Very cold polar outbreak August 3rd-5th

Chris W · Unread post by **Chris W** » Thu 01/08/2019 19:38

As there’s been active discussion of this today and a signal for potential sea-level snow, or at least very cold temperatures and strong wind this weekend, after the initial southerly covered in the previous event thread I thought it time to start this thread up.

It must be emphasised that snow is hard to forecast and if it falls it may not be heavy, but this is a notable event.

Cantab03 · Unread post by **Cantab03** » Thu 01/08/2019 19:51

Off to Westport via the Lewis Pass early tomorrow morning, hopefully getting through before too much settles around the top of the road. Back again later Sunday, so could be an interesting drive! Yes Sunday is rather interesting to watch and see exactly that unfolds over the next wee while!

Bradley · Unread post by **Bradley** » Thu 01/08/2019 20:18

Latest EC model run has lifted the snow level to 400m in Canterbury - still plenty of time for it come back down though...

snowchaser01 · Unread post by **snowchaser01** » Thu 01/08/2019 22:05

Bradley wrote: ↑Thu 01/08/2019 20:18 Latest EC model run has lifted the snow level to 400m in Canterbury - still plenty of time for it come back down though...

Latest EC run on the windy model has sea level still.. not much but 1cm in CHCH on sunday night...

Bradley · Unread post by **Bradley** » Thu 01/08/2019 22:39

snowchaser01 wrote: ↑Thu 01/08/2019 22:05
Bradley wrote: ↑Thu 01/08/2019 20:18 Latest EC model run has lifted the snow level to 400m in Canterbury - still plenty of time for it come back down though...
Latest EC run on the windy model has sea level still.. not much but 1cm in CHCH on sunday night...

Check it again now, Windy was quite late updating EC data tonight so it may have been this mornings run you were looking at still...

snowchaser01 · Unread post by **snowchaser01** » Thu 01/08/2019 23:04

Bradley wrote: ↑Thu 01/08/2019 22:39
snowchaser01 wrote: ↑Thu 01/08/2019 22:05

Latest EC run on the windy model has sea level still.. not much but 1cm in CHCH on sunday night...
Check it again now, Windy was quite late updating EC data tonight so it may have been this mornings run you were looking at still...

Correct, but now GFS going for about a cm overnight Sunday into Monday.... so it is still very up in the air so to speak.

Bradley · Unread post by **Bradley** » Fri 02/08/2019 08:12

It’s certainly cold enough but there is just literally no precipitation with the coldest air, EC this morning now has 0.0mm for both Sunday and Monday - great snow making weather for Mt Hutt though

snowchaser01 · Unread post by **snowchaser01** » Fri 02/08/2019 08:13

Bradley wrote: ↑Fri 02/08/2019 08:12 It’s certainly cold enough but there is just literally no precipitation with the coldest air, EC this morning now has 0.0mm for both Sunday and Monday - great snow making weather for Mt Hutt though

GFS has a wee bit, but you're right not a lot. 2cm in CHCH sunday morning.

There is a decent amount of moisture that crosses the country on Sunday, that was initially forecast to cross over Canterbury which would have provides a few cm to very low levels... that is now forecast to cross over Marlbourough...

Bradley · Unread post by **Bradley** » Fri 02/08/2019 08:23

snowchaser01 wrote: ↑Fri 02/08/2019 08:13
Bradley wrote: ↑Fri 02/08/2019 08:12 It’s certainly cold enough but there is just literally no precipitation with the coldest air, EC this morning now has 0.0mm for both Sunday and Monday - great snow making weather for Mt Hutt though
GFS has a wee bit, but you're right not a lot. 2cm in CHCH sunday morning.

There is a decent amount of moisture that crosses the country on Sunday, that was initially forecast to cross over Canterbury which would have provides a few cm to very low levels... that is now forecast to cross over Marlbourough...

I always look on the bright side of things so let’s go with GFS on this occassion then

To be fair though GFS has been performing pretty darn well though this winter so 1-2cm of the white stuff or at the very least some flurries is certainly not out of the question...

snowchaser01 · Unread post by **snowchaser01** » Fri 02/08/2019 08:26

Bradley wrote: ↑Fri 02/08/2019 08:23
snowchaser01 wrote: ↑Fri 02/08/2019 08:13

GFS has a wee bit, but you're right not a lot. 2cm in CHCH sunday morning.

