LomondSnowstorm

I can see the logic for this certainly - firstly you've got the lighter initial stuff (which, judging by the radar, looks to be a little bit further east than expected so far), which should be mostly snow to low levels. Then, as the main band hits tomorrow, things look pretty decent - wet bulb freezing level below 500m for most: The problem really comes from the upper air temperatures away from the coast - the temperature gradient is quite marked, with only a few miles between the -4C and 0C isotherm: As a result I don't think it's ridiculous to think that we could see freezing rain, particularly at higher levels across Dumfries and Galloway, but overnight if the warm sector does creep further north that could be a risk for central areas too. Wednesday morning is where the precipitation totals start to ramp up on the UKV, some serious intensity flagged up with two occlusions straddled across the country: While the precipitation type has this as a bit of a mix I do think there's some potential for this to be low ground snowfall at least with the northernmost band, with a pretty reasonable looking freezing level and that intensity doing a lot to tip things the right side of marginal (again, aside from the possible problems with modification from the east coast or the upper level warm front): The ICON model is quite different on this, with the heaviest stuff coming on Tuesday afternoon: It does, as it tends to do, look a bit more favourable for snowfall tomorrow than the UKV - the freezing level for example is very widely 300m or lower, and you can see the frontal boundary incredibly clearly: Basically moving with the southern edge of the heaviest precipitation within the occlusion. Finally, the NMM looks a bit more similar to the UKV (which I think you'd expect given the UKMO this morning is a bit different in how far north and east it brings the low and how much longer it takes to bring the easterly in in some form compared to the 0Z GFS and ECM) in terms of the front tomorrow: There's still a lot of moving parts here, and the nuances of the timing of fronts, and how and where the low splits (if for example our low ends up weaker and further west or stronger and over us) is really not easy to pin down - Wednesday night for example seems far too far out to make a reliable forecast for at this stage: What we do know is it will be some level of easterly flow, with a fairly stark frontal boundary somewhere in the vicinity of Scotland. edit: I misread the UKV chart - the 'ramping up' of the intensity is just the timescale changing from 1 to 3 hours It's still fairly intense precipitation there on Wednesday but not so much of a difference from the other models which have some precipitation around then too.

I was just going to post the ECM snow depths, crazy stuff! The ECM is certainly looking better than it was 24 hours ago, no real sign of that massive warm sector it came out with and a very impressive easterly to follow with major snow as the front moves back south. The UKV is a bit meh in comparison for central areas, in large part because it brings the low further north again and with it the higher upper air temperatures, but quite incredible depths for the northern half of Scotland if it came off too. I do think half a metre is almost certain quite widely above around 300m or so, that's been very consistent in the models, but I think the key to the totals for lower levels is how much melt we have to deal with through the week and where the front ends up on Friday/Saturday, as that's really where those totals pile up: Near the east coast certainly up to Friday it's likely to be very marginal but the intensity combined with the cold air starting to undercut from the north/east would probably do the trick for wherever the front ends up, likely followed by convective snow from the east.

A slight dusting here overnight with slightly more back in Freuchie after the showers pepped up there later on in the night. Looks like a bit more pepping up in the Forth again, so while the modification near the coast is pretty bad we could still see a bit of snow further inland from these showers. The 12Z runs so far from the GFS and UKMO continue to hold reasonably firm in keeping the -5C upper air temperatures in place for the most part, with this being the most dicey part: Once again we see a very promising looking setup, particularly further inland and further north, with a lot of precipitation for the next week and the vast majority of it currently modelled as snow: UKMO is fairly similar but I do have some concerns about the -8C line not quite managing to get as far south/west as we'd like for eastern parts: It does get there by the end but we could do with the low moving a little further southeast than currently modelled - it's very much a knife edge situation. The reason for this is build up of heights over the Med and into Italy - this leaves the low to gradually fill and, in the better scenario we're seeing now, sink into Iberia. From seeing how these setups go previously, though, I suspect it's going to tip one way or the other a bit more decisively - either the heights to the southeast will clear a bit more, with something very very special as far as snow and cold goes for us, or the low ends up phasing with the next one over Southeast Greenland and we end up in a messy battleground setup again. I tend towards the former because we do seem to be seeing a bit more consistency with the vortex splitting over the Arctic and far less 'purple' over Greenland, and while this doesn't necessarily guarantee a smooth ride it does give you a very good chance of seeing the deep cold come our way by next weekend. And I forgot to mention the best of the bunch - the GEM, which has consistently lived up to its name and delivered the most stonking output I've seen since March 2018: through to: It won't come off as cleanly as that, but if it did, you would be talking in feet rather than inches, easily...

