The weather is turning more unstable as we track through the coming few days, with scattered showers and thunderstorms expected to develop on Friday for a large chunk of the inland near a trough. The base of that same trough could bring some moderate to heavy showers about sections of the coast tomorrow and over the weekend, with some areas scoring more than 50mm of rainfall.

Next week, we are seeing the onshore flow expected to linger as the trough becomes more stationary over the central and northern inland of the state. Near and to the north and east of the trough is expected to see showers and thunderstorms, to the south and west of the trough dry weather to continue for the inland over the next few days at least.

The trough over inland regions is expected to retrograde westbound as the easterly winds freshen and this will mean the showers and thunderstorms will extend to most areas by mid to late next week and the humid and warm weather spreading throughout. Under this guidance, the first wave of the wet season for the east coast may unfold with frequent showers and onshore winds.

Lets take a look


Rainfall Next 10 Days

Rainfall is on the increase across the state, especially for areas on and east of the divide where the concentration of onshore winds will continue for the best part of this period and the interaction of the inland trough and frontal waves moving up the coast, leading to some heavy falls. The trough over the inland today which has delivered a few thundery showers over the southeast of NSW and into the ACT and points north and west will be the main feature over central and northern areas of the state during the weekend and next week. So expect the uneven distribution in rainfall for inland areas, which is likely to become more widespread next week. Coastal areas should get a good spread of rainfall with many areas clearing 25mm for the period ahead and scattered accumulation from 50-100mm possible.

Thunderstorm Forecast Friday

Thunderstorms are expected to redevelop over the central and northern inland of the state with thunderstorms turning severe along the Great Dividing Range where wind convergence as a southeasterly flow moves up the coast meets the inland westerly. Storms could produce heavy rainfall leading to flash flooding and damaging winds. Thunderstorms should contract north from the southern areas of the shaded zone through the afternoon and clear the Central coast at night.

Flash Flood Risk Friday

Thunderstorms have a high risk of producing flash flooding over the spine of the Great Dividing Range during the afternoon and evening and these will be steered towards the east and northeast. The risk does taper off the further east you go as the topography enhancing these storms is lost and they then weaken moving into the southeast flow which is more stable.

Damaging Winds Risk Friday

A low risk of damaging winds with thunderstorms over the inland areas near and to the east of the trough during the afternoon.

DATA - Refer to video for further analysis and comparison in the model data

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

No change to the guidance from the short term but I will focus on the medium term, looking at the tropical weather now throwing some interesting solutions onto the table, these will chop and change so do not be seduced by them yet, but be aware that the tropics will be influencing rainfall late February into early March. East coast of NSW and QLD looking wet with onshore winds and showery periods with the positive SAM. That signal is increasing now on most modelling. There will be tropical moisture coming southbound in the medium term but where that occurs remains to be seen but be aware there are severe weather events now starting to appear on the charts and more details on that can be found in the video.

00Z GFS - Precipitable Water Values - Next 2 Weeks

The biggest shift from this morning is the moisture spreading from north to south in the modelling, now the location of this will chop and change. But it highlights the influence of the MJO being in phase in conjunction with the positive SAM. This opens the gates for moisture to pool and remain stagnant over the nation in the absence of cold fronts to sweep the moisture out. We saw the impacts of that in January and that was quite disruptive and damaging to many inland areas. So it is important to be weather aware. Exceptional moisture content is appearing on some of the charts but caution is advised on anything more than broad analysis, it is too difficult to be specific right now but the potential is there for some nasty weather events for parts of the nation.

00Z GFS - Rainfall Accumulation - Next 10 Days

Refer to video for further analysis

00Z CMC - Rainfall Accumulation - Next 10 Days

Refer to video for further analysis

00Z GFS - Rainfall Accumulation - 2 Weeks

Refer to video for further analysis and your fly around.

A closer look in - as mentioned this will continue to chop and change and the placement of any wild card tropical systems will result in a narrow band of heavy rainfall coming through interior parts and spreading the rainfall into the east. Also note the SAM over the eastern areas.

I will have a look at the modelling and all things rainfall tonight after 9pm EDT as we are starting to see values come up and more analysis coming up from 8am EDT Friday.

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