terrain and the state of being Disrupted tripling MP costs when moving closer to an enemy unit, while 3. GD and 1. ID can move and assault most of the time. As will soon become clear, that will (finally!) lead to the destruction of at least part of VI Siberian Corps.
I do need to keep in mind that the Russian Guards can still move and assault as well.
The B quality division 1st Grenadier Division is near Radomsko. As my cavalry has better mobility, it doesn't give my opponent the kind of advantage he would enjoy against the D quality Landwehr.

An overview screenshot will hopefully make it easier to follow the action.
In what will soon be the I. Reservekorps bridgehead, a charge by a brigade of 8. KD is about to ruin breakfast of a Cossack sotnia by destroying it outright. The first units of I. Reservekorps will move across the bridge afterwards. I'll construct bridges across two Bzura hexsides, for practical reasons. That will make it easier to move units in or out. As soon as the bridgehead is secure, the bridge engineers will pack up one of the two bridges.
1. ID is ready to push south-west from the second bridgehead, ideally pushing one of the Siberian divisions towards the Bzura. The other seems to be south of their position by now. The western brigade of 41. ID will move towards Piatek and will clear the area around the Mlogoszyn bridge. The eastern brigade will try to apply some pressure on the Russian reservists between it and the I. Reservekorps bridgehead.
Having brushed aside the cavalry units facing it, 3. GD is now south of Piatek and will advance east. It turns out that 2nd Infantry Division moved to the area south of 3. GD, but that's not enough of a threat to an A quality formation to consider halting the advance.
There are 11 hexes between 3. GD and 1. ID, by the end of the Dawn turn there would be 7.
West of Leczyca, XVII. Armeekorps will roll with the blows until II. Armeekorps arrives. The field guns of II. Armeekorps are already in position behind 36. ID.

Kavallerie Korps Hauer and IV. Korps (k.u.k.) will move north, I haven't decided yet where they'll go. 2. KD (k.u.k.) is crossing the Warta at the bottom of the screenshot, 9. KD (k.u.k.) is moving after IV. Korps (k.u.k.) in the center.
XXIV. Reservekorps with 48. RD, in the lower left of the screenshot, will assist Korps Posen with holding Sieradz.
Korps Breslau is still slowly withdrawing west, I'm trying to hold the objectives for as long as possible.

No Russians showed up in front of the cavalry screen. HKK 3 (minus 8. KD, which is at Lowicz) will stay in the area, to keep Russian cavalry or the Grenadiers from flanking the Landwehr.
Again, note the favourable loss points ratio. The Russians lost nearly 12.000 Men in the last 8 turns, while my losses were 4.261 Men.