Very light snow here but it is settling - we'll see if much else comes this way in the next 15 or so hours before the flow cuts off. The NMM does suggest not totally negligible amounts possible for Fife through to maybe Cumbernauld overnight: Whereas the UKV generally has much patchier precipitation and further south (no precipitation accumulation and hard to really post something illustrative since the individual showers are tiny!). ICON also relatively low on totals but more clustered around the Forth: That distribution seems pretty reasonable to me given the wind direction and current radar but I think the totals are being underestimated a wee bit - we've already seen 3-4mm precipitation since 6pm to the southeast of Edinburgh (albeit the mesoscale models often don't show the initial precipitation very well anyway):

Shower incoming here now, looks like approximately 1/-1C so I think most likely snow... Very interesting charts in the longer term, with the easterly coming into sight and some frontal snow potential on Tuesday(please god will one of them hit properly/not melt after two seconds/end up at my aunt in Birmingham's instead). Far too much uncertainty on the 'big' possible easterly next week to have much faith, beyond a likely easterly flow following Tuesday's low. That could be a pretty decent couple of days in and of itself though:

Evening folks, some more interest over the next few days although, as ever, pretty marginal. Sort of sleety here, if you squint, but I think with both tonight and tomorrow the intensity will be pretty key in determining where we see things staying the right side of marginal (some backedge potential I'd say in both cases), and coastal modification, tonight from the west and tomorrow, eventually, from the east, will be a factor. Certainly seems like the foreseeable will stay cold enough for snowfalls and beyond that there's certainly reason to think we're pretty well placed for more cold spells, and maybe some proper deep cold at some stage too, as we head into February. I'm up bright and early at 7.15am for a presentation (the perils of doing a Masters remotely from a different time zone!) but I'm hoping to have a little more time after that to dig into the charts and nowcasting properly.

Agreed - I do think they perhaps should've accounted for the wide range of possibilities, especially since the UKV was somewhat out on its own as far as not really giving very much precipitation (although ironically it flipped around over the last 24 hours) but a crazy amount of model uncertainty even earlier today on how this was going to unfold.

Fascinating watching the radar (well the constant light snizzle isn't amounting to much here yet!). The precipitation is already starting to move southwards now as far east as Stirling and that very heavy pulse of precipitation haring up Tyneside and towards the Borders. Let's see where it ends up...

Quite an exceptional upgrade from the UKV's output over the last 24 hours: Some very impressive totals being flagged up, and with marginality becoming less of an issue further east with a bit of intensity the elevation differences might not be quite so strong (I'm still a bit wary of modification at the most exposed coasts when the winds get up but away from there).

Absolutely - glad to see the 15Z UKV sticking to the 12Z UKV's output with the front pivoting round in the early hours. It does broadly seem to be following that, at least, as far as I can tell, although it's very much a complex picture still. I can report some light snizzle in Coatbridge and snow in Freuchie - seems like inland bits of Fife are pretty nicely set up for this one, which is probably fair enough because Freuchie seemed to miss out on basically everything in the last few weeks since I've left

The thing that is giving me some hope for later (as far as precip goes maybe more than marginality at the moment) is comparing the current radar to the model output: To me, the UKV looks to have a better grasp on the current situation in that: there's a line of precipitation to the west of the Solway Firth there's moderate precipitation around the Irish Sea the heavy stuff over East Yorkshire is better defined on the UKV The NMM then goes on to move the precipitation almost entirely out into the North Sea over the next couple of hours, whereas the UKV sees more pushing northwestwards: I would tend to think the UKV will be closer on that at least, but we don't have too long to wait. If it is right, things do look better going into the evening where we should start to see rain turning to snow

Bit of an odd flip around overnight from the UKV and GFS - the UKV 12Z looks pretty good for snow, with precipitation getting significantly further west than on previous runs and the front pivoting over a much wider area of Scotland (hence the warnings I think): The GFS on the other hand has a more elongated low but also manages to bring the warm sector just a bit too close to us when the front does move southwards in the early hours (although still decent snowfall potential for the eastern Borders and inland parts of Aberdeenshire and the Highlands: The ICON has things a bit further south and east like the GFS too but with a bit of a clearer snow risk from the second front (not quite sure how much that's a figment of the precipitation mask or a real difference but the freezing level and dewpoints both look fine enough for snow on the ICON for most of the night and at the time where the front moves over from the north): I would tend to think the UKV is maybe a little better on this now we're into the realm where mesoscale modelling has particular value but I'd also be a bit wary going against both the GFS and ICON in terms of placement. What we really want to see over the next few hours if we want a decent snowfall is the front starting to move northwards rather than northeastwards. At the moment everything is moving very much SW-NE, which is in line with both all the modelling for this timescale, but the divergence really comes in over the next few hours, with the UKV showing the low moving more directly northwards while the ICON moves this out into the North Sea then northwards. All to play for still, and even with the ICON setup there's still a fair bit of potential from the front moving back southwards, but if you're looking for the snowier scenarios it's really make or break time.

