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

[Joe Levy]

Not as heavy in Exeter now, but still falling thick and fast! Looks like we have about 10cm on cars, with 15cm on the grass

[Guest]

LOADS OF MEMBERS ARE ASKING - WILL WE GET MORE SNOW THIS EVENING?

Quite apart from the posts on here, I've now had 7 PMs enquiring about the prospects for later today. Well, I'm still enjoying the current snow band which has already produced another 12 cm in 90 minutes and it's almost white out conditions right now (currently 1130) and down to nearly -2c. I want to get out in the snow soon to get some pics. I also run a full time online business from home and I have some work to do. I'll have a quick look now and give it my best shot. I need to keep posting the radar, infra red and temp charts to keep an eye on things and then I'll examine the micro pattern:

                  Live Radar - UK view                      Live Radar - France view                          Live Radar -  Germany view                          Live Satelitte                                     Live Infra Red Satelitte  

        

                    Live UK Temps                                    Live Euro Temps                                     Live Euro Pressure                      Live NW France View Pressure    24hr to 1148 GMT NW France View Pressure 

          

Firstly we need to focus on the current and live charts. Right now most of central southern England, the south-east and east are pretty clear of any snow. The snow in the south-west will continue for about another 12 hours (Devon) and up to 24 hours (Cornwall). There is a small patch of snow drifting westwards from Belgium which may hit the far south-east this afternoon. This was linked to a wider band of snow over northern France and Germany. It does seem to be fizzling out and I do not believe that we need to bother too much by looking east (unless further developments show up out there later on); those deeper colours on the infra red are starting to fade but keep checking for renewed developments - the chart represents deeper and thicker cloud which is not always producing precipitation but usually is. The snow shower activity in the east and north of the UK will continue but should gradually weaken as the HP to the north slowly sinks towards northern Scotland. A few lighter snow showers may develop again over East Anglia this afternoon. So we can discount any more of those showers reaching our region (except perhaps a few in north Oxon if those East Anglian ones develop).  Most of today's snow has been developing in the circulation of the minor LP over the mid Channel. There is a small centre that shows up just north of the Brest Peninsular and a bulge (or slight trough) of LP north-west from there. Several model runs have been showing (on and off) further small developments in the air stream in the eastern Channel - so we need to focus on that area. I always like the Met O fax charts and the excellent Arpege model which has been almost spot on with the Channel disturbance so far:

      Met O Fax at 0600 Sun Mar 18th         Met O Fax for 0600 Mon Mar 19th     Arpege 6z - Pressure 30 hrs to 1200 Mon    Arpege 6z - Jet 30 hrs to 1200 Mon   Arpege 6z - Wind 30 hrs to 1200 Mon 

        

The Met O are showing the wriggling frontal system (the one that cleared south through us on Saturday morning and brought in the very cold air) to push southwards into France by 0600 Monday (shown as a cold fornt again on the second chart). So unless a further wave develops on the front, we can probably discount any more activity from this source. Next we need to keep an eye on that circulation in the Channel. The third charts shows that the bulge (or trough of LP) in the air stream pointing north-west does develop a temporary minor cell of LP. I've already accounted for this in yesterday's and this morning's updates. It move westwards just south of the south coast from roughly south-west of the IOW right now to just off the Lizard Pensinular by late this evening. Then it dives back southwards and merges back into the main LP centred over Biscay by Monday morning. This is enhancing the snow over south-west Dorset and south Devon now and then, more especially, over Cornwall later today and this evening. Unless this feature changes course, stalls or deepens slightly further (all fairly unlikely in my view but by no means impossible) other parts of our region cannot expect any further action from this feature.

Next we need to look for other waves, disturbances and/or minor features developing further upstream towards the eastern Channel. Given the exceptionally cold surface and upper temperatures and the easterly flow (with east-north-easterly winds blowing the cold air off the land and not in from the sea at the surface) and the large temp contrast with the Channel (sea surface temps there are 5c to 6c in the east and nearer 7c in the west near to the coast) as well as some instability in the upper and middle flows, we cannot rule out anything turning up unexpectedly. There is another very minor bulge or kink in the easterly flow showing up at around 0200 Monday on the pressure chart. This may come to nothing, may produce a little light snow or it may develop a little further. The latter two scenarios are not suggested on their 6z run (12z run due out around 1600 or so GMT).

Next we need to look at the upper flow. A lot of the enhanced snow activity in the south and now south-west was caused by an upper cold pool moving from Poland westwards across southern England and then south-west over Cornwall. This is an upper LP and helped to drag in the sub -10s 850s last night. If you look at the jet chart you can see the upper LP pushing south-westwards through Cornwall right now. Then it's predicted to move out into the western Channel this afternoon before pushing south and then south-eastwards into central France by Monday morning. There is a minor or shallower upper LP or shallow cold pool  showing up over Denmark and pushing south-westwards but this seems to be steadily weakening and is probably nothing to be excited about.

