NSW - RAIN INCREASING IN COVERAGE EAST FOR FRIDAY BUT HEAVIER FALLS COME THIS WEEKEND.

OVERVIEW

An upper low is moving into the state today and that is bringing the last ingredient to see rainfall becoming extensive throughout the next 4-5 days. Once again the placement and speed of this feature will determine who gets what in terms of heavy falls in the coming days, but there is a chance that inland areas could see a lot more than what the models are forecasting right now.


Widespread rainfall is expected to contract eastwards as a trough slowly lifts northwards later this weekend and into next week as a high begins to nose into the Bight.


Rainfall may be ongoing for much of next week along the coast fringe but inland areas should begin to dry out by early next week bar the far northeast where rainfall may linger.


SHORT TERM

It is all about the severe weather over the east which has been well documented throughout the past few days. Now we have to watch where the banding sets up and how far inland that comes in the easterly flow. Under the upper low, the rainfall could be productive as well, the placement is expected to be quite tricky to pin down but most inland areas (away from areas west of Hillston to Bourke) should see 5-15mm but higher totals are likely.


Rain along the coast will begin to increase later tomorrow and persist off and on through the weekend and into next week as the low pressure trough and centre waft around the broad upper low. That upper low begins to shift north and east during early next week seeing the rainfall intensity coming down. Showers will continue but the intensity winding down.


Fine weather will return to much of the inland with high pressure nosing in. Frontal weather underneath the high pressure belt will begin to move into southeast Australia leading to more traditional weather developing, so drier weather across the inland and showers and windy weather skirting through southern areas from next weekend.


LONG TERM

The east coast block is expected to move out by later next week and frontal weather which should be glancing through the southwest of the nation. That frontal weather will begin to track eastwards through the end of next week with stronger systems launching through WA then these look more likely to come across Southern Australia with more intensity as we track into the second week of July.


So once we lose the extensive rainfall over the north and east of the country, the weather is expected to return to more traditional conditions. Whether it can overcome the rainfall deficits over southern and Western Australia will be the question but right now it is unlikely.



AREAS TO WATCH

The SAM phase is important to watch over the coming week, if we see it head back into a negative phase then the frontal weather coming through in the second week of July could be very productive given the location of the wave action over the Southern Ocean.


The Indian Ocean is forecast to remain warmer than normal and this will feed moisture into the jet stream, whether it does it with the next wave of active frontal periods in the first part of July will be the issue, but most climate models support above average rainfall for July.


WEATHER VIDEO PM - THURSDAY 30TH JUNE 2022

FORECAST

Rainfall Next 10 Days

Rainfall is expected to be well above normal over northern and eastern areas of the state with some rainfall totals sitting well above the norm for this time of year. Severe weather relating to flash and riverine flooding is possible through the weekend and next week. Rainfall will be moderate over inland areas of the state from the Riverina through the Central West and into the Northern Inland. Rainfall variable with relation to the slow motion of the clumps of convection. Near dry out in the far west. Rainfall along the coast will continue through Sunday and Monday with a low dictating the spread and location of the heavy falls. The rainfall will clear the interior from Monday and the coastal areas will see the showers becoming less frequent from later in the week as the flow pattern tends back westerly.

Rainfall could be very heavy along the coast with the onshore convergent rainfall through Friday into Sunday and then with a developing low pressure system moving down the coast from northeast which could produce some very heavy rainfall early in the week before conditions clear. Rainfall over the inland is dependent on the placement of the upper low leading to widespread rainfall, but exactly where remains to be an issue on the models but numbers are coming up.

Rainfall along the northern coast also increasing in the previous model runs with a trough deepening along the coast and a new upper low over the interior also leading to widespread rainfall developing with some locations along the coast expected to see heavy falls from later in the weekend and into early next week. This area carries a lower confidence in rainfall spread due to the issue related to the trough and the upper level low over NSW and also whether we see a low pressure system for over the region before it shifts southwards. Models are shifting towards that idea.

