Freezing Weather Discussion - Widespread Snow Tonight/Tuesday

Morning Everyone

Introduction

Firstly, a few points. The overnight outputs, especially that of ECMWF is much better in the medium term with a more sustained Easterly flow. A rewned, fairly potent due Easterly flow, is now likely to be developing into the weekend. Also, the overnight ECMWF shows no sign of a breakdown again until T+240! UKMO 00Z is another excellent run, with a shortwave feature moving down across the country between T+96 T+120, undercutting, with a strong Easterly flow developing. Into the medium term there is, at present, no sign of a let up in these conditions, with renewed blocking quite likely from Scandinavia to Greenland, Ireland being under an Easterly flow.

Snowfall Distribution & Potential

What I find a bit perlexing about the latest Met Eireann update is that the overnight ECMWF 00Z Guidance is once again holiding firm about the snowfall threat, in Eastern and Southeastern areas in particular. With the risk as mentioned last evening for Western Atlantic Seaboard areas into Thursday, when a Shortwave feature will run down the country, hitting into the cold air in place, as a Blocking High builds over Scandinavia.

Here are some of the overnight ECMWF Precip Charts:

Tuesday Night



Wednesday Morning



Wednesday Afternoon



UKMO 00Z

Also holds constant regarding the snowfall risk. The main risk periods include the period from 01.00 to 07.00 tomorrow, when it models the cold front moving down across the country. In models this as remaining intact, all the way down, even strengthening in Eastern areas:



It also models a further risk of snowfall quite widely in the East and Southeast, later on Tuesday and into Wednesday, very much in line with the latest ECMWF guidance. Again, that's not to say that these are entirely correct but these latest runs are almost even better than the ones of last evening & do clearly suggest the potential for snowfall in the risk areas that were mentioned last night. Also, most model guidance now prolongs the Northeasterly flow into Thursday.

GFS 00Z is not as good into the medium term but I suspect it's picking up on a signal initially picked up upon by the other models and subsequently dropped, as overnight, all other NWP Guidance supports a renewed, potent Easterly flow developing towards Friday onwards.

Summary

In summary, the snowfall potential, as discussed last night largely holds firm on the vast majority of guidance. Again, there are no certainties in this setup, the evolution is complex and snowfall is very difficult to predict and model. From all of the available NWP Guidance, the risk of the overnight GFS 00Z evolution with much slacker conditions, is about 35%, with a solid 65% support for a renewed Easterly flow. Equally, it would be positive to see a fairly rapid reversion from GFS, preferably by later today. Some of the other Guidance has modelled this GFS evolution before, bus has subsequently dropped it. UKMO appears to be, by far, the most consistent at the moment.

SA

darkman2 wrote: »

No but im very familiar with the problems on Yellow Walls. It was like walking a road in Siberia yesterday and not much better today. Cars skidding and not moving at the same time, pedestrians falling etc. It's very bad. The council are muppets.

Muppets is an understatement!!:(

owenc wrote: »

yes ill be happy if it comes tonight and delivers 15cm (like thats ever going to happen) and then somewhere i know would be shut... maybe...

ah you never know when snow will fall, the weather will do as it pleases one morning...(if you havent been lampost watching all night that is) you might wake up to a few inches, ill pray for snow in Coleraine as well as Navan tonight and hopefully that place you know will be shut;)