End of June cold shot.

[Tracy Herbert]

Oh crap, that’s going to make driving home to Rakaia from Christchurch interesting on Monday night.

[matttbs]

This to me looks more like a Southland/Otago event, too SW for anything significant to happen in Canterbury

[NZ Thunderstorm Soc]

The Port Hills might get a sprinkling of snow next week after this next wild system moves over delivering all that rain on the West Coast.

[TonyT]

The number of ECMWF ensemble members putting some (very small amounts) snow on the ground for Christchurch in the Monday to Wednesday time frame is slowly increasing with each run. A few days ago it was 2 out of 50, with today's 0Z run we are up to 7 out of 50 (so 14% probability).

[TonyT]

And with the 12Z run we are now up to 17 out of 50, so 34% probability.

[talbotmj15]

I think its safe to say the cold air is certainly there next Monday/Tuesday. Its just wind flow direction and moisture to me for any kind of snow. Certainly a good system but jeez the models are really struggling to pin point its actual course. I wouldnt be surprised to see the moisture pickup at the last minute and see a quick 10cm to 1-200m. Wind direction only has to shift a few degrees and it changes everything.

[Tracy Herbert]

I see MetService now have rain changing to snow on Monday for Methven, Rakaia and Christchurch.

[TonyT]

I think its safe to say the cold air is certainly there next Monday/Tuesday. Its just wind flow direction and moisture to me for any kind of snow. Certainly a good system but jeez the models are really struggling to pin point its actual course. I wouldnt be surprised to see the moisture pickup at the last minute and see a quick 10cm to 1-200m. Wind direction only has to shift a few degrees and it changes everything.

It largely hinges on how "sharp" the trough is to the east. The "pointier" it gets, the greater the advection acrosss the temperature gradient, and the beefier the showers will be. However, looking more and more like a coastal/Peninsula event, if it happens. (Model forecast maximum of 6 degrees on Tuesday!)

[talbotmj15]

Latest GFS starting to put the system further north and a windflow change to more S than SW. 4 days ago it was showing as a WSW then the last few days its gone SW and now showing S. Trending in the right direction. Interesting that as i suspected as soon as the wind direction changed from SW to S the moisture ramps up at the same time. looking at around 15-20mm on the plains. fingers crossed it continues this trend. now i mention it the models will probably start to pull back again. lol

[Razor]

I see MetService now have rain changing to snow on Monday for Methven, Rakaia and Christchurch.

Thats no longer the case. Rain, clearing for Monday in ChCh now

Too far out to hang ones hat on for sure

[Chris W]

Metservice going moderate on severe SW gales for the entire South Island east coast on Monday, snow amounts likely very low for Chch but it's going to feel a bit nippy.

[talbotmj15]

Current data suggesting a very cold SW turning SSW and chain showers later monday. Could see some Beefy chain showers on the plains if it holds a SSW pattern. I do note places like Arthurspass are projected to see like 50cm and queenstown between 20-30cm. Just shows there is some good moisture in the system but only really getting into otago and southland with Chain showers further north. tonights EC will be interesting. GFS has shown a strong S -SSW system for the last 2 runs.

[darcyplumb]

We are well overdue for a decent snowfall here in Ashburton. I don’t think it will be this system that delivers the goods. SW is often dry for us

[mikestormchaser]

We are well overdue for a decent snowfall here in Ashburton. I don’t think it will be this system that delivers the goods. SW is often dry for us

Unless the flow goes S-SW I think ashburton will be cold but dry. Heavy frosts at night.
It does look very cold come Tuesday but to me nothing that we haven't seen In recent years.
These are systems you want colliding with the low pressure systems from the north but we just don't seem to be getting that sort of set up as of late. I don't see any hype with this cold outbreak.

[darcyplumb]

We are well overdue for a decent snowfall here in Ashburton. I don’t think it will be this system that delivers the goods. SW is often dry for us

Unless the flow goes S-SW I think ashburton will be cold but dry. Heavy frosts at night.
It does look very cold come Tuesday but to me nothing that we haven't seen In recent years.
These are systems you want colliding with the low pressure systems from the north but we just don't seem to be getting that sort of set up as of late. I don't see any hype with this cold outbreak.

2011 is the last decent snowfall that I can recall. We’ve had flurries since then and the odd day of an inch or so of accumulation. Still a few months of cold to come

[Bradley]

Yep Mike this looks to be one of those run of the mill cold snaps we normally see a few times in a winter. Perhaps some people are getting excited because it’s the coldest air we’ve had since last September lol

[Cyclone Tracy]

Not quite at the 100 hours out mark yet to take anything serious but EC & Icon throwing in some thundersnow around the Banks peninsula early Tuesday morning was entertaining on this mornings 12z runs.

[TonyT]

With the 12Z run, 6 of the 50 ensemble members put snow on the ground in Chch on Tuesday so 12% probability. None of those are more than 1cm. 40% bring snow to 200m, but almost all want to keep that snow on Banks Peninsula so the Port Hills may be the limit. Likely to be an inland event on Monday and a Peninsula event on Tuesday, with the Plains very likely missing out altogether. Model forecast maximum for Chch on Tuesday has risen to 8 degrees.

[mikestormchaser]

Expect some good heavy frosts next week. Inland temps could plummet to the -10s coastal fringes down to -4s not fun for people starting early and working outside!

[Razor]

2011 is the last decent snowfall that I can recall. We’ve had flurries since then and the odd day of an inch or so of accumulation. Still a few months of cold to come

11 July 2017 here. Vividly seared onto my brain and my youngest was born that day. Drove from Lincoln to Cashmere that night with snow falling and made a snowman on our front yard the next morning. Wasn't a huge fall but a couple of cm's settled overnight

[Chris W]

Not quite at the 100 hours out mark yet to take anything serious but EC & Icon throwing in some thundersnow around the Banks peninsula early Tuesday morning was entertaining on this mornings 12z runs.

Wouldn't mind that at home, one can dream

Not seeing anything spectacular but falling snow would be great even for a time. Let's enjoy that (if it comes) after some grey dross and soakings lately!

[Dean.]

Around 5cm in 2016 in Ashburton and only a few skiffs of snow since

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[spwill]

Good news for Wanaka and Queenstown for school holiday skiing.

[Chris W]

GFS kinking the isobars a little more on Monday's front, so SE then SW, but still possible it goes critical SW after the front passes through. 850s consistently initially -3C going down to -7C so still cold, strong wind looking very likely. Uppers very cold around -36C so it looks fun for a few hours and the wind persisting after that.

[Bradley]

Yeah GFS still has snow on the ground in Christchurch on Tuesday morning, around 1cm whereas EC wants nothing to do with it!