NSW - A DRY FEW DAYS WITH A HIGH OVERHEAD BUT THE RAIN SET TO RETURN MAYBE SUNDAY INTO NEXT WEEK.

OVERVIEW

Enjoy the drier weather across the state as we see high pressure nudging in from the west tonight and tomorrow and there is the chance of a few showers through southern areas, but the coverage of rainfall is not expected to be widespread or heavy.


For the remainder away from the south, dry through to the weekend and expecting still a sharp drop of temperatures coming through over the weekend for frosty starts but lovely sunny days under the high.


From Sunday, we could see an increase of instability with a weakening change rolling through. There is likely to be moisture surging southwards from the tropics, and from the westerly winds out of the SA and WA, so all that moisture converging with the instability developing over the state will result thick cloud cover and scattered showers and possible thunder into early next week.


SHORT TERM

That sets up a fairly active period of weather for the state with a series of fronts and troughs rolling throughout Southern Australia with these impacting southern and central areas of the state. A band of moisture feeding through the jet stream will move into the frontal boundaries as they roll in from the west will see thick cloud cover buildup and lead to areas of rain and thunderstorms emerging throughout the state as a strong trough and front passes throughout the new week.


A stronger frontal boundary will move through later next week to keep the rainfall chances going before conditions begin to ease as a new high moves in. But that may be short lived, with further moisture and unsettled weather moving out of the west once again and moisture lingering over the northern and central interior may be drawn back over the state with widespread falls possibly emerging into the medium term.


LONG TERM/AREAS TO WATCH

An active weather pattern is well due for Southern Australia which has been singing out for widespread rainfall for a while now and this week may provide that rainfall to return to the state via a few frontal boundaries, a large-scale low-pressure system and moisture surging into the jet stream and feeding into the frontal weather.


The combination of the sub-tropical jet stream that is laden with moisture meeting the northward surging cold dry air of the Southern Ocean could result in fairly vigorous and active weather with areas of rain and thunderstorms developing but also the risk of severe weather as deepening low pressure systems emerges as the air masses battle each other.


The weather over the north of the nation also expected to become more humid and unsettled with scattered showers possibly returning to coastal areas during the morning and overnight hours, a sign of the times.


Heat values over the interior likely to remain very much above average as we see persistent ridging and easterly winds sit over the tropics, and this ingredient is important for rainfall numbers to increase for the southern and eastern states as that airmass clashes with the colder air out of the south.


FORECAST VIDEO PM - WEDNESDAY 27TH JULY 2022

FORECAST

Rainfall Next 10 Days

A relatively dry few days coming up, we have a few showers possible in the far south and southeast over the coming 24hrs but once they are gone, the weather looks to be mostly fine and settled for many as we track a high over the state. The high will settle in for the weekend and be to the east by Sunday. Now as the high moves to the east, it will make room for the moisture and rainfall chances to increase over the west of the state with a weakening front and trough. Moisture surging out of the north and northeast in advance of this feature and in combination with the moisture surging south and southeast from WA will coverage with the system moving through so rain may be back on the cards from as early as Sunday or Monday. A stronger system that moves through WA from early next week offers the better potential for widespread rainfall across the state as this feature drags in deeper moisture yet, and a larger cloud band looks to engulf the state with widespread falls statewide, heaviest on and west of the divide and over the Southwest Slopes.

Rainfall is increasing over the northern inland of NSW as well with another deeper upper trough lingering through early next week and the additional system moving out from the west being drawn into this moist unstable air and we may start to see multiple bands of rainfall coming through QLD into NSW and then along the eastern coastal areas as well.

The heaviest of the rainfall for now is expected to be on and west of the divide and a lot of this will fall on the snowpack as rainfall through next week before we see marginally cooler air to come bringing additional snowfalls. This is the decaying portion of a shorter snow season. Flooding may develop in parts of NSW in response to the snowmelt and heavy rainfall potential.

WEATHER ISSUES

Severe Frost and Freeze Conditions

Still eyeing off the risk of severe frosts Friday through Sunday over the region identified, but this may come down in risk. With higher humidity values creeping in during the weekend, we may only see one nasty cold night for the region Friday into Saturday but overall, the risk is still sufficient to flag this issue into the weekend for many of you. I think Saturday will be the peak of conditions and the area of risk will be more specific from tomorrow with daily charts issued.

