NSW - RAIN INCREASING TONIGHT WITH LOCAL THUNDERSTORMS - SEVERE WEATHER TOMORROW DICTATES FORECASTS

OVERVIEW

Showers and thunderstorms have commenced through the southern and central inland of the state with widespread cloud increasing throughout much of the inland as a strong cold front and low pressure trough approaches from the west, lifting the deep moisture surging in from the north and northwest of the nation.


A batch of moderate to heavy thunderstorms continues to build over the SE inland tonight with rain extending north tomorrow tih the chance of moderate to heavy falls developing over the Central Tablelands during Thursday and extending into northern inland areas during the evening. All of this likely on and west of the divide.


Coastal and far western areas should see the least amount of rainfall through this period with the chance of showers present, but persistent moderate to heavy rainfall unlikely at this time.


SHORT TERM

A vigorous period of weather is set to bring widespread falls to large areas of the nation with strong to gale force winds, with all activity peaking during Thursday. The risk of thunderstorms also bring the risk of damaging wind gusts for many areas inland of the coast. Some destructive wind gusts over 130km/h possible over Alpine areas this evening with the heavy rainfall will make conditions feel like a cold cyclone.


Conditions start to ease from the south and west during Friday as the trough lifts northwards and then contracts the rainfall out of the state by the weekend with the showery weather to continue in the moderating westerly flow.


Next week starts dry. I think we see a nice slab of ridging move in and that will settle the pattern down for a wee bit however, we are seeing widespread moisture plumes developing over northern and western parts of the nation that may be drawn south and east into frontal weather coming out of the west mid to late next week.


LONG TERM/AREAS TO WATCH

That will be the major factor to watch next week, however the forecast confidence is remaining poor at this time, due to the contamination of the data with the wild weather unfolding during the coming few days. Once we know how the system resolves over the eastern areas of the nation, will we understand how the system next week builds.


The SAM is forecast to remain negative through this week and into the weekend. I am leaning towards the SAM turning back negative next week, just a gut hunch, no science on that, but watching that closely and will clearly know if that is a right call. But if it is, then the high pressure will be pushed northwards and allow the westerly winds to also lift northwards as we see the pattern remain fast flow for the south of the country.


If that happens, then moisture over the northwest and western interior may be dragged into the frontal weather passing throughout the south of the country leading to more widespread falls and cloud bands.


Also, watch the weather over the northern parts of the nation with the humidity possibly building up in line with the heat engine starting to crank into gear.


WEATHER VIDEO PM - WEDNESDAY 3RD AUGUST 2022

FORECAST

Rainfall Next 10 Days

The warm front is through and the airmass is rapidly destabilising with the risk of widespread rainfall forming out of thunderstorms that emerge tonight with the risk of moderate to heavy falls and severe weather these. All the action over the inland of the state tonight and spreading further east and north during Thursday before easing from the south Friday. Scattered showers will continue during Saturday and Sunday over the southern inland, once again mainly west of the divide with the risk of thunderstorms over the interior as a southwesterly flow redeveloping and seeing the cooler and drier airmass shift north next week. Another round of rain and thunderstorms are forecast to develop from mid to late next week with another system coming through SA but that feature remains up in the air, impacted by how this current event resolves.

Rainfall will extend northwards through the NSW inland and heaviest falls are on the ranges and points west where we may see widespread above average rainfall. The rainfall extends along the QLD border and back to the NE of SA with the far southwest and western areas likely seeing just light and patchy falls now between the rain bands, which is common for these setups.

Heavy rainfall will lead to areas of flash and riverine flooding with significant storm risk tonight and tomorrow as the unstable weather moves in from SA and the moisture peaks in association with the low pressure. Rainfall eases from Friday though showers won't clear until Sunday. More rainfall may be back from mid next week.

Rainfall favouring areas exposed to the westerly and southwesterly wind regime over the coming 3-4 days with heaviest falls in those regions, but there is additional rainfall chances next week with further fronts which may impact SA and VIC before reaching NSW.

WEATHER ISSUES

Thunderstorm Forecast Wednesday

Thunderstorms are ongoing parallel to the coast of SA and VIC today ahead of a cold front that should approach later today. Thunderstorms are forecast to break out behind a warm front this morning with the airmass warm and conditionally unstable with the risk of severe thunderstorms forming this evening in the southern and central inland of NSW and then overnight that risk develops further northwest into northeast SA (see chart below for Thursday) Damaging winds and heavy rainfall the main issues. Small hail may develop with the stronger cells, but that risk is conditional. The warmer it gets this afternoon the more likely severe weather will develop over NSW.

