Thursday's Arctic Surge

[Nick F]

Nick, what are you thoughts on the snow potential for Yorkshire from the cold front? Yesterday seemed to show conflicting forecasts, with the GFS indicating a sleet to snow event, but the BBC showing a 90% rain event.

Definately think there will be some back edge snow for much of the UK as the cold front moves south, whether it will be a brief period of snow or not remains to be seen though, I suspect the further north you are the more likely you are to see the greatest snow amounts, but I don't think accumulations will be that great maybe 1-3cm - as the front looks to pass through fairly swiftly. Nowcasting will be the best tool to see how much snow is going to fall when the front passes through.

[helen of the north]

In the last hour it has come on right gusty up to 46mph from NW and lashing rain. -27mb drop in last 6 hours. Currently, 1013.3 mb . 4.1C

[rogski]

Apologies if this is off-topic but it is a question about upcoming conditions across much of the UK and I can't see anywhere else as appropriate to post.

If any of the experts here were driving from Bristol to Warrington on Friday evening and then from Warrington to Aviemore on Saturday what would be the safest route to follow, east or west or is nowhere safe from potentially heavy snow? As an alternative would it be safer to head over to County Durham in the east as an alternative to Warrington?

I rather get the impression that nowhere is safe to be honest and disruptive snow could pop up anywhere but much of the discussion in places like the Models thread is quite confusing for a newbie like me, with people popping up and bemoaning conditions in their area then others contradicting them. I get the impression though that the west might initially get the brunt of the snow or is it just the coasts and both east and west ... hey I'm confused!

Edited December 16, 2010 by rogski

[Neilsouth]

http://www.raintoday.co.uk/heatmap

^ shows the cold rushing across the uk during tomorrow

[Thundery wintry showers]

Apologies if this is off-topic but it is a question about upcoming conditions across much of the UK and I can't see anywhere else as appropriate to post.

If any of the experts here were driving from Bristol to Warrington on Friday evening and then from Warrington to Aviemore on Saturday what would be the safest route to follow, east or west or is nowhere safe from potentially heavy snow? As an alternative would it be safer to head over to County Durham in the east as an alternative to Warrington?

I rather get the impression that nowhere is safe to be honest and disruptive snow could pop up anywhere but much of the discussion in places like the Models thread is quite confusing for a newbie like me, with people popping up and bemoaning conditions in their area then others contradicting them. I get the impression though that the west might initially get the brunt of the snow or is it just the coasts and both east and west ... hey I'm confused!

On Friday I suggest you stay away from high ground (which will probably have major accumulations of snow tomorrow) and the west coast (which is likely to see snow showers firing in on Friday). The question of Warrington or County Durham is a tricky one but if pushed I'd suggest Durham because the heavy disruptive snowfalls on Saturday (which are likely to considerably surpass anything that tomorrow or Friday produces) are expected to reach Warrington earlier and with greater certainty.

[peterf]

On Friday I suggest you stay away from high ground (which will probably have major accumulations of snow tomorrow) and the west coast (which is likely to see snow showers firing in on Friday). The question of Warrington or County Durham is a tricky one but if pushed I'd suggest Durham because the heavy disruptive snowfalls on Saturday (which are likely to considerably surpass anything that tomorrow or Friday produces) are expected to reach Warrington earlier and with greater certainty.

good shout that.

great thread NICK F,enjoyed reading it.peter

[Nick F]

A fair drop in temperature in the early hours of the morning across the north as the cold front cleared through, at 6.20am it was 7C at Newcastle, then at 0650am it was 1C, a drop of 6C in 1/2 hour!:

Observations for NEWCASTLE, United Kingdom (EGNT)
Location: 55.03N 1.70W 81 meters
0850Z 15 Dec 2010 to 0920Z 16 Dec 2010 
STN     TIME ALTM   TMP DEW RH  DIR SPD GUS VIS  CLOUDS          Weather     
     DD/HHMM hPa    C   C   %   deg m/s m/s km                               
==== ======= ====== === === === === === === ==== ======= ======= ============
EGNT 16/0920 1007.1   1   1 100 320   2     10.0  FEW010  BKN030
EGNT 16/0850 1007.1   1   1 100 350   3      5.0  FEW005  BKN008 SW-
EGNT 16/0820 1007.1   1   1 100 350   4      3.5  BKN008         RW-S
EGNT 16/0750 1007.1   2   1  93  10   6      6.0  BKN008         RW-S
EGNT 16/0720 1007.1   2   2 100  20   7      5.0  BKN008         RW-S
EGNT 16/0650 1007.1   1   1 100  20   9      3.0  BKN008         SR
EGNT 16/0620 1006.1   7   5  87 280   9     10.0  FEW012  BKN027 R-
EGNT 16/0550 1007.1   7   5  87 280  10     10.0  BKN049
EGNT 16/0520 1008.1   7   6  93 280  10     10.0  BKN045

