The 1500 UTC MesoWest surface plot shows a phenomenal confluence line over the lake with westerly to west northwesterly flow west of the lake (and at Hat Island) and NNW flow on the east shore.
An aspect of this event that is quite fascinating is the cloud band evolution. Note how the bands over the lake have pushed southwestward over the past hour and become oriented a bit more across the lake axis.
The east side team reports that the frontal stable layer is still over the lake aloft, with a base near 600 mb. Thus, this remains a case of fairly shallow convection. They also found a northerly low-level jet about 400 m above ground level, which is consistent with the MesoWest data above. Very interesting.