The cool bay and Bass Strait is having a big impact as I suspected it would. It has lead to morning cloud lingering into the early afternoon yesterday and then until around 10:30am this morning, and then after the cloud cleared sea breezes kicked in very rapidly and kept the temperature down lower than BOM could predict even after two goes at it.
The bay is around 2 degrees cooler than at the same time last year thanks to cooler than average weather since around mid October. Last summer the bay got so warm by early/mid Jan that we barely saw a seabreeze develop at all, and when it did it didn't lower the temperatures and this was one of the major factors in Melbourne and southern VIC recording one of the hottest summers ever.
Tomorrow will get hot very quickly tomorrow, however I'm still a little skeptical on these super high temps being thrown around. I'm not saying that it won't be 40C in Melbourne tomorrow but IMO this is at the upper end of what I would expect given what the models are saying. The air is not going to be super dry tomorrow nor the wind particularly gusty. Most models I am looking at are saying around 38C in Melbourne tomorrow and much cooler the further south you go, eg. just mid 20s on the southern Mornington Peninsula, which indicates that there will still be extensive sea breezes near the coast. (I remember being down at Apollo Bay one summer day when it was 20C max when Melbourne was 40C with strong northerlies so it does happen).
BOM seems to be going with a big Foehn wind effect off the ranges as is often the case in northerlies, however this is most pronounced when the air is dry and the northerlies are strong.
I am still saying 38C in Melbourne tomorrow but I'll probably be wrong as usual.
The weekend is looking fairly wet. Saturday is going to be a damp and cloudy day, probably misty up here and cool with the southerlies coming through. Sunday looks like another spike in temps up to high 20s in low lying areas with humidity and the trough deepening. GFS has high instability values, it should be stormy and wet but we will see.