NSW - HEAVY RAINFALL SOUTHEAST, SEVERE STORMS FOR THE EAST AND FINE WEATHER FURTHER WEST.

* There will be a system reboot overnight and I am doing some back of house activity ahead of the Apple App being launched tomorrow night. Details to come *


The slow progression of the severe thunderstorms and heavy rainfall is expected to continue moving east over the coming 48hrs as we see a ridge nudging in from the west. But before then, we have a soggy few days and as advertised, flood watches and severe thunderstorm warnings in place to deal with.


Next week we see the pattern flip after the showers along the east coast clear. The fine and warmer weather over inland areas in the coming days will begin to move eastwards and the blow torch is set to be turned on.


A shift to Summer time is expected during the coming week and this will be the first chance to dry out for some areas as we see the pattern reset over the nation.


Thankfully the MJO pulse is heading into the Pacific and we will be spared that influence for now, but it will only be short lived.


Let's take a look at the latest details.

FORECAST

Rainfall Next 10 Days

Rainfall is expected to be heavy at times over the southeast in the coming 48hrs with a few spots expected to record up to 300mm maybe touching 400mm in those wetter areas as the onshore push combined with a deep upper low overhead produce areas of thumping rainfall. The northern portions of NSW will see a reduction in rainfall, but it will persist over the far northeast with some areas expected to see severe storms until about Friday. All modes of severe weather are expected to feature as we track throughout the period. Come the weekend the rainfall and the thundery weather will be gone and we can enjoy the chance to dry out. Hot and dry weather will eventually come to an end from later next week with the next trough, BUT we have about 5 days to dry out!!

Thunderstorm Forecast Thursday

Severe thunderstorms this afternoon will ease slowly this evening before we see them back on the cards for the northeast of NSW where the air aloft is warmer and more unstable. Deep moisture in place and the veering of the winds with altitude (ample wind shear) will support deep convection and strong to severe storms. All modes of severe weather is possible. The weather is expected to be drier the further west you go through the state with a stable dry airmass running up in southerly winds on the western face of the circulation.

Flash Flood Risk Thursday

Flash flooding related to thunderstorms is expected to be very high over the northeast third of NSW and running down the GDR into the Central Tablelands as thunderstorms run over the same ground and move slowly. The weather expected to be supportive for dangerous flash flooding. Flash flooding may develop over the southeast from early in the day as wrap around feeder bands of rain form on the southern side of the low pressure system.

Damaging Winds Thursday

Damaging Winds are expected to feature with the strong to severe storms, mainly over the northeast and central areas of the state. Strong winds may develop over the southern Alpine areas mainly over the eastern slopes as a low deepens nearby.

Large Hail Risk Thursday

Large hail a moderate to high risk over the northeast of the state, especially about the GDR where the convergence will form with the northeasters and northwesters clashing with a trough nearby.

Riverine Flood Risk Thursday to Saturday

Heavy rainfall with a low pressure system about southeast NSW will lead to moderate flooding about some catchments. Heavy rainfall with slow moving thunderstorms will lead to flash flooding, that flash flooding renewing flood peaks over wet catchments.

DATA


00Z GFS -Surface Pressure Pattern and Rainfall Distribution - Next 16 Days

Significant rainfall is expected to unfold over the southeast of the nation during the course of the next 2-3 days with a deepening upper level low passing through NSW and deepening off the east coast. This will cause some flood risks down through the southeast of NSW and eastern VIC. The severe storm threat continues for the next 2 days over eastern NSW and QLD before the weather eases over the weekend. The heat is on next week with a significant pool of heat heading southeast and east from the northwest of the nation. So more summer like conditions expected for southern Australia. The north of the nation remains in routine weather leading to prolonged build up conditions. The west will turn cooler, which will be welcome after the heatwave this week. The cooler weather enhanced by a cold front developing next week for the SWLD. Watching that fast flow pattern in the medium term that will send a nasty heatwave across the nation and then the rain returns with a very deep moisture supply ahead of Christmas as you can see here and in the PW values below.

00Z GFS - Precipitable Water Values - Next 16 Days

We see a nice tongue of drier air coming through the east and south of the nation from next week, the high humidity will be replaced with a decent period of drier and more stable air which will be welcome for many of you who have been swimming in recent weeks. The dry air also extends back to WA with cooler conditions in a fresh westerly wind regime through much of next week. The tropics is where you should find the persistent moisture during this time of year and that is where it will be from about early next week with the showers and storms thinning out even up there, thanks to high pressure aloft. But watch that moisture return and combine with the high heat, a very robust atmosphere is being progged on the medium term portion of the outlook, something that I will monitor in the days ahead.

00Z GFS - Rainfall Accumulation - Next 16 Days

More can be found in the video above.

A closer look in - rainfall will continue to chop and change with the placement of the upper low. A 10-20km shift for those in the southeast of the state can make a massive difference so pay attention to the forecasts. For the rest of us we dry out from the weekend in the east, the west of the state, feeling the dry settled weather already.

More to come from 7am EDT.



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