SMU

Just to add @ 192 the SE corner after a sustained NE flow is back down to -9c based on the same rationale - if this run actually varified then near time that may well upgrade to -10 / -12c s

Morning all I mentioned the other day the advent of the surface High pressure would support the potential of possible snow & cold, also a few weeks ago I mentioned that as we approach the near time the GFS & subsequently the ensembles usually upgrade the cold as the depth of the airmass is identified - we are now down to -10c on the ECM & -9c on the GFS when 2 days ago -7 was the lowest value in the UK- also the models now swinging to perhaps an ENE flow - sustaining the -7c flow as opposed to the initial ( moreso GFS ) ESE flow mixing out the uppers to -3 do I expect to see snow falling here at sea level in Kent- yes, snowcover probably not - but the local hills maybe ! lots of snow chances seemingly scattered at all angles for all IMBY's.... s

The GFS 18 has moved significantly ( again ) towards the UKMO 12z with heights suddenly over iceland appearing at 132 & low uppers remaining over the UK in situ.... another day of solid momentum for cold with upgrades - -although I dont want to Jinx it !!

Possibly but I believe 100% that over a large swathe of the Uk at 216 & 240 you would be close on ice days should the ECM varify...

Well the ECM almost trumps the UKMO but the UkMO has lower heights over the UK at 120-144 & probably slightly lower 850s At 216 -240 the UK surface temps close to sub 2c days with mainland Uk at -9c 850 in very still air. very cold over night if theres any snowcover ! S

UKMO t72 shows the -8c line reaching the wash moving steadily south, it also shows a pretty large swathe of -10c air over scotland- if ws then refer to the UKMO 96 then it would be feesable to assume that the -10c line may penetrate further south - all the way to the wash with the -8c/-9c line more widspread - perhaps to London by then. That indicates that over the last 24/48 hours weds & thurs are progged to be colder than expected with Maxes of only 1-4c instead of 3-7 initially- Sharp frosts will develop overnight- Theres also a band of PPN crossing the UK at T72 heading SSE - could become more wintry..... S

Afternoon- Lets not underestimate the 12Z UKMO One of the best runs of the winter, more so because there is deep cold ( -8c) at T72 At 144 the flow allignment means minimal mixing of Mild uppers from the ESE & another cold pool dropping into scandi for continuation of cold thereafter... As said - the best run of the year because the cold is not +6 days away- also plenty of snow opportunities - even in the far SW ! S

For those that want snow rather than rain from the SW then the advent of high pressure in this location is great news .... s

In terms of polar sourced air this is the boom chart of all winter -

A very very good 24 hours of model runs with each suite the cold for weds is signalled to be a smidge further south Confidence tonight extends to around t84-96 with the -8c estimated to reach the M4. post that its all about the angle of the slider & then its interaction as the parent low drops south in the atlantic.... could be a big snow event for some....

* disclaimer * if it goes t*ts up dont blame me- The models this eve - in particular the ECM/GEM/JMA have increased the flow of CAA over the UK at 96/120 this is crucial to the potential of any snow event for lowland britain- - for scotland a low sliding into -4 / -5c air would probably suffice however those sort of uppers in the south are still to high - we ideally need embedded -8c but -6 may be ok- also this is true polar air so unlike the atlantic pish from last week dewpoints will be lower - all in all we couldnt have asked for a better ECM tonight.... s

Anyone belittling the UKMO today should review the GFS 12z at T72 A 100% swing to the UKMO 00z.

Afternoon The UKMO is certainly a peach of a run & loading the cold into the UK in the later stages however to get there ( T96 ) is wants to bring that atlantic low through a ridge of high pressure - This scenario has been modelled before but with very minimal success - the model that gets the low over the top of the ridge with flattening has historically been correct so its the GFS ( sadly ) that would usually be in favour here however the UKMO would certainly signal a profound pattern change.... s

Dewpoints across the whole of the SE ( apart from kent ) have dropped by 1c in the last 1 1/2 another update at 11

Possibly Oxford - dew points are stationary though !

All rain at the moment in Greenhithe im tracking the dew points - no decrease yet, coldest in Kent !

