Yes it is Q is correct we have had this discussion before -3 is enough in certain situations especially with any s easterly element (dryer air)

Not to mention also any slack and evaporation elements involved 

 

I didn't say you can't. I was disputing "easily"

 

I didn't say you can't. I was disputing "easily"

I'd stand by it. There are many situations where -3C is enough to be confident the precip will be snow. Ahead of a warm front with coherent precip the lapse rate is low (due to WAA advection at high levels), the air is very dry and the wind tends to be slack.

Provided the front is coherent and some cold air was established before it came in (even 1 or 2 days of a mediocre northerly would be enough) I'd be very suprised to see rain with T850s at -3C.

The snow event at around 192 hours is exactly that scenario which is why you can almost ignore the uppers and know the precip will be snow away from the far west.

The end of this week isn't quite that clear cut ofc, occluding low rather than a strong warm front into cold air.

 

 

No it's not, you are misreading the charts. That would be snow for a time in Scotland and rain elsewhere, then soon rain for all.

Yes and no.

It would be snow for all higher ground from the Midlands and Wales northwards with snow to all levels in Scotland, aside from coastal locations as always.  Inevitably with a warm sector driving eastwards it would turn progressively to rain away from higher ground in Scotland.

 

I'd stand by it. There are many situations where -3C is enough to be confident the precip will be snow. Ahead of a warm front with coherent precip the lapse rate is low (due to WAA advection at high levels), the air is very dry and the wind tends to be slack.

Provided the front is coherent and some cold air was established before it came in (even 1 or 2 days of a mediocre northerly would be enough) I'd be very suprised to see rain with T850s at -3C.

 

The snow event at around 192 hours is exactly that scenario which is why you can almost ignore the uppers and know the precip will be snow away from the far west.

The end of this week isn't quite that clear cut ofc, occluding low rather than a strong warm front into cold air.

 

You're basic point is sound but I don't think you're correct to apply that scenario to the approaching warm front at T+198.  Just a look at the projected temperature profile of the air masses and the rate of progress of the front suggest it's not the scenario you describe.

If the incoming warm front was sliding SE more quickly and/or slowing down or on a more southerly track to start with then I'd say there was more chance but the evolution in this run just isn't like that: the warm sector punches too far north and east.

 

You're basic point is sound but I don't think you're correct to apply that scenario to the approaching warm front at T+198.  Just a look at the projected temperature profile of the air masses and the rate of progress of the front suggest it's not the scenario you describe.

If the incoming warm front was sliding SE more quickly and/or slowing down or on a more southerly track to start with then I'd say there was more chance but the evolution in this run just isn't like that: the warm sector punches too far north and east.

Yes the snow would be tempory for sure outside of Scotland, but the front is definitely coherent enough to give a significant snow event initially for mainland Britain.

It seems like a cold spell of sorts is brewing - I've noticed that all too often when one occurs it's preceded by a period of cold and dank weather just like we're having at the moment.

ICON model goes for things turning very wintry across North West England late Friday and into early Saturday:

It's still up for debate how low the snow line will get, but some northern hills could have quite a dumping, I would suspect. I personally get a feeling it will be very localised for lower levels, with evaporative cooling being the determining factor.

 

This one:

https://www.theweatheroutlook.com/twodata/reanalysis.aspx?year=1990&month=Dec&dom=09&var=tmp&region=Eur&level=850&hour=00

 

Remember it well Brian started off as heavy rain on the Friday and Friday Night then as a Northerly wind kicked in during the early hours of Saturday it turned to Heavy Snow with over a foot of Snow by lunchtime on the Saturday.

ICON model goes for things turning very wintry across North West England late Friday and into early Saturday:

 

It's still up for debate how low the snow line will get, but some northern hills could have quite a dumping, I would suspect. I personally get a feeling it will be very localised for lower levels, with evaporative cooling being the determining factor.

I tend to keep an eye on the height of the freezing level in these situations; on Friday morning it's close to ground level in many areas and typically only 200-300 metres ASL across the whole country. I think anything falling from the clouds with any intensity at all will reach the surface as at least a wintry mix, with snow likely with some elevation.

So the best thing is to ignore posters if they annoy you. It's 15:25 and no user accounts have been deleted yet today. Frankly it's not what I expected and I'm a little disappointed. Perhaps someone will help me out and give my itchy finger an excuse to press the button. 

So the best thing is to ignore posters if they annoy you. It's 15:25 and no user accounts have been deleted yet today. Frankly it's not what I expected and I'm a little disappointed. Perhaps someone will help me out and give my itchy finger an excuse to press the button. 

How about 

Arsenal are currently crap 

Sack MA 

Quick Edit ................obviously I don't want to be deleted 

A snowy surprise is possible almost anywhere on Friday.  Very marginal and a definitely a nowcast event.

Much better positions of the initial LP on Thursday Friday, keeps the majority of the UK inside the Colder air

Snow depths by Friday Morning

Going to be an interesting end to the week

 

I'd stand by it. There are many situations where -3C is enough to be confident the precip will be snow. Ahead of a warm front with coherent precip the lapse rate is low (due to WAA advection at high levels), the air is very dry and the wind tends to be slack.

Provided the front is coherent and some cold air was established before it came in (even 1 or 2 days of a mediocre northerly would be enough) I'd be very suprised to see rain with T850s at -3C.

 

The snow event at around 192 hours is exactly that scenario which is why you can almost ignore the uppers and know the precip will be snow away from the far west.

The end of this week isn't quite that clear cut ofc, occluding low rather than a strong warm front into cold air.

 

Well yes, as you have just stated above it requires a lot of preconditions to come together at -3C, so not really "easily", that's all I'm saying.

It's getting exciting. I tend to come here every year most days between September and March just to see what you guys are saying for snow and cold. 

I'm in Scotland, rural East Ayrshire, 200m above sea level. We had some cracking frosts in September and early October but not much of note since. 

Much better positions of the initial LP on Thursday Friday, keeps the majority of the UK inside the Colder air

 

Snow depths by Friday Morning

I look forward to the reports of 9cm of snow in Hampshire on Friday but I'm not holding my breath. 

Interesting WAA going to the Western side of Greenland at T192 on the GFS.

Interesting WAA going to the Western side of Greenland at T192 on the GFS.

 

 

Aye - we frequently hear the saying "complex area of Low Pressure" 

Its rare we say " a complex area of High Pressure", as usually theyre pretty well defined jelly fish like slabs on the maps..

But that area to the north of us is very much a big complex High pressure cell that has all sorts of complications going on

Maybe that WAA will kick it into touch