31st - 3rd August heavy snow event Mid-North Canterbury

[talbotmj15]

Seems we could see a significant snow event mid late next week for Mid-North Canterbury. All the main models show very good consistency. Fresh lambs starting to fall as well so this could cause a fair amount of disruption.

First decent system since beginning June. Welcome back Winter we missed you!!

[Chris W]

I’m not sure about the consistency, GFS looks keener and colder than both the UKMO and EC but it is looking cold on all three counts. Positioning of the low that could drag very cold air up is in question, currently the GFS has it furthest east but UKMO is out west. Also 4 days out in which a lot can change. It looks like the snow line could lower quite a bit but I’m not picking sea level at this stage, just too far out.

Edit - MetService saying this in their Outlook: https://www.metservice.com/warnings/sev ... er-outlook

[Bradley]

A huge upgrade in EC’s latest model run in terms of moisture - Christchurch now in the gun with 80-100mm over the Wednesday/Thursday period next week Snow level still holding around the 400m mark but this could be a epic dump of snow above the 800m mark in the Canterbury high country...

[NZ Thunderstorm Soc]

Yes, looks like a cold wintry event coming up if everything comes to what models and forecasters come to predict.

[NZstorm]

The mid week system looks to become more active over Canterbury. So snow levels could drop to 100m on Wednesday.

[Richard]

Could this be the first snow in four winters ?

[talbotmj15]

EC gone mad. 34cm for 300m in mid north Canterbury. GFS holding at 17cm for 300m. Seems a bit high IMO. Looking at some maps though the Air reaches from well down onto the Antarctica which we havnt seen for some time. Certainly looks the most consistent in the models and the most likely this year for a low level event. Next weekend looks like a chain shower setup with even colder air pushing the snow level to around 100m.

[Cyclone Tracy]

2 cents worth.

EC and GFS 00Z have similar synoptics to June 12, 2006. EC showing 'mesoscale snow banding' that is assisted from a convergence off the ocean, pointing an atmospheric snow gun between Ashburton and Christchurch.


UKMet is still not convinced on the above.

[Razor]

Hmm and heres me thinking GFS are increasingly looking at "Critical SW flows" for most of the fun which will send it out to sea beyond the first wave

[Bradley]

EC now going for 5-10cm of snow down to sea level on Wednesday for Christchurch

[melja]

Yes it does look that way but IMO it's a more south Canterbury event for the heavy snow.

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[Cyclone Tracy]

EC & GFS now coming more into line with the UKmet on moisture and freezing levels. Still sizeable differences on the placement of the first upper low though.

[Chris W]

MetService now going for snow to fall down to 300m in the South Island, watch for heavy snow above 500m and especially above 800m.

[talbotmj15]

Seems very conservative as usual. Most data suggests heavy snow above 2-300m. Not above 500 or 800m.

Its no wonder the farmers dont follow them. This is how farmers have lost stock over the years because they get no warning before an event hits. Most farmers i talk to always tell me they like to be told how it is. They need a headsup early to move stock. If it doesn't happen no dramas.

[melja]

Depends what you define as heavy

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[talbotmj15]

Depends what you define as heavy

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Based on M/S isnt it 10cm in 6hours below 500m?

Or did i miss that?

[Bradley]

Both GFS and EC have backed off on the 50mm of rain for Christchurch on Wednesday in this mornings run but interestingly the updated forecast with NIWA is for 50mm for Christchurch - in the last few months the NIWA forecasting system has been doing quite well with rainfall totals so perhaps we are still in for one last twist with EC and GFS in tonight's/tomorrow mornings updated runs...

[Razor]

Both GFS and EC have backed off on the 50mm of rain for Christchurch on Wednesday in this mornings run but interestingly the updated forecast with NIWA is for 50mm for Christchurch - in the last few months the NIWA forecasting system has been doing quite well with rainfall totals so perhaps we are still in for one last twist with EC and GFS in tonight's/tomorrow mornings updated runs...

Yes Metservice only has 5mm for ChCh. To me it looks a very hit and miss system, some areas will get some good precipitation, others not

[NZ Thunderstorm Soc]

According to the media, this system is going to shock many people?

[Chris W]

That might be due to the wind chills, they were mentioned on Stuff as having been lacking lately, which is true.

GFS and UKMO both seem to have more of a southeasterly component to the low, taking precipitation inland away from Chch/shadowing from the peninsula. Foothills upwards are looking in for more significant snow, and as such there is now a warning for the high country and also foothills south of the Rakaia:

https://www.metservice.com/warnings/sev ... 090243.000

[talbotmj15]

Big upgrade by MS with warnings now for 15-20cm of snow to 400m. Also extended up to kaikoura. And a heavy rain watch for chch city. Which im not seeing as its very SE!

[Chris W]

Not as much on the MS rain maps, they are keener on a SSW direction. I don't think they are trusting GFS.

Warning text has snow to 200m north of the Waimak.

[Bradley]

Tony what are your thoughts on some people now saying that snow is a chance tomorrow morning to sea level?

[TonyT]

Tony what are your thoughts on some people now saying that snow is a chance tomorrow morning to sea level?

There's a greater chance of winning lotto!

This will be an inland event, not a coastal one. So that kinda rules out sea level.

[Bradley]

Tony what are your thoughts on some people now saying that snow is a chance tomorrow morning to sea level?

There's a greater chance of winning lotto!

This will be an inland event, not a coastal one. So that kinda rules out sea level.

Exactly what I thought, no data in any of the models supports snow to sea level