Thunderstorm Forecast Thursday

Thunderstorms are forecast to increase overnight and through Thursday and this will lead to areas of heavy rainfall over the southeast of NSW and northeast VIC. Thunderstorms also carry the risk of producing damaging winds and heavy rainfall away from the southeast inland with destructive winds possible over parts of interior NSW with the strongest storms. Hail may also feature with thunderstorms over the northern inland of NSW in advance of the rain band moving up the NSW ranges. For the southern coastal areas of SA and VIC, a strong cold front will move through leading scattered showers and local thunderstorms, some strong wind gusts are possible with thunderstorms however, strong gradient winds will be in place in response to the low approaching.

Damaging Winds Wednesday to Friday

A lot of confusion in the media about the wind warnings that are being issued and that is not boding well for interpretation. So bottom line it is windy. We have one wave of strong winds through overnight and this morning, another wave of strong winds moves through SA and into VIC tonight and Thursday and another wave of strong winds on Friday and Saturday as the low moves through to Bass Strait. Those winds coming through IN WAVES like spokes rotating around on a wheel, will come through at regular intervals. Over the southeast inland of NSW, scattered thunderstorms are likely to produce damaging wind gusts overnight and into Thursday, with that risk expanding through outback NSW and into SA. So, there are two bands of rainfall I spoke about on the weather video this morning and there are two areas of damaging winds to watch in the i coming 2 days.

Flash Flood Risk Next 2 Days

Very heavy rainfall is expected to develop post this warm front moving through the southeast inland of NSW with storms igniting later today and tonight and this helping to kick off the massive rain band that will lay over eastern VIC throughout northeast SA and stretch over NSW and then into northern border areas with QLD during Thursday night into Friday. The highest rainfall rates will be over the elevated terrain and mainly on and west of the divide. A very high risk is forecast nearby Canberra and over the Alpine Peaks through to the eastern Riverina.

Riverine Flood Risk Coming Days

The heavy rainfall on the snowpack has been the concern here since a week ago, quite frankly it is remarkable that this is only being picked up in the media. Remain weather aware as the guidance is unchanged here. The risk of flooding will continue into early next week as rainfall eases. Peaks can be expected to flush through major river systems a long way away from the heavy rainfall threat.

MEDIUM TERM FORECAST

AUGUST 10TH-17TH 2022

Moisture Watch

Moisture is likely to approach the west of the nation with another jet stream cloud band emerging through the Indian Ocean and possibly appearing ahead of cold fronts moving into the southwest of the country. There is moisture coming into SA but frontal weather may knock that moisture eastwards and into QLD, but with not a great support for low pressure to be assigned with that moisture, conditions may just be cloudy at this stage. But the forecast confidence is low.

Rainfall Anomalies

Very low confidence forecast and understand that this will change as we get the pieces of the puzzle organised following the current rainfall event to see how that impacts the pattern in about a week from now. So expect this to change.

Temperature Anomalies

The heat engine builds and the humidity also increasing across the nation's north with the heat levels coming up in total for the tropics. Cooler bias still remains over the southeast and eastern inland extending back towards the central interior but this is of low confidence and will be based upon whether we see cloud and moisture spreading through the jet stream with force out of WA. Milder days on the way for WA at this stage in northeast to northerly winds.

DATA - Refer to the video for further information and context surrounding the severe weather issues over the southeast and the potential for follow up rainfall for parts of the nation next week.


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

More details can be found in the video at the top of the page.

00Z GFS - Precipitable Water Values - Next 2 Weeks

More details can be found in the video at the top of the page.

00Z GFS - Rainfall Accumulation - Next 10 Days

Refer to the video for more context and analysis

00Z CMC - Rainfall Accumulation - Next 10 Days

Refer to the video for more context and analysis

00Z GFS - Rainfall Accumulation - Next 2 Weeks

Refer to the video for more context and analysis

A closer look in - not much change to the guidance and more details can be found in the video for the period ahead as we have multiple systems on the board.

More coming up from 8pm EST with a look at the models and rainfall focussing in on the medium-term forecast as we need to see what is next on the weather maps and plan for that.

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