It is tough to forecast snow here across the UK and Ireland at the best of times but in March it’s even more challenging as you have multiple factors to consider which perhaps you wouldn’t during mid winter including potentially warmer ground and higher sun angle which radiates more energy through clouds and down to the surface which can warm the lower atmosphere slightly, resulting in rain or sleet and not snow. It could also snow heavy and simply not accumulate.

You, my subscriber was told about the increased snow potential since last Saturday and last Sunday I released a public video on facebook and twitter stating that very cold air was returning this weekend into early next week, backed by the fact the indexes were favourable and so too was the overall pattern and the trend through this winter with it’s ‘progressive’ nature. What do I mean by progressive? Well the pattern across the hemisphere is fluid despite all the blocking and when you’ve a blocked pattern but it’s fluid, then it’s only a matter of time before the cold reaches you if indexes remain a constant. So, there’s my evidence and reasoning behind my ideas. Not just model watching and calling the shots when it’s obvious!

Folks, this ‘wild’ endgame to winter was spoke of back last autumn. The winter I believed was closest to us was 2009-10 given the parameters with the ENSO, global SST’s, very warm North Atlantic which would likely favour more blocking etc. The setup last summer across the UK as well as other more global factors were all similar to those back in 2009. I stood by the fact that 2009-10 was not going to be matched this year in terms of intensity but 2012-13 would be a weaker version. Though weaker, I was copnfident we would see plenty of cold and snowy periods and like 09-10, we needed to watch closely the February-March period. Interesting given what’s coming.

I stated in my video last Sunday about a good chance we may find a surface low develop underneath the upper low, positioned south, southwest of the UK which could throw moisture up into the cold air diving in from the ENE which could spark a snowstorm!

There are many factors which has to be considered when it comes to this situation evolving. How fast does the cold air get in before the moisture gets fed north into Southern England. How cold is the actual air, is it cold enough to support snow in the first place? When it does snow, will it stick and accumulate? How warm is the ground? What about the strength of the March sun beaming through the clouddeck, could that warm the lower atmosphere as well as ground too much?

Like with the US Mid-Atlantic scenario, these are all factors being looked at and there is a very fine line between a great forecast and a complete bust.

I want to show you the GFS vs ECMWF snow scenario across the South of England and how the ECMWF isn’t favouring things while the GFS is more bullish.

ECMWF

surface chart

24 hrs

[s2If current_user_can(access_s2member_level1)]

36 hrs

Shield of precip barely makes it into the SW of England and though the column should be cold enough to support snow down to the ground, with heaviest precip holding to the south, any snow which does fall may have a hard time sticking. While the ground has been heated properly, the incoming cold air looks strong enough to cool ground temperatures fairly quickly and should allow accumulation but it needs to come down fairly hard.

850mb temps

24 hrs

30 hrs

850 temps certainly appear cold enough with the -5 line near to the South Coast if only moisture could push north which it may well still do as newer runs of this model come in.

snow chart

24 hrs

Though the air appears cold enough to support snow, unfortunately you need moisture too and with this latest run of the ECMWF, no real moisture gets into the South of England in order for a snowstorm to unwind.

36 hrs

The model shows only the Pennines seeing snow which is wrong as it’s been snowing over eastern counties this afternoon and evening and more is likely throughout tonight.

Below is the GFS which is much more bullish and has been persistent through much of the week.

GFS

surface chart

30 hrs

36 hrs

Note a fairly nice band of modest precip over the South at 30 hrs with greatest mnoisture content pushing into the SW. Remember that the colder the air, the higher the ratio of snow. 1 inch of liquid produces more inches of snow depending upon how cold the air is. If we get  5 to -10C air through a good chunk of the air column and thrown a decent amount of liquid into it, we could see a decent 6 inch snowfall over interior SW England.

850mb temps

24 hrs

 

 

30 hrs

snow chart

24 hrs

30 hrs

With this newest run of the GFS, notice the highest moisture content and therefore snow focuses on the SW with lesser amounts easter east along the south coast.

What remains open is how far north the moisture extends. The air will be increasing drier the deeper you go into the cold air mass but any moisture which makes it through without evaporating, could bring a coasting to as much as a few inches to places quite far north, perhaps through Birmingham etc.

Also notice much of the country shown to see some snow. The blues represent where your likely to see a few inches, darker blue perhaps 6. Anywhere could see snow showers over the next few days, especially over eastern areas of both the UK and Ireland.

VIDEO UNFORTUNATELY HASN’T WORKED! WILL TRY TO GET ONE UP TOMORROW MORNING…

[/s2If][s2If current_user_is(s2member_level0)]

Join a subscription plan, [s2Get constant=”S2MEMBER_CURRENT_USER_DISPLAY_NAME” /]!

[warning]You do not have a valid subscription to access premium content exclusive to members. You will need to join a subscription plan if you would like to continue.[/warning][/s2If][s2If !is_user_logged_in()]

Sign in to read the full forecast…

Not yet a member? Start your 7 day free trial

Create your free markvoganweather.com account today to get unlimited access to Mark Vogan’s premium articles, video forecasts and expert analysis for 7 days.
[/s2If]