NSW - SEVERE THUNDERSTORMS STAY OUT WEST. WARM WEATHER FOR THE WEEK AND MOSTLY DRY ELSEWHERE.

There are a spot or two of showers along the east coast over the coming days but no significant washouts are expected for areas away from that trough of low pressure that is anchored along the SA border.


Severe thunderstorms will continue overnight and into Tuesday before starting to ease on Wednesday through the west. Isolated falls of over 50mm have been observed with thunderstorms in the western and southwest inland areas in recent days and that risk will continue for the next 36hrs. Flash flooding is a risk more than damaging winds and large hail.


By the end of the week, the trough gets pushed out and weakened with the coverage of thunderstorms becoming more widely separated. A new trough will push through SA and into the state Friday and across the weekend with a drier airmass to follow.


Settled weather for much of the east is likely. A low pressure system is expected to develop off the coast but far enough away that the impacts will be low at this time.


Lets take a look

FORECAST

Rainfall Next 10 Days

Rainfall is forecast to be scattered over the western parts of the state overnight and through Tuesday with some of the storms producing heavy amounts of rainfall given the reasonable moisture profile across the state. The trough will be the mechanism for rainfall over the coming days so if you are not near it, just partly cloudy conditions with the low chance of a shower. A few morning and overnight showers at times along the coast, mainly north of Sydney at this time. The coverage of rainfall below average for this time of year, which is welcome for parts of the east coast. Another trough should sweep through later Friday and over the weekend with the chance of a few more showers and storms, but many areas going dry through the next 7-10 days is a fair chance. More rainfall opportunities do exist beyond this period.

Thunderstorm Forecast Tuesday

Thunderstorms will remain active over the Upper and Lower Western stretching into the far western areas of the Central West and Riverina. Storms will likely be severe closer to the SA border where heavy rainfall leading to flash flooding is the main concern for now. Damaging Winds and Large Hail may also occur, but the risk is low to moderate in these zones.

Flash Flood Risk Tuesday

Thunderstorms will develop in a fairly moist and unstable airmass leading to a moderate to high risk of flash flooding occurring. The rainfall rates in some isolated communities has been near 50mm/hr and that is sufficient for flash flooding.

Large Hail Risk Tuesday

Large hail risk remains low to moderate through the western border areas near to the trough is slow moving throughout the region.

Damaging Winds Tuesday

The heavier and larger thunderstorms are forecast to produce gusty winds, a low to moderate risk of these turning severe with damaging winds a risk.

DATA - Refer to the video for further information on the daily breakdown in the short and medium term.


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

The confidence in the forecast is quite low as outlined in the video. Understand that the volatility in the SAM and the MJO being a little slower in recent updates means that moisture spreading throughout the nation could be out of phase with the frontal weather passing south of the country. But the GFS is on it's own in the short term when it comes to passing moisture later this weekend throughout the nation with a cloud band producing patchy falls throughout SA, VIC, NSW and QLD. So understand that this will change. Tropics look active and the weather over the FNQ region looks to be very wet near the persistent trade winds.

00Z GFS - Precipitable Water Values - Next 2 Weeks

Moisture distribution continues to be quite volatile from run to run, so there is difficulty in placing the moisture beyond the severe thunderstorm outbreak over the south and east of the country. So this will continue to impact the rainfall distribution as we move through the coming few days and so expect changes for southern and eastern parts of the nation. Over the tropics, you will find the significant moisture continue to kick off storms most days, with the heaviest moisture reserved for FNQ. Moisture does build offshore WA in the medium term but does that connect with the long wave trough building in the Southern Indian Ocean and bring in a large cloud band towards the end of the month? That remains to be seen.

00Z GFS - Rainfall Accumulation - Next 10 Days

Refer to video for further information

00Z CMC- Rainfall Accumulation - Next 10 Days

Refer to video for further information

00Z GFS - Rainfall Accumulation - Next 16 Days

Refer to video for further information

A closer look in - the weather over the region is highly conditional upon the SAM being in phase with the MJO and spreading moisture across the nation to be captured by troughs and low pressure that are moving west to east.

More details coming up looking at the models and all things rainfall from after 9pm EDT - we will see what the data sets are looking like for the medium and longer term and whether there is more rumbling about the Autumn Break that has been lurking on the charts.






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