NSW/ACT SEVERE WEATHER RISK - HEAVY RAINFALL LEADING TO FLOODING

The severe weather event is largely unchanged from yesterday in terms of the speed, orientation and spread of the rainfall throughout the period. Severe weather in the form of flash and riverine flooding is the main concern yet again.


There is also severe weather potential next week which I will outline here in a broad sense as I want to get this current system off the board before talking about that event.


Lets take a look

FORECAST

Rainfall Next 10 Days

Rainfall is forecast to be widespread and heavy over coastal areas between Narooma to about Gosford with moderate falls for remaining coastal areas. Some areas between Ottford to Ulladulla could see 300-400mm of rainfall in this zone extending west into the coastal escarpment through Macquarie's Pass. There is some chance areas around the Blue Mountains could see 200mm of rainfall in areas recording landslips and slides. This weather event may not be on the scale as previous events, but it is running over very wet ground and the impacts will be high impact. Scattered storms on and west of the divide with areas of light to moderate rainfall could see general falls of 10-40mm for the Riverina (mainly east) through the Southwest Slopes up over the Central West to the Tablelands and over the Northern Inland and Northeast. Some areas on the eastern side of the GDR from Canberra north to Bathurst through to Scone could have falls closer to 70mm. So it is a dynamic system. Another system next week could bring further severe weather risks and additional flooding.

Southeast NSW Rainfall Next 10 Days

Heavy rainfall developing tomorrow afternoon and into Thursday poses the greatest threat from around East Gippsland through to about Ulladulla. From Thursday into Friday the heaviest of the rainfall will be on by but the showers will continue for coastal areas. The ACT seeing the bulk of the rainfall from Wednesday night through Friday morning and that includes much of the regions to the west, south and north of here too. The weather clearing the inland areas from Saturday as the trough weakens and dry weather Sunday before the next change.

Central West NSW Rainfall Next 10 Days

Rainfall could be heavy with thunderstorms over areas along the GDR through to areas westwards. From about Lithgow to Katoomba eastwards and southwards towards the Goulburn region and beyond, this is where the rainfall could be widespread and heavy leading to additional riverine flooding.

Northern NSW Rainfall Next 10 Days

Rainfall likely to be less intense over northern areas but with the showers and thunderstorms across the region, the distribution will be uneven but under storms heavy. The coastal areas and adjacent subtropical regions will see widespread showers and some of that could be heavy but at this time not as heavy as the southern areas. But keep watch on the showers and thunderstorms that will be approaching from the northeast this weekend with moisture spreading towards the coast from the weakening tropical low out to sea.

SEVERE WEATHER REGIONS

Severe Weather Watch - Heavy Rainfall - Thursday through Saturday

Severe weather a high to very high chance to unfold from later tonight into Thursday and easing from Saturday for the state. Flooding along the coast and severe thunderstorms over inland areas with flash flooding and small hail is the main issues.

Flash Flood Risk Thursday through Saturday

No real change to the guidance related to flash flooding but the focus has shifted a little further south from yesterday and that is good news for residents in the northeast districts for now but still keep watching. The rainfall rates could top 40-50mm an hour in some locations from Sydney southwards to the VIC border over the coming days. Moderate rainfall over inland areas over a long duration could see some low impact flash flooding develop too. Thunderstorms over interior parts of NSW will deliver a risk of flash flooding but the coverage of thunderstorms is scattered at best with many areas missing out on a storm. But be weather aware.

Riverine Flood Risk Thursday through Saturday The flood risk is growing for the Metropolitan coast southwards to the VIC border and for the adjacent coastal escarpment where falls in this zone could clear 100mm throughout the period widespread but spot falls throughout this zone could nudge 300mm. So this will once again see rivers rise through to moderate flood levels once again at least, possibly major flooding again.

Thunderstorm Forecast Wednesday

Thunderstorms are forecast to emerge near the developing upper trough and low as it works into western NSW. The main area of thunderstorm activity will be located over the southern and central inland during the afternoon and possibly over the northern inland of NSW during the night hours.

Thunderstorm Forecast - Thursday

Thunderstorms are forecast to develop near the significant upper level low which will slow to a crawl over the southern inland of the state. Storms may produce heavy rainfall leading to flash flooding and large amounts of small hail as well given slow storm motion. Storms may feature amongst the large areas of rainfall along the coast however it will be the bands of heavy rainfall more than thunderstorms causing the problems.

SEVERE WEATHER RISK - Monday through Thursday Next Week

Another round of severe weather is possible with yet another low pressure system developing over the southeast with heavy rainfall and damaging winds possible for southeast Victoria through much of southern and central coastal NSW with the potential for an ECL. Some models also have the low pressure further north so at this time, being this far out, the forecast is broad and low confidence. We have to get this current system off the board before we get a better look at this event, but there is more severe weather potential next week.

DATA - More details can be found in the video at the top of the page. Please refer to that for further context around the severe weather issues.


18Z GFS Surface Pressure Pattern and Rainfall Distribution - Next 5 Days

Refer to the video at the top of the page for more.

12Z Euro Surface Pressure Pattern and Rainfall Distribution - Next 5 Days

Refer to the video at the top of the page for more.

12Z CMC Surface Pressure Pattern and Rainfall Distribution - Next 5 Days

Refer to the video at the top of the page for more.

18z GFS Rainfall Accumulation - Next 5 days

Refer to the video at the top of the page for more.

12z CMC Rainfall Accumulation - Next 5 days

Refer to the video at the top of the page for more.

12z Euro Rainfall Accumulation - Next 5 days

Refer to the video at the top of the page for more.

18z ICON Rainfall Accumulation - Next 5 days

Refer to the video at the top of the page for more.

More coming up in the broader update this afternoon, I am under the weather and with family in town so will be covering off the important parts through the coming days so check back regularly. Routine state based forecasts for the evening periods will resume on Sunday but I will keep you posted on the severe weather threats in the coming days.




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