Starting to lie on the cars here despite not really getting the heavier band, certainly nice to see it settling again! Quite glad I held off on doing a summary of the 15Z UKV because, well here's a comparison between it and the 18Z UKV: I expect another 4 upgrades and 2 downgrades before morning

The ECMWF is coming out and again looks pretty reasonable for snow potential. One indicator that may be useful from their page is the 925hPa temperature - while I've previously used the 950hPa 0C level from the Euro4 for example as a decent indicator of where snow is likely the low surface pressure means 0C and 925 hPa is probably good enough in this setup to highlight where we're likely to see proper snow. For tonight, this is what we have: And the precipitation for the same timescale: Comparing with the FAX charts from earlier: Basically, the southern edge of the warm front that's currently edging northwards towards us is the dividing line between snow to low levels (well 50m or so and a bit inland at best) and rain. The other factor that's going to limit snow potential further east is the surface wind: Dewpoints are likely to rise just a bit too much for snow in most of eastern Scotland even if you do get a bit of intensity, so you'll need a bit of elevation here for anything much tonight. Here's a comparison of the NMM forecast skew-ts for midnight tonight to illustrate, between North Lanarkshire and Fife: While this isn't a massive difference on the face of it that 70m extra on the freezing level and slightly more 'stable' layer near the surface compared to the one on the left is probably enough to make a difference. Comparing for the key timeframe tomorrow night, at midnight, and we can see that it's very finely balanced at the 925hPa level on the ECM: There's a few factors impacting here - firstly the upper warm sector associated with the low, with the 850hPa 0C line not too far off the coast: This is not too likely to impact away from the eastern Borders and coastal Aberdeenshire but because of the uncertainty over the track of the low any westward correction could lead to rainfall, most likely freezing rain, even to higher levels in the east. There will also be the coastal modification at the surface, both in the northeast with the northerlies and potentially towards western coasts. This will depend on the shape of the low, which has varied a bit, as a more easterly flow would introduce additional areas of marginality on top of the upper warm sector. In general, though, surface temperatures and freezing levels look reasonable enough on the NMM at least, sub 500m away from the northeast: and surface temperatures around 1C on the ECMWF: I'll do another post on the UKV, which I see has just updated, and precipitation totals later on, but I just wanted to give an overview of what to look out for in the next day or two from a marginality perspective. I think it's starting to turn sleety here which makes sense with reports of temperature of 0C in Airdrie but primarily just wet for now - I wouldn't be surprised to end up with a slight covering by around midnight though.

Certainly doesn't seem to be a lack of precipitation on that midnight screenshot (although quite how you end up with that sliver of rain from Perth through to Crianlarich is anyone's guess ) I was tempted to start a summary now but I think I'll wait until at least the GFS and UKMO are out and hope there's at least something approaching a consensus. I've noticed a bit of a dip in temperatures around Clydesdale in the last hour or so, I guess, where precipitation is heaviest. That potentially bodes well for our chances of snow later on. The ICON, which seems to have a reasonable grip on current temperatures at least, has it fairly widely as snowfall to low levels by midnight: Moreso inland though, and for the east coast I think dewpoints will just be a bit too high: Temperatures generally around 1C for pretty much all the central belt though so I'd think it has a shot of settling, albeit it does move away in the early hours. The UKV is relatively similar on this actually, dewpoints close to 0C for the central belt and continued fairly intense precipitation around midnight, so certainly something to watch out for.

I'll look at the temperature profile in more detail now that we seem to have at least some degree of consensus that there'll be a fair whack of precipitation for most of us. Still a lot of details to work out, for example the ICON has the main risk to the north of the central belt as far as settling snow goes, but I do think we can have some confidence that somewhere is going to end up hitting the jackpot tomorrow...

Synoptically yes, and yet the UKV looks if anything even more out of line with the precipitation modelling than the GFS or ICON (both of which give a fair whack of snow and a good amount through Wednesday night well into Thursday for most of us) UKV has the front pivoting around the borders but with the second band of precip (I guess, presumably, a cold -edit: actually it's occluded - front if I was looking in more detail) well to the north again by midnight on Thursday. It would maybe come back over us but a fair difference from the 21Z run. The 03Z goes out further so hopefully that'll shed some more light but while things are moving in the right direction as far as the position of the low going further west the "stand off" remains in some form (this may change by the time I'm properly awake!).

