This day 9 years ago was also a classic . Snow overnight into 22nd, then snowed all day and into the night.  Max 0c. One of the best snowfalls for Decades let alone late March with snow still present at Easter.

Summary charts show cold temps across the far north of Europe, warming nicely along Med coasts, mild-ish between with a few local cold spots in the mountains (Alps, Carpathians, Caucasus, even a suspicion of cooling in N Scotland week 2). A couple of dry patches centred France and Greece week 1, replaced by broad swathe of wet weather, Atlantic through Britain to Urals week 2, the only really dry weather in N Africa by then.

Jet running N and S of UK week 1, then across UK and into C Europe week 2, rather intermittently

GFS - HP near UK combining with LP over Iberia bringing up fine and dry weather from the S until Mon 28th. The HP then collapses and the LP which has been hanging around the Baltic extends W-wards and combines with that Iberian LP to reverse the winds to N-lies through the following week, effects mainly felt in N and E of UK. By Sun 3rd the Atlantic is back with SW-lies, and the controlling LP moving NE to Hebrides 975mb and on to Scandinavia by Fri 8th with winds going round from SW to W to NW, becoming cooler

GEFS - mild* and dry to Tue 29th when all ens members show a dramatic drop in temp (op & control 10 C widely below norm but less in SW) recovering at various rates (op & control to 5C above norm by Sun 3rd, other members more slowly) and convergence on seasonal norm by Fri 8th. Some members show rain as early as 29th, more general around the 3rd, more continuous in S but some big occasional totals in N.

ECM - the N-lies shown on GFS after the 28th stay the other side of the N Sea, and after that the pressure over the Atlantic is not as low ,but neither does it stay out to the west , instead pushing a series of shallow LPs across the UK from Fri 1st

* I think GEFS takes a day-night average, otherwise I'm sure it would be showing warm this week, not mild. I've just been out walking on the Downs in shirtsleeves.

I am not claiming that major snowfalls at this time of year are impossible , just that showers that form from inland convection usually don't settle during the day and tend to be a mostly day time event

True, though the lake effect is still a thing even at this time of year, and those showers can give deposits at night.

In order to get snowcover during the day you need a 'feature' coming into the cold air.

Can only speak for Ireland, though I believe Scotland in particular was affected greatly by the same event, but the snowfalls of April 1st 1917 were amongst the some of the worst (best ) ever experienced in this country:

HeavySnows1917.pdf (met.ie)

Very likely 'lake effect' too given the largely NW stream and the regions affected. 

GEFS having second thoughts about the cold spell.

In big picture terms the 12Z is an upgrade for the cold spell, but the spoiler shortwave delays it significantly.

How this shortwave behaves will not be resolved any time soon.

good stuff  👍 hopefully the trend will be a continuing dilution until we are left with nothing more than a brief cool waft

Sledging, two miles west of Taunton, Somerset, at just 30 metres above sea level, 19 March 2018:

https://youtu.be/RwWPlT371I8

.

That video does not negate Tom's point imo

By that I mean, you have provided no info/synoptic charts to contradict Tom's initial point re lake effect snow.  The snow in the video could have been frontal related for all I know.

 LLTNP 105m asl 

WX summaries: 0C isotherm steadily retreating NE-wards and Med coasts warming nicely; Russia and (inland) Turkey below norm, most of Europe above. The bone dry area has in week 1 shrunk to a small patch over the W Baltic; week 2 shows significant amounts of rain in a broad band from the Atlantic to Russia, and any dry weather pushed well south.

Jet - little activity  and well N and S of UK to Thu 31st then persistently over or near S of UK with an occasional loop

GFS op - HP over UK persists until Mon 28th when LP over Scandinavia slowly extends SE-wards with eventually a small closed-circulation LP projected to Denmark 990mb Fri 1st bringing down N-lies. HP re-asserts itself with ridge from the S Sun 3rd (Stav Danaos on BBC also saying cold will be short-lived) . Then by Wed 6th the traditional Atlantic LP is back, 980mb Scotland, moving to Scandinavia but leaving a trough 980mb in the N Sea Sat 9th and NE-lies from somewhere near Spitzbergen.

GEFS - mild to Tue 29th (as noted yesterday, this is probably an average of warm day and cold nights), then a drop to 5-8C below norm for most ens members until Sun 3rd when a quick recovery to mild/warm with a probable downturn appearing at first in the N at the very end Sat 9th. Rain starting Fri 1st (a couple of days earlier in N) and not giving up. 

ECM - similar to GFS though the cold spell around the 1st is slower to develop and not so intense

According to GFS yes but the BBC ramping the cold for next week and the Met too to a degree .

Sadly the ECM 12z looks unpleasantly chilly for a while. In fact all the main models except the GFS 12z do. Hopefully it’s on to something.

Well I wouldn't hope too much as the GFS was still fairly cool and unsettled.

Probably too little, too late to save my CET guess.

I think we'll be at around 8.0-8.2c before adjustments.

I was keeping my fingers crossed for it to be kept down to around 7.8c, then adjusted down by, say, 0.3c to 0.4c

I doubt it will be that high, if we get a cold finish could still end up low 7s, 7.1 or 7.2 perhaps

Wx summary showing a sharp decrease in area of 0C isotherm, by week 2 confined to Scandinavia and extreme N Russia. At the same time the Med is warming nicely esp in the E and over to the Black Sea. UK subject to moderating influence of Atlantic and cooling somewhat. Ordinarily damp in Europe week 1, fairly wet everywhere except the far S/SE week 2

Jet much as yesterday; no action near UK until Fri 1st when the stream establishes across England and/or France

GFS op : current HP collapsing Tue 29th with LPs moving across from the W (980mb NW of Ireland Fri 1st, 965 mb Rockall Mon 4th) the second of these diving SE (990 mb E Anglia Wed 6th) dragging in cold N-lies behind it for a few days before HP re-appears from the S Sun 10th. The promised N-lies for early next week have been cancelled, though still present weakly in FAX and more strongly on last night's BBC forecast though hedging bets this morning.

GEFS : mild to Tue 29th, cool to Sat 2nd (for the majority, though quite a few ens members v cold), v mild around Tue 5th cooling to norm later (mostly; op and control cold outliers Thu 7th). Rain on and off from the 29th, heavier in the N.

ECM : the 29th appears to be the critical day when ECM diverges from GFS. LP appears over France, not from the Atlantic, 995mb Brittany by Fri 1st with a NE-ly from Scandinavia Wed 30th to Sun 3rd before pressure rises again

Yes I notice that - the GFS show anything but cold weather if anything it shows mild but ECM still go for cold as does the BBC and Met office!? - We shall see?