Not such a great drop as front cleared through, but was 8C at 3.50am this morning in Glasgow, now down to 1C:

Observations for GLASGOW, United Kingdom (EGPF)
Location: 55.87N 4.43W 8 meters
0850Z 15 Dec 2010 to 0920Z 16 Dec 2010 
STN     TIME ALTM   TMP DEW RH  DIR SPD GUS VIS  CLOUDS                  Weather     
     DD/HHMM hPa    C   C   %   deg m/s m/s km                                       
==== ======= ====== === === === === === === ==== ======= ======= ======= ============
EGPF 16/0920 1010.8   1   0  93   0   0     10.0  FEW008  SCT020  BKN028
EGPF 16/0850 1010.2   1   0  93  70   2      4.0  BKN006                 SW
EGPF 16/0820 1010.2   1   1 100  40   4      5.0  BKN006                 SW-
EGPF 16/0750 1009.2   3   2  93 110   4     10.0  SCT016  BKN030
EGPF 16/0720 1009.2   3   1  87  80   2     10.0
EGPF 16/0650 1009.2   5   3  87 320   5     10.0
EGPF 16/0620 1009.2   6   3  81 300   8     10.0
EGPF 16/0550 1010.2   7   4  81 290   8     10.0  FEW024
EGPF 16/0520 1010.2   7   5  87 290   8     10.0  FEW017  SCT023  BKN042
EGPF 16/0450 1010.8   7   6  93 280   7      8.0  FEW012  SCT017  BKN022 L-
EGPF 16/0420 1011.9   7   6  93 280   5     10.0  FEW012  SCT017  BKN023
EGPF 16/0350 1012.9   8   6  87 290   7     10.0  FEW012  SCT018  

[rogski]

On Friday I suggest you stay away from high ground (which will probably have major accumulations of snow tomorrow) and the west coast (which is likely to see snow showers firing in on Friday).

The question of Warrington or County Durham is a tricky one but if pushed I'd suggest Durham because the heavy disruptive snowfalls on Saturday (which are likely to considerably surpass anything that tomorrow or Friday produces) are expected to reach Warrington earlier and with greater certainty.

Thanks for the detailed reply, it's really useful.

Do you think heading through the Midlands Friday evening and then over east and up to Durham would be okay(ish). The alternative is to go via London but I don't fancy that!

BTW, I do have winter tyres and chains but it's more about avoiding potential traffic chaos and getting stuck in that.

[Bod]

Here's a quick look at the situation, from the 12z actuals and predictions.

First off, the wider european plot:

The low pressure is positioned in Sweden with a central pressure of 981 hPa. The warm and cold fronts can clearly be seen by the kinks in the isobars.

Here is the corresponding satellite image:

You can clearly see the differing air masses there, well specifically you are seeing the height of the cloud tops - the IR image shows the temperature of the water vapour.

If we take the satellite with precipitation overlaid:

I would draw on the fronts roughly like this:

Now. if we zoom in on the UK surface analysis, we can see the temperature drops behind the cold front. Widely 5-7c before the front and 2-4c immediately behind with that dropping down to 0-1c by the Borders and widely below 0c in Scotland as the cold air digs in.

Lastly, we can compare the actual results with predictions from the GFS and the NAE. Here is the GFS prediction:

Here is the NAE prediction:

Comparing these they seem pretty close. The GFS, because of its resolution looks like more of a broad-brush of where the precipitation will be - not bad. The NAE also looks a bit broad and has slightly underestimated the speed of the front and overestimated the precipitation but otherwise not bad all round. One last image - the UKMO surface pressure chart for 12z, which looks pretty close to me (as you'd expect at this range):

What will be interesting to see later on is how much back edge snow (if any) there is towards the South and whether the front largely fizzles out - it doesn't look particularly vigorous to me (yet).

[xerxes]

Well on the ground, the initial CF has just gone through Alton with a spell of torrential rain and hail albeit brief. Wind shear of about 60 degrees. 2M temps were 6.3C at the onset and are falling quickly, now 4.6C, that in 10 minutes and still going

[summer blizzard]

Nick, can you apply your analysis to saturday and sundays areas of low pressure.

[DanN]

As summer blizzard mentions above, that would be really interesting to read if Nick has the time and maybe from Bod as well...