MesoWest observations show a 40F temperature at Hat Island, but temperatures ranging from the high 20s to low 30s surrounding the lake.
The morning sounding from KSLC, taken at about 6 am, suggests that the deeper cold air moved in a bit more quickly than suggested by the NAM forecast from yesterday afternoon. The frontal inversion base is near about 650 hPa, whereas the NAM had it at that level at about 9 am.
We'll see if we can get the lake-effect going as the upper-level trough moves in the next few hours or if other factors (moisture, solar forcing and lake-breeze development) put a damper on it. It's always a battle to get the lake going during the day, so this will be an interesting case (as they all are to inquisitive minds!).