Cold Spell - Feb 7th to 13th 2021 - Technical Discussion

Michelle Dillon was on with Clare Byrne there, she said that its looking like the cold could win and we could have the battle continuing into next week.

Warnings will be issued on Wednesday

Verbatim, the 18z GFS holds out a strong prospect of an almost nationwide snow event, but when I check its snow and precip panels, I see signs of underestimation of potential there, so would take the snowfall panels with some caution as they may be underdone (in central counties in particular, they seem to be assigning a much larger snow shield effect to the southeastern hills which I don't think would be valid given the frontal dynamics in play).

The scenario on offer is this -- cold air is only pushed back very slowly, to about a Waterford to Mayo line, late afternoon Thursday, then it pushes back and regains about a county-wide advantage for most of the evening and overnight, is then pushed back slowly into Friday at which point the event begins to taper off anyway (energy rotating further north for a time) so the cold air is never pushed very far east before it begins to ooze back to the west for another boundary event Sunday night into Monday. Then there's a more rapid breakdown event for later in the week but with the progressive bias of the GFS in mind, that could be just another boundary skirmish and not a total bye-bye to cold as depicted.

With this first event, potential appears to be well into the 10-20 cm range and could end up 20-30 cm closer to the event. Cold is very well entrenched and the surface flow would be from the southeast across 8 C ocean surfaces all the way back to the Channel so you would think the lower mid-level atmosphere would be juiced up nicely as the Atlantic front tries to push in against it all. The snow changing to rain scenario probably applies more to West Munster and southwest Connacht than other regions. If this model depiction is anywhere near accurate it will be a very significant snowfall and fairly prolonged, it could go for 24-36 hours in some places.

Another feature worth tracking is that now there's a more robust push of very cold uppers into Ulster by Wednesday that (with short sea crossing in northeast low level flow) could push temperatures down to -3 to -5 C in Ulster, and almost that cold spreading into parts of the midlands and Leinster as a result, especially if there's any snow cover laid down on Tuesday prior to this starting. (-13 C 850s are shown intruding from Scotland into east Ulster by Wednesday 12z).

Certainly some similarity to the dynamics of the Jan 1982 snowfall event in play here.

Downgrades all round this morning, less snow Thursday into Friday and then milder air wins out for weekend, unusually consistent across the models too!

Could still change but bad morning .

Zogabomb wrote: »

That is in regard to the weekend though, Thursday still looks interesting, no?

Oh still snow widely Thursday and into Friday but amounts also reduced a little.