LomondSnowstorm

I think very unlikely in Perth at low levels sadly, the boundary will be fairly nearby but the dewpoints are, not what you'd want, to say the least: South of the Tay and away from 250m+ I think the focus really has to shift to Friday evening at the earliest when the cold uppers start to come back down, and probably also to just hoping the rain or sleet stops for a bit because the flooding situation could become pretty bad.

I was thinking about the relative disappointment of the front for most of us (sleet trending to rain now here), but also the totals we're already seeing and are likely to see in Aberdeenshire and the Highlands. While clearly it was much easier to get decent frontal snowfall for lower levels in winters past, I do think that in order to get the crazy snowfall totals without very cold uppers you do tend to end up with a lot of folk sitting with cold rain or slush. I know we've discussed this before but the 1978 blizzard had these uppers before the front moves east: Even if it is a bit rubbish for those of us not affected, it probably is worth it because this snowfall could be talked about in that sort of vain for years and decades to come, and even then we still get a shot at easterlies and maybe even some snow at Hawesy's house, which really would be a historic event .

I was going to say A nice extension of the warning to eastern Scotland for Monday and for further west on both days and seemingly accounting for the possibility of Forth-Clyde streamers judging by the positioning:

Having thought about it a bit more, and looked at the ensemble perturbations, I think the UKV's 'modest' projections (still pretty good for a lot of eastern Scotland to be fair) come from the UKMO making a bit less of the low than the other models. While in some ways you want this out of the way, it's quite important that it isn't so weak that the flow becomes overly slack and is more due east/ENE when it sinks and moves east towards northeast France. The models have slightly strengthen this today and with a slightly less angry low coming out of the US we end up with a much longer easterly from both the GFS and the ECM, whereas the UKMO, while still decent, develops the low a bit less and means we end up with a flow that's stuck as a bit more southeasterly, a bit slacker and also is a bit divergent for Western areas. I didn't really buy the GFS overdoing the low to the point of near destruction a couple of days ago, but equally the UKMO tends to underestimate these lows a bit, and generally you do see more disturbances which lead to enhanced snowfall closer to the time, so I do think it'll work out nicely for us (I'll post actual charts once I'm properly awake and have the laptop on ).

I had to resort to using the ESRL NOAA plotter for that one Just around -40C, converting from Kelvin, so again fairly impressive. It's quite funny how poorly the ICON did at modelling the precipitation in 2018 even at close range:

A good point, 2018 was exceptional and I think we'd struggle to get close to that (although I suppose it coming a month earlier will also work in our favour both in terms of the North Sea not having cooled quite as much and less sunlight). The 500mb temps on the ECMWF are actually a bit stronger, at least if my colour picker app is right (I wish they'd label a few isobars for us!), -36C over central Scotland by Sunday midday: I'm a little sceptical of that myself though given the ICON only has it around -32C Neither is exactly this though:

I mean, it's possible but I'd imagine the models are underestimating the convection a fair bit as usual. I'll take a closer look at the forecast soundings tomorrow (fat lot of good that was the other day though) and see if there's anything we can take from it, ideally a lot of snow.

Turning pretty rapidly to proper snow again here, and I think at least some chance it'll lie - the nearest weather station reporting 0.7/0.3C. Still time to firm up on the details of the easterly but really, sub -8C (and indeed -10C) uppers and an easterly flow for a few days at least is an excellent starting point.

Yeah I was going to say, aside from the fact tilts a bit more northerly as time goes on, it's pretty well due east to start with then goes ENE as far as wind direction goes. I'd say this is pretty much perfect tbh: Almost a straight line from Sweden to the west coast, perfect for streamer development.

I think that's a fair gripe although yesterday's 12Z barely had them arriving at all, so I think we can probably deal with an extra few hours

Some major upgrades on the current weather here according to the aptly named 'Accuweather' - from 5C to 2C in 20 minutes The fact it was sleeting outside was maybe a tip off that something went badly wrong with whatever model they were using, but a little bizarre all the same.

The 0C dewpoint isotherm has crossed the Tay now, we should be seeing snow more widely into Fife and Tayside:

Tomorrow night and Friday I think are trending that way sadly, I'd think Friday's warning for here would be better placed tonight from what I've seen since I do think we should be seeing it turn properly in the next few hours. Saturday onwards still looks good though, Met Office has it barely getting to 0C from Sunday onwards with snow here, which looks about right...

