South West and Central Southern England Regional Weather Discussion 03/03/2018 Onwards

[Evening thunder]

Some nice moderate snow for the last hour or so here  Big flakes at times too, although it's not settling anywhere much except the moss blobs on the neighbour's roof lol. Just easing off now though. Temp dropped to 0.8C but now up to 1.2C.

We had some flooding on the rivers around here Thursday morning with up to 40mm of rain in the Blackdown Hills, so with the snow/freezing rain on the 1st/2nd March there's been some weather this month. Using the lowest total from my snow cores on the 2nd, we've already had 120mm of precipitation here this month.

 

[Frosty hollows]

2 hours ago, ajpoolshark said:

To help pass the time, lets play a game....Netweather South West Thread Bingo.....no prizes for the winner apart from the accolade of being a bit of a smarty pants

Post of the year ????

[Frosty hollows]

We've got some settling here but mainly in sheltered spots.  Ground temp hasn't got above 4 here this week so that helps!

Back to snizzle after that initial band passed through. Looking forward to the main event

[MrNooo]

Snow, on and off all morning here, small grains to reasonably large flakes, bitter out in the wind, met a chap who came from Chipping Norton and he reckoned they'd have circa 2" of laying snow, wasn't sure to believe him to be honest. Birds are very busy on the feeders here this morning!

[Leon1]

am i going to stay up all night to see this snow or does it come before midnight!

[Frosty hollows]

5 minutes ago, MrNooo said:

Snow, on and off all morning here, small grains to reasonably large flakes, bitter out in the wind, met a chap who came from Chipping Norton and he reckoned they'd have circa 2" of laying snow, wasn't sure to believe him to be honest. Birds are very busy on the feeders here this morning!

May well do up on the Cotswolds.  I'm further south and at sea level and it's settled here albeit not in huge amounts 

[Frosty hollows]

1 minute ago, Leon1 said:

am i going to stay up all night to see this snow or does it come before midnight!

It's going to be freezing all day tomorrow so if any does settle it'll still be there when you wake up !

[khodds]

2 minutes ago, Leon1 said:

am i going to stay up all night to see this snow or does it come before midnight!

I’ll be up practically all night anyway.. Work doesn’t finish until 3am.. loading the car up with a shovel, salt, blankets... what else might I need?!

Edited March 17, 2018 by khodds

[khodds]

The wind is incredible!! Bins are flying everywhere ?

[MrNooo]

2 minutes ago, Frosty hollows said:

May well do up on the Cotswolds.  I'm further south and at sea level and it's settled here albeit not in huge amounts 

You must have had more than us in the night then, am 360ft above sea level here and the grass is green as!!!

[karlos1983]

0.6c here DP dropping steadily now also. Ground temps will plummet 

[Wilxy]

Think I'm a bit to far North tonight but lets wait and see what happens its a bonus anyway as i'm still happy with what I got from the other week, and its nice to see all of SW England in amber warning again as its about time we had some decent falls of snow down here after years of being in the worst place!

[offerman]

Can’t really see where all today’s snow is supposed to move in from ? 

Or has it not developed yet? 

[EllyTech]

5 minutes ago, khodds said:

I’ll be up practically all night anyway.. Work doesn’t finish until 3am.. loading the car up with a shovel, salt, blankets... what else might I need?!

A lovely hot flask of tea! 

[jethro]

36 minutes ago, stevofunnelcl said:

snow init !! - and not even amber warning until tomorrow, i read it, they are talking about wet snow, potentially heavy and lasting for much of the day across the south-west. The wet snow could bring down power lines / branches... i didn't realise it was that heavy

Back in February 2009 the foot of heavy snow we got here flattened my workshop and brought two trees down, wet snow weighs an absolute ton. Hubby back and warming up in the bath, they were on the top of the Mendips when the heavy stuff came down, silly people, can't say they weren't warned. Snizzle here now with the odd bigger flake thrown in.

[khodds]

Very light dust falling here, no accumulation yet but just like the beast I. Nice and dry stuff! 

