We’ve included a Multi-Level Cloud Forecast Layer for all weather models. This layer combines the individual low, medium and high cloud layers into one.
You can find this done on other sites too, but here we’re using a particular color scheme and blending approach so you can identify the cloud layer mix in a given area at a glance.
Often, you’ll see the layers composited one on top of the next from Low to medium and high. That makes it hard to know exactly what the cloud mix is if the top layer is fully overcast.
Here’s an example screenshot of the UK - always a cloud gold mine 
- using the UK Met Office 2km model:
Some definitional things first, from the Met Office documentation:
- Low Cloud: Fraction on horizontal grid square occupied by cloud in the low-level cloud height range: from 111m (~350ft) to 1,949m (~6,500ft)
- Medium Cloud: A fraction of horizontal grid square occupied by cloud in the mid-level cloud height range; from 1,949m (~6,500ft) to 5,574m (~18,000ft)
- High Cloud: Fraction of horizontal grid square occupied by cloud in the high-level cloud height range; from 5,574m (~18,000ft) to 13,608m (~44,500ft)
Not quite sure whey they change their phrasing for medium cloud, but that’s how it is…
For comparison, here are the individual layers:
Low Cloud
Medium Cloud
High Cloud
In somewhere like the UK, it might make sense to look at the low cloud layer by itself, given that’s the layer the photographer will be most affected by, and given the frequency of low clouds at these latitudes. But looking just at the high cloud layer alone is likely to give a misleading impression.
The multi-cloud layer allows you to identify low, medium and high clouds where they occur alone - the individual layer colors are preserved as is, and also in pairwise combination (e.g. medium and low clouds together appear as purple), and where clouds exist at all levels (low + medium + high cloud creates a shade of neutral gray).
Example: Sunrise Wed 9 September
Here’s the forecast for tomorrow morning in the southwest of England around sunrise:
You can see that the area under the map reticle (cross hairs) shows medium cloud overhead, but clear to the east. That could allow for decent sunrise.
In the contrast, if you were further inland to the northeast, where there is more continuous low cloud, the chances are somewhat slimmer.