MEDIUM TERM FORECAST

August 2nd- 16th 2022

Moisture Watch

A vigorous weather pattern unfolds next week and that will spread rapidly into the Bight with a deep low surging through WA on Monday next week and then into the Bight from Tuesday. That system will drag in loads of moisture from the north and northwest as well as via easterly winds running over the warmer waters of the Coral Sea. There will be residual moisture lingering from the weakening system coming through the southeast during Monday and Tuesday over QLD, NSW and VIC. Another strong cold front is forecast to emerge in the southwesterly flow behind the low mid to late week before the low moves into the southeast. A stronger system approaches the west at the end of this period with another surge of moisture running into the feature offshore and this may cross into the SWLD by the 9th. Moisture over the north may be apparent in the increase in heat values but rainfall may be inactive due to upper ridging. A very dynamic period of weather expected.

Plenty of moisture spreading throughout the second week of August, but as I keep mentioning, the relationship to low pressure is key to seeing widespread rainfall developing along each of these ports. The higher chance of rainfall for this period is expected over the southern parts of the nation as we see the negative SAM in place. A low chance of an upper trough over northern Australia could activate moisture for northern QLD and spread that south and east throughout the state, but that is a low confidence solution. Clearing rain from the week of active weather prior over the east as the system moves into the Tasman.

Rainfall Anomalies

Widespread rainfall is clearly evident on the charts spreading through southern Australia but the full impact of the developing negative IOD is now appearing in the forecast packages. This is a cycle that will be repeated time and time again in the months ahead. For now, the heaviest rainfall chances over the SWLD of WA contains the risk of severe weather too. In the east and southeast inland, the risk of heavy rainfall over snowpacks could lead to flooding developing throughout northeast VIC and southeast NSW. Widespread rainfall through the interior may be moderate but this is the driest time of year for many areas of the interior, so it does not take much for the green to be on the charts through this region.

The rainfall anomalies forecast very tricky to pick ahead of time as the models have begun to diverge in the longer range. I am going to keep the higher chances of rainfall over southern and southwest areas of the nation with the negative SAM phase still likely to play out over the course of this period. How much moisture gets involved as per what we are seeing in the short term remains to be seen. Note that an upper trough may be lurking over northern areas of the nation during this time and that could result in widespread cloud cover forming over the north with elevated rainfall chances, but this will become clearer as we move throughout the back half of next week.

Temperature Anomalies

A warm airmass has developed in the past week and is expected to strengthen and slowly extend eastwards under an upper ridge over the tropical north. The warmer air will be likely transported south and east ahead of a long wave trough bringing dynamic weather through the country next week with a strong northerly wind ahead of that leading to the warmup in the east and southeast and a colder southwesterly flow on the western flank of that same trough leading to below average temperatures with showery air over the west and Bight region.

Warmer air will continue to push southwards into the eastern and southeast inland ahead of cold fronts and troughs with a warm moist airmass with rain and cloud, the air will be still sitting above normal in terms of temperatures leading to above average overnight temperatures and seasonal to above seasonal temperatures in the east. On the other side of the long wave trough, a persistent colder westerly wind regime will spread from the WA into the Bight leading to colder than normal day time temperatures and seasonal nights. Gales may develop as the airmasses clash over the nation.

DATA - Refer to the video for further information


18Z GFS - Surface Pressure Pattern and Rainfall Distribution - Next 2 Weeks

I have posted the pressure pattern from earlier today so you can compare it with the video information where I use the latest data. Idea is still the same, the main message I want you to take away from this update is that the low pressure in relationship to the moisture will dictate who gets what in the outlook and that will continue to chop and change in this dynamic and energetic weather pattern.

00Z GFS - Precipitable Water Values - Next 2 Weeks

The moisture values are still unchanged over the coming weeks and the guidance is expected to stay very much on course with moisture spreading from northwest to southeast throughout the nation with moisture then thinning out a tad over Southern Australia as the pattern becomes more dominant westerly with the wave train but the deeper moisture over northern Australia needs watching. We could see major moisture surge over the NT and QLD which may lead to above average and early season rainfall coming through in the medium term in the presence of an upper trough.

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

I can't gain access to the zoomed in charts this evening as there has been an error in some of the coding and distribution of data tonight, but I will take a look to see if that is resolved later this evening.


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


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