Wow is all I can say, this is why I love winter with all its drama.

The deep low set to come over or close to northern Scotland is not even on
the charts yet but it will develop explosively as a shallow wave is excited
on the low-level baroclinic zone in the North Atlantic. This then phase
locks with an upper trough and high PV coming south from west of Greenland
and rapidly deepens late Wednesday into Thursday and is then steered by the
jet towards Scotland. The depression looks like being warm cored meaning
that close to the centre wet-bulb freezing levels will be up around 400
metres or so asl but deep cold air will be tucking in round it. Winds could
well exceed 70 knots (hurricane force in northern Scotland) and as the cold
air tucks in, blizzards (heavy snow and severe gales) are likely on hills
above 200 metres asl bringing white-out conditions in the mountains. Given
the warm core as part of the seclusion process the snow is likely to be of
the wet sticky variety and hence poses a significant risk of ice accretion
on power lines, especially Thursday evening when some truly horrific
conditions are likely in northern Scotland and the northern Isles (possibly
with power cuts). The winds will also generate a surge down the North Sea
which is being discussed elsewhere. The London barrier will be raised no
doubt and Holland should worry.

Now the cold front will sweep SEwards on Thursday, the main feature being a
rapid fall of temperature with possibly a short spell of sleet/snow on its
back edge, even on low ground in England. Before then though the air in the
warm sector is quite mild and may give rise to temporary snow-melt in some
upland areas. Then we have a frosty ridge on Friday.

Meanwhile the very cold (exceptionally cold?) air over Greenland will
continue to leak south lowering North Atlantic SSTs even more and push the
baroclinic zone a notch further south meaning that the next rapidly
deepening Atlantic low could slam further south into the UK early next week
after some respite over the weekend (rain and hill snow but just normal
wind). Further ahead I cannot see any end to this cold westerly zonality
which will tend to get even colder with time due to lowering SSTs and the
time of year!

Phew, I think that's enough from me!

Exciting cheers,

Will
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