[jethro]

6 minutes ago, khodds said:

I’ll be up practically all night anyway.. Work doesn’t finish until 3am.. loading the car up with a shovel, salt, blankets... what else might I need?!

Biscuits, torch and camera.

[SilverWolf]

1 minute ago, tomjwlx said:

Think I'm a bit to far North tonight but lets wait and see what happens its a bonus anyway as i'm still happy with what I got from the other week, and its nice to see all of SW England in amber warning again as its about time we had some decent falls of snow down here after years of being in the worst place!

The BBC forecast (yeah I know...) had the area of snow eventually moving from the London area through Gloucestershire into South Wales as it’s nothern bit... so might be a late night yet! 

[Leon1]

1 minute ago, offerman said:

Can’t really see where all today’s snow is supposed to move in from ? 

Or has it not developed yet? 

ye same here, i was wondering where it was on the radar or when it would show.

[OldBloke]

Continued heavy snow on the East side of Dartmoor. Fields, cars and roofs now getting an even covering. Thankfully, the gritters were out this morning so locally, roads are still clear.

[Guest]

TONIGHT'S AND TOMORROW'S SNOW

At last the snow has reached Exmouth   0.5c fairly light (1200) and medium flakes. After my bullish forecast earlier I was beginning to doubt myself - no I wasn't   I must keep an eye on the live charts, radar and satelitte etc while I write this post! The fronts chart does not auto update - I'm not aware of one that does. The old Met O site used do update them regularly but dropped that extremely useful feature 2 years ago.

        

        

I'll start with the good news before I move on to the very good news! The narrow line of snow over our region is the cold front clearing south-south-westwards. There are still a few slightly heavier burst on it but it's mostly light to moderate snow. The very cold air is undercutting so quickly and almost all the snow is the dry powdery stuff. The ground surface (down to 10 cm below) is still 4c to 5c - hence the melting and only slight settling. This will change as the surface (not the lower 9 cm) cools to nearer zero later today. Then almost all the snow will readily settle and start to accumulate. There will be very little sunshine to melt it today and especially tomorrow which will be an ice day for many of us. The snow showers further north are spreading out slightly (with small gaps between them) but have been intensifying with white echos showing up. It's the snow showers pushing into East Anglia and down the M4 corridor that we need to keep an eye on. Once the cold front clears just to our south (more or less stalling in the English Channel) more snow showers will develop over the south-east with a Thames streamer likely this afternoon. As the flow backs slightly from east to east -north-east and with a strong wind - it's these showers that should spread right across our region later this afternoon. Some are likely to be pretty heavy and many parts should see some accumulations by this evening. Now let's move on to the very good news!

Met O Fax Charts:   0600 Sat Mar 17th                                    0000 Sun Mar 18th                                1200 Sun Mar 18th                                 0000 Mon Mar 19th                                  1200 Mon Mar 19th       

                       

We can see all the fronts that cleared through our region this morning. By midnight the main cold front (the last one in the queue that brought in the sub zero temps) has stalled in the Channel. They show a Thames streamer and a Lincs streamer (the toothed quasi stationery black trough lines). Now this is where it gets trickier. Various models have (or "had") very slightly different solutions. I'll look at some of those in a minute after I've gone through the Met O thinking. They develop a wriggle in the cold front and then a minor LP on it. They show this developing in the eastern Channel over the far north-western French coast and near to the Kent and Sussex coasts. There would already be more continuous snow around and to the north of the front and the snow shower activity slightly further north and north-westwards (say south of the M4 for a change!) is also likely to intensify. By midday tomorrow they show this feature in the south-west approaches and moving westwards. The trailing occluded front remains in the Channel and much of southern England and more especially the south-west is likely to have seen some "at least" quite heavy snow. Much will depend on the exact track of the minor LP, whether it deepens at all and how far the fronts push northwards. The south Midlands and south Wales "may" also see some of this continuous snow or at least enhanced snow shower activity. By midnight Sunday into Monday they show the front well clear of the south-west but stretching west-north-westwards from the Brest Peninsular through the Channel with the easterly flow right across our region again. That flow is still over much of  southern England during Monday - already lasting longer than predicted until yesterday. Let's look at the excellent Arpege pressure charts for some greater detail and their take on this from their 6z run. 

