Cold Spell Discussion (19/12/09) (Band of Sleet to Snow to push south)

force eleven

nacho libre wrote: »

what a memorable event that was- nearly a foot of snow had accumulated in parts of the northwest by the end of that cold spell.. it may not be prudent to mention polar lows in the current setup but at the same time it's no harm to dream.

Well, that one caught us by surprise, because I remember there was a light dusting of snow on the ground that morning, and wintry showers were forecast mainly for the north and west...sound familiar? Then high cloud drifted in and a light snow started to fall that morning, I remember thinking it would only be a light shower, but it kept going, heavier and persistent for hours until darkness. Now I would love a repeat of that, and there is always a chance once we get the weak front through, we could get one.

kleefarr

Kilkenny City outskirts...

Temperature: 1.7 °C
Dew Point: 1.4 °C

Snow 98% gone.

@ nacho

Those look like little peps of showers which is the front basically sadly which is looking like a squib anyway heading south.
It's initially bringing modified atlantic air with higher humidity-hence the rise in dewpoints.
The modified atlantic air has reached as far south as me now with an air temp of 3.9c and a dp of 1c

Zero dp or below for snow on this front-if you havent that then expect sleety drizzle.

Looks like conditions in annamoe for supercell will be very borderline for snow at this rate of going.He may even see rain.
It's looking iffy for mr boots now aswell up in annagh to be honest-though it will turn to snow if it lasts long enough.
I'd hate to see the snow level rise to nearly 1000ft.
I very much doubt it -it may rise to 800ft or so or lower if near ground a lot higher.
Now cast if ever there was one!

Same analysis applies to the west by the way providing the front gives prolonged precip.
I stand by what I think will happen after the front passes ie plenty of snow showers will develop from donegall to cork.

The reservation is that the snow level is rising temporarally to about 800 ft it seems as too much atlantic maratime air is seeping in ... aka a warm sector.

maquiladora

Just had a look at wet bulb temps for tonight on thre 06Z GFS.

Have to say, starting to look like a major downgrade. Hope transfers to the snow showers but I can't see them getting very far inland...

Bremner

Sorry if this is in the wrong thread. Need to tvl to SW Donegal via Monaghan and Omagh tomorrow. Is it correct that heavy snow falls are forecast for Norn Iron tomorrow? Thanks

Pangea

Bremner wrote: »

Sorry if this is in the wrong thread. Need to tvl to SW Donegal via Monaghan and Omagh tomorrow. Is it correct that heavy snow falls are forecast for Norn Iron tomorrow? Thanks

Yes just seen the bbc forecast ,heavy snow for northern ireland on sunday and monday

nacho libre

force eleven wrote: »

Well, that one caught us by surprise, because I remember there was a light dusting of snow on the ground that morning, and wintry showers were forecast mainly for the north and west...sound familiar? Then high cloud drifted in and a light snow started to fall that morning, I remember thinking it would only be a light shower, but it kept going, heavier and persistent for hours until darkness. Now I would love a repeat of that, and there is always a chance once we get the weak front through, we could get one.

That's the thing with a polar low they develop out of the blue so you can't really forecast them in advance.


for anyone wondering what they are and how they are formed:
http://www.weatheronline.co.uk/reports/wxfacts/The-Polar-low---the-arctic-hurricane.htm

nacho libre

maquiladora wrote: »

Just had a look at wet bulb temps for tonight on thre 06Z GFS.

Have to say, starting to look like a major downgrade. Hope transfers to the snow showers but I can't see them getting very far inland...

this was my fear after the front cleared, that, yes, it would get quite cold but largely dry out with showers confined to coastal counties.

still, i hope Black Briar is right, otherwise i will shake my fists furiously skywards.

Im so dissapointed. sad even But it was fun while it lasted.

Bremner

Pangea wrote: »

Yes just seen the bbc forecast ,heavy snow for northern ireland on sunday and monday

Thanks Pangea

maquiladora

nacho libre wrote: »

this was my fear after the front cleared, that, yes, it would get quite cold but largely dry out with showers confined to coastal counties.

still, i hope Black Briar is right, otherwise i will shake my fists furiously skywards.

:mad:

lucernarian

If there was lots of wamer maratime air engaging with the system, ppn would be more enhanced than what we're seeing. But perhaps it just won't perk up until it reaches NI.

maquiladora

Jake1 wrote: »

Im so dissapointed. sad even But it was fun while it lasted.