Rainfall over in the west is light and patchy and many areas going dry for the period. Rainfall returns via weak cold fronts over the southwest later next week and into the following weekend. Some rain areas over the central west and southern inland will remain slow moving so if you get under one of those, you could see a 10mm of rain in a few hours and cold temperatures before that clears early next week.

SEVERE WEATHER WATCH - NSW

An upper low is moving into NSW today and remain slow moving over the interior from Friday and into the weekend, leading to showers over the inland. But the upper low will help to draw in deep moisture from the north and east with a trough forming along the coast. It will be this trough that increases the risk of severe weather over parts of the NSW coast from Friday and then persisting through the weekend with the risk of high impact flash flooding with the slow-moving areas of heavy rainfall near the coast and then damaging winds developing in the presence of a surface low during the latter part of the weekend and into early next week. Also watching the heavy rainfall threat spilling south from QLD into northeast NSW later in the weekend and heavy rainfall in pockets under the upper low over the inland.

FLASH FLOOD RISK - NSW

Flash flooding is a high risk at this stage, could easily lift it to very high chance over parts of the coast from Wollongong to Narooma with a trough on Friday night into Saturday and over the Northern Rivers and then extending up and down the coast this weekend into early next week. A low risk at the moment under an upper low over the inland, particularly Central West during Saturday and Sunday with slow moving areas of rainfall, this may extend towards the Southern Tablelands and Southwest Slopes and ACT, placement of the upper low key. While it has been drier the past 2 weeks or so, be aware that it won't take much to get the runoff going again.

RIVERINE FLOOD RISK - NSW

A moderate to high risk of riverine flooding developing once again along the coast from Narooma northwards with a few pockets where the risk is higher in relation to the topography and shape of the coast and how the trough/low pressure behaves and sets up. Understand that this forecast is a heads up and the risk zones will become more refined as we move forward through the days ahead, but we could see conditions supportive of flooding emerge from Friday night onwards through the weekend and into early next week. With the upper low over the inland we could see 40-50mm in scattered pockets falling over wet ground, it won't take much to get some further peaks down the river systems which are leading

MEDIUM TERM

July 8th - July 15th, 2022

Rainfall Anomalies

Relatively seasonal conditions forecast across most of the nation, though there are some increasing signals on the modelling, some quite aggressive, for rainfall being above average over the southeast and south of the country and possibly about the southwest. I would like to see more modelling on board for the higher rainfall chances to be extended into SA and NSW but right now I am not convinced of it.

Temperature Anomalies

There has been a shift towards a cooler bias across the nation in recent days and while I am seeing that colder bias, I am not confident on it being as cold as models suggest so keeping things milder over the east and southeast, cooler over the north and northwest and across western parts of the nation.

DATA - Refer to the video for further information.


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

As mentioned, there is so much going on in this active pattern and to cut down reading time, refer to the video at the top of the page.

00Z GFS - Precipitable Water Values - Next 2 Weeks

Moisture levels remain excessive along the east coast with some very heavy rainfall totals to develop for this time of year in response to that. The deeper moisture moving out of the NT, through QLD and into NSW and then remaining along the east coast, which is representative of the positive SAM phase. Overall, the pattern will breakdown mid next week, meaning that conditions along the west coast and through southern Australia will remain dry and settled under high pressure. Moisture will overcome the drier airmass over in the west by the end of next week, that moisture then spreading along the southern coastal areas bringing up the chances of rainfall for southern Australia once again and drier air moving back over the eastern and northern parts of the nation.

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 - your rainfall totals will bounce around for interior parts and along the coast of NSW in the days ahead and with an upper low, no model is going to tell you exactly what to expect so stay close to the guidance as things can change every 3hrs under these conditions. So volatile weather to continue. The wettest weather the further east and north you go. Rain eases during mid next week before frontal weather returns.

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


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