The India Meteorological Department (IMD) on Friday issued an alert for heavy rainfall in north Bihar over the next 24 hours.

The monsoon trough line that is positioned over north Bihar, along with a cyclonic circulation over west Uttar Pradesh, is expected to bring heavy showers in northern parts of the state.

Places like Patna and Gaya in southern Bihar, on the other hand, are expected to receive light rain over the next two days. The state capital has not witnessed rain over the past couple of days.

Ashish Sen, the director at Patna meteorological centre, said: "The monsoon trough line has shifted towards north Bihar. Moreover, a cyclonic circulation over western parts of Uttar Pradesh is also bringing heavy moisture in north Bihar. We expect heavy rain in north Bihar, especially in the north-eastern parts of the state over the next 24 hours as a result of the two weather systems."

The Met chief has, however, said the state might face a dry phase after five days because of the southward shift of the monsoon trough line. "The monsoon trough is moving in an oscillating manner and it is expected to start shifting southwards after two days. As it gradually shifts below Bihar, the state would receive a dry phase for a few days," said Sen.

The evening bulletin of India Meteorological Department (IMD) on Friday stated that the Northern Limit of Monsoon (NLM) - an imaginary line drawn on the map by meteorologists to mark till where they deem the wind - was passing through Veraval (Gujarat), Surat (Gujarat), Ratlam (Madhya Pradesh), Jhansi (Uttar Pradesh), Lucknow (Uttar Pradesh), Pantnagar (Uttarakhand), Dehradun (Uttarakhand), Una (Himachal Pradesh) and Jammu.

The weather bulletin further stated that Bihar was expected to receive fairly widespread to scattered rainfall till Sunday.

Southwest monsoon made its foray into Bihar through the north-eastern districts on June 17. The normal date of onset of monsoon in Bihar is June 10 and it covers the entire state in two days.

Met chief Ashish Sen claimed that monsoon made a normal onset in the state this year with rainfall observed at most places over the past week. "The distribution of rainfall has varied with the movement of the monsoon trough line. The southern parts of the state are receiving comparatively less rainfall over the past days as the trough line was shifting northwards. Overall, the northern parts of the state have received comparatively more rainfall than the southern parts," said Sen.

IMD, in its first long-range forecast issued on April 12, had predicted above normal rainfall - 106 per cent of the long period average - in monsoon this year but a report by the IMD's Pune meteorological centre in the third of week of May stated that the eastern region of the country would get comparatively less rainfall and the deficiency in Bihar would be around 10 per cent. Normal rainfall in Bihar over four monsoon months, June to September, is 1,024mm.