NSW - CONDITIONS MILD MID WEEK - EYES ON THAT NEXT RAINFALL EVENT THIS WEEKEND.

And boy have there been some interesting signals from the models as we track into the weekend and into next week, with heavy falls over the northern districts but some models placing the heavier rain shield over the southern and central parts of the state. It is a dog's breakfast out there.


That renders me curating regional rainfall and temperature forecasts quite useless as they will change from run to run too much so keeping the forecasts conservative and looking for trends in the data more than specifics at this time, just so you understand the approach to spring time forecasting.


Reacting to models from run to run, will cause you to lose your hair....again!


Lets take a look.

Rainfall next 10 days

Rainfall is expected to be limited to the southeast areas during the week with the weakening front the most likely feature Thursday to bring that limited supply of precipitation through, quite extraordinary how quickly this system has dissolved from where we were 36hrs ago. The next feature to bring more widespread rainfall opportunities lay in the back half of the weekend and into next week with a deep trough combining with a rich moisture supply from the north and east. I am broadening the rainfall amounts, but not identifying an area of heavy rainfall just yet, as that represents the uncertainty. The takeaway is, more likely to see rainfall later this weekend over the northern and eastern districts, lighter and lesser chance of rainfall for the far southern and southwest districts....at this time.

Thunderstorm Forecast

The chance of a thunderstorm on an upper trough passing through ahead of the front and colder weather during Wednesday afternoon. The storms should be around 20000ft off the ground and non severe, and likely to be just a few claps of thunder amongst a batch of showers. Gusty winds are possible but not like last frontal passage.

Frost Forecast Wednesday

A low chance of frost over inland areas as the winds drop out under high pressure, but the day will warm quickly in a northerly flow.

DATA


Euro 00z - Surface Pressure Pattern and Rainfall Distribution - Next 10 days

The models are well place on the short term forecast package with a front passing through the southeast of the nation Wednesday and Thursday bringing a burst of showers. Maybe some thundery showers and gusty winds over the outback of SA, western NSW and southern NT into QLD with this feature later tomorrow. Now the nation remains quiet until the weekend when we have the deepening low pressure trough over Central Australia combining with deep moisture throughout the interior, this allowing a large scale shower and thunderstorm event develop. The areas of greatest impact likely to be southern NT, northern SA and western NSW and QLD at this stage. This area of low pressure likely to slowly creep through to the east. The placement of this event is what the models are struggling with and I will have further to say after 9pm, but at this time the rainfall looks heaviest through southern QLD, NSW and northern VIC. Out west another strong cold front is expected to bring a further burst of colder than normal weather with showery periods early next week. IF this front comes in from the west earlier than GFS, than we will see a clearance of that system over the east quicker, but there is not great guidance upon that idea. Therefore the trough over the east may take the best part of next week to lift off the east coast but the moist unstable airmass may continue if the front does not arrive. Up north, baking weather with showers and thunderstorms in the afternoon and evening, in random scattered locations.

Euro 00z - Precipitable Water Anomalies - Next 10 days

This again paints the picture such as the GFS with the movement of moisture through the nation being repeated multiple times during the coming 7-10 days but if you watched the video, you see this trend continue. That supports the forecast bias of rainfall in the short and medium term with higher chances of above average rainfall through northern and eastern Australia. For the west, dry air behind cold fronts, will suppress rainfall for inland areas of the state and while keep temperatures colder than normal in the southwest inland, it will also stop rainfall developing for the medium term in that northwest corridor.

Euro 00z - Rainfall Accumulation - Next 10 days

Rainfall accumulation across the nation carries a low confidence from the weekend and as outlined in the video surrounding the GFS, it comes down to placement, scale, intensity and speed of the systems progress through the nation. The higher chance of rainfall can be found in the shorter term with this weakening cold front.

A closer look in

GFS 00z - Rainfall Accumulation - Next 10 days

Refer to the video surrounding the crazy outputs from the GFS over the past 24 hours and where do we go from here and can we take it seriously?

I will have the full model wrap on all things rainfall and severe weather potential coming after 9pm. As you can see the confidence is not especially high in this outlook which is normal for spring.



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