First of all I want to take a look at the next 48 hours which is a real headache as it’s complicated.

The complicating factor is that we have a weak Atlantic frontal system trying to make inroads into the Northern UK but the question is, how does this interact with the cold air in place. Does it warm it enough to produce rain to low levels, do we see initial warming, then dynamic cooling or colder air perhaps wrapping on on the rear of the boundary with initial rains transitioning over to snow, do we see the cold stand firm in the lowest mile of the atmosphere with the warmth and moisture riding up and over the cold, dense air which forces the moisture to fall through the column, with the temp remaining below freezing and therefore keeping the precipitation as snow all the way to the ground. These are all questions you must consider with this situation. No easy forecast.

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Showers are falling in the north with rain to low levels from what I can gather. Temps are in the 3-4C range up there but it remains near or for some, below freezing down here and as the sun drops, so the column cools and as showers run south, this colder low level atmosphere may support snow for the low levels of the Central Belt tonight but the air is also very dry so these showers and clouds may even evaporate. This can make way for unexpected clearing of skies which can in turn produce a much colder night under the stars. That is what I believe happened last night. There was a few reports of it trying to snow around Glasgow and even here in Lennoxtown, it almost looked like there was an odd flake on the frostcover this morning.

Since the start of the week, I have been saying about the intensification and deepening of the cold layer from midweek on and how this may support more snow than rain. The mild Atlantic air and moisture is being forced up and over top of this ‘lower level’ cold pool sitting over the UK but is this deep enough, extending the often needed, lowest mile of sub freezing air in order to support snow to near sea level. Is the air cold enough to support snow down to street level in say Glasgow, Edinburgh, Carlisle or even Manchester? The BBC seen to have been swaying more to rain but I am not convinced. With this setup, all it takes is a warm layer or a 1C difference somewhere in the mid or low levels, we can see warm leysr slice in between the overall cold column and this is enough to bring rain, not snow to the ground. These scenarios of warmth in between cold, can lead to freezing rain, a far worse problem given the subfreezing ground.

BTW, there will be plenty of clear skies again tonight and over the next few. Where they stay clear all night, temps may dip to near -10C in the coldest spots and even where cloudy but then clearing through the night, temps may go from a comfortable -2 to -6 or 7 within just a few hours. This is a cold and stagnant air mass!

Interestingly, the GFS does see snow at low levels tonight and tomorrow.

Here’s the NCEP GFS 6-hourly Snowfall (in inches) this evening through Saturday from the Weatherbell site.

18 hrs

24 hrs

The ECMWF isn’t as bold on the snow for the UK as the GFS is for the next 36 hour period, however it is slightly more optimistic about the next and bigger system set to push in off the Atlantic on Sunday but appears to still keep the snow north of the Central Belt.

Here’s the ECMWF Control for Friday & Saturday. 850 temps certainly look conducive for lower level snowfall. Especially with surface temps 0-4C by day, -1 to -6C by night.

Friday

Saturday

What About The 2nd, Stronger System Which Arrives Sunday?

Notice the wedge of warmth to the west of the UK in the charts above? This shows the warm air lifting north ahead of an advancing cold front but as you’ll notice in the charts below, that warm air gets quickly replaced by cold air rushing in on the backside of the front. Interestingly, the timing in the latest run is delayed and the front doesn’t appear to reach the west coast till Monday rather than Sunday.

72 hrs (Monday AM)

Below is the 90 hr for late Monday and you can see the 540 rain-snow line pushing off the south coast and colder air rushing in on the rear.

Below is the ECMWF surface precip/heights for 102 hrs (Tuesday AM). Note a 988mb low east of Scotland with north flow and the 540 line way south.

Below is the snowcover for Tuesday at 96 hours according to the NCEP GFS (Courtesy of WeatherBell). Note the swath of snow on the ground for much of Scotland extending as far south as Manchester.

Also note the massive snows over Scandinavia and down over the Alps with a decent covering across the heart of Europe.

Here is the ECMWF for the same period.

Further Snow On The Models For Late Next Week?

Check this out by 162 hrs, (next Friday) the first chart shows the surface pattern with a high to the west, low to the east, cold north flow blowing over the UK and the 540 to the south. The second chart shows colder 850s. Finally, the third chart optimistically has more snow on the UK map, extending as far down as Manchester.

1) Surface chart

2) 850 temps off ECMWF

3) Snowcover

The ideas particularly for next week are speculation and a lot can change but all this is worth keeping an eye on.

I shall post more on the longer term pattern shortly.

Stay tuned.

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