MUMBAI, May 18 -- Despite a yellow alert, Mumbai saw measured amounts of rainfall on Saturday. However, more pre-monsoon rain is forecast for the upcoming week, with a yellow alert slated till Wednesday, except for Monday. A low pressure forming over the Arabian Sea off the coast of Karnataka on May 22 will increase rain activity over Maharashtra from Monday to next Sunday, according to the India Meteorological Department. Isolated areas in Konkan are expected to receive heavy to very heavy rainfall. Mumbai continued to be overcast and humid on Saturday, as spots across the city saw rainfall in the range of 10mm to 20mm in the morning, mostly between 8am and 9am. IMD forecasts this weather to continue till Wednesday. Thunderstorms, lightning, and light to moderate rainfall with winds at 40-50 kmph are expected in isolated areas in Mumbai, Thane, Palghar, and Raigad till Friday. The two exceptions are Mumbai and Palghar on Monday, when a green alert for light and moderate rain is issued. The southwest monsoon is advancing earlier than usual in the south, as per the IMD.Sabah Virani...