Was that the big thunder snow event ?

I was cycling home from work and it started raining heavily, about 10mins from home the thunder and lightning started and by the time I got home the rain had turned to heavy snow.

i dived indoors, and a few minutes later I remembered I’d left my lights on, and when I went out to switch them off my bike was covered in ice. Certainly one of my more memorable commutes ! 

(Sorry, off topic)

More to do with the pattern IMO - if you collapse HP south too quickly due to modelling the jet a bit off due to lack of data, then you're more likely to allow milder air in far too quickly, might have the jet angle wrong so it pushes mild air further NE than it should etc. The lack of data isn't causing the model to under or over estimate the air temperature, it's just causing (or maybe causing) an incorrect modelling of the wider pattern such that the end pattern is one in which milder air is brought in. 

Given the current wandering HP setup has often been a tweak away from cold or mild, it's not overly surprising that a change in how the jet is modelled could tip it towards a milder setup too quickly or too conclusively. That's been and presumably still is being played out in the ens and tweaks to starting positions. 

Entirely possible I'm wrong of course, but that's my take on what may have happened - it's certainly a little suspicious that we had 2 days of runs which were seemingly increasingly keen on collapsing the HP fairly quickly and then we're back with a more robust HP hanging around for longer and bringing the chance of repeated Northerly incursions. 

Just the standard rule of 'what goes upgrade must go downgrade' and vice versa. Frankly the rollercoaster has been steadier than usual. I think I first suggested things might get interesting after xmas a week ago, and the models have been signalling this even before that. The height rise in Greenland has had rock solid support for ages. In the short term the only thing that has really changed is how that 'slicer low' from the north behaves. And things could still change back so beware!

It was think the temp dropped from 6 to about -1 in that time dramatic videos of the snow wall that day (an actual one) not the false media ones now.

with regard to models could well be interesting snow potential next weekend looks high further North and East the better.

A nice snow pictures thread might even start, potential for a slack low and own cold pool developing

ECM run looks a beauty. 

Yes. It's quite startling how, an hour or so ago, the overnight min temps on that app have suddenly flipped to consistent minus twos and minus threes everywhere in the south west from next Saturday onwards. 

Fits in with what Darren was predicting we would see once we got the 12z models in today.

This was my thoughts. It wasn't anything to do with mild vs cold. Although I am pleased with the way the models and looking this evening for various reasons. 

Will be interesting looking at the extended part of the ECM later along with the ens. 

An encouraging day in model land and coinciding with me finally shedding the germs I've had for the last week or so, meaning I'm probably viewing the charts more optimistically too 😂

Cold pooling is rare. We have had it. Most recently in December 2010. January 1963 delivered it  as well with daytime maxes temperatures in lowland England well below -5C and -8C in some places. 🙂🙂🙂

Fun little feature shown to hit Scotland on the ECM at circa T200ish, starts as a little LP to the east of Finland:-

Spins over Scandi:-

Still spinning down in the flow:-

Hit's the mainland, with snow on it's eastern flank:-

It rapidly loses integrity after that and by T240 it's pretty much done with just a few showery bits (of rain) over Wales and Cornwall. 

Ignoring the charts that almost certainly won't verify as shown stuff, the ECM extended run is nice with HP only sinking in deep FI - the ens are pretty solid too, with a bit of a mild spike circa 7th Jan, albeit not universal and even at the end in deep FI the majority of scatter is at or below the average line. 

Potentially fun times if tomorrows pixels don't shift again!

Mogreps had caught my eye. Big shift colder today.

It's not really sinking as such but it does fail to have even weak blocking developing over Greenland and as a result the core of the HP ends up just to the west of Ireland and the flow over the UK is cold but slack under HP and milder air is rolling round the HP cell and towards us. 

It's not a bad run so far by any means, nor was the 12z, it's just triggering my random amusement finder that it's now the least nice chart generator, having arguably been the nicest 3-4 days back. 

Exactly. It's random!

Is this the "thundersnow" event of Jan 2004?  I remember it well.  

Seems to me in winter in recent years the best way to get the Atlantic Train going after a blocked set up is from a northerly....hope I'm wrong

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

Interesting times to be able to test, compare and contrast with past blasts, and see what a northerly is able to deliver in mid winter 2026.