NSW - SHOWERS AND STORMS INCREASING FROM THE WEST.

The weather is expected to turn more humid overnight and you will wake to a soupy more unstable airmass across your Wednesday, heralding a more unsettled spell for NSW.


It has been well documented today on the process in the medium and long term, so lets take a look at the latest data and your forecasts below.

FORECAST


Rainfall Next 10 Days

No change in the guidance in the distribution of rainfall and you may notice a broadening of the heavier rainfall coverage but please understand that some areas will see more and less than the guidance below. The rainfall gets underway tomorrow with showers and thunderstorms passing into the west and north of the state. The showers and thunderstorms will approach the GDR tomorrow night. Showers and thunderstorms turning to areas of rain over much of the state during Thursday with moderate falls about, some heavy falls possible with thunderstorms. Friday and into the weekend, showers and thunderstorms will persist with a soupy moist northeast flow. The better coverage the further east you go. Another trough will move into the west of the state this weekend and that will invigorate thunderstorm activity during Sunday and through early next week.

Rainfall Next 3 Days

The concentration of rainfall will be through the southern Riverina and northern VIC into central VIC with this first trough. Scattered falls of 5-15mm elsewhere through from eastern SA to southern QLD and the east coast seems reasonable.

Thunderstorm Forecast Wednesday

Thunderstorms may develop from early in the day over the western and northwest areas from left over convection in SA. The storm coverage will redevelop along and to the east of the trough moving into the western inland during the afternoon and evening and this slowly progressing eastwards later. Some storms may turn severe in the western districts.

Flash Flood Risk Wednesday

As advertised through last week and the weekend, this period will be very humid and with those higher moisture values through the atmosphere, flash flooding will be a moderate to high chance with storms IF they turn severe. Rainfall rates of 50-70mm/hr possible in the taller and broader thunderstorms.

Damaging Winds Risk Wednesday

Damaging winds are a moderate risk with the stronger thunderstorms during the afternoon and evening. Heavier thunderstorms will also be capable of producing strong downbursts and this leading to localised wind squalls up above 90km/h.

Large Hail Risk Wednesday

A low end risk of large hail at this stage, I think the atmosphere lends itself to being more favourable for flash flooding and damaging wind risks Wednesday.

DATA


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

The pressure pattern is largely unchanged from this morning and I will point out that this is the more conservative approach to the short and medium term, and yet there are still severe weather events and heavy rainfall for many parts of the nation. Your number will vary as you track through the next few days. I will reaffirm the issue in forecasting rainfall and temperatures in this environment is very tricky. Now we have one trough moving through now into the end of the week, that gets stuck over the southeast and eastern inland. The next trough emerges out of WA through Friday and moves eastwards and drives more showers and storms from SA through to the eastern inland of the nation over the weekend and next week. A third feature is the one causing the most interest, now the Euro has had it in recent runs like the GFS, an upper low over WA moves into the moist and unstable air trapped over the eastern inland forms a potential severe weather event right at the end of the run into the medium term. This carries low confidence and there is no skill in being specific other than mentioning it in the way I have. The northern tropics unsettled and humid and the southwest of the nation mostly dry until we see that potential upper level system at the end of the run.

Euro 00z - Precipitable Water Anomalies - Next 10 Days

Deep moisture is now moving through SA and into VIC and NSW, you may have noticed the afternoon cumulus in the east under the warmer layer at about 10000ft, that is indicating the low level moisture is increasing and tomorrow the whole of the south and east will feel very tropical. This tropical air is set to stick around for much of the nation away from the tropics for most of this outlook period. It will spawn rain and thunderstorms for many areas with heavy falls in random scattered pockets in multiple states. The drier air seems to be trapped over the SWLD with onshore southerly winds and the upper ridge keeping things calm until about day 9-10. For now this weather coming through in the next week is unusual in terms of the scale and depth of the moisture this early in the season.

Euro 00z - Precipitable Water Values - Next 10 Days

The hotter the colour, the more moisture to work with and there is plenty on the board. There is a mixed bag in the period next week with models unsure how to handle the moisture to the north, does it come south of is it kept north over QLD, NT and WA thanks to ridging? We have to wait and see, but in the short term, it is soupy for most of the country. GFS in the video shows you when the moisture escapes south into colder air aloft, this scenario shows you the ridge holding firm and keeping the moisture and wet weather further north. We simply have no way of knowing if this will occur this far out, there are too many moving pieces ahead of it.

Euro 00z - Rainfall Accumulation - Next 10 Days

More details in the video.

A closer look in

GFS 00z - Rainfall Accumulation - Next 16 Days

More details in the video. This is IF the upper low heads south in the medium term and again this remains low and I suspect that the model will change overnight.

More details coming up tonight with a look at the full model spread on the rainfall outlook, as many people are looking at that most of all.





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