There is a decent amount of moisture that crosses the country on Sunday, that was initially forecast to cross over Canterbury which would have provides a few cm to very low levels... that is now forecast to cross over Marlbourough...
I always look on the bright side of things so let’s go with GFS on this occassion then To be fair though GFS has been performing pretty darn well though this winter so 1-2cm of the white stuff or at the very least some flurries is certainly not out of the question...

I think its a situation where it's cold enough... so any precip is going to be white in colour...

Richard · Unread post by **Richard** » Fri 02/08/2019 09:12

yes its going to be very cold alright, but I just dont see any precipitation happening for the eastern half of Canterbury at this stage

snowchaser01 · Unread post by **snowchaser01** » Fri 02/08/2019 09:15

Richard wrote: ↑Fri 02/08/2019 09:12 yes its going to be very cold alright, but I just dont see any precipitation happening for the eastern half of Canterbury at this stage

My gut feeling is we will see a wee bit, but nothing write home about... icing sugar sprinkle

Bradley · Unread post by **Bradley** » Fri 02/08/2019 10:31

GFS has 12 hours of thickness levels below 522 starting from 6am Monday morning, quite a decent time period for any snow to fall in the city though I'm thinking banks pensinsula will be doing substantially better out of this then Christchurch...

mikestormchaser · Unread post by **mikestormchaser** » Fri 02/08/2019 10:33

Coldest air is coming in early monday morning now. 700mb sits at -18 and the 850mb is -7 6am monday with a tiny little bit of moisture. Might get a dusting to ground level

otherwise just bring on spring and our thunderstorm season again!

mikestormchaser · Unread post by **mikestormchaser** » Fri 02/08/2019 10:44

That SW change later today could bring few heavy showers/ hail to just looking quickly at tonight's change

Cantab03 · Unread post by **Cantab03** » Fri 02/08/2019 11:12

Just been through the lewis pass, snowing heavy at the summit currently.

Razor · Unread post by **Razor** » Fri 02/08/2019 11:30

I am just not seeing this at all. Critical SW flow as mentioned the other day. Banks Peninsula maybe, the rest of us, very low chance of anything surely?

snowchaser01 · Unread post by **snowchaser01** » Fri 02/08/2019 11:44

I think bottom line is, it's cold enough... so i don't know what MS are on about saying snow flurries to 500m??

But as everyone is saying there is not much (if any) moisture. Latest GFS has a couple of mm with the thickness below 520 and 850mb temp of -7deg...

EDIT: From what I can see, (going from GFS here). Initial light showers before 8am Sunday with flurries to 300m. Then early Monday morning with light showers again with snow flurries to near sea level.

Chris W · Unread post by **Chris W** » Fri 02/08/2019 11:45

This isn't all about snow, it's going to be very cold and windy. Snow (or any kind of precipitation) on Sunday is looking less likely for eastern Canterbury, but down south is more likely.

snowchaser01 · Unread post by **snowchaser01** » Fri 02/08/2019 12:37

MS 3 day maps have updated. Show significantly more moisture (still not much but some) for Sunday and Monday morning...

harveyt86 · Unread post by **harveyt86** » Fri 02/08/2019 13:00

Currently looking like rather low snow levels across much of the North Island on Monday morning. Might be a dusting in a few places not used to seeing much snow!

Cyclone Tracy · Unread post by **Cyclone Tracy** » Fri 02/08/2019 13:11

Latest EC 18Z run is putting a dusting of snow at a latitude of 37 S on Table Mountain near Coromandel on Monday morning.

Richard · Unread post by **Richard** » Fri 02/08/2019 13:18

I see MS's 3 day map now showing a reasonable amount of precipitation Sunday, snow looking more likely now, but Amberley north though.

snowchaser01 · Unread post by **snowchaser01** » Fri 02/08/2019 13:36

Richard wrote: ↑Fri 02/08/2019 13:18 I see MS's 3 day map now showing a reasonable amount of precipitation Sunday, snow looking more likely now, but Amberley north though.

The trend is it moving south over the last couple of runs.. still going for chch north.

cbm · Unread post by **cbm** » Fri 02/08/2019 13:43

Cyclone Tracy wrote: ↑Fri 02/08/2019 13:11 Latest EC 18Z run is putting a dusting of snow at a latitude of 37 S on Table Mountain near Coromandel on Monday morning.

That happened in 1996. It was unusal enough for the TV news to fly a Helicopter up to record it. On that day Auckland aero did not get above 8.7C which would be one of its colder ever days. There was a good coating on the hills around Wharepapa South SE of Te Awamutu which have not seen any other time.

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