NSW - SEVERE WEATHER TO PEAK OVERNIGHT, EASING TOMORROW. MORE SEVERE WEATHER THIS WEEKEND.

The severe weather threats continue for the coastal communities from Newcastle southwards in particular with the threat of damaging flash flooding, winds and destructive riverine flooding possible over the next day or so, with the riverine flooding sticking around for about a week or so.


Rain and moderate falls extends inland to the Great Dividing Range and thunderstorms and showers are building west of the divide tonight ahead of the cloud band in the east. Some flash flooding is possible over the course of this evening with thunderstorms before easing during Thursday inland.


Another severe weather event is possible this weekend with widespread showers and thunderstorms developing near and towards the east of an upper low that is expected to spread through the state from VIC this weekend. Storms could pack high impact weather as well for areas being hit hard now.


There is a signal that drier air, which will keep most of far western and northwestern NSW dry for this week may creep across to the remainder of the inland with sunnier skies and a chance to dry out.


Lets take a look

FORECAST

Rainfall Next 10 Days

Heavy rainfall developing this evening for large areas of the central and southern coast with extensive light to moderate rainfall stacking up over the inland near the Great Dividing Range. The falls over 200-300mm will be found closest to the low pressure system making landfall and 50-100mm widespread along the length of the coast south of Taree. Severe thunderstorms over the inland may also produce falls of 50mm in quick time tonight. The weather should begin to wind down tomorrow afternoon with showers decreasing throughout however another round of severe weather is expected this weekend. An upper low is forecast to drive heavy showers and thunderstorms for southern and southeast of NSW with the ACT also in the firing line from this event. Flash flooding the main risk at the moment. The severe weather will extend up over and to the east of Great Dividing Range Sunday and into Monday with the upper low weakening and opening up into a trough, which will combine into a trough with heavy falls possible on the coast. The drier weather will return to parts of the inland next week, but it may be short lived with indications we could see another round of higher humidity returning from QLD.

Thunderstorm Forecast Thursday

Severe thunderstorms over parts of the inland tonight will begin to contract east and clear towards the Great Dividing Range on Thursday. On and to the east of the dividing range, we could see thunderstorms trigger life threatening flash flooding after midnight tonight until about midday Thursday before the risk eases as the low pressure system weakens inland. A layer of warmer air in the mid layers should keep the storm risk very low over the inland, with afternoon cloud the only real impact on Thursday.

Flash Flood Risk Thursday

Heavy rainfall with areas of rain and spiral bands of thundery weather near a low coming in from the northeast towards the Central and Southern coasts of NSW is expected to drive rainfall rates over 50mm/hr in some locations leading to high impact flash flooding. The risk tapers off for the inland

Damaging Winds Risk Wednesday into Thursday

Strong clockwise winds near the landfalling low pressure system is likely along the coast, with the strongest winds along and to the south of the low as it moves in. So that looks to be between Sydney and Ulladulla at the moment. But keep up to date with the warnings. Severe thunderstorms over the northern parts of the state could lead to destructive straight line winds.

Large Hail Risk Thursday

Large hail, possibly giant hail, along the hinterland during the afternoon inland of Coffs Harbour through to about Eumundi in QLD. Large hail also a risk over broad region during the afternoon and evening with favourable upper level winds north of a westward moving low bringing the chance of supercell thunderstorms.

Tornado Risk Thursday

The landfalling low pressure system will bring a low to moderate risk of waterspouts hitting land over the central and southern coastal areas. Supercell thunderstorms are a moderate chance over the northeast of the state with the risk of a tornado or two during the afternoon and evening.

Severe Weather Risk This Weekend

The severe weather risk returns from Friday through Victoria with a deep upper low moving in from the Bight. It will drift east northeast through the southeast inland of the nation driving showers and thunderstorms. These storms will be able to produce significant amounts of rainfall thanks to the very high PW values across the region. Damaging winds and large hail also possible with favourable wind shear available as well. There may be a renewed burst of heavy rainfall along the coast into next week with the trough tapping into easterly winds.

DATA - Refer to the video for further information for the daily breakdown and looking at the medium term


00Z GFS - Surface Pressure Pattern and Rainfall Distribution - Next 2 Weeks

Refer to the video for more where I will cut down the amount of reading tonight, however the major weather event on the east coast in the short term, Anika passing through northwest WA feeding a trough moving into the southeast which runs into residual moisture over the eastern inland, will lead to another severe weather event for NSW, VIC and QLD this weekend. And the chance of a little quieter weather? What are the chances?

00Z GFS - Precipitable Water Values - Next 2 Weeks

Another soupy 7 days for the east and north of the nation but the drier air is trying to push the wet air out of the region but it is having a tough time. While there appears to be quieter weather in the medium term, I do not buy it. Not with the positive SAM phase which could eclipse the phase we have just endured. So on that logic, wetter conditions into the medium term for the east and drier weather for the west seems like a logical outcome for the moment. The MJO is the wild card hustler at the moment, will it redevelop and increase moisture over the northern tropics?

00Z GFS - Rainfall Accumulation - Next 2 Weeks

Refer to video for further information

A closer look in - the GFS has been underplaying the rainfall in recent events so expect some tremendous rainfall along the coastal escarpment in the coming 2 days (Robertson near Nowra sitting on 300mm so far this week and 60mm at Molong in an hour a good example of this).

More coming up tomorrow from 8am EDT. I want to get this rainfall event in the east and TC Anika through the nation before revisiting the medium and longer term rainfall projections with heaps of contamination in the short term with these events so a better look tomorrow or Friday.


Also remember that upper level lows equal weather model woe, the models and guidance is always very low when the upper level lows are in town, so be aware that surprise weather from severe storms to heavier rainfall than what was forecast for your region is possible in the east.



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