Polar Blast - August 7-11

SnwAddct · Unread post by **SnwAddct** » Wed 05/08/2015 12:18

Thought I would get something started as it looks likely that majority of NZ will experience a cold outbreak and also that the Central NI and various other places will see quite a decent dump of snow on Saturday with the snow level dropping to around 600-700m in the NI with plenty of moisture around and even lower in the SI

Bradley · Unread post by **Bradley** » Wed 05/08/2015 12:32

The moisture levels are going down day by day for Christchurch with this one, EC only has 5mm for Us now

matttbs · Unread post by **matttbs** » Wed 05/08/2015 13:17

Yea nothing to write home about, only got 7mm in the models here now. Never got into this one, didn't 'feel' right

melja · Unread post by **melja** » Wed 05/08/2015 14:47

Roll on spring and warmth:mrgreen:

jamie · Unread post by **jamie** » Wed 05/08/2015 14:52

Ruapehu looks to be in line for a dumping

spwill · Unread post by **spwill** » Wed 05/08/2015 15:05

Looks a decent Wintry spell for Otago/Southland, heavy snow showers for exposed coastal areas on Saturday.

SnwAddct · Unread post by **SnwAddct** » Wed 05/08/2015 15:54

jamie wrote:Ruapehu looks to be in line for a dumping

Yeah its looking favorable for sure. Its going to need it after the 100mm+ of rain they would have received by this time tomorrow.. According to their website figures they have already lost 20-30cm of base since yesterday with another very heavy burst of rain due tonight..

jamie · Unread post by **jamie** » Wed 05/08/2015 15:59

Looks like it's snowing down to the car park now tho.

Bradley · Unread post by **Bradley** » Wed 05/08/2015 17:59

Interesting that Metservice has a 'chance of snow' for Christchurch's forecast for Sunday

einzack · Unread post by **einzack** » Wed 05/08/2015 18:08

I'm more interested in seeing if Reefton can hit anything like these overnight lows the computer is forecasting for over the weekend......
Quite a polar blast....

NZstorm · Unread post by **NZstorm** » Wed 05/08/2015 19:13

Latest run of GFS points to some snow showers to sea level for Dunedin and Christchurch on Sunday. Have to see if that stays in modelling.

Also, a trough crossing late Fri/Saturday morning time frame will give widespread snow for inland Southland to Canterbury. 5-15cm to 300m.

The front crossing the North Island Saturday morning will be a snow maker and will drop the snow level down to National Park level.

Bradley · Unread post by **Bradley** » Wed 05/08/2015 19:17

Yep there's a 12 hour period from late Saturday night to Sunday midday where the thickness is 522 or below with -7C at 850hpa - easily cold enough for sea level snow for Christchurch but where is the moisture?

matttbs · Unread post by **matttbs** » Wed 05/08/2015 20:16

Bradley wrote:Yep there's a 12 hour period from late Saturday night to Sunday midday where the thickness is 522 or below with -7C at 850hpa - easily cold enough for sea level snow for Christchurch but where is the moisture?

I reckon metvuw has clawed some moisture back into this thing also Weatherzone is showing a decent period of moderate snow for canty

NZstorm · Unread post by **NZstorm** » Wed 05/08/2015 20:22

Bradley wrote:Yep there's a 12 hour period from late Saturday night to Sunday midday where the thickness is 522 or below with -7C at 850hpa - easily cold enough for sea level snow for Christchurch but where is the moisture?

Gfs showing precipitable water values along Canterbury coast 8-9mm with a short wave crossing. Have to see how this looks in successive runs.

SirSlingy · Unread post by **SirSlingy** » Wed 05/08/2015 22:01

Feeling hopeful about this one for the Ruapehu skifields... am heading down there Saturday morning for four days... hope the roads are all open!

Tim S · Unread post by **Tim S** » Thu 06/08/2015 10:09

Bradley wrote:Yep there's a 12 hour period from late Saturday night to Sunday midday where the thickness is 522 or below with -7C at 850hpa - easily cold enough for sea level snow for Christchurch but where is the moisture?

Exactly, moisture, or lack there of, will be the issue for most of the east coast of the south island. Still even without heavy snow this is going to be a significant polar event as wind chill temps are going to be very low for a good 24-36 hours over a reasonably large area of the South Island and higher areas of the North Island. Plenty of lambs being born in the last few weeks around otago so not good news for them and I'd imagine the story will be the same in other regions?

SnwAddct · Unread post by **SnwAddct** » Thu 06/08/2015 12:24

Precipitation for NI looks to be at its heaviest early morning Saturday.. Should bring a decent amount of snow back to Ruapehu..

matttbs · Unread post by **matttbs** » Thu 06/08/2015 12:25

Metvuw has upped moisture for the last few runs and gfs has also. Around 28mm for my area now which could make things interesting. That's the most consistency I've seen with this event so far as earlier in the week every run flopped the opposite way to the run before it.

TonyT · Unread post by **TonyT** » Thu 06/08/2015 12:52

matttbs wrote:Metvuw has upped moisture for the last few runs and gfs has also.

The Metvuw maps are the GFS data.

matttbs · Unread post by **matttbs** » Thu 06/08/2015 12:54

TonyT wrote:
matttbs wrote:Metvuw has upped moisture for the last few runs and gfs has also.
The Metvuw maps are the GFS data.

You learn something every day

Bradley · Unread post by **Bradley** » Thu 06/08/2015 13:53

The data used is obtained from the United States National Weather Service. These charts are updated approximately every 6 hours and provide forecasts up to 180h ahead of the time they were issued.

Bradley · Unread post by **Bradley** » Thu 06/08/2015 14:43

Interesting that Metservice seem to think Monday might be the day for heavy snow for Canterbury:

During Monday a high should begin moving onto the country from the west. However, rain and snow is likely to continue in eastern areas and snow could become heavy in higher parts of Mid and North Canterbury and along the Kaikoura Coast. There is low risk that snow accumulations above 400 metres in these areas (including Banks Peninsula) will warrant a warning.

Bradley · Unread post by **Bradley** » Thu 06/08/2015 20:29

NIWA's rain model going for around 30-35mm for the period from Friday to Monday, EC 's latest forecast has also doubled its morning forecast to around 15mm. EC also going for around 50mm for next weekend!!

NZ Thunderstorm Soc · Thu 06/08/2015 21:04

I'm not expecting much from this system, but it would be nice if this El Niño, this spring will deliver some thunderstorms, not rain/showers which could be thundery

matttbs · Unread post by **matttbs** » Thu 06/08/2015 21:34

From metservice;

*New Area* CANTERBURY Plains and Foothills: Heavier showers are possible from Friday evening and may bring snow levels down to 100-200 metres. There is still some uncertainty where these heavier snow showers will occur. There is a risk that some places along the Plains and Foothills above 200 metres may receive around 5cm of snow in a short period of time during Friday evening or early Saturday morning.

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