This probably has happened in the past, and I just haven't noticed it, but the East Coast of Aussie (especially near Sydney) seem to be getting a W/NW arch right now, much like we do here in Canty
(at least, that's what it looks like on to me.....)
Specks of high cloud on that day with some sunny periods & 21oC, we do get an “arch†here at times especially when we get an NW-W cloud band moving E from inland & the “arch†here usually heralds the arrival of clearing skies, however this is not always the case, sometimes it will bring rain to Sydney such as yesterday when it rained moderately at times & sometimes it will bring cloudy & dry weather and sometimes hot, windy weather especially around Spring when temps can rise to over 35oC. There have been some examples of when it’s been overcast and cold for most of a day then skies clear, the sun comes out, temperatures can rise considerably in the matter of a few minutes or hours, and the wind becomes hot and dry & quite gusty at times if a change is coming from the S or SW, however our "Arch" is not as good or intense like the Canterbury one.
I remember when I was in Canterbury on holiday some years back and saw the “Arch†that I had heard so much about, that was the best example I have ever seen in my life, it was so vivid and I remember the colour was sort of red/brown & looking yonder to the Alps, could see that it was raining on the other side - such a big contrast.