While the cold air is here, a lot of uncertainly lies in the forecast as mild Atlantic air tries to erode the cold over the UK late tomorrow and Friday. The question is, will the cold win out by either keeping the front back west or will it allow the front to penetrate inland but turn rain over the snow as the moisture hits the cold air or will it rain and warm up? I find it hard to believe that this building cold will give up without a fight. What’s interesting is that whatever happens, the cold comes right back in. If it snows and accummulates, then the stage is set for a very cold first week of December.

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Before I get into the rain-snow threat for Friday, check this out below.

The three charts below (courtesy of WeatherBell Model) show the latest NCEP GFS temperature anomalies (F), these are impressive and show a brutal period for Scandinavia and no warming in the next 16 days for the UK.

Next 7 days (Impressive given this is averaged over the 7 day period!)

Next 16 DAYS

There is often challenges in forecasting when you’ve got this setup.

I want to show you the 850 temps projected by both ECMWF as well as GFS as the system tries to work east into the UK tomorrow night and Friday.

Here is the GFS 850s for Thurs/Friday

24 hrs (Thur)

36 hrs (Fri)

Here is the ECMWF 850s Thurs/Friday.

48 hrs (Fri)

Notice the cold at 850 isn’t disrupted, keep in mind that cold air is dense and therefore sinks, so any warmth would likely ride over top of this cold which has been building, the fact that the GFS and ECMWF hold the cold up at 850, suggests to me that the air temperature underneath and down through the column should be cold enough to support snow rather than rain once the precip gets inland. The Western Isles and up and down the West Coast of Scotland the UK overall may see rain or a mix but if this precip gets inland, I believe rain will turn to snow and down to low levels. The cold ground would also support this snow lying.

The main snag in all this I think would be the dryness of this air which could evaporate a lot of the incoming moisture so all we may see is cloud.

This system doesn’t appear to disrupt the cold too much, Friday, like tomorrow will see 2m temperatures holding throughout the day at 2-4C with nights, even with possible cloudcover diving below freezing. If there is clear skies then widespread -4 to -8C is likely.

Finally, check out this 6-hourly NCEP GFS Snow accummulation chart from today through December 6 off the Weatherbell site. Looking good.

 

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