https://worldclimateservice.com/2021/01/22/mjo-forecast-and-stratospheric-warming/

I think this link was posted over the weekend, but here it is again anyway. A very interesting read regarding the influence of  SSWs over subsequent months especially when linked to high MJO activity in the Western Pacific (currently modelled over the coming weeks).

No probs, its actually facinating to see the uncertainty so large at such a short range. Its because, I guess, a very slight difference in how the shortwave develops will have massive consequences for the temp of the airmass.

This is a perfect example of why deterministic forecasts are not good for this sort of range.

For my area tommorow there is a 33% chance of disruptive snow, 33% chance of sleety mush and 33% chance of rain and turning very mild.

If we end up with the former (but even the later) scenario there will be egg on faces for those organisations just going for the middle ground to try and cut any losses.

The other thing I have at the back of my mind is that these sliders tend to not make as much progress NE as expected. Like on the radar tommorow morning if the rain is 50 miles further SW than expected it would have huge implications for the forecast for the rest of the day. Models will be totally useless. Just like how they were yesterday when the radar had the band further NE than expected.

Interesting Quantum, many thanks, Admire your passion and optimism, would be nothing more romantic than an unexpected snowfest where the mild air is beaten away. 33% chance of something decent , is certainly worth keeping an eye on.
Surely the precpitation intensity will be key too. Alongside the uncertainty in the models above, Met Office automated based on UKV has 2c then 1c with sleet here tomorrow and sleet and rain on Thursday. It is very borderline.

Indeed, arguably that's the main limiting factor for tommorow's event. They are also correlated, heavier precip is linked to a colder airmass because its asociated with the 2ndry low developing more and keeping the winds easterly rather than south westerly.

Even if tommorow's event ends up being light rain that doesn't negate the risk of Snow on Wednesday/Thursday though particularly since it will likely be a far more coherent feature although its probably less likely if tommorow doesn't deliver.

You can bet they all have the forecast rain here spot on every single time with the easterly influence.

Modest upgrade for the ICON12Z?

It would be nice for a large part of central northern Britain to get more snow over the coming days, however looking at the models and this morning’s fax it looks like the warm fronts will cross most of England before the chasing cold front catches up with it. I would expect the possibility of some freezing rain as the warm air rides over the cold pool with some fog over the hills and a steady thaw setting in south of the boarder by midnight tomorrow..

That said the charts are changing and if the fronts are delayed and become occluded than it could all change but as it looks right now I doubt it.

Thursday onwards is where it looks more interesting.

For somewhere with this. 12Z ICON is an upgrade on the 6Z.

To sum up what I'm thinking. Probability of snow tommorow:

Central belt northwards: 80%+ (though cannot rule out some initial rain before turning to snow in e.g. Glasgow)

Lowland N England north of Ripon: 60%+

Yorkshire and Humber: 50%

Most of the Midlands, E Anglia, north of the M4: As high as 30%

For somewhere like Glasgow or Edinburough 2-5cm of snow out of tommorow's event is virtually guaranteed.

This is as far as the mild air gets according to the ICON12z.

However note that the cold air in southern scotland pushes back south in time for Wednesday nights event.

ICON12z is a big upgrade on 6Z for Wednesday nights event.

Cold air pushes south much faster. Nothing dramatic yet but a few hours after this (not yet loaded) when the rain turns to snow in the N midlands it will look impressive.

I’ll report back to you lol 

I’m in the highest part of Glasgow so fingers crossed 🤞🏻 

OK it goes whoosh at around 65h

Freezing level drops as frontal zone approaches.

Honestly I think you'll have no problem. With some elevation its virtually 100%.

AROME12Z

ARPEGE12Z an upgrade on the 6Z

Should do a bit better than the ICON12z for the Wednesday night/Thursday morning snow event.

Thursday morning has the -4C T850 line across most of NE England!!!

ARPEGE12z as expected has a disruptive snow event for the N Midlands and Yorkshire for Wednesday into Thursday.

There is no ARPEGE12Z ensemble suite, but this deterministic run is alot better than the 6Z mean for Wednesday night/Thursday.

Not much change for tommorow's snow event though. Still very marginal for Yorkshire and N england. Less so for the central belt.

ICON 12z looks about right for the north...

Seem the Wed/Thurs one had been push further south on each run.

A couple of days ago, wasn't all the cold air meant to be swept out of the way by midweek??