NATIONAL WEATHER PICTURE - MORNING EDITION FOR TUESDAY MAY 11TH 2021.

HEADLINES


  • Upper low has developed over southern NSW on Tuesday.

  • Severe Thunderstorms likely in the warm sector in NE NSW and QLD.

  • Heavy rainfall leading to flash flooding over the SE of NSW and Gippsland

  • Dry weather under high pressure for the remainder of the nation.

Areas of rainfall and thunderstorms are currently occurring in scattered pockets around NSW, VIC and QLD this morning. The activity will continue to ramp up with the chance of severe weather in the northeast third of NSW and eastern parts of QLD.


Thunderstorms have the potential to produce large hail, large amounts of hail and damaging winds today. Heavy rainfall leading to flash flooding is a higher risk about the SE of NSW and Gippsland in Victoria. There is the chance of waterspouts off the South Coast and Gippsland coasts with the risk of destructive winds.


Thunderstorms are already active over parts of northern NSW and southern QLD where a trough is beginning to lift moisture into thunderstorms. The trough is being invigorated by the upper low and improving wind fields.


Satellite picture showing scattered showers and thunderstorms over NE NSW and southern inland QLD moving southeast. Valid 8am Tuesday 11th May 2021.

Thunderstorms as mentioned will continue to become more widespread across both states this afternoon. Severe thunderstorms are possible.


Thunderstorm Forecast - Updated Tuesday 11th May 2021

8/10 or 80% chance of a thunderstorm forming with 25km of a given point within the dark red zone. The risk tapers down by 10% per colour down the radial.

Just because you are shaded in DOES NOT mean you are in line for a thunderstorm directly hitting you.

Thunderstorm Forecast for QLD - Updated Tuesday 11th May 2021

8/10 or 80% chance of a thunderstorm forming with 25km of a given point within the dark red zone. The risk tapers down by 10% per colour down the radial.

Just because you are shaded in DOES NOT mean you are in line for a thunderstorm directly hitting you.

More details can be found in the Severe Weather Update for the region in separate notes.


The upper low is slowly meandering along through southern inland NSW today, and on it's southern flank we can already see widespread rain and a few storms along a trough that is feeding off easterly winds. Showers and thunderstorms rotating around the centre over southern areas of NSW with small hail, moving into the Snowy Mountains and ACT. And in the warm sector, scattered showers and thunderstorms bubbling away along a trough along the NSW/QLD border.


Satellite Picture - Showing that rotation over the southeastern parts of NSW and northeast of Victoria, with heavy rainfall forming just offshore the coast wrapping northwards. Valid 8am EST May 11th 2021

The national picture does show the remainder of the nation is very quiet with high pressure keeping things dry and stable over the mainland. Another front is on the approach to the southwest and west of WA, however, the upper ridge being so strong, will see this frontal system fall apart on approach during Wednesday. Meanwhile the moisture is continuing to increase over the tropics once again, being pulled in by upper level winds, but this will have a larger impact over QLD.


Satellite Imagery - Valid 8am EST Tuesday May 11th 2021.

The upper pattern does show the low pressure system over NSW drawing in the moisture from the east leading to heavy rainfall over the coming 48hrs. It won't be until a front comes across on Thursday and knocks the upper low out to the east during Friday and the winds veer back to the west, drying out the whole eastern seaboard.


The showers and colder weather returns back to the southern parts of the nation, with a series of fronts over the weekend, bringing in showery cold air, with local hail and wind squalls. Snowfalls are likely to redevelop over the Alpine areas.


The frost risk with the high ridging in from the west during the weekend, will increase dramatically and there is a risk of severe frosts over inland NSW and VIC with the lighter winds and dry cold airmass in place.


Warmer weather under a firm ridge through WA. Temperatures will remain above average for the majority of the next five days with easterly winds continuing. A weak trough may bring showers to the coast during mid week, but it will back to dry for the remainder of this week into the weekend with warm weather.


The tropical north will remain mostly in dry season, though Cape York and Arnhem Land still seeing residual showers in onshore easterly winds and a wave passing to the north.


Euro 12z Upper Air flow pattern at 18000ft for the coming 10 days. Valid May 11th 2021.

The rainfall will be heaviest early on this week over parts of SE NSW and Eastern Victoria with localised flash flooding possible. Scattered falls over the eastern seaboard, mainly on and east of the Great Dividing Range from NSW through QLD.


Showers increase for SE SA, southern and mountain Victoria and Tasmania with a series of cold fronts later Thursday through the weekend with moderate falls for parts of Victoria and Tasmania.


After a dry spell, the west coast of WA will likely see rainfall return next week with the next series of cold fronts on the approach, linking into the moisture out of the Indian Ocean.


The east coast will dry out later this week with cooler than seasonal temperatures returning.


EC 12Z run - Rainfall for the next 10 days Valid 11th May 2021.

The airmass over much of the inland will be dry with lower chances of inland rainfall continuing for the next 10 days. A slab of dry air over the northwest of WA and across the Top End will remain in place keeping the region in dry season proper conditions. Some of this drier air may be drawn south into the central interior ahead of frontal weather next week, leading to above average temperatures redeveloping over much of Australia after a colder spell this week.


Note the high moisture content connected to the easterly winds early in the period over the southeast of the nation, that will lead to a high risk of flash flooding over the next 48hrs.


Euro 12z run - Moisture values over the coming 10 days - Valid Tuesday May 11th 2021.


So away from the southeast and east of the nation over the coming days, it is relatively quiet elsewhere with a large high moving into the west. That high will eventually dominate the east of the nation coming up this weekend and into next week with a much drier picture ahead of rainfall developing out west.


Want more information? Tailored forecasts or book in a weather chat with me? email me a karllijnders@weathermatters.org


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