The classic textbook cold frontal passage ?
I recall from my youth - and yes I can remember back that far - that a Cold Front approach consisted of a wall of very black cloud moving in from the South/Southwest more often than not with a well defined 'Roll Cloud' along the leading edge. If you were lucky you could see the row of Cumulonimbus anvil tops as well.
The actual arrival consisted of a healthy squall followed by precipitation of rain or maybe hail often accompanied by thunder and lightning. Then usually a rapid clearance behind with a cool south/southwesterly wind.
For many years now all we seem to get is a layer of low stratus and a wind change but little or no significant weather until maybe three or four hours later.
On Sunday however I was parked outside the local supermarket, waiting - as you do - for the Mrs, when a 'real' cold front arrived.
The above photo actually shows the back end of it as it races away towards Kaikoura and later Wellington.
Our temp dropped to 6.7c