Potential Nationwide Snow Event Sunday 8th August 2021

[Bradley]

Certainly looks like the models are aligning and pointing towards the more drastic end of the spectrum. Interesting couple of days or so ahead

I trust Mrs Razor is safe somewhere?

Did I read your statement correct Tony in that you expect 1-5cm to settle in Christchurch by Monday morning?

[TonyT]

To me this looks like at least a repeat of 2011, the possibility of a repeat of 1992 is on the table.

[darcyplumb]

To me this looks like at least a repeat of 2011, the possibility of a repeat of 1992 is on the table.

Tony, in your blue skies post this morning, would you classify Ashburton as south Canterbury? Just trying to figure out which part of the puzzle we fit into.

[Storm Struck]

I'm seeing the 700mb aligning with the 850mb from about midnight Sunday into early Monday, - 18c on the 700mb and - 6c on the 850mb.
This is the window I see a typical SSW chain snow periods then showers to sea level for the city and the peninsula.
Accumulations are always questionable but from memory we've had some reasonable events in the past under this set up, July 2011 snowfall which had convective cloud tops added to it allowing more moisture thus snow through those SSW feed zones.
It should be quite an interesting event I feel and in different stages too.

[Dean.]

To me this looks like at least a repeat of 2011, the possibility of a repeat of 1992 is on the table.

Tony, in your blue skies post this morning, would you classify Ashburton as south Canterbury? Just trying to figure out which part of the puzzle we fit into.

Well our local rep team is called Mid Canterbury

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[darcyplumb]

Tony, in your blue skies post this morning, would you classify Ashburton as south Canterbury? Just trying to figure out which part of the puzzle we fit into.

Well our local rep team is called Mid Canterbury

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Yes I know we are classified as mid Canterbury but I didn’t see that mentioned in the post (unless I’m blind, which is also possible)

[darcyplumb]

Well our local rep team is called Mid Canterbury

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Yes I know we are classified as mid Canterbury but I didn’t see that mentioned in the post (unless I’m blind, which is also possible)

Haha, turns out I’m blind!

[Dean.]

Well our local rep team is called Mid Canterbury

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Yes I know we are classified as mid Canterbury but I didn’t see that mentioned in the post (unless I’m blind, which is also possible)

Yes we are often quoted as South Canterbury in the media...would not be suprised if we see snow falling on Sunday morning here at over 100 metres

[Bradley]

To me this looks like at least a repeat of 2011, the possibility of a repeat of 1992 is on the table.

Both events in 2011 were normal southerly outbreaks though, this will be a warm adventure event won’t it? Or were you talking about in terms of snow amounts?

[darcyplumb]

Yes I know we are classified as mid Canterbury but I didn’t see that mentioned in the post (unless I’m blind, which is also possible)

Yes we are often quoted as South Canterbury in the media...would not be suprised if we see snow falling on Sunday morning here at over 100 metres

I do feel for the farmers with their young stock but as a townie, I really hope we get some decent snow.

[mikestormchaser]

To me this looks like at least a repeat of 2011, the possibility of a repeat of 1992 is on the table.

If its as bad as 2011 chch will receive more than 5cm.
Tony this must be one of a forcarsters worst nighmares to really pin point exactly what could happen. Exciting but daunting tasks

[snowstormwatcher]

Yes I know we are classified as mid Canterbury but I didn’t see that mentioned in the post (unless I’m blind, which is also possible)

Yes we are often quoted as South Canterbury in the media...would not be suprised if we see snow falling on Sunday morning here at over 100 metres

I consider anything North of the Rangitata River Mid Canterbury.

Regarding this event I wouldn't be surprised at all if most of South Canterbury largely misses this event just like many previous events. Last time I seen a decent amount snow below 100m in South Canterbury was 7th of June 2008 When 3-4cm fell right down to sea level in Timaru.

[Cyclone Tracy]

Upper trough is starting to extend equatorward from the polar vortex towards NZ, Macquarie Island with patchy sea level snow now appearing.

[Lawrence]

Yes we are often quoted as South Canterbury in the media...would not be suprised if we see snow falling on Sunday morning here at over 100 metres

I consider anything North of the Rangitata River Mid Canterbury.

Regarding this event I wouldn't be surprised at all if most of South Canterbury largely misses this event just like many previous events. Last time I seen a decent amount snow below 100m in South Canterbury was 7th of June 2008 When 3-4cm fell right down to sea level in Timaru.

I've got this map if it helps any

images.jpeg

[mikestormchaser]

To me this looks like at least a repeat of 2011, the possibility of a repeat of 1992 is on the table.

