I think Friday will be much like any other.
There might be a bit of a kerfuffle at airports / ports as no-one seems to know what will be needed re: travel documents / insurance / customs documents etc.. but this will only affect you if you are unlucky enough to be near Dover or 1 of the major airports.
The border in Northern Ireland will need to.close, we will break the GFA, we will be international pariahs and we will have betrayed our own citizens in NI and our nearest neighbours in RoI, we may see a return to the troubles.
I teach English in France and a few of my students have told me that for the last few months they have been almost exclusively manufacturing for the UK to have everything exported before B-day.
If this is true across other countries, the UK will seem pretty normal for a week or 2.
Then we will notice things disappearing from shops and what's left becoming more expensive as stock decreases.
As stocks diminish companies unprepared will start to go under and job losses will follow.
There will be lots of worry (in some cases justified) regarding supply of essentials such as medicine and fuel as we scramble to find / import things sending produce. If you are unlucky enough to be dependant on insulin or radiation treatment for cancer you would be at great risk.
In the following weeks / months people and businesses who can leave will leave.
The UK will fall into a severe recession. This will impact the whole of the EU who while they will not suffer as badly will be impacted which will just add to our current lack of popularity.
Some people will make a lot of money out of this (disaster capitalists and such)
We will make terrible deals with other countries because our politicians are inept and we will be desperate and alone. This will lead to consequences such as increased immigration visas (for them not us) and the privatisation of the NHS (trump red line) and probably many others unforseen at this stage.
We will blame the EU, remainers, remain politians, Labour politicians, lib Dem, snp, Teresa May, all other countries that don't immediately come to our aid (We are Britain don't you know) Johnson, rhys-mogg, Farage, ourselves in roughly that order.
Obviously I could be completely wrong too. Honest answer 'who the fuck knows' bit with the current shitshow at Westminster it isn't going to be good.