Finally, the wind chart tells us more than just the strength and direction of the wind. It shows minor kinks and waves in the flow. That slight wave that I mentioned showing up in the pressure chart is even clearer on the wind chart. It shows up later this afternoon and early this evening moving over south-east England. Then it moves south-westwards in the flow out into the mid Channel. You can see a convergence zone developing for a short while there at about 0800 on Monday but rather than moving towards southern England it rapidly slides south-south-westwards and then down into Biscay. From all this, I think I'll predict some heavy rain for Biscay early tomorrow morning

Overall, I am not very optimistic about new snow prospects for this evening. We need to stay glued to the live radar, satelitte images and the pressure charts. The 12z and 18z  Arpege and other high res models will be interesting. Something might develop out of the blue or one of the minor disturbances I mentioned might become more significant.

The snow is temporarily lighter right now (1320) but there's over 15 cm out there and I'll get some pics later. It's -1.5c and the radar suggests some more to come before it all clears westwards later this afternoon or early this evening. Right now the snow depth is not far off the early March depth and the temp is only slightly higher than then but no freezing rain in sight. Pretty impressive.

EDIT: in the last half hour or so the activity to our east does seem to have increased again slightly. So definitely keep an eye on the live satelitte and radar charts. I'll be back soon if this develops further.

Edited March 18, 2018 by Guest
Correct typos and check charts

[Argyle1980]

1 minute ago, Jake Riding said:

How bad? 

Only just started, small flakes blowing in the breeze 

[hooch5]

Snowing Heavily for the last hour- Met just gone Amber for Monday (further Snow) this could turn out to be quite an event for parts of the southwest.

[Argyle1980]

Getting heavier as I type with the breeze freshening. Can’t see the top of the city for it.

[Leon1]

so how heavy is the stuff tonight going to be?

[fromey]

Well after a high of 0.3c the temp and dew point  are dropping, down to 0.1 c and dew of -3.8c 

[Frosty_wsm]

58 minutes ago, Nights King said:

Feature in southeast is growing.. 

Weather app on my phone shows snow from 8pm to 1an, that was removed earlier when I checked but it's back again. 

[stevofunnelcl]

here, there was some overnight, that readily settled. Roofs had a good covering first light this morning.

then dry for a few hours, even a glimpse of the sun, snow on roofs largely disappeared, then snow returned

small flakes to start with, has now turned to proper big flakes and coming down hard, surfaces turning white again

[EllyTech]

21 minutes ago, TQWX said:

Welcome to the English Riviera where the sun shines all the time! A few of the pics I managed to grab earlier during the blizzard in Torquay. The first photo of the bridge and date palm, if you click on my profile you can see the same place during summer!

Wow its plastered. Amazing to see!

[Leon1]

strange picture of band to south-east, seems to be intensifying

[Barbel]

Threatened to turn to rain just now but still light snow. 10 cm in places. Great fun making ⛄️Not a breath of wind.

[EllyTech]

David, Bring Back1962-63 you are such a prolific writer! Wonderful record you are making of this event. Thank you for posting your analysis!

[*Stormforce~beka*]

54 minutes ago, OldBloke said:

On my side of Dartmoor (East) I now have 12" of standing snow. This is more than the Beast from the East mark 1. Looks like a further 12 hours of snow too.

I'm moving to Cornwall! You guys get mega dumpin's!

[Leon1]

[karlos1983]

12 inch bingo alert ? @ajpoolshark ?

[Timer]

Some photos of snow today in and around Colyton.

Easing off now - probably 10cms plus. Temperature rising a tad  +0.3C now

[Argyle1980]

It’s coming down thick n fast with the flakes increasing in size.

[EllyTech]

3 minutes ago, Timer said:

Some photos of snow today in and around Colyton.

Easing off now - probably 10cms plus. Temperature rising a tad  +0.3C now

 

 

  

 

 

 

[Skullzrulerz]

Snowing a lot in st austell but not sitcking to paths or roads???

[Dean E]

Had some lightning reporting on the radar and from other sites. Anyone witnessed this?

Area's near the South Coast of Devon (Plymouth area too) looks like to pick up some increased snow totals in the next few hours as the bands slowly creep N/NWards.

Some impressive bands with this system.

[karlos1983]

EURO4 really goes for tonight 

With further accumulations

[alex12]

really hope this band of snow comes northwards!!  

[Leon1]

1 minute ago, karlos1983 said:

EURO4 really goes for tonight 

With further accumulations

is that snow then coming from the south-east going to pep?

[Man With Beard]

Is this going to be the "Biggie" for south Devon today? Very jealous! Lived there for a very very long time in hope for this day, had to put up with 30 minutes of sleet while the rest of the country got covered so so many times. Well seems it's payback time. Anything over 6 inches is massive down there. If you live in Devon or Cornwall, keep the reports coming in please!!!