Kasim Awan

ICON brings in 2-5cm along the South Coast. Those south of the M4 need to watch with interest. Could be a rogue run but this potentially isn't a done deal yet.

Not the case most models have snowfall in tightly packed areas the risk of snowfall elsewhere is rather low. For any given location away from the main risk areas the chance of significant snow 5-10%.

As rare as you posting in this thread?

It has the orographic adiabatic cooling in the trough hence the rain west of Pennines. As I mentioned this is definitely possible if the trough core is strong, however is the best case scenario for those over and to the east of the Pennines. More trough energy also means less showers into low level NW England. If the trough isn't too defined there will likely be a phase of light NW winds with good streamer potential and a full freezing sounding right down to near the coast, on the exact coast accumulation will struggle with mixed phase precipitation possible.

NW England probably the place to be during this cold spell.

I was analysing the operational run bring dry not making a prediction posts like this show a lack of understanding. It will be dry for most anyway, just because the North is getting snow doesn't mean the majority wont be dry.

Looking more likely now that an active trough will push into Northern England on Monday night to produce snow showers on it's front into low level parts of NW England / NW Midlands before an active core with heavier and more persistent precipitation moves into central areas of northern England. On the lead a complete below freezing sounding means locally significant accumulations to lower levels are possible between the NW coast and Staffordshire. As the heavier core makes progress there is the potential for a mild sector to raise the snow line to the west of the Pennines in particular, with orographically lead adiabatic low level dewpoint cooling reducing this risk to the east of the Pennines. There is uncertainty with regards to the extent of this mild sector therefore the extent accumulations to low levels to the west of the Pennines within the trough core is uncertain. A stronger concensus should be reached by tomorrow evening. The longevity of the system is also uncertain. On some model output a slow moving front could produce 20cm+ >250m over the central Pennine region. Other output keeps such core significantly weaker which would limit snowfall. Uppers of -3/-4C in the mild sector support snowfall down to 250/350m with potential for lower in evaporative cooling. Again this is likely to change. Low level areas should look for a reduction in the trough signal for less marginality like shown on the ECM. More certainty on the main core tomorrow evening.

Looking more likely now that an active trough will push into Northern England on Monday night to produce snow showers on it's front into low level parts of NW England / NW Midlands before an active core with heavier and more persistent precipitation moves into central areas of northern England. On the lead a complete below freezing sounding means locally significant accumulations to lower levels are possible. As the heavier core makes progress there is the potential for a mild sector to raise the snow line to the west of the Pennines in particular, with orographically lead adiabatic low level cooling reducing this risk to the east of the Pennines. There is uncertainty with regards to the extent of this mild sector therefore the extent accumulations to low levels to the west of the Pennines within the trough core is uncertain. A stronger concensus should be reached by tomorrow evening. The longevity of the system is also uncertain. On some model output a slow moving front could produce 20cm+ >250m over the central Pennine region. Other output keeps such core significantly weaker which would limit snowfall. Uppers of -3/-4C in the mild sector support snowfall down to 250/350m with potential for lower in evaporative cooling. More certainty on the main core tomorrow evening.

Yes on Monday potentially. The flow is now veering a little to North Westerly for good Pembrokshire activity looking more temporary. We don't have a low stuck over the UK we have a progressive system with defined snow risk areas so less risk of troughs forming at short notice the vast majority will likely stay dry.

The setup coming up is not conducive for "troughs popping up everywhere". It's conducive for snow to northern hills, Cheshire gap snow showers, and snow into France.

I see things from a more statistical and synoptic perspective vs stratospheric or telleconnection such as yourself. This perspective has been significantly against anything substantial aswell. No amount of isolating specific telleconnection drivers can overcome the factors we have discussed. Yes flooding a significant concern now with the south westerlies forecast.

Hi John I know you follow my posts and appreciate that but I'm afraid the upcoming cold spell will likely be snow free for the majority of the UK with the snow chances from troughs looking to affect Scotland and France. Thanks, Kasim.

Atlantic very close at 144h the toppler next week looks quite temporary. Ecm snow free for 90% of UK.

10/15% chance imo.

I'm not sure why we are all so adamant that snowzilla 2010 will suddenly appear out of nowhere via troughs etc. That ship is sailing now. As far as I see it the only low level areas away from Scotland / Northern Ireland in with a chance of significant snow from this cold spell are inland parts of NW England / NW Midlands. This may change.

It absolutely has. Very evident for around 3 weeks now.

It never did - look to our South over the Azores and over the US. The reason this cold spell has gone wrong is evident right now. The Iberian high is far too strong which pulls the high away from trying to move into Greenland. This limits the Greenland high resulting in the cold easterly being too far North. Then the Atlantic can quickly return. This all likely to be a result of not enough SSW forcing in place as I discussed with @Cheshire Freeze. To conclude you can discuss the finer details of telleconnections but until the basics are in place such as strong SSW, low pressure into Iberia, optimal setup over the US, it's unlikely that a significant or sustained cold spell will materialise.

To add to that, the unstable northerly flow which would have provided the conditions needed for the troughs on 17th/18th now looks to only last 24 hours before being shunted east by very mild air so no, troughs will be very limited and snow chances South of Derby are slim. We need the France low to move North or a more prolonged northerly. Very strong signal for the Atlantic to return around the 19th/20th. Personally I never saw more than 4/5 days of cold, the Azores and Canadian signal plus the signal of statistical weather forecasting which I use suggested only temporary cold with the Atlantic being too strong. I think statistical forecasting is a very strong method. UKMO 168H. These snow totals look fair from the ICON.

Looks like 4 days of snow to northern hills then a return to very mild weather. I can't see where snow Midlands South is coming from there isn't any forcing. And the phrase "disturbances will pop up everywhere" is wrong because the northern side of the low into France is not optimal for trough development. If we are very very lucky a trough will form and bring some snow but this is rather unlikely.

Not particularly likely if it isn't on the output and will only affect a very small few. If this cold spell was to be snowy widely we would be seeing it on output now.

Never once looked favourable for more than 4-5 days of cold / snow in the North.

Warm sector in the trough.

Yes, cold air can't deflect big lows the impact is only in terms of keeping the surface cold for slightly longer.

I would say around 25/30% chance of significant snow between Derby and the South Coast from this cold spell. This means some places will get snow but only 25/30% of these areas.

Yes a distinct lack of snow given the potential and depth of cold no spinning that.