Residents planning an outing this weekend are advised to carry umbrellas as weathermen claimed that clouds which surfaced in the skies over the capital on Friday, are expected to cause rainfall during the weekend.

On Friday evening, too, the capital witnessed light rainfall.

The Met department claimed that the likelihood of showers is because of the combined effect of a strong western disturbance and its induced cyclonic circulation across Bihar.

Patna is also expected to receive intermittent rain with thundershowers during the weekend.

“A strong western disturbance that originated over Pakistan two days ago was passing through Uttar Pradesh (UP) on Friday. It is now moving eastward towards Nepal. The western disturbance has also formed a cyclonic circulation over UP. This combined effect of the two external weather elements led to formation of cloud in the lower level of the atmosphere,” said Ashish Sen, director, India Meteorological Department (IMD), Patna.

Western disturbance is a term used in describing an extra tropical storm originating in the Mediterranean, which causes winter and pre-monsoon season precipitation across northwest India.

The last time a western disturbance affected Bihar was on February 7, leading to trace rainfall in the morning.

Sen added: “The clouds are expected to lead to intermittent rain in Patna till Sunday. There are possibilities of one or two spells of thundershowers but the exact forecast can be given only six hours in advance. Apart from Patna, the districts in the north-west parts of the state are expected to receive more rainfall, along with thundershowers at isolated places.”

The sudden overcast weather is leading to temperature fluctuation as well.

As the cloud cover restricts the radiation from the earth’s surface to rise in the upper layer of atmosphere, the minimum temperature on Friday stood at 14°C, which was almost two notches more than that recorded on Thursday. The same cloud cover restricts solar radiation to reach the earth’s surface, leading to a drop in the day temperature.

“We are expecting a slight fall in the maximum temperature. Against the prevailing 26- 28°C, it is expected to come down to around 22-23°C. Subsequently, a slight rise in minimum temperature is also expected. Against the prevailing 12-13°C, it is expected to shoot up to 16-17°C,” said Sen.

Sen added that the cloud cover is expected to clear by February 18. However, the residual moisture content is likely to lead to light fog formation on that day and February 19.