If its as bad as 2011 chch will receive more than 5cm. The 2011 event was a very cold advection event with THK levels as low as 512 from memory.
Tony this must be one of a forcarsters worst nighmares to really pin point exactly what could happen. Exciting but daunting tasks

( edit: sorry i àccidently requoted myself rather than edited what i wanted to add)

[Lawrence]

To me this looks like at least a repeat of 2011, the possibility of a repeat of 1992 is on the table.

I agree, it's looking like moisture levels are fairly decent,south Canterbury misses out as it's shadowed in this one but probably will get something to sea level.Worse hit will be North Canterbury only due to the length of time that low hangs.But definitely this seems like a sea level event for the mid Canterbury area and Christchurch.

[darcyplumb]

I consider anything North of the Rangitata River Mid Canterbury.

Regarding this event I wouldn't be surprised at all if most of South Canterbury largely misses this event just like many previous events. Last time I seen a decent amount snow below 100m in South Canterbury was 7th of June 2008 When 3-4cm fell right down to sea level in Timaru.

I've got this map if it helps any images.jpeg

Thanks. I was confident in my knowledge of mid Canterbury being between the rakaia and rangitata rivers.

[TonyT]

To me this looks like at least a repeat of 2011, the possibility of a repeat of 1992 is on the table.

Tony, in your blue skies post this morning, would you classify Ashburton as south Canterbury? Just trying to figure out which part of the puzzle we fit into.

Ashburton is firmly in mid canterbury

[TonyT]

To me this looks like at least a repeat of 2011, the possibility of a repeat of 1992 is on the table.

Both events in 2011 were normal southerly outbreaks though, this will be a warm adventure event won’t it? Or were you talking about in terms of snow amounts?

There is very strong cold advection forecast for this event

[TonyT]

If its as bad as 2011 chch will receive more than 5cm.

Certainly, but forecasting that is a little bit out there!

[Lawrence]

Just in.....
To all households on Selwyn Gets Ready,

MetService has issued a Heavy Snow Warning for Marlborough south of Seddon and Canterbury north of Mount Hutt.

A rapidly deepening low is forecast to move across New Zealand from the west on Sunday, bringing heavy snow to low levels. Heavy snow may disrupt travel in affected areas and could damage trees and powerlines. Cold conditions may cause stress for livestock.

Snow is possible down to sea level, and is expected to become heavy above about 200 metres where 15 to 30 cm of snow is forecast to accumulate, or possibly more at higher levels.

People are advised to keep up to date with the latest forecasts in case any changes are made or further areas are added.

Check MetService for the latest information - https://www.metservice.com

The Civil Defence team will continue to monitor the situation over the coming days.

Please share this message with your neighbours.

Regards,
Emergency Management Team
Selwyn District Council

[Bradley]

The latest run of GFS has no snow for Christchurch at all, the question is does GFS not do well with picking up warm advection events or does it not think that sea level snow for Christchurch, warm advection being taken into account and all, is still not going to happen?

[TonyT]

The latest run of GFS has no snow for Christchurch at all, the question is does GFS not do well with picking up warm advection events or does it not think that sea level snow for Christchurch, warm advection being taken into account and all, is still not going to happen?

Unsure where you are getting that idea from, the 0Z GFS run total snow accumulation map is almost identical to most of the previous runs over the last 48 hours, and certainly shows some snow for Christchurch, 6cm in fact. This is similar to the 12Z run which showed 7cm, and about half of the 18Z run which predicted 12cm.

Oh, and as I said before, there is strong cold advection in the lower troposphere from later tonight.

gfs-deterministic-nz_wide-total_snow_10to1_cm-8510400.png

gfs-deterministic-NZCH-tmp_qpf_snow-8294400.png

[Bradley]

The latest run of GFS has no snow for Christchurch at all, the question is does GFS not do well with picking up warm advection events or does it not think that sea level snow for Christchurch, warm advection being taken into account and all, is still not going to happen?

Unsure where you are getting that idea from, the 0Z GFS run total snow accumulation map is almost identical to most of the previous runs over the last 48 hours, and certainly shows some snow for Christchurch, 6cm in fact. This is similar to the 12Z run which showed 7cm, and about half of the 18Z run which predicted 12cm.

Oh, and as I said before, there is strong cold advection in the lower troposphere from later tonight.

gfs-deterministic-nz_wide-total_snow_10to1_cm-8510400.pnggfs-deterministic-NZCH-tmp_qpf_snow-8294400.png

Oh I was looking at the 00z GFS run on the Windy app, is there somewhere better then that for looking at GFS data?

[TonyT]

Oh I was looking at the 00z GFS run on the Windy app, is there somewhere better then that for looking at GFS data?

Based on what it seems to be telling you, anywhere else would be better. Meteologix is a good site.