I have never understood the obsession with the idea of the UM being unreliable at T+144. The verification stats suggest that it is up there with GFS in terms of accuracy, if not more accurate. I have seen plenty of occasions in the past when the UM has caught on to a trend more quickly than the other models, shown a different evolution at T+144, and been proved right. Like you say though, ECM will be interesting. The UM T+144 chart could bring snow to many, the main question to ask, assuming the block makes it that far NW of course, is whether the block can hold for a while.