The shear line and the trough of the low-pressure area (LPA) inside the Philippine Area of Responsibility will be affecting the weather conditions of the country Wednesday, Pagasa said.

The LPA was last tracked over 990 kilometers east of Eastern Visayas on Tuesday evening and is likely to develop into a tropical depression within 24 hours.

Pagasa said the through of the LPA or the extension is affecting parts of the Visayas and Mindanao.

While the shear line is triggering rains in parts of Luzon.

The word shear line is a more technical term for "tail end of the frontal system" —when the end point of two different kinds of wind (warm air and cold air) have met or converged.

Pagasa said it has raised the heavy rainfall warning No. 4 under the shear line weather system.

The effect of shear line and through of LPA will bring moderate to heavy with at times intense rains over Metro Manila and Calabarzon.

Meanwhile, light to moderate with at times heavy rains will prevail over Central Luzon, Bicol Region, Eastern Visayas, as well as in Caraga and Davao Region. Flooding and rain-induced landslides during these weather conditions are possible.