The met office have issued a severe cold weather alert to go with the high pressure between 1800 on Sunday 19 Jan and 1800 on Tuesday for all of southern England with the exception of London.
Current alert level: Level 2 - Alert and Readiness
Issued at: 08:47 on Fri 17 Jan 2020
There is a 70% probability of severe cold weather/icy conditions/heavy snow between 1800 on Sunday 19 Jan and 1800 on Tuesday 21 Jan in parts of England. This weather could increase the health risks to vulnerable patients and disrupt the delivery of services. Please refer to the national Cold Weather Plan and your Trust's emergency plan for appropriate preventive action.
High pressure will build across the country over the weekend and into early next week. This will bring a spell of dry weather and light winds, with overnight frosts becoming widespread. The cold overnight temperatures will be offset by generally fine daytime conditions with sunny spells. However, fog patches will develop across central and southern areas Sunday night into Monday, suppressing daytime temperatures in places where slow to clear. Later Monday and into Tuesday, freezing fog may become more widespread although confidence decreases. Some cloudier conditions are also expected to spread southwards and bring less cold conditions, but the speed of this progress is a little uncertain at present.
http://www.metoffice.gov.uk/public/weather/forecast/#?tab=map https://www.metoffice.gov.uk/public/weather/cold-weather-alert/?tab=coldWeatherAlert&season=normal#?tab=coldWeatherAlert