Final post of the evening - the UKV has edged a little closer to the rest of the mode output and brings the front/low a bit further south after the pivot: Certainly a positive trend, and hopefully one that continues tomorrow...

I immediately thought of you when I wrote that sadly It isn't the worst setup for you but I do feel like the upper air temperatures associated with the centre of the low are going to be too high, and the wind speeds too high at the surface. St Andrews might have a little more luck though, maybe?

Well I suppose in the sense I'm now stuck in North Lanarkshire until the restrictions ease I'm somewhat 'locked up', especially with the amount of coding I've had to do for my Masters recently, but fortunately nothing quite that drastic I have managed to squeeze in some nice walks though - while I do miss the Lomonds there's enough decent walks within North Lanarkshire or the 5 mile limit of the local authority to keep me occupied in between uni work and chart watching, especially when the lochs freeze up:

Hi folks, apologies for a relatively lengthy absence there despite some pretty interesting weather (a couple of modest snowfalls here in Coatbridge before a quick thaw the second time). The upcoming potential (I'll leave it at that for now) has got me intrigued though, and it's very difficult to say quite where we're heading. I think I'll leave a full summary until tomorrow, because we're really looking at a massive range of outcomes for most of us with both a foot of snow and completely dry entirely possible, away from the immediate coast, but so much depends on the timing, placement and angle of the low that is really impossible to pin down even at this range. The most recent ICON, which generally tracks with the ECMWF, has slightly lower totals than the mammoth amounts we saw on the (synoptically pretty similar) 12Z for southern Scotland but with more for Fife: We saw some level of convergence between the UKMO and other models as far as the placement goes, but as was previously posted the UKV is categorically not playing ball, bringing everything much further north much earlier and, while giving some snowfall chances tomorrow night further east, really doesn't see anything on Wednesday night. It will be interesting to see how the Met Office responds if there's no convergence between their modelling and the ECMWF/GFS - I'd imagine tomorrow night is something like a yellow warning for ice and snow for the Borders up to maybe Fife, but beyond that it would seem to be quite incredible if we have some divergence between the TV forecasts and the Met Office warnings. The UKV is an excellent model, so I'm not necessarily saying it's going to be wrong on this, but I do think that when the uncertainty is around the track of a low rather than the intensity of precipitation associated with a front/convective precipitation/ mesoscale processes per say, I don't know that it's really that much better than the ECMWF or GFS and their respective mesoscale models. Certainly the latest GFS does seem to at least maintain a reasonable snow risk and potential for similar accumulations to the latest ICON: Longer term, the latest ECMWF monthly (great minds think alike Mr Frost!) and continued strat disruption is quite promising, as well as the pattern which immediately follows this potential frontal snowfall and possible secondary lows moving in from the northwest behind it, but hard to look past the potential for Wednesday night just yet even if it could easily end up as a non-event for most of us.

Unfortunately yeah, it does seem to be relatively pronounced: And (I think not helped by the wind direction being from nearer the coast) having an impact at lower levels too: Seems likely that it'll take a bit longer to be squeezed out from the central belt, one of the times the topography helps us as far as limiting the impact of warm sectors arriving from the north: and at upper levels it seems to be a bit further west and closer to this secondary shortwave feature in the North Channel (seems a relatively common theme recently!): and squeezed out by the approaching northerly air too. The 950hPa temperatures seem ok for the central and southern part of Scotland, allowing for the fact it's a bit higher up than last time given the relatively high pressure, but with a chance of sleetiness or freezing rain the closer you are to the coast or further north before the northerly sets in properly: Even then I think that is more likely to follow behind the precipitation, so areas in the yellow may still see it mostly as snow with some backedge sleet or more dreaded freezing rain (I do fancy my chances more with being in Coatbridge though, I have to say). I think BFT is right though - the front could well hang about a bit longer than expected and it does have a similar look to that 6th December 2010 snowfall, which had a similarly modest look about it to the Met Office (I remember a good discussion on here that the 18Z looked quite tasty the night before but still not enough to merit more than a yellow morning until the M80 was almost shut, but I digress!). The uppers were certainly nothing special then, either: I reckon it's unlikely to quite be on that scale, but probably more the intensity rather than the marginality that's going to be the issue in terms of getting a proper dumping - the pressure/geopotential is quite a bit higher in our case and the feature is a little less pronounced: Anyway happy lamp post watching! I suspect we may be back at it after this sooner than we think, once the models finally figure out how to handle the strat warming (just the pub run but the range of possibilities is very high still even for next week):

