My name's not Stephen! 😁

Last night's 18z GFS incidentally brought an absolute deluge here in the far SE - of rain and sleet, continously chucking it down for over 24 hours with temperatures a couple of degrees above freezing - having been cold enough for snow before and after. 'Course, back in the 80s when it was 1.5C cooler [Faversham 61-90 vs 91-20] that'd have shown as a foot of snow instead. 

It was the second run in a row to raise temperatures, and it would be incredibly unpleasant were it to come off. Thankfully next weekend is still a long, long way off, and we've seen many a time a low forecast to hit the south that ends up bringing snow to the middle of France instead - most recently of course the Christmas Day snow-bringer. 

Included for posterity, as a snow fan I'd hope things either get a degree or two colder or that rain misses us entirely.

https://ukwct.org.uk/weather/xc.jpg 

We already have one, and as the MetO noted in their deep dive before Christmas it's the strongest block of that type in that area at that time of year for 45 years. The models are a cavalcade of blocking as a result, and the "holy grail" of a diffluent changing to an omega and back again has been shown by a fair chunk of the output over the past few days. 

("Rex" is the American term btw, they're diffluent blocks in UK English). 

Back in the 80s the old wives' saying was whatever New York had, we'd get two weeks later. You could rely on snow most winters even down here, but the saying no longer applies (the Big Apple is still as snowy as ever, but we're certainly not!)

Back to the here and now, the 0z ICON is much like the 18z GFS was last night in so far as it goes - I've a feeling the next big question will be that low to the south at the weekend, which has the potential to be a snow-bringer for many, but just bringing rain down here to the far SE. Like GFS, ICON shows a fair bit of snow cover down in the SE, with the exception of parts of Kent, where we just get lots (and lots) of rain.

Here's the ICON's 180 "snow on the ground" chart. You can see the white bit of Kent jutting out in all its soggy splendour.

https://images.meteociel.fr/im/19/19043/icon_16_180kbw9.png 

Definitely won’t be bone dry set up as we under low pressure influence so most of us should see decent snow events from features and snow showers .  No chart this morning show fully HP over the UK.   

https://meteologix.com/uk/model-charts/euro/europe/temperature-850hpa/20260113-0000z.html 

It looks like a generally cold run, with an Atlantic low's warm sector approaching but occluding as it crosses the UK around 216, then cold digs back in from the north.

The 300 chart shows a very deep low over France, of course it won't come off like that but it's incredibly rare to see!

https://meteologix.com/uk/model-charts/euro/europe/sea-level-pressure/20260110-1200z.html 

If this come off surely we will see lot of snow or even snow storms with strong ENE flow.  Agreed if so rare but nice for a change for this deep low over France and not NW Scotland. 

The ensemble data paint an increasingly cold picture for a while at least.

(Off-topic but anyone going to Braemar for a break for the start of January may have a rather wintry time: https://www.bbc.co.uk/weather/2654965  )

Heading north to the Hebrides today. Great weather for the journey north …. Will be keeping an eye on the models for the journey home next weekend ! 

https://www.wetterzentrale.de/en/show_diagrams.php?geoid=50893&model=ecm&var=2&run=0&lid=ENS&bw=1 

That’s fair point and  there is clearly a strong, established blocking regime in place, and by any definition it’s exceptional for the time of year. Whether we call it a Rex block or a diffluent block is largely semantic, and the Met Office analysis backs up just how anomalous the current pattern is.

Where I’d still be a bit cautious is in separating “a block exists” from “a snow-producing block for London.” The northern height anomaly is undoubtedly there, but the southern component  particularly the placement, depth, and longevity of any cut-off low  is still evolving in the guidance. Until that side of the structure fully locks in, the block remains more supportive than deterministic for snowfall in the South East.

I'd say a bit less, but nationwide snow regardless.

See this GEM sequence for snow up to 240 hours - very promising IMBY - and if it verifies (big. If) it will be the first snow since 2021. 

This is where I trust gut over guidence. Going by the forecast windflow alone, I already know I'll see more snow showers than that model suggests.. but that isn't to say that the forecast wind direction is nailed on at this early stage! 

FAX - a mostly N-ly influence, but at first HP 1035 mb W of Ireland ensures that the air has a long track via Iceland so will be marginally warmer. Later (Thu 1st) an LP dropping SE-wards to Norway introduces direct N-lies for a day before they drift off to the east. A large LP 990mb west of Spain is an interesting new development.

