I've been learning about snow forecasting in the UK. I've learned an important feature is the atmosphere thickness, specifically the 528 line:
Pressure decreases with altitude, and thickness measures the difference in height between two standard pressure levels in the atmosphere. It is proportional to the mean temperature of this layer of air, so is a useful way of describing the temperature of an airmass.
Weather charts commonly show contour lines of 1,000-500 hPa thickness, which represent the depth (in decametres, where 1 dam = 10 m) of the layer between the 1,000 hPa and 500 hPa pressure levels. Cold, polar air has low thickness, and values of 528 dam or less frequently bring snow to the UK. Conversely, warm, tropical air has high thickness, and values in excess of 564 dam across the UK often indicate a heatwave.
Looking at the detailled pressure forcast I can see this line isn't there today or tomorrow morning:
But if I scroll the bar to tomorrow afternoon, it appears:
Am I missing something here? This seems to be consistent when I've been checking this though the week. Why does this forecast only appear in advance?
I'm defineatly not imagining this, the line that appeared 22nd Dec in the above images is now not there until 23rd Dec.... I don't get what's going on here?