NSW - WARM END TO THE WEEK - RAIN DEVELOPS SUNDAY.

We have a warm airmass with temperatures well above average this afternoon over inland areas, that will be taken a few degrees up over the Friday into the weekend as the northwest to westerly wind regime drags in the dry desert air into the eastern inland.


But once again there is the chance of frost overnight with the clearer skies developing, in between belts of high cloud. That cloud is elevated well into the atmosphere so it won't help to keep a lid on temperatures falling, but not as cold as this morning.


Frost risk Friday morning.

The weather will start to cloud over further on Friday, we have seen some of that high cloud moving through today, but it should increase during Friday afternoon with areas of light spitty rainfall for southern inland areas and along the VIC and southwest SA border. Falls less than 2mm for the state now, the front is too far south.


The moisture is a little deeper than I have been expecting to see along the eastern coastline given the winds are starting to veer into the northwest. Will see if that low level moisture remains in place tomorrow. For now the cumulus clouds are fair weather on and east of the divide and high cloud, cirrus, floating through the jet stream.

Another warm few days this weekend the weather is expected to turn during Sunday. Temperatures well above the longer term average with a gusty northwest flow. Some locations could crack 30C over the far west and northwest.

But it all comes crashing down, by Tuesday some areas could get down to single figures for a maximum on and west of the GDR with a dry cold airmass.

I prepared this on social media and I will use this here, a very large drop in temperatures likely early next week. Farmers beware of the risk to stock and frosts likely to be severe over inland areas as well.

A slab of moisture is expected to sweep through the jet stream coming in ahead of the stronger front via SA with a band of rain likely to form through extreme eastern SA but more likely over NSW and VIC during later Sunday into Monday ahead of a cold airmass that will surge northwards in the early part of the new week. Love how the model shows the low pressure system forming and wrapping dry air in over the mainland in the southerly winds.

As you can see, some models have been flirting with the idea of a low pressure system developing along the front as it passes through the southeast of the nation. That would enhance rainfall for southern areas of the state but also run rainfall up the NSW ranges. Patchy rainfall would reach the coast under such guidance but the confidence is not especially high just yet.


There are more systems into the latter part of next week with more moisture to work with floating through the tropics, being drawn south and southeast.


00Z GFS Surface Pressure Pattern for the coming 16 days

The pattern still evolving in the short term, a thundery change over WA bringing moderate rainfall today expected to move east, with the system due in southern SA tomorrow now likely to only bring very light rainfall to the southern inland, more cloud cover than anything else for NSW, the better chance of rainfall for coastal areas of SA and VIC. Now the latest update is increasing the risk of a stronger front passing over the southeast states Sunday with rain increasing later on Sunday into Monday. The falls could be moderate over eastern VIC and through much of inland NSW with moderate snowfalls for Alpine areas, possibly running up the GDR. A sharp colder shift is expected to sweep the eastern states next week after a warm weekend. Then we see a low form offshore NSW with the system remaining slow moving offshore for much of next week, holding up the weather pattern meaning a benign week is possible next week. Out west, another front may be knocking on the door by this time next week with another band of rainfall, that system will eventually sweep the southern states introducing the next chance of rainfall. But the timing and scale is determined by that block in the Tasman if the low becomes slow moving. The north will have waves of humidity moving east to west through the period with the chance of showers from time to time.

00z GFS Rainfall for the coming 16 days

Rainfall is increasing for the system Sunday through Monday for the southeast states, that clearly is the main event in the coming 5 days. That is following rainfall over the southwest of the nation today that brought some reasonable falls. The wet weather will be accompanied by cold air so some of the precipitation likely to be snowfalls. The weather will tend to clear from Tuesday next week with the chance of showers developing for coastal areas if the low is close enough to the coast. The weather drying out over much of the inland of the nation thanks to a southerly flow and high pressure so will have to watch how the low develops in the Tasman and the watch the next cold front approaching the west coast of the nation this time next week. The tropics could see an increase in showers at times during the two weeks.

00z GFS Precipitable Water Anomalies next 16 days

The PW anomalies ahead of the system tomorrow and through the eastern inland on Sunday will see rainfall chances coming up during Sunday through Monday in particular, and the anticipated shift to drier southerly winds will clear the moisture right out of the nation. The drier air takes over much of the nation next week before the next surge of moisture passes through WA from the northwest with a cold front. And the tropics may see moisture surge back in with the trade winds. That may propel moisture across the north and west of the nation through the end of the month then shifting southeast ahead of the frontal weather in the medium term.

00z Euro Surface Pressure Pattern for the coming 10 days

The weakening front from WA which has triggered the showers and storms over the southwest today is expected to move east with patchy rain for SA, VIC and extreme southern NSW. Heavier rainfall expected over western TAS with topographic rainfall. The weather remains mild as it clears this weekend throughout the south, the moisture hanging back inactive over inland areas of the nation with cloudy skies, but the majority of the nation dry. The next system starts to move into the southeast states bringing a band of rain through VIC and NSW with showers for SA, the heavier rainfall is expected back over the eastern inland west of the divide. The Euro in step with GFS now forming the low over southeast NSW then placing it offshore and keeping it stationary next week blocking the frontal weather coming out of WA. That means the weather over WA could turn wet and windy once again this time next week with a string of below average days of temperatures while the east remains settled under high pressure. The tropics will see showers early this week with an impulse of moisture passing over the northern tropics from east to west.

00z Euro Rainfall for the coming 10 days

Rainfall most widespread over the southwest of the nation tonight with the front passing eastwards. Then the rainfall becomes more scattered over SA, through VIC then into southern NSW with the front sliding southeast pulling moisture through from northwest to southeast on the northern flank. Patchy rainfall of 1-2mm at best. The largest rain event this week will be over VIC and NSW during Monday with the cold front linking up with moisture and turning that all into a low pressure system as it passes east. The system sending a shot of dry air through the eastern and northern inland and high pressure then suppressing rainfall chances. The west will see rainfall return from mid next week with the next set of fronts.

00z Euro Precipitable Water Values next 10 days

The PW anomalies are increasing ahead of the system coming in on Sunday and now we are seeing better agreement on the rainfall coverage for the Sunday to Tuesday. Then a shot of dry air is propelled through the eastern inland on the western face of the low pressure that is rotating offshore the east coast of NSW. That will see rainfall chances rapidly decline next week. Out west the moisture returns with frontal weather approaching with windy colder showery weather developing. After an early taste of build up conditions, the weather will dry out over northern Australia thanks to the cold outbreak.

Rainfall for the next 10 days

Rainfall numbers are coming up during the outlook with a low pressure system now likely to form along a cold front coming through on Sunday through Tuesday. With moisture hanging back through the inland, combining with the warmer than normal weather, this will clash with that cold air and help to promote larger rain areas to develop, some heavy at times. The low forms off the south coast and will bring some much needed rainfall through the southeast which has missed out. Then we dry out with the cold southerly racing through mid week. More rainfall opportunities exist beyond this but I am not drawing them in at this time, it sits just outside of the window of 10 days.


I will have a climate update for Spring 2021 at lunchtime tomorrow plus your AM forecasts and a medium term forecast as well.




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