(Exmouth UPDATE: 1300 now and moderate "dry powder" snow with larger flakes and starting to settle - I am right under the cold front and it's down to 0c - many of you should be below zero by now).

         0000 GMT Sun Mar 18th                            0060 GMT Sun Mar 18th                         0900 GMT Sun Mar 18th                         1200 GMT Sun Mar 18th                           1500 GMT Sun Mar 18th

        

        1800 GMT Sun Mar 18th                             2100 GMT Sun Mar 18th                       0000 GMT Mon Mar 19th                          0300 GMT Mon Mar 19th                        0600 GMT Mon Mar 19th

         

The main fairly slack LP is centred over much of central and southern France by midnight tonight. Arpege show a minor LP cell developing just west of the Cherbourg peninsular. This deepens slightly during Sunday and pushes slightly north-westwards. to lie about 50 miles south of the Lizard by 1500. It slowly pushes westwards and then south-westwards to end up just west of the Brest Peninsular by midnight Sunday/Monday. It then drifts slowly southwards into Biscay during Monday. There are signs of "possible" further disturbances showing up later on Monday near the Channel but that's already too far ahead with all this uncertainty on the micro detail. I'll pick up on that tomorrow morning.

I've had a look at the other models and the GFS 0.25 Hr is very similar to Arpege. In fact I feel that there is pretty good agreement on the 6z runs for the next 24 hours or so.  Things could change on the 12z output but it looks like the minor LP will skirt along the Channel just off the south coast. How much the old front reinvigorates is difficult to tell. The extreme temp contrast with the sub zero surface temps, very low dew point temps and sub -8c (or lower) uppers over southern England (and all of the UK) will engage with the warmer air to our south. Unlike two weeks ago, when we had storm Emma doing battle with the Beast, this time we have a minor LP feature and the deep cold will win this initial battle. There is even a possiblilty of some extremely heavy snow with a full on blizzard and I will not be surprised to see the already expanded amber warning area being further enlarged and possibly a red area from roughly the IOW westwards through to Cornwall and uo to about 50 to 100 miles inland. There is no point in my showing any snow charts, which many of you will do anyway. Just watch it all develop. This may well be an all nighter   

I'll be back with another (briefer) update this evening.  I've now got a slight covering here but still melting on the roads and pavements - just below zero now too, which is not bad for the south coast in mid March at 1400!   David

 

EDIT: To answer a few recent queries - the overnight snowfall will almost entirely develop in situ - just watch the radar this evening and the infra red satelitte. I'll update these quite regualrly during the evening and probably overnight too. Also, we have yet to see the snow showers develop over the Thames estuary - just the first signs right now and we'll get some of those later this afternoon. as well. Down here on the south coast we're having continuous moderate snow. The cold front has stalled very close to the coast and "might" produce more "earlier" snow than forecast. 

Edited March 17, 2018 by Guest
Correct typos and check charts

[karlos1983]

14 minutes ago, offerman said:

Can’t really see where all today’s snow is supposed to move in from ? 

Or has it not developed yet? 

 

12 minutes ago, Leon1 said:

ye same here, i was wondering where it was on the radar or when it would show.

Not developed yet. Should start showing on the radar towards the SE this evening 

[Wilxy]

13 minutes ago, Leon1 said:

ye same here, i was wondering where it was on the radar or when it would show.

watch for developments in the highlighted area during the afternoon this is the same area that should move towards us during the night!

[Leon1]

another heavy snizzle shower but the difference is, this time, it's beginning to look a lot like christmas  settle a bit

Edited March 17, 2018 by Leon1

[Ben Sainsbury]

Powdery snow here in Bristol now, hopefully we can get a thin layering of powder snow before some much larger flaked wet snow tonight to bring some decent accumulations!

Edited March 17, 2018 by Ben Sainsbury