Just got to buckmore park with the kiddies air up here in orbit at 150-200M is feeling dry & cold i would hazard a guess 5c here 0c dewpoint .... s

Rubbish then - probs later in the day.....

Surely places like buxton & up to the cat & fiddle will have snow by now @ 600M ? s

Infact it has enough movement in the tanks to change the picture to this ( low res only so far ) 54 00z 48 06z looking good..... s

GFS 06z 36 v 42 00z makes further incremental steps towards the euros by moving the shallow low over the UK further south- another 1-2 steps & we may well be seeing snow on the map on the leading edge for the SE.... s

Morning based on what I put in the model thread last night I think the snowline will be around 3-400M tomorrow when the front arrives lowering to around 200M around 6 & lowering further overnight PPN intensity will be the key ! S

Thanks Shaky The thicknesses across t48 ( the mildest point ) are very very good in the SE if we look at the following 3 images of euro 4 partial thicknesses - T 42/45 & 48: at T 48 this is where the PPN is : so my suggestion would be rain spreading SE - & where it lies at T48 no front edge snow infact at T48 minimal about except at height, however the thicknesses & dewpoint suggest that some snow will already be falling - however what the EURO4 doesnt have is the height of the 0c isotherm. Because of the lapse rates I would suggest more saturated than normal so perhaps 3/400 M & above all snow. if we move onto t60 ( UKMO ) the milder wedge is mixed out - This suggest that as darkness decents weds all parameters move past the borderline point - * sub 2c dewpoint for transitioning sleet * - 5c 850 air mixing out the warmer layer * partial thicknesses of sub 1290 DAM spreading west from the East & east from the west! whats missing is the height of the 0c isotherm - probably lowering to 100m The forecast should then move on to say that overnight weds with The above falling into place the rain will steadily turn to snow for most - especially further North & with a smidge of elevation. Ground level accumulations would depend on how the PPN rates fair in bringing that ZDL level down to ground level. The models have suggested a secondary wave developing along the front siding SE towards the South coast across East wales & the midlands, this may well be the trigger for accumulations in this area. you will also not the progs suggest the SE clings onto a developing pool of sub 1290 air with 1280 DAM thicknesses pushing west out of france - so as the front edges into the SE overnight weds then it may well turn to snow as well - PPN rates dependent... best regards s

I mentioned this in my post this morning Ref cambridgeshire etc ( getting snow ) the updated UKMO shows a shallow system over the SE at T72 with low heights & probable snow I think the models are underplaying the forward edge potential.... s

Morning All I think its been about 4-5 days since I posted - the last time it was showing the snow potential for England at about day 8. Since then the models should be commended for their consistency around the timing & progess of the front, kudos to them all. Whats changed since my post ( ironically in the 12's of the day I posted ) was the switch of 2 variables that supported snow - thats was : * The angle of the WAA off the atlantic into the front * The angle & depth of CAA being fired back into the front from the continent- At the time I posted all parameters were favourable for snow with the theta E values around 8c & a cold pool around -6 @ 850 with sub zero dewpoints After that day especially the inmediate 24 hours all models moved to a slightly flatter solution - This then modified all the paratmeters to a place where the signal was rain as opposed to snow- - uppers modified to -2 to -4 - Theta values of 8c were ushered east into the continent to be replaced by the 12-14 line & dewpoints moved to be forecast above zero - Since that day the models have ever so slowely edged back to a colder solution but not quite as cold as the initial projection - the Theta values at day 3 ( T72 / 00z Thurs ) are around 10c - the uppers in the best case scenario ( UKMO / ECM ) blend are circa -5c in the SE & dewpoints close to zero - So we have gone from all snow to all rain to a very borderline scenario with evaporational cooling the wildcard - heres the UKMO & ECM for 00z thurs As we can see the cold air does filter back into the SE as the front decays- So I would say we have a rain to snow event more so possible accumulations to the North at elevation ( as ever ) usual places like the Derby peaks, pennines etc look in the firing line- futher south more borderline relying on evaporational cooling- Maybe a surprise for SE ( more especially for the NE part of the region ) - cambridgeshire etc as the PPN feeds into the continental air For info GFS 00z was the warmest run out the big 3... aperge also cold with snow.... max snow depth forecast - 10cm at the cat & fiddle S