Cold Outbreak Saturday 29/9/2012

[Nick Sykes]

Hey All

After the current warm spell there looks like there will potentially be one of the strongest cold outbreaks of the year affecting Victoria on Saturday. GASP, CMC and GFS have very low thickness values over Victoria Saturday morning with values of less than 528. 850 temps look to get down to about -3 to -4 so not that cold, but 500mb temps are around -34, -35 according to GFS, so a strong upper trough. I expect there to be widespread cold air storms with hail with this system. Could be an interesting Grand Final

Go Hawks,

Nick

[Gordon]

Some on the ski forums are now picking this as the coldest outbreak of the year, which would be pretty extraordinary for the end of September! I'm working outdoors all day Saturday so that should be a character-building experience...

[johnno]

Gasp still exists????

[johnno]

You mean ACCESS Nick ?? Yep looks to be the coldest outbreak of the Year Gordon.

[Nick Sykes]

Yep I meant ACCESS, still thinking old school.

[stratospear]

06Z GFS has 500HPa temps down to -36c over Melbourne on Saturday morning. A seriously unstable atmosphere and even more so now that the Bay has warmed up a couple of deg in the past week...

Bucketloads of hail possible on Saturday IMO.

[Karl Lijnders]

I think you will find that the airstream could be too westerly and this leaving the best of the precip along the coast and here in Melbourne, we will rely on the diurnal heating. So I am still not convinced despite the colder air. I think a shower or two for Grand Final with a possible thunderstorm and hail. The showers will be more frequent to the southeast and coastal suburbs.

That said, 10-20mm over the southeastern suburbs looks OK but 1-5mm for the remainder.

The BoM will probably scale back the forecast at the last minute.

No snow for the Dandenongs/Macedon at this stage.

[fr_303]

Got my tickets for the game, is the rain going to be as bad as they are saying at the MCG or will it be ok?

[Gordon]

Latest BOM forecasts are still bullish for Saturday snow above 600 m in the Central District (and South-west, Wimmera etc.) with 'snow likely about the nearby hills' in the Melbourne forecast. Also 'morning snow showers' for the Mt Dandenong.

[stevco123]

That cold pool looks amazing on the Sat Pic. I was a bit sceptical of BoM's 500m for snow, but it looks more possible now as it is moving a bit further north. Could be lots of graupel/soft hail as well in the suburbs.Depends on the direction of the wind. The more southwesterly the better

[Gordon]

[quote="hillybilly
Actually its pretty common that you get the coldest "cold outbreaks" in spring. The Antarctic Sea ice is at its closest to Australia and the long-wave-troughs/ridges tend to have greater amplitude in spring. Up until the last few really lean years which have been pretty much snow free in the Dandenongs, we used to get most our snowfalls between August and October (in 2003 we had 4 snow days in September).

[/quote]

Yes good point, if I look at our snow records we've had our share this late - guess the contrast with the weather midweek made tomorrow's forecast seem more unusual than it actually is.

(PS: 25 mm of rain since this morning, the last 4 mm in a very heavy shower just now. Down to 5 C.)

[droughtbreaker]

Snowfall events tend to be more common later in winter and into spring but always more productive early to mid winter when the ground is coldest and the sun at its weakest (so the day does not warm up). Spring cold outbreaks are generally very vigorous but short lived as fronts tend to be sharper and faster moving in spring and the sun warms things up very quickly, whereas in winter snow often falls when there is a slow moving low in the area slinging very cold air up and around it and little diurnal heating. The end result is more substantial snow events in winter and mainly flash in the pan events in spring.

Tomorrow is touch and go for snow in my area, i.e. 520m asl and if it occurs it will most likely be associated with an intense shower around mid morning with temps significantly above 0C. I can't see temps staying in the low single figures at 500m for long at all. Pretty much just the first few hours after sunrise. The summit of Mount Macedon is a much better bet but even then it relies on showers to develop purely out of the upper trough and cold unstable air over land because inland moisture will be at a premium thanks to westerly flow.

[Rivergirl]

Severe Weather Warning
IDV28000

Severe Weather Warning
for damaging winds
for people in the North East, South West, Central and West and South Gippsland forecast districts

Issued at 9:41 pm EST on Friday 28 September 2012.

Weather Situation

Strong northwesterly winds over the northeast Alpine areas will ease early Saturday morning. Squally west to southwest winds are expected to affect southern Victoria Saturday, particularly coastal areas.

Winds around 60 km/h with damaging peak gusts of 90 to 100 km/h are forecast to affect parts of the Southwest, Central and West and South Gippsland districts, mainly about coastal areas. Strongest gusts are likely to be with showers and thunderstorms.

Winds over the northeast Alpine areas around 65 to 75km/h with gusts to 100km/h are expected to ease Saturday morning.

The Severe Weather Warning for parts of the East Gippsland forecast district has been cancelled, but the situation will continue to be monitored and further warnings will be issued if necessary.

The State Emergency Service advises that people should:
Move vehicles under cover or away from trees.
Secure or put away loose items around your house, yard and balcony.
Keep clear of fallen power lines.
Don't drive, ride or walk through flood water.
Keep clear of creeks and storm drains.
Beware of fallen trees or debris on the road.

For emergency help in floods and storms, ring your local SES Unit on 132 500.

The next warning will be issued by 5:00 am EST Saturday.

This warning is also available through TV and Radio broadcasts; the Bureau's website at http://www.bom.gov.au or call 1300-659-217*.

[nafets]

Well my weather station is forecasting clear skies, wow... !

[stevco123]

Wow...the temps have dropped by 5 degrees and more in places beating the forecast minimums. Was 9.9 at 10pm here and now its 5.8. Mount Dandenong down to 2 and Ballarat down to 1 !!!! I guess it just depends on where the precipitation falls now for there to be snow. I wish people were still awake to report on any snow in the above areas, especially as there are showers in the area.

Hope to hear stories and see pics in the next few hours. And I'll visit mount Dandenong myself if it does snow.

[Gordon]

Snowed here earlier this morning & has stuck above ground - outdoor furniture, bushes etc. 0 C or thereabouts for several hours now so anything that falls will be snow - just a question of if and when!

[Dane]

All the showers are staying to the south at the moment.
Might be like the August 2005 event where is snowed to sea level at some places near the Coast and also dumped snow at Korumburra. It would have been cold enough for snow in the Melbourne suburbs but the showers stayed south so even the Dandenongs got no snow that day while Korumburra had more than 10 cms of the stuff.

[nafets]

WIth the flow now more WSW i think theres more of a chance for snow in central areas, and rain on the grand final! Not sure though

[93ben]

Would like to know if it's going to be snowing in this front http://www.bom.gov.au/products/IDR023.loop.shtml#skip" onclick="window.open(this.href);return false; over the dandenong ranges as the BOM states for the Melbourne area. Partly cloudy. Scattered showers, falling as snow above 500 metres in the Dandenong Ranges this morning. Local hail and thunder. Winds westerly 25 to 40 km/h with some stronger squalls.

[mick]

Its on its way now. just at the heads, that will be snow on the nongs if its going to happen today, keep an eye on this band the coldies are behind it.