A low is starting to form off the southwest WA coast, and will bring a wet and windy end to the week for the South West Land Division.

The system, otherwise known as a 'cut-off low' due it's upper level features, will break away from a trough and strengthen over the next 24 hours as it nears the southwest coast. Rain should become more widespread for coastal areas during Friday morning, becoming heavier throughout the day as the system moves east. By midnight Friday, parts of southwest WA should have collected over 15mm of rain, possibly more in places if thunderstorms form.

What's likely to be the main characteristic of this system is the wind gusts. As the low nears the coast, gusts mainly from the southwest could exceed 80km/h, possibly higher for the most exposed coastlines and around Rottnest Island. The strongest winds are likely to occur during Friday afternoon, but should ease significantly in the evening as the system moves inland.

Parts of the south coast should have a wet and windy Saturday morning as the system looks to take a southeast turn and head over the Bight.

The system will move away relatively quickly, however brisk winds in the wake of the system will hang around for most of the weekend, bringing cool-to-mild temperatures until Monday when warmth returns.