No great change to the overall outlook yesterday evening, I see! The GFS(P) 18z yet again plastered the UK in snow, it was very consistent yesterday.
The ECM strat charts:
https://www.geo.fu-berlin.de/en/met/ag/strat/produkte/winterdiagnostics/index.html haven't changed much since Friday either. The SSW is still ongoing and is forecast to end on the 20th - the best part of three weeks after it started. It's shown to affect 30hPa, but 50hPa doesn't quite go negative on this run... the vortex is well and truly split, however.
The ECM ensemble means last night show a decent-sized cluster, perhaps even a majority cluster, for a low pressure, accompanied by a chunk of the polar vortex, to cross the UK. Now, where have we seen that before? Oh yes, the GFS(P)!
As has been mentioned in passing from the NW post, the ECM was a very cold suite last night with the majority cluster on the cold side. You can see this via the 10th/90th percentile charts quite nicely - there's more scatter on the warm side than the cold side:
https://weather.us/forecast/2639577-reading/ensemble/euro/temperatur850 With ECM mean maxima for London pretty much matching the GEFS in the 10 day+ time frame, i.e. 2 or 3C, the signals for a noteworthy cold spell are the strongest they've been this winter. Another exciting day of model-watching beckons!