It's a bit surprising to me since they do sometimes get it right (November 2010 and I think February/March 2018 they were pretty well bang on with it), and you'd think with the UKV, which actually can resolve convection, they should have a better idea, but you still see the same misses quite frequently.

As far as today goes - it is a gradually improving picture as far as snow prospects go. This is the picture at the moment: To this evening: And wind speeds easing too: As a result we'll start to see temperatures dropping and becoming more conducive to something a bit wintrier: The 250m wet bulb freezing line is also going to head south, so I think even in the next few hours we'll start to see rain and sleet turning to snow and wet snow turning to snow that might actually stick: You can already see the impact of this on dewpoints, with almost everywhere north of Dundee seeing DPs dropping to )C or below. While precipitation will generally start to ease, I'd think there'll still be enough coming through to give a risk of a covering as the back edge of the front move back south, and we'll see some more showers coming in through the evening too: I wouldn't necessarily expect too much but equally I wouldn't be surprised if it delivers an inch or two, probably moreso to areas that do well from an ESErly with the showers: Tomorrow morning will be trickier, in that I expect some initial snowfall that's quite likely to turn to rain, but less so the further north and west you are. We'll see on the 12Zs quite how far north the models take it as there seems to have been some convergence between the UKV and GFS setups in northern extent to a compromise position that still sees the Highlands taking a pasting, but that could change.

I'd think so - this far out you'd need to be pretty certain to put a warning out. The reason they've done it south of the border is closer to the trough you've got more organised snowfall on Monday, which will be showing up much more clearly in the models than our convective snow (oddly enough there was a question on how well models represent convection/why they sometimes do a poor job on my exam!). I think that's pretty standard from what I recall from previous events - a couple of easterlies we've had have barely had warning until well after the snow started falling

Still snowing here but not lying, but the intensity looks a little better and as colder uppers start to come back in from the east later on today I think we're going to see the lying snow level drop from ~200m to ~100m or so. If the UKV doesn't change in the next run or two, expect and expanded warning for this evening to include the central belt, probably at least some of Fife too... I'll post more after my exam at 8am (damn time difference!)

I mean again it's not quite as nice as this morning (although I think Thursday morning is worth flagging up for a possible big frontal snowfall and later Thursday further north) but still gets the job done:

It has tried very hard to settle here but alas it just doesn't seem to be happening for now, the heavy pulses on the radar haven't really materialised on the ground here to the extent you'd expect (I wonder if topography has anything to do with it with the wind so strong) but we'll see if that changes overnight. I'm going to assume it'll be largely dry until morning and avoid posting until morning after the ECMWF - got a (virtual) exam in the morning, ironically on weather modelling, and I think there's only so far you can argue to yourself that this is revision without taking the Swearing AGAIN

I think that's possible, and it's true that we often find the flow gets a bit less 'clean' closer to the time, particularly talking about the initial onset of the easterly. I would say though, the ECM was absolutely not having it at all with an easterly as recently as Sunday morning, for example: And even the 12Z on Sunday only had the -8C line cross Scotland once. It's been a weird one in that the GFS up to now has outperformed the ECM (as metallikat said!) but now the GFS, at least based on the output so far today, has been a bit slower on the cold.

Given what it's showing compared to the other models I'm very happy to put a health warning on its output

Encouraging signs at the nearest weather station (Airdrie) ahead of the next lot of heavier stuff moving in, down to 0.6/0.2: Just stating to get going but it's certainly snow here

The UKMO is still solid GFS is a bit frustrating and nail biting but just about alright for here from Sunday on: I am a bit concerned certainly because we aren't too many changes away from a significantly worse outcome but we should hopefully get a resolution on the pesky low by this time tomorrow. What I would say is I think a 'clean' transition to an easterly is less likely, not that most of us could really describe the current conditions as clear cut, but I'd think the low will at least hang around enough on Thursday and early Friday to cause continued marginality but also potentially significant snowfall, most likely but not exclusively for Aberdeenshire. The GEM (which I unfairly overlook sometimes relative to its performance) looks solid too

Definitely snow here, struggling to really make much of an impact as far as settling goes but it's certainly trending in the right direction.

I think the next wave could be a bit more promising - that band seemed to push temperatures down a fair bit so we're seeing more like 0C across South Lanarkshire and higher bits of West Lothian and 1-2C rather than 2-3C a bit lower down.