Kasim Awan

It is. The evolution 160-220 is looking like a repeat of the one we have at 120-150h. The level of mixing is still to be resolved in the output. It is likely to be lower than the first go.

The low breakaway of energy from Greenland is looking increasingly possible now. This is a slow mover, moving into low heights & v low surface dew points. As @snowking explained yesterday, T850s under low heights & slack conditions can produce a better temp profile than T850s 5/6C lower in a flow with strong winds & >1000mb. Big recipie for surprise snows with this output.

The GFS 06Z has moved towards the ECM in producing a greater northerly component here at 150h. Euro model is favored in bias terms when dealing with low modifications.

300m plus will be the day time non evap cooling snow line I think..

Euro4 churning up precipitation associated with the trough. Possibility for temporary lowering of the snowline with this - North York moors producing some orographic lift too.

ECM had that easterly for day 10 a few days ago. Goes to show that D10 charts are useful for picking out longer term trends in the model, and that the EC has supported the GFS evolution seen tonight. This increases my confidence a bit to.

Many would be dubious about the 160-200 synoptics verifying if we were starting from scratch i.e. a flat westerly flow.. But we already have, now in the reliable, the "starting" synoptics which would likely yield and definitely support this outcome. So my confidence is elevated.

Think we've found a good solution for a potential final synoptic evolution?. The credibility is there both in terms of synoptically validity & in model support.

GFS Is..

Notice the uppers @ 200h. The initial cool spell leaving improved surface parameters. Upshot - less impressive synoptics will be capable of wintry weather post 200h.

The GFS 18Z sides with the GEM 12z. The dive SE and slight amplification towards Greenland D7+ is very reasonable. On the surface this yielde a temporary Easterly, before another go at a Northerly shot.

Few flakes.

Interesting.

Potential for a very weak front to produce a few flakes in NW Eng Xmas day.

I think by Xmas day we will be in a position data wise to discuss potential snow outcomes 27th-29th.

A surface inversion will almost certainly develop inland from 2 days in that flow. This will massively help with snow opportunities 29th/30th. An inversion essentially gives you as good snow parameters as the altitude of the summit of the inversion by removing the milder air between the surface and the summit. So it's like being 300m up if there was no inversion. I do think it's a very fine margined set up - these have a potentially high impact yet low to moderate risk.

I agree. Best to keep an understanding of the overall progression. Analysing changes east / west sorts is useful for binary changes i.e. if a low manages to do trough disruption and the domino effect synoptically - not micro details.

I remember in 2013 when the ECM coughed up these rather bizzare solutions. Possibly a sign the model is having difficulties modelling the background factor conjuncture we face at present.. At the very least the model is getting rid of the Atlantic. Some negative aspects about the run. These if expressed as westerly vectors in the actual outcome may promote low spawning and surprise precipitation events.. A good EC12z and I'm not going to over analyse it. The evolution of a low diving south with renewed amplification seems likely but I think it will be a messy evolution to cold D7-10.

The ECM produces a smaller and more complex pressure profile within 200 miles of the minimum pressure, this producing more convergence and therefore shortwave activity. I feel this is much more valid. Esp given as the GFS has a tendency for dartboard simplification.

You're right. 2010/2013 style conditions are some way away. Yet as many have said many a time - the moderated uppers still provide snow potential. It would require more to come together, but the return would be fruitful for some.

144 would be very wintry somewhere north of the low core. Temps will get quite cold overnight 28th 29th so where the precip swings on the northern flank, morning snow event possible.

Perfect for IMBY.

I think there is a tendency for people to get overly dependent on the Numerical Model's first solution of how the cold will occur. The evolution is constantly changing, and the route to cold will evolve with each run. Good sign something is a foot because we are at least dealing with model attempting to resolve blocking outcome - this a sign a background factor is at work.

Amazing GEM. Surface Easterly then a "low of polar origins" about to dive SE.

The GFS is good. D7 to D9 we see an easterly develop which is, theoretically, a credible possible outcome given the tendency for these ridges to pull away SSE. Also, higher heights are spawned to the NE connecting to the area E of Svalbard which seems juxtaposed to produce H pressure at present. This all promoting a temporary easterly.. This produces wintry surface conditions. Next. The low diving SE from Greenland is also credible, given that there is a trend for amplification and a NW-SE jet prescribed nicely by the EC 00z op; this could well become cut off and run another attempt at an easterly around D10.