Cold Spell Discussion cont: Tuesday, Wednesday - more heavy snow risk

redsunset wrote: »

poor country track forecast

I would not take too much notice of that. It's a marginal situation with a few miles being the difference between rain and snow. The 00z GFS, for example, had widespread snowfall Wednesday night and the ECM does not agree with the UK Met Office on the posistioning of Low Pressure which makes a really big difference to the prospects.


Looks like either way Ulster is gauranteed a hammering on Tuesday and Wednesday.


BTW the 06z GFS, whilst it brings snow for a time to many areas on Tuesday, is actually on the mild side of the ensembles (the thick green line). The average (the thick white line) indicates more wintry conditions then the op run.

redsunset wrote: »

Oh i know its not gospel and will swing to and fro and will end up being a nowcast i feel.

As for the north like you said,the UKMO sure have some confidence for wintryness.


Northern Ireland: Co Antrim
Co Armagh
Co Derry
Co Down
Co Fermanagh
Co Tyrone
Heavy Snow Wed 24 Feb
There is a moderate risk of severe weather affecting parts of the UK. Rain spreading north may turn to snow and has the potential to give accumulations of more than 15 cm of fresh snow in places.
Issued at: 1042 Sat 20 Feb

This is what the UKMO shows precip and temperature rise. Clearly North Leinster and Ulster in the firing line. But further south too. Places like Dublin for example - alot of precipitation and temperatures 1 - 3C.






But it will change over the next few runs. Risk could be further South or further North.

Deleted User wrote: »

Indeed.
What darkman2 is not taking into account is that winds from the irish sea with no lengthy cold surface feed,will bring in positive dewpoints.
Thinking otherwise I'm sad to say is dreaming.

Remember the famous sunday snow in the early january spell, that cork got but we didn't get on the East?
Twas a lot colder then than it is now and it rained due to the positive dewpoints/warmer air advection from the irish sea ie no real cold source left.

Lets not let dreaming over rule basic weather science.

That low pressure going a few 10's of miles north or south of where it is will change who gets snow on high ground and 20 miles plus inland but it will not make a half worth of difference on the coast in the East.

Nonsense. Im well able to read the charts and take all factors into account. For example if you don't think the ECM charts above would bring an appreciable amounts of snow to Eastern coastal counties then I don't think you are reading the charts properly and seem unfamiliar with the dynamics surrounding a frontal event. We don't need a cold air source - the cold air is already over us and that won't change until the fronts clear through - which won't happen incidentally. Dew Points should remain around 0C generally or a little below. (Away from Southern and maybe Southeastern areas but that's uncertain)

Deleted User wrote: »

Even Evylyn just now mentioned "away from the coasts" darkman2.

I see so you think that the less cold air coming in off the sea with higher dewpoints is somehow going to magically deliver snow when colder 850's last january [the day cork got its snow as it had a land breeze] delivered rain?

I'd like to borrow your magic wand please with all due respect because thats what I'll need

The risk is for high ground and well inland.

No, she did not mention, "away from the coasts" - even if she did I don't particularly need to pay attention to what she says anyway considering the charts are right in front of us.

The setup coming is very different to the one you are referencing. Firstly SST's are at the lowest point of the year. Secondly the rotation is taking precipitation out of the UK where it will also be snowing. Thirdly 850 temps of -4 or lower are all that are required in a frontal event as things like evaporative cooling take place. You want to reference an event - then take a look at the 1982 statistics. If that was progged tomorrow you would no doubt be talking about the wind off the sea. 850 temps where -4 generally and sub -5 to the North. The temperatures progged in the Irish Sea by the UKMO are 2 or 3 degrees in the North Irish Sea, 4 or 5C further South. 2 or 3C and sub zero dew points over the sea is not magically going to turn the snow from Britain back to rain like a click of a finger. It may be different closer to where you are as SST's may be slightly higher there (again it's very uncertain) but here the UKMO progs temps 1 - 3C, Irish Sea temps 2 or 3C and 850's at -4 along with persistent precipitation. Not that I think the UKMO is cert to come off. All the models are contradictory to some extent atm. So in this case this argument is elementary because things are so marginal as regards posistioning that a few miles here or there is the difference. But I don't support this theory of yours that a wind off the Irish sea automatically = no snow. Clearly it does not. And probrably won't on Tuesday either especially further North up the coast.









Just using GFS there as example of why BB is wrong with automatic assumptions about Dew Points in the Irish Sea. Of course it is very possible we could end up the wrong side of marginal - but equally possible things will favour snow even more.