Kasim Awan

Yes it's flatter at 168h however it is still building heights near Newfoundland. So still meridional overall.

GFS also sending more energy south which will help sustain any easterly by adding to the -NAO environment. It also helps keep the area of Griceland flow anomalies entact.

Looking good IMBY.

The ridge can not sustain forever. Ultimately it will flatten & reamplify..

ICON is sending trough energy SE on a highly tilted jet. This would keep the overall mean flow in the north east quadrant. Out to day 10 would be cold on the surface & potentially quite snowy for some.

The Arpege solution has 200mm of falling snow - unlikely to produce less than 10cm

The GFS is always too far out with the precipitation relative to the low centre at this range. Clearly evident for the 2019 event. Forecast is way too north. So whilst I agree about nowcasting, I also think probabilities can be appointed to the various solutions. Additionally I think we will see further tigthening around a solution by tomorrow's 6z.

Images discussed.

The hi res appear somewhat tighter in their resolvement of Monday's snow. The ARPEGE & others produce a more easterly track further north across N Eng before swaying the precip more S of SE. The upshot is that a line from Liverpool to Bristol sees falling snow with the potential for >10cm as hinted at by the Arpege's pivotting before less of a push south east. This before more of a wintry mix on the south coast later as the precip looses it's cold by the time it heads south. This solution is currently favoured with some sway both W/E possible e.g. refined to Welsh Borders or West Wales & as far N.E. as Leicester... A middleground again speculated here by the HIRLAM however this could be a false sense of security - with a more W/E outcome possible. The GFS is well north which seems unrealistic. So Welsh borders, Far west Mids & perhaps W Country atm favoured.

I still can't see any valid reasoning for any negativity this morning. There is a signal for zonal energy, however there was a signal for zonal energy in 1962/63. The processing & outcome of this zonal energy is more likely to be meridional. E.g. heading south & producing an easterly component or toppling east. The models may struggle a little with this processing of zonality, promising that there are some good ens in there. The main uncertainty is seen around Greenland. As you can see, a higher spread in the possible pressure values. This is a binary logic - it reflects that there is a division in the members between the zonal energy heading north & heading south relative to the ridge. The former producing lower pressure in that region and vice versa. I'm calling a middle ground to this binary logic which would ultimately send zonal pressure both ways producing a surface easterly before a northerly influence. In either case, because of the merodinial upstream pattern almost any mechanism of processing the zonal energy will lead to further cold. Ultimately there may be temporary upfluxing in temps before a dive again. This being 1 possible solution atm, and somewhat supported in the op. For the other look at the GEM.

The ukv does seem a fair middle ground, gven the gfs is now on board with a more northerly track Icon produces an easterly component to the ridging which is the logical progression at this range

You can be bone dry in a 970mb low as the convection will be mostly around the edges (showery feeds) where the pressure gradient is stepper, and the centre usually more stable like the eye of a hurricane. In this area ppn will be from shortwaves. Atm Monday looks like an early & late thing for some.

I have a feeling Tuesday isn't modelled very well yet. The uncertainty on Monday contributing to this. From experience these snow systems tend to stall out near their penultimate end & produce prolonged light to moderate snow. Once the earlier precip has been dealt with we may see these options being shuffled around in a more accurate mannor.

Hopefully you'll get heavy enough ppn to erode that maritime layer.. Valid worry as a more northerly track would take the heavier stuff inland. The result could be ice pellets for some.

The difference this time is a slightly lower ppn intensity requirements for snow - then about 40% now >65% of the precip will be snow Mon AM. The upshot of this is greater confidence in accumulation once the low track is resolved due to the lesser precip intensity requirements. ECM Hi Res does seem good at resolving at ranges >T60. However if it was too far west then I would bank that it might be marginally too far north right now anyway. Oxfordshire south for me but I at least see the room for a move to EC. GFS as you say also makes this progression to EC slightly by promoting a wrap up of precip across the SE Monday day. That needs a watch.

ICON in with a weaker low. This reduces outward expansion and thus keeps the fronts closer to the 500mb centre and thus more land coverage. M4 as the Northern boundary, before the secondary area Mon night further north..

Well overdone that. Last time I checked snow doesn't settle on the sea unless the Euro4/meteociel has been on the vino too tonight.

Just the weather?!

Spot on explanation re the waving. Bouts of polar jet injection are somewhat neccessary to sustain the overall pattern. During the approach of the wave the synoptic pattern may appear flatter. Due to the larger scale continouscpattern of recurring high amplification the wave will likely be broken again. This is a cycle of continuous injection and amplification which at the large scale we are seeing already.

Thanks both for the comments. I'm mostly a snow event geek however I also take time to view model output and trends and compared to some others on here I have a lot to learn too. It can take a while for newbies to grasp this concept. It is key though to properly interpret the data and avoid sudden reactions. The overall trend is strongly swayed towards a highly amplified pattern with an Arctic blast signwave (repitition). There will be deviations because ultimately all layers of meteorology takes on situational uncertainty. E.g. in radar watching, showers can change direction, crop up where unexpected.. This is reflected in model output too almost as a law of meteorology. Now imagine a very complex shower pattern, forecast weeks out.. I'd rather focus on the larger picture (shower direction, timing & main areas) as opposed to micro details. In a similar way I would also prefer to stick to "larger picture" pressure & temperature trends. However, logic and understanding should be applied i.e. this shower pattern usually does x y z, as can also be applied to longer term forecasting. This is the best meteorology can offer and is why the pros stick to the trends and logic rather than micro details for both showers & the long term forecast.

You know things are looking decent when even the minority option is good

Cold for most (-1 to 4C) very cold for a select few (-2 to 1C) i.e. high ground, snow cover & fog Some moderation from North sea

Only time will tell. It certainly has potential.

The 12z output remains highly blocked and cold going forward, and whilst not at the level the gfs had a few days ago, is still enough for cold& snowy conditions. Plus an inversion is highly likely to develop reducing upper requirements for surface cold. So those bfte charts are not the end all.

Whilst I must agree the cold at this period is not 100%, I feel you are both failing to see the bigger picture which is that any zonal energy is highly likely to add to the colder picture. This is because of the sharp NNW-SSE alignnent of the jet that we currently have. Lows become immobilized to the SE due to the merodinial 500mb flow. Look at the jet for Monday and the jet for 3rd Jan. Therefore the low heights will likely be shunted SE in a somewhat similar mannor to the new few day. This can not be described as zonal, Imo, as the upper waves are still heading away from climatology. Hope this helps. K.