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09-12-2017, 10:22   #1
pistolpetes11
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Snow and Ice Warning : Saturday(PM)/Sunday 9th/10th Dec - TECHNICAL ANALYSIS ONLY

This is the Technical Scientific thread for discussion on tonight and tomorrows possible snow event, will it snow in my back garden at such and such a time will just be deleted or merged into the other thread which will be linked below



https://www.boards.ie/vbulletin/show...p?t=2057817783

Last edited by pistolpetes11; 09-12-2017 at 10:28.
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09-12-2017, 10:31   #2
Rebelbrowser
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I wonder could I ask again a question I posed in the other thread, namely what is different about this set up from normal that gives the big snow risk? I thought you would need deep imbedded cold for such a battleground scenario to occur but I dont see that in the upper temps. What am I missing?
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09-12-2017, 10:45   #3
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Technical question, as mentioned in the other thread about heavy perception, would met eairann take into account, evaporation snow fall into account when making there forecast for snow fall tonight, as well as the low temperatures
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09-12-2017, 10:47   #4
Neddyusa
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Anyone care to make lying snow max predictions for ME stations tomorrow and Monday morning?

Sun - Mt Dillon 16 cm

Mon - Gurteen 21 cm
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09-12-2017, 10:51   #5
17-pdr
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6Z Hirlam for +24 hrs. Indicates the maximum northward position of the front before it starts pulling away to the south and east again.

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09-12-2017, 11:03   #6
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It is important to note- that whilst i don't know the actual parameters behind the above snow chart. In general rain/snow type charts will shade in snow even if there is only a small amount of the precip falling as snow.

Indeed as of yesterday - the EC was showing 50-50 rain and snow in the precipitation for Dublin region. Inland it was 90%+ snow.
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09-12-2017, 11:52   #7
Gaoth Laidir
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Dublin TAF shows light rain from midnight, tempo sleet from 3 am as light variable winds increase easterly 15 gusting 25 knots from 2 am. The airport may be about the extent of the marine layer, further inland should see more of a snowy nature.

Knock is hell for leather snow...

TAF EIKN 091100Z 0912/1012 VRB03KT 9999 FEW010 SCT025
PROB30 TEMPO 0916/0921 3000 BR BKN005
BECMG 0921/0924 11012KT 3000 -SN SCT003 BKN007
TEMPO 0923/1012 1200 SN OVC002
BECMG 1001/1003 08015KT
TEMPO 1003/1006 09016G26KT BECMG 1010/1012 05013KT=

Quote:
Originally Posted by Rebelbrowser View Post
I wonder could I ask again a question I posed in the other thread, namely what is different about this set up from normal that gives the big snow risk? I thought you would need deep imbedded cold for such a battleground scenario to occur but I dont see that in the upper temps. What am I missing?
You won't see that in the upper charts. Looking at 850 hPa temperatures is useless in this setup as we're not talking about convective snow in normal lapse rates. The sounding below shows how temperature is actually fairly constant with height through the bottom few thousand metres, and is at or below zero. 850 hPa temp is only -2 °C, which would not normally hint at anything other than rain.



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Originally Posted by ZX7R View Post
Technical question, as mentioned in the other thread about heavy perception, would met eairann take into account, evaporation snow fall into account when making there forecast for snow fall tonight, as well as the low temperatures
As the whole lower atmosphere is completely saturated there is no scope for evaporative cooling.
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09-12-2017, 15:13   #8
Meteorite58
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Raining lightly now near Tralee at 5.1C ( could see the mountains get a bit whiter before they became obscured by cloud ). Will be interesting watch the front move into the colder air as it moves up the country later this evening.













No doubt driving conditions Sunday/ Monday going to be testing for a lot of people,

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09-12-2017, 15:17   #9
JCX BXC
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Temperature quite low here, while Clare is on a yellow rainfall warning I wonder could heavy precip drop the temperature enough to have a flurry?
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09-12-2017, 15:18   #10
Gaoth Laidir
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The ECM Extreme Weather Index is high for total precipitation by tomorrow night.

Attached Images
File Type: png ECM EWI.PNG (207.8 KB, 3597 views)
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09-12-2017, 15:21   #11
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Frontal rain bearing cloud off the SW




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09-12-2017, 15:35   #12
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The fact that we have a pair of low centres by morning - one off Wexford but another in Galway Bay - could lead to some subtle variations in the exact extent of that easterly marine layer in the east.



The 12Z ICON has the main bulk of precip back further south, in line with the other models. Note that this model has a known drizzle bias, so it may be overdoing the precip slightly.



Lastest forecast soundings are still showing heavy (wet) snow for many low-lying areas of the midlands and west during the morning.
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09-12-2017, 16:18   #13
 
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I feel this event is going to be very much a nowcast.

There'll be surprise falls for some, and others who appeared to be in more favourable areas prior to the event may face disappointment.

That low off Rosslare could drag some colder air further south east possibly?

I'm down with flu symptoms and stuck in Portlaoise Was looking forward to getting some pics at home as i'd rate our chances of a decent fall at 70% or so.
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09-12-2017, 18:20   #14
JCX BXC
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Almost forgot about the TAF's!

Knock:

BECMG 0921/0924 11012KT 3000 -SN SCT003 BKN007
TEMPO 0923/1012 1200 SN OVC002

Light Snow from 9pm, temporarily moderate from 11pm. Gonna be a white out there!

Shannon:

TEMPO 1009/1014 3000 -RASN

Periods of sleet from 9am-2pm tomorrow.

Dublin

TEMPO 1002/1009 11015G25KT 3000 RASN

Periods of sleet betwen 2am-9am

That's it, nothing for Casement or Cork in the 5pm TAF's other than rain.
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09-12-2017, 18:49   #15
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I'm a bit worried about the extent of cloud cover across the country this evening. With that in place there won't be much cooling in that central slab of the country where snow could fall. Almost everywhere us still above zero at the moment. With cloud on the increase its an uphill battle to hold onto our cold layer. It could swing the wrong side of marginal for low levels, or at least a wet mix. Need it to clear a bit.
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