Polar outbreak June 19th to 21st

[David]

Metservice going for highs of 12 and 11 here for Fri/Sat. I thought we would struggle to even make it to 10C given how cold the air mass is forecast to be.

But maybe I'm not too good at estimating max surface temp using 850mb temp charts. What are your thoughts NZstorm?

[LittleTreeHouse]

Re chch city I note there is a fair amount of south east in the flow- won't the peninsula shelter the city? Also note met service going for temps around 4 degrees with the precipitation so that would mean rain and sleet not snow

still, early days.

Yes I noticed the difference between closest forecast for us in Southbridge (I use Rakaia) and the forecast for the city - the temps were quite different and Chch city was saying "wintery showers" where as Rakaia says snow lowering to sea level. I never really know what to look at for us - we're more coastal than Rakaia, not really that close to Ashburton, lower than the BP? it sucks not being big enough to be on the map

[NorthSwell]

Bring it on..... Have Coffee Car and camera ready warm hardy souls and capture the event.

Guess my morning sports ground will be cancelled on Saturday but I'll just catch all the folk heading to Hutt, surely they will be needing a good coffee!!!!

[CHCH Weather Chaser]

Metservice have the overnight low for us here in CHCH on Sat as -6!

I also note on the rural Canterbury timeline (next 48 hours) from from 6am-10am the temperature is 1 or less with 28mm of rain.

[CWUweather]

Metservice have the overnight low for us here in CHCH on Sat as -6!

I also note on the rural Canterbury timeline (next 48 hours) from from 6am-10am the temperature is 1 or less with 28mm of rain.

Surely that doesnt mean rain..............

[CHCH Weather Chaser]

Metservice have the overnight low for us here in CHCH on Sat as -6!

I also note on the rural Canterbury timeline (next 48 hours) from from 6am-10am the temperature is 1 or less with 28mm of rain.

Surely that doesnt mean rain..............

Sorry i should say precipitation.

[CWUweather]

Much better that would fall as snow i would imagine

[Inny Binny]

well i've got an exam on thursday morning and i'll probably stay up most of the night for this...so...it better happen, lol.

[spike_01]

Looking like I might get a bit of snow here in the hills of Welly.. Got a few cm's a couple of years ago..

[matttbs]

-9 overnight for Timaru on sat

[jamie]

cant see any action (low snow) for us up here. very much an east coast event this. snow-forecast.com is throwing out some crazy accumulations. Will be avalanches for sure!

[Storm Struck]

The CD getting in on this early, preparing people for the worst just in case.
http://www.stuff.co.nz/national/8809346 ... ed-to-know

Different reports coming through from all sources of the media but half of that they do themselves, sometimes I wonder if they should have forecasters working in the media so they actually have understanding of the weather without making things sound 10x worse.

[kiwisk8er]

Bluebridge Ferry has posted on twitter that they're looking to get hold of everyone traveling with them on Thursday and Friday, due to the stormy conditions.

[Avalanche]

Phil from WW mentioned the southerly arriving late. The weather maps havnt changed its still a thursday/Friday event.

[mikestormchaser]

Re chch city I note there is a fair amount of south east in the flow- won't the peninsula shelter the city? Also note met service going for temps around 4 degrees with the precipitation so that would mean rain and sleet not snow

still, early days.

Any max temps isthe absolute maximum razor, it may not even reach 4C untill 2 or 3pm when the snow level lifts a tad then drops.

[Razor]

Re chch city I note there is a fair amount of south east in the flow- won't the peninsula shelter the city? Also note met service going for temps around 4 degrees with the precipitation so that would mean rain and sleet not snow

still, early days.

Any max temps isthe absolute maximum razor, it may not even reach 4C untill 2 or 3pm when the snow level lifts a tad then drops.

yes but their 48 hour charts have 4 degrees as the minimum, mainly higher. Maybe put this down to inconsistent computer vs other info?
as time goes on it does appear there is slightly more 'warmth' in the mix. Tomorrow will tell more!

[TonyT]

Off topic posts removed. Stay on topic please folks, and tomorrow morning we will start a new thread for actual event reports and discussion, leave this one for any late forecasting tidbits

[Lynley]

The Met Office's "Severe Weather Watch" for Dunedin (& elsewhere) refers in one place to "the likelihood that snow will reach and exceed warning amounts", in another place to uncertainty as to "whether accumulations will reach warning amounts", and in yet another place to "the possibility that accumulations may approach warning amounts". What does this mean? What are "warning amounts"?

[David]

The Met Office's "Severe Weather Watch" for Dunedin (& elsewhere) refers in one place to "the likelihood that snow will reach and exceed warning amounts", in another place to uncertainty as to "whether accumulations will reach warning amounts", and in yet another place to "the possibility that accumulations may approach warning amounts". What does this mean? What are "warning amounts"?

http://www.metservice.com/warnings/weat ... g-criteria
For snow, warning amounts are:
"Widespread* snowfall below 1000 metres on the North Island or 500 metres on the South Island with a snow depth of 10 centimetres within 6 hours or 25 centimetres within 24 hours"

[Razor]

Correct me if I am wrong but latestGFS for chch airport looks to be rolling with 85mm of rain and is too warm for snow and has 530 thickness

[mikestormchaser]

need to start counting the thickness out of the equation from 2mro onwards or even now.
as i said last night to me this is a warm advective set up, and as nzstorm explained how that works with the models picking up the warmer air with the moisture and the low.
You may get a surprise or two

[TonyT]

I think you are probably right Razor, could be just too warm for sea level snow on Thursday although it will come down low. It will be close. Friday looks more promising for snow showers to sea level. Winds are still near gale and temps will struggle to be above 5deg, so its still a major storm. 85mm is going to cause a lot of problems for the city on top of the rain we had in the last few days, and pressures are low too, which will bring the seas up and restrict drainage. If this was an autumn or spring storm we wouldn't be so obsessed with snow level, but would still be nervous due to raiin, wind, and temp.

[Richard]

Correct me if I am wrong but latestGFS for chch airport looks to be rolling with 85mm of rain and is too warm for snow and has 530 thickness

Latest GFS is saying about 140mm for this area,surely thats far to much one would hope.

[Razor]

I think you are probably right Razor, could be just too warm for sea level snow on Thursday although it will come down low. It will be close. Friday looks more promising for snow showers to sea level. Winds are still near gale and temps will struggle to be above 5deg, so its still a major storm. 85mm is going to cause a lot of problems for the city on top of the rain we had in the last few days, and pressures are low too, which will bring the seas up and restrict drainage. If this was an autumn or spring storm we wouldn't be so obsessed with snow level, but would still be nervous due to raiin, wind, and temp.

that's a worry, indeed. Cheers Tony will sit back and see what it all evolves into tomorrow and beyond

[Talbotm]

So sea level snow out of the question in any decent numbers then?? All those times we are always lacking moisture and this time theres too much moisture and its warmed up the Thk levels