It's just a downgrade for the front this evening, there may be other events in the next few days that the models haven't picked up on. Where are you located?

maquiladora

National Forecast


19 December 2009 11:50

Today

Bright spells and scattered wintry showers. Showery rain and sleet will extend southwards during the afternoon with some snow on higher ground. Top temperatures of 3 to 6 degrees but temperatures will fall quickly this evening with sleet or snow showers following and icy stretches developing.
Tonight

Very cold tonight with a severe frost. Occasional hail and snow showers also, chiefly in Connaught, Ulster and west Munster with some accumulations of snow likely. Minimum temperatures of 0 to -4 degrees leading to icy stretches.

http://www.met.ie/forecasts/

lucernarian

Sounds like a likely forecast. What shall next week bring...

2004 at least had some snow showers for christmas.

maquiladora

maquiladora wrote: »

It's just a downgrade for the front this evening, there may be other events in the next few days that the models haven't picked up on. Where are you located?

Im in Lucan Co Dublin.

maquiladora

Jake1 wrote: »

Im in Lucan Co Dublin.

Well the west and north are looking like the most likely places for snow showers in the days ahead but there's always a chance of some showers not dying out and reaching you.

ninebeanrows

The front is developing as warm air is ingested in from the west.

Sure the front is still well to our north, will enhance in representation as it reaches NI.

A brief period of rain followed by heavy snow is likely.

Although precip will probably just last around 1-2hrs and be heavy in nature.

Mildest temps to the west would indicate the further north and east the better however precipitation intensity and the movement of the cold air wrapped into the front will be the main thing.

maquiladora

maquiladora wrote: »

Well the west and north are looking like the most likely places for snow showers in the days ahead but there's always a chance of some showers not dying out and reaching you.

cheers. Even if they reach Kildare, I can run up the road

maquiladora

Front now on the visual sat loop : http://www.sat24.com/gb about 20/30 miles north of N.I.

munsterlegend

wonders what met eireann mean by west munster?! surely cork as well!

it will be interesting watching the showers later tonight as to what path they take..hope they travel inland...still a bit if uncertainty as to how things may work out.

maquiladora

Weathercheck wrote: »

The front is developing as warm air is ingested in from the west.

Sure the front is still well to our north, will enhance in representation as it reaches NI.

A brief period of rain followed by heavy snow is likely.

Although precip will probably just last around 1-2hrs and be heavy in nature.

Mildest temps to the west would indicate the further north and east the better however precipitation intensity and the movement of the cold air wrapped into the front will be the main thing.

WC did you see the wet bulb temps chart I posted on the last page for 9pm tonight? Doesn't look great for snow with those figures?

patneve

Meeeh, this is an extremely difficult evening to forecast, glad I'm not a forecaster! There are two big factors to look into: the intensity of the warm sector and the presence of precipitation after the colder air has come in...For me in Dublin I'd say we'll get light/moderate rainfall with DPs of 2 and air temps of 3-4 degrees, we might get back-edge sleet/wet snow when the colder air does dig in. It will be short-lived, and I expect a starry sky tonight. Looks good for snow up North and West tonight though!

ninebeanrows

As you can see here;

The temperature gradient is very big, uppers go from around -3c to -11c in the space of just ~80 miles.

This is a great example of a potential event. Like the front could be a dampsquib or else deliver thundersnow and drop 3 inches in 30 minutes.

Will be very interesting to watch its passage.

munsterlegend

why don't met eireann give a potential if there is a chance of serious snow occurring? surely its better to be wrong on the side of caution or is it very remote possibility?

Deep Easterly

ninebeanrows

maquiladora wrote: »

WC did you see the wet bulb temps chart I posted on the last page for 9pm tonight? Doesn't look great for snow with those figures?

The idea of this isn't that conditions ahead of the front will be condusive to snow though, they are in a way slightly irrelevent obviously having a cold enough base will help greatly as we already have some low level inbuilt cold on the ground, this mild stuff wont get to deep into the lower atmosphere before it engages with the very cold air pushing south.

Its a light rain... sleet... heavy snow event to me, but all depends on the fronts intensity.

ninebeanrows

munsterlegend wrote: »

why don't met eireann give a potential if there is a chance of serious snow occurring? surely its better to be wrong on the side of caution or is it very remote possibility?

Because current projections would suggest abit of rain then a lashing of snow but probably only amounting to a a small dusting for most that will just turn to ice later on.

However these cold front passages are notoriously difficult to forecast and you can only give a guide as to how they will act.

Look at the satellite pics and hope to see it really exploding to live over the coming hours with a definite tight shape to it.

john 1994

i tink limerick is goin to get snow tonite :D:D

patneve

we can monitor it here:
http://www.meteox.co.uk/h.aspx?r=&jaar=-3&soort=laatstebeeld

and here:
http://www.raintoday.co.uk/

still not very intense, hopefully it will develop when more milder air pumps into it