NSW - SHOWERS INCREASE TONIGHT - HEAVY RAINFALL AND SEVERE WEATHER THREAT MID TO LATE WEEK INLAND.

OVERVIEW

A fairly active week of weather is expected to unfold with a series of troughs and strong cold fronts tapping into deeper moisture levels spreading out of the Indian Ocean via the tropical low wafting offshore the northwest of the country.


A significant band of cloud and rain is currently moving throughout the southeast and eastern inland of the country, covering over much of the inland. Moderate rainfall is ongoing this morning for many but will begin to lift northwards throughout the state and clear by tomorrow.


A stronger and more vigorous weather system is forecast to emerge from Wednesday which cause some damage to crops and certainly cause some issues with the domestic power supply over the elevated terrain with destructive wind gusts of 120km/h and more likely to emerge ahead of very heavy rainfall Thursday.


Riverine flooding is also possible along the system as passes throughout the region. This system is forecast to produce falls over 100mm for Alpine areas and 50mm+ for the windward slopes of the GDR.


SHORT TERM

It is all about the wave train that is moving throughout the state this week with bouts of moderate to locally heavy rainfall for the inland in a gusty northwest to westerly flow. The peak of activity forecast from Thursday to Friday before conditions ease during the weekend as the flow relaxes and opens up.


This will be an entree to what is expected to be observed through the remainder of Winter and into Spring 2022. Widespread falls via the moisture surging through the Indian Ocean and passing into frontal weather moving in from west tom east. Some widespread rainfall events similar to this over the state can be expected in the coming weeks and months ahead.


LONG TERM/AREAS TO WATCH

Once we get this system off the board, does the moisture linger over the southeast and eastern inland or is it transported offshore? That is the question that remains unanswered today and for most of this week, will remain unanswered. Understand that there will be rainfall events coming and going for northern and eastern Australia reflecting the moisture content that is present.


There is uncertainty on the scale of the frontal weather that is passes from west to east and whether the negative SAM remains in place. If we see the negative SAM in place, this will lead to further strong fronts to pass through and the vision of this is not quite clear so expect further changes to the weather pattern and forecast in the coming week as we deal with the active weather in the short term. How the pattern evolves this week will impact the weather that develops in the medium term.


WEATHER VIDEO PM - SUNDAY 31ST JULY 2022

FORECAST

Rainfall Next 10 Days

Areas of light to moderate rainfall is expected to expand over the inland of the state tonight and spread to the ranges overnight and into Monday with some light falls generally but there may be a few more falls over 15mm in some locations. This event will give great insight into how much moisture is available for higher falls mid this week with the next wave of low pressure. Areas of rain and strong to gale force winds will likely develop from Wednesday night and peak through Thursday and ease during Friday and contract north, mainly on and west of the divide. Heavy falls over 100mm possible over the Southwest Slopes and Alpine region may lead to flooding. Falls over 50mm about the ACT and western slopes of the GDR from the VIC border to the QLD border may be observed. Conditions conducive to support only light falls along the east coast at this time. Conditions ease during the weekend with showers decreasing and the flow pattern relaxing with a weak ridge settling in behind the large long wave. Further moisture and rainfall may sit just north of the NSW border during the weekend which may creep southwards again.

The heaviest of the rainfall is expected on and to the west of the divide with a very tight rainfall gradient setting up on the peaks which is going to lead to areas of flash and riverine flooding. Rainfall along the slopes and peaks will be falling on snow and that snow likely to melt so excessive run off is possible. The heavier and more prolonged the rainfall, the more likely we see flooding throughout the region.

The rainfall extends up the NSW GDR but heaviest on Thursday on and west of the divide with falls also extending into Friday with the chance of moderate rainfall as far west as Bourke, but the heaviest of the falls more likely east of here towards the ranges. The east coast seeing very light falls at this time.

WEATHER ISSUES

DAMAGING WINDS -WEDNESDAY TO FRIDAY

Strong gradient northwesterly winds are forecast to develop during Wednesday afternoon for Victoria and overnight for NSW and peak during Thursday, especially over elevated terrain where winds could exceed 130km/h in Alpine areas. Heavy rainfall with strong land gale will cause significant disruption throughout the southeast of NSW and northeast of VIC. Prepare now for power outages throughout the end of the week if you are living in elevated parts of the southeast.

RIVERINE FLOOD RISK - THURSDAY TO FRIDAY

Severe weather related to rainfall rates over 30mm/hr for a 6-12hr period could lead to high impact flash flooding throughout the region, in combination with snow melt coming off the mountains, there may be some higher chances of riverine flooding in areas exposed to these high run off rates. Flooding is a high to very high chance for the end of the week and into the weekend and this risk may be expanded further to the north in NSW.

AUGUST 7TH-14TH 2022

Moisture Watch Next Week

The moisture content across the nation is expected to remain in place but there is a high degree of uncertainty surrounding impacts and thus, leaving the whole nation under risk is the right call and then we can work back from there throughout the week as the data becomes clearer rather than moving the yellow shading around drastically responding from run to run.

Rainfall Anomalies

Some areas may see lingering rainfall with the southwest of the nation and running along the northern tropics the most likely to see any above average rainfall chances. Some moisture lingering throughout the interior may spit out some patchy rainfall and a few showers in onshore winds for the east coast with a departing long wave is also possible. Seasonal rainfall will continue with frontal weather for the south and southeast.

Temperature Anomalies

The big shift in guidance has been the victory for the cooler air to shove the jet stream further north and dam that warmer air back over the heat engine, but that will break and come south through mid-month. The question will be with the warmer air, does it shift southwards into moisture and then interact with strong cold fronts or troughs again?

DATA - Refer to the weather video to get your latest short- and medium-term breakdown.


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

Refer to the video to get your latest short- and medium-term forecast information and to get the context behind the forecasts that are delivered.

00Z GFS - Precipitable Water Values - Next 2 Weeks

The moisture loads for the central and eastern parts of the nation are off the charts quite frankly and will result in very intense rainfall rates for the eastern and southeastern inland and along the Great Dividing Range. A deep moisture supply over the northern and eastern inland of the nation looks to return throughout the medium term and this is an area to watch but will be impacted by the evolution of the system this week so that moisture remains of low confidence. But certainly, some very strong signals for further rainfall exists from mid-month too.

00Z ICON- Rainfall Accumulation - Next 7 Days

Refer to the video for more context and analysis

00Z GFS - Rainfall Accumulation - Next 10 Days

Refer to the video for more context and analysis

00Z CMC - Rainfall Accumulation - Next 10 Days

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00Z Euro - Rainfall Accumulation - Next 10 Days

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00Z GFS - Rainfall Accumulation - Next 2 Weeks

Refer to the video for more context and analysis

A closer look in - excessive rainfall in the east headlines the forecasts but other areas of SA and VIC will see reasonable rainfall which has been observed in spots today. The rainfall rates will continue to come and go with frontal weather in this region with the conditions peaking rainfall wise throughout Thursday and Saturday with the passage of the low pressure. Ahead of this the rainfall peaks throughout the southeast inland with moderate to heavy falls leading to that flash flood risk.

More coming up from 8pm EST with a look at the models and rainfall for the medium term.

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