Another band of rainfall is expected to approach WA during Friday with a strong cold front passing through later in the day.

This system will bring a burst of moderate to heavy rainfall as it passes over, but should be less intense as the systems earlier in the week.

Rainfall totals are expected to be in the 20-50mm range once again for parts of the southwest and west coasts, including Perth. Thunderstorms will also feature along the axis of the front passing through with locally heavy rainfall and gusty winds.

Rainfall for the next 10 days - Valid Thursday 8th of July 2021.

Rainfall will be frequent over the coming 10 days, but there will be breaks too. Strong fronts on Friday, later Sunday through Monday, Tuesday and Wednesday next week will continue to bring more moderate to heavy rainfall. Another set of fronts looks to impact from Friday through next weekend.

The showers will ease again during Saturday as a new ridge approaches.

However, there are more fronts to pass through the region later Sunday into Monday and periodically next week with the unstable westerly winds continuing through the period.

12z Euro Surface Pressure Pattern and Rainfall - Valid Thursday 8th of July 2021.

Note the moisture moving through the Indian Ocean, on the periphery of the coldest air where it is interacting with above average temperatures over northwest WA. The shower coverage will increase for the southwest with each front passing through.

12z GFS Pressure Pattern and Precipitable Water Values for the coming 2 weeks. - Valid Thursday 8th of July 2021.

Those fronts next week have the potential to tap into large scale moisture plumes over the Indian Ocean Basin, thus increasing the risk of cloud bands and more inland falls. So that will be an element to watch over the coming few days.

Lets have a look at the risk elements for Friday with the passage of the front.

Thunderstorm Forecast Friday - Valid Thursday 8th of July 2021.

Widespread showers developing with a cold front, turning to rain areas. A line of thunderstorms embedded in the areas of rain will move through with gusty westerly winds and possibly some hail. The storm duration will be brief. Following the cold front, cold air may bring further thunderstorms to the west and southwest coasts overnight into Saturday.

A 90% chance of thunderstorms within 25km of a given point within the pink shading, the risk tapers down 10% per colour down the wheel.

Hail Risk Forecast Friday - Valid Thursday 8th of July 2021.

Hail is possible with the cold front but no large hail is expected. Cold air following the front overnight into Saturday could bring small hail to the southwest coast with cold pool moving through, though this will clear off during Saturday morning.

Low - 5-20%, Moderate - 21-40%, High - 41-60% chance of small hail observed within 25km of a given point.

Damaging Winds Forecast Friday - Valid Thursday 8th of July 2021.

Highest chance of damaging winds attached to the passage of the frontal system later Friday. There is a chance of some high wind squalls with showers and storms that follow the front for the far southwest, between Bunbury and Albany overnight into Saturday.

Low - 5-20%, Moderate - 21-40%, High - 41-60% chance of damaging winds observed within 25km of a given point.

Farmers and Graziers Forecast - Friday - Valid Thursday 8th of July 2021.

Cold wet and wintry weather developing for the southwest once again though condiitons will ease during Saturday before they return to high risk levels early next week with more frontal weather building.

More details to come.

18 views0 comments