Reply To: Northern England, (NW & Yorkshire) weather discussion January 2021

[Kasim Awan]

Good evening. A cold air undercut tomorrow evening is likely to combine with pivotting to produce a general lowering of the snow-line. The positive is that most high res place the pivotting over Northern England with some output shifting it south into the Midlands, which creates some uncertainty. With the pivot placed over the West Pennines, Manchester, Lancashire, Cheshire, Derbyshire and West Yorkshire there is a *risk* of some heavy wet snow to 50-100m temporarily in a fairly localized area where intensity is met in the pivot. The uncertainty is due to dynamics in the pivot which are still not resolved, mostly related to the definition of the cold air draw-in. The uncertainty created means statistically a 175m settling snow contour is gauged with a risk of mixed conditions below. This falling perhals to 100m on the eastern Pennines before lifting into Lincolnshire as the pivot looses vorticity. Again, this is a standard (median) snow line accounting for both: 1) The potential is there for the above, given the very low freezing level achieved by the GFSP 12z and ample cold air draw in on the Harmonie, Icon, Arpege and Wrf.
2) The potential is also there for a much less defined front given failed vorticity which would limit snow to 300m+ which looks likely to retain snow showers on Thursday before the snow line slowly falls. This to 200ft or so by Saturday AM & given the trough is weak expect some fair shower activity on a WNW wind which produces some good interest.

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