GFS Op - continues where FAX leaves off and by Sun 4th the cold air delivered this week is interacting with that LP 990mb N France for strong NE-lies and the prospect of snow in many places even the south (or maybe cold rain near the S coast). HP then moves in from the SW with milder air on a W-ly until Fri 9th when a twin centre trough (995mb Ireland, 990mb Norway) swings down across Britain bringing cold weather back from the NE persisting to Tue 13th when HP again moves up from the SW .

ECM - like GFS to the 4th but the LP over France is weaker, basically leaving the cold air from the N static over Britain until Thu 8th  (no sign of HP-driven W-lies) when an LP 995mb develops off E Anglia. This fills but on Sat 10th the LP generally lurking in the SW deepens 990mb Paris and brings what looks like a snowfest for S England before it moves off to Germany for Mon 12th.

GEM - starts out like FAX but keeps the direct N-lies on the 'wrong' side of the N Sea so nothing dramatic for Britain. It concurs with GFS on the twin centre trough, but the Irish end deepens 990mb before crossing to the N Sea and reinforcing the N-lies Thu 8th. No sign of a deep LP over France in this model, nor in GFS.

AIFS - London, maxima 5C with a dip Wed 31st, but from Sat 3rd to Wed 7th near-ice days. Then back to 3-5C with occasional rain. Edinburgh similar trends but a couple of degrees colder.

GEFS - good agreement on 5-6C below norm to Wed 7th (mild blip on New Year's Day), mean temp recovering to a little below norm but with a bigger spread of ens members. Rain (just possibly snow anywhere but very likely on the east coast), in small quantities in many ens members after Sat 3rd.

So it's ECM vs the rest for snowfall

We may potentially be creeping towards a bit of agreement on how HP develops near Greenland and how that interacts with HP in the south ( ish?) Atlantic, with a lobe of the HP being pulled south and letting LPs wander through somewhere near the UK. ECM serves up something of a box of delights in this run with the first LP being snowy for areas further North:-

Before we get another one that brings snow for areas further south:-

That's probably overly optimistic for MBY but shows the potential with the setup and LPs pushing in to cold air and in a way which doesn't just bathe the country in mild stuff. 

GFS does  take a slightly different route and the southern HP lobe doesn't sink as much and instead collapses over the UK. It does reboot post then though and brings more cold air in. It's also in the minority in its ENS in that kind of milder 'blip' at the time fwiw. 

GEM is a bit quicker to break the colder flow than some of the models although the setup is similar and it's chilly enough for the LPs to bring a wintry mix pretty much anywhere in the UK.

All in all looks good for at least 5-7 days of colder weather, with convective snow for favoured/prone areas initially and possible some more widespread events depending on how the pattern evolves. I rarely do that well from the LPS bumping in to cold air scenario but there's definitely potential in the setup and it wouldn't be surprising to see some disruptive snowfall for some areas over the next 7 days if things develop as currently shown. 

Current forecast:

Late December 2000 analysis:

I can't post it but shows more on the WXcharts. Not that it matters really. 

I explained why that's likely the case a couple of days ago, but it's worth repeating for lurkers in particular. ECMWF provides snow depth as m of water equivalent, so the generated depths have been adjusted to be reasonable for the UK, where conditions are often marginal or less clear cut. The values are derived from metres of water equivalent; that is, the depth the water would have if the snow melted and was spread evenly across the whole grid box.

In colder and drier continental climates it is often reasonable to assume a higher snow depth to water equivalent ratio, due to lower compaction and colder boundary layers. However, for the UK the assumption here is a 5:1 snow ratio, corresponding to a snow density of 200 kg m⁻³.

I think this explains why in recent years even some pros (I won't name them here) have bandied around ridiculous ECM snow depth charts.

https://nsidc.org/sea-ice-today 

I would think that is exactly the information that is programmed into the models at the start of the runs to produce the output shown. Perhaps a bit less so in the AI models, but probably not.

Anyway back to the model output and the 06z GFS op run looks consistent with previous models (out to day 6 so far).

I dont like northerlies for the reasons we can see.  Looks mostly dry for the south.  

Surprised, (but shouldn't be, really) at the lack of ice around Newfoundland down to Maine, especially given all that frigid air that has been spilling into that region over the last few weeks. Shows how insanely warm the ocean temps are these days now.