Ben Sainsbury

FV3 shows a very snowy Southern England, Tuesday night into Wednesday. Uppers well on our side of marginal.

Typically when looking at precipitation type charts, if you want to approximate accumulations, normally 10mm of rain accumulating corresponds to 100mm of snowfall accumulation. So a ratio of snow 10:1 rain, therefore 10mm corresponds to 10cm of snowfall. This is ratio can vary however depending on air mass and direction of wind.

Yes this! And this is where one recent event springs to mind. Until we’re at T48-72 regarding the low then I expect no less than more changes.

Led the way when models were picking up the potential easterly and then led the way when it decided to drop the easterly

Snowfall possibilities for the south look good on ICON 18z, from T63 through T120, the uppers remain around or colder than -5 at 850hpa so not a bad start!

By T132 on the ICON 12z, the building blocks are in place for a decent north-easterly by T180... hopefully! Azores high moving westwards with heights extending towards Greenland, Arctic high beginning to edge south and low heights moving into Southern Europe.

I do have slight random coverings here but obviously am much further east compared to you.

Yes the snow flakes are so huge, literally feathers like someone said.

Now just starting snowing in Reading with big flakes!

Currently in Reading and waiting for this wave of showers to pass over, temps/dewpoints seem a degree or two too high unfortunately.

Not sure if anyone's posted these, but EURO4 looked quite impressive for coverage of snow showers through Tuesday and the Met Office fax charts show this well. The following are for midday tuesday and tuesday night/wed, both show various troughs moving across the country showing increased precipitation and few small accumulations likely from these in places. Favoured areas look to be western areas.

I'm not quite sure if EURO4 gives tomorrow's possible snow event justice. It looks underwhelming for most and feel like we should see more snow on the back-edge of the front. Thickness look in and around the 528 dam mark. Dew-points marginal at around 0 or 1'c. 850hpa temperatures look between -5 and -6'c; -7'c across parts of East Midlands. 2m Temps look around 2'c I just cannot see how these parameters represent no snow potential along the back-edge of the front, I mean EURO4 shows no snow potential whatsoever for North England southwards.

ICON 6z is coming out at the moment and so far trough dropping more of a SSE direction compared to a ESE direction.

As many have said already it is a knife-edge scenario! The low coming out of the US is EXTREMELY hard to model, and the likeliness of any models nailing its track and intensity down at this time is still unlikely. Until we know how it acts in the next 48 hours is crucial to what we see. If the low takes an unexpected track we could still see large changes at such a small range. I hardly see people comment about the GFS P when it does verify better than the standard GFS. Don’t forget GFS P also follows the ICON & ECM solution.

GFS P 12z by T222 showing a SIGNIFICANT snow event for the majority North England southwards as we see the low undercut.

GFS P 12z, following a similar route to its 6z run just a slightly slower evolution, very good nevertheless! By T138, the Azores and Arctic highs have linked and we looked primed for a very cold E/NE'ly.

What even is happening to the GFS 12z by T300, I've not seen anything like this ever. Oh my the easterlies!

Conversely, the pattern is extremely volatile within the 4/5 day time frame and will lead to differences thereafter and it is model discussion so why not comment pre 96? No malice intended I just don't see a problem! Safe to say I think GFS 6z will get there, just appears to be a slower evolution. Less amplified as others have noted too! Also the GFS is painting an extremely snowy 24 hours from T90 onwards.

GFS P 18z, by T102 it is clear that much more energy is being sent southwards in comparison to 12z.

Final post from me, I'm having way too much fun over a GFS chart. Am I right in thinking the down-welling of easterly winds in the troposphere has fully occurred by this point

According to the GFS 18z, much of the UK spends between T162 to T384 under -8 uppers! That corresponds to 8/9 days in a row with temperatures not getting above freezing... almost!

What trigger low are you on about? The one moving off into Eastern Europe? ALERT: -14 uppers along the East Coast of UK!

Anyone for -16'c uppers?; that cold pool over Scandinavia tho...

Look at the Arctic High spreading towards Greenland, I'm confident that we'll see an easterly here. Hope we can see the heights out in the Atlantic link up.

Nothing too much to note on GFS 18z at the moment by T66... The low coming off the US East Coast is a tad further west along with the rest of the pattern to the west of the UK. Fingers crossed for an improvement going forward now.