I’m not disagreeing 100%, but part of your logic is off. A weaker wave that causes lighter Precip would also be accompanied by less SW flow. Temps almost across the board look upper 20’s at most. Decent rates at all and it accumulates most places.
edit to also say what Chris said about the subsidence is partially true as well. More uniform areas of Precip are to be expected, even if the overall scheme isn’t terribly heavy.