Lovely! I can certainly attest to the paths on the Lomonds being deathtraps - had to avoid the paths entirely on the way back down East Lomond yesterday and trample down the grassier parts (which were fortunately not too bad). Also a bit of a hairy drive back down to Falkland from Craigmead with the yellow ski warning light on the whole time

Bit of a tricky forecast this one - I do feel the dewpoints are a bit high through the day tomorrow but it does get a bit better over the next few days. Currently sitting at 0C here and pretty stable for the last couple of hours. As the showers come in tomorrow (around midday or so) the upper air temperatures are at least not prohibitively high, although generally you would want at least -8C from an easterly: Temperatures at the surface though are, on the face of it, a bit high: I would say that the NMM certainly has a tendency to overdo the coastal modification, and as it has something similar I guess I wouldn't be that surprised if it was maybe a degree or so cooler: The modelled sounding for midday tomorrow for here is not entirely discouraging, with the freezing level at 950hPa, but with it being saturated at lower levels the dewpoint and wet bulb temperature are certainly on the high side at lower levels: By midnight the situation is marginally better, with dewpoints certainly lower at the surface, and I think it's not inconceivable that, if the modification is indeed a bit overegged by the models we could well end up with sleety/wet snow during the day turning to lying snow by nightfall, at least if you're not at the immediate coast and have a little bit of altitude on your side: We can see more generally that the modelled dewpoints aren't especially far off 0C, and if you're looking at heavy precipitation (which the modelling seems to suggest) it's possible that we can end up with a situation not dissimilar to the other night where it was marginal but many areas saw lying snow: Part of the issue is the wind direction and speed - inland it's a bit more northerly and very weak but near the coast we can see a relatively fresh ENErly wind: This is decent for the shower track, but will cause a fair bit of modification, potentially more than the previous brief easterly snowfall. However, when showers do get further west this should be less of an issue there: (I should say I started this post before the 15Z UKV came out but it looks pretty similar up to this point!) I think our best shot of some lying snow more widely to lower levels is Monday morning - temperatures will be relatively low as winds drop a bit but there'll still be fairly widespread precipitation around: Beyond this, dewpoints are likely to continue dropping but as we move closer to the centre of the high it'll be very dependent on the angle of the flow - really you need to be fairly near the coast later Monday into Tuesday for precipitation as it won't move so far inland. But certainly there's a lot of opportunities there as the flow gets slacker and surface temperatures lower. I do think the heavier precipitation may help us, as KW says - if you hit a streamer it's possible we can nudge temperatures enough in our favour to get the snow to settle and then progress from there, but it might be a bit of a losing battle at points. Midweek certainly looks interesting as well - a lot depends on the angle of attack from the next low but there's a real possibility of a frontal snowfall without marginality concerns: The ECMWF similarly flags up this risk from Wednesday afternoon into Thursday night : In summary, lots to keep an eye on over the next few days. As we saw this morning small scale features can pop up at short range, and we already have some snowfall on the models on every day from tomorrow right out to Friday and Saturday. The medium term picture is getting a little more complex with the possibility of the block toppling a bit, but I do think the big picture still seems very promising with the continued forecast of a SSW and some signs of a quick reaction in the troposphere. While we know this doesn't guarantee cold and snow, it's certainly a major help as far as creating the conditions necessary for high latitude blocking to continue to dominate. On a personal note, I should also say that from tomorrow I'm (temporarily) moving to Coatbridge to stay with my girlfriend, so my weather reports may be a bit confounding if you're looking to see what the showers are falling as in Fife

Interesting outlook - while I can't really argue with the vast majority of the forecast, especially the bit about it not being the sort of 'beast from the east' with direct sourced Arctic air for England at least, I don't think it's necessarily true that the airmass will be universally warmer either - more locally the air is coming from Scandinavia, and we do see significantly sub -5C upper air temperatures (albeit with significantly higher surface pressure) for the first time since Christmas Eve: And I'm not sure it's likely, on the current runs at least, for that yellow tongue curving into the Baltic to really have much of an influence up here anyway (the high will end up pretty much over us for a bit and then, hopefully, the cold reload will come from the Arctic as the vortex is torn up). The sort of modest, slack eastnortheasterly shown on that chart though, with enough of a cold pool for a bit of convection but not enough that it really shows up on the models, is just the sort of setup that can produce unexpected snowfalls here...