Where did the daily temperature variation go? Currently central and northern Europe are experiencing a very cold, false-spring like weather phenomenon.

When i look at local weather charts, the daily temperature cycle seems to be completely gone, and replaced by a constant -8°C to -10°C, see below for an example of southern Sweden. 



Taking a look at ventusky.com we also see that the cold air is being advected from colder regions in Europe to southern Sweden, as seen in this screencap:



Other locations don't display this behaviour any more:
The farther south I look, i.e. Berlin and Munich, the stronger the daily fluctuations get again, see both for comparison:





This 'constant temperature' seems odd enough for me to ask the question:

Is the constant temperature here in southern Sweden for a few days a lucky coincidence of temperature advection sources, or is this a known phenomenon and there is some interesting physics behind this?
There are (at least) five factors at play here:


the cold air advection from the north east has driven temperatures down
the cloud cover traps longwave radiation sort of like a blanket, keeping the night time temperatures from dropping
also, the cloud cover prevents solar radiation from reaching the surface and warming it
the relative humidity is near 100%, indicating that the dew point is nearly the same as the air temperature.  Dew point serves as a minimum possible temperature, so this also prevents the air temperature from dropping
precipitation traveling through the lower atmosphere will evaporate, having two effects: cooling the atmosphere and maintaining a high dew point


(5) is only really a factor during the day when temperatures would normally be on the rise.  The precipitation will keep the diurnal heating to a minimum.