I didn't say it would verify,  just thought it was an interesting run to go from low level snow in southern England to 850s above the July average. 

https://www.wetterzentrale.de/en/topkarten.php?map=2&model=ecm&var=1&run=12&time=240&lid=OP&h=0&mv=0&tr=24#mapref 

Predictably the op is a genuine outlier for 850 hPa temperatures when it brings in that mild air mass, pretty much unsupported across other measures as well (500hPa temp, height of 0c isotherm, 2m temp).

Can the forecast blocking cause an SSW? Or contribute to one ? 

Not the place for political discussions I know, but I wonder if what Keir Starmer and Rachel Reeves deciding to do away wih automatic winter fuel payments for pensioners this year has had anything to do with this!

Of course, winter doesn't not start and end in November, but the irony of a early cold spell as now indicated by the models would not be lost on me.

My understanding is that is works the other way round, with a 2-3 week delay from upper wind stalls/ reversals. 

I would have thought that any wintry prospects in the south for next week would be helped with a flabby situation to become established once (and if) the deeper colder air becomes established.   Any vigorous developments along the southern trough would need a very flat and favourable orientation in my view, and of course the more vigour, the less chance of that.

Yes understand that by wasn’t sure if a blocking pattern could have the necessary impact to facilitate a warming??

https://x.com/TWOweather/status/1856456380930052153 

It's a good question,  I'm not sure tbh. 

Yes. Sudden stratospheric warnings are caused by specific blocking patterns. Usually you’d want to see a Ural HP/Aleutian LP pattern as a precursor.

Just google what causes a SSW, essentially tropospheric waves deflect up into the stratosphere to rapidly warm it. So yeah, our terrestrial weather is ultimately the mechanism.

Probably. We've seen SSWs following European blocking in the past, where a very blocked and cold spell here has been followed by an SSW. January 1987, for example, and Feb 2010 saw a split SSW after an extended spell of blocking (which moved eastwards after bringing us a very cold spell in Nov/Dec 09, during January we had southerlies instead as the block moved slightly east).

“Sometimes the usual westerly flow can be disrupted by natural weather patterns or disturbances in the lower part of the atmosphere, such as a large area of high pressure in the northern hemisphere. This causes the Polar Jet to wobble and these wobbles, or waves, break just like waves on the beach. When they break they can be strong enough to weaken or even reverse the westerly winds and swing them to easterlies. As this happens, air in the stratosphere starts to collapse in to the polar cap and compress. As it compresses it warms, hence the stratospheric warming”

https://www.metoffice.gov.uk/weather/learn-about/weather/types-of-weather/wind/sudden-stratospheric-warming 

GFS Op - HP over Britain or to the west of it, though GFS unlike FAX doesn't show the embedded front moving S-wards later today. From Sun 17th the HP collapses and N-lies set in under the influence of LP 975 mb Denmark. Secondary LPs arise where the N-lies interact with a warm Atlantic, though not as dramatic as shown yesterday; one now running along the Channel to Dover 985mb Thu 21st, and then HP re-asserts itself from France (briefly milder SW-lies before back to cold) before an elongated W-E trough lies across Scotland 990mb Tue 26th, and another Channel runner 985b Thu 28th. 

ECM - Similar to GFS at first then the Channel LP arrives a day earlier, i.e. Wed 20th, and then moves N-wards up the N Sea, instead of trundling on to Poland, thus in this model refreshing the strong N-lies (no sign of milder SW-lies)

GEM - produces a secondary in the N Sea Wed 20th at the same time as a Channel runner. These merge and move S-wards into France so giving an E-ly spell of weather from Fri 22nd.

GEFS - temps dipping to about 6C below norm for a week from Mon 18th but then (with less ens agreement than yesterday) the mean recovers to norm (sooner in the SW) and stays there. A lot of rain from Sun 17th especially at first in the S, less in the N (but snow for higher ground in the N, even an outside chance for hills in the S). 

Not too eloquent or accurate but fairly pertinent in the silly season. The GEFS easing off 850s so that we’re looking at a three day NW spell - low dps and minima notable for November but as it stands not especially potent.

Obviously that could still change. But its honestly not that cold. Obviously snow can still happen when 'stuff slides into cold air', but I've wasted too much of my life hoping for these sorts of events that seem to guarantee snow in Sheffield and nowhere else.

https://www.wetterzentrale.de/en/topkarten.php?map=1&model=ecm&var=1&run=0&time=360&lid=OP&h=0&mv=0&tr=24#mapref 

Two major snow events before midweek.

ECM open data since launch has been delayed by 1 hour but as far as I am aware the essential data sets are available without delay and always have been. It's possible the open data delay has been reduced or removed and if that is the case charts will appear earlier by default on TWO (and probably elsewhere). What I can confirm is they now go out to t+360 hours.

On TWO the essential data generated charts go out to t+240 and are here:

https://www.theweatheroutlook.com/twodata/ecmwf.aspx 

The open data ones which go out to t+360 hours are here:

https://www.theweatheroutlook.com/twodata/ecmhr.aspx 

Here's the first t+360 ECMWF IFS MSLP / 500hPa chart on TWO.