An India Meteorological Department (IMD) update on Thursday said that isolated thunder squalls could stalk sub-Himalayan West Bengal and Sikkim region and the Northeastern States during Friday and Saturday.

The causative upper air cyclonic circulation over Bihar and adjoining Jharkhand of the previous day had metamorphosed into an upper air trough extending south-southwest into Rayalaseema.

This would allow moisture-laden southeasterly winds to blow inland from the adjacent Bay of Bengal waters to fuel convective activity over parts of peninsular India also.

Meanwhile, fairly widespread rainfall has occurred over east Uttar Pradesh and the Northeastern States and isolated over Bihar, West Bengal and Sikkim during the 24 hours ending Thursday morning.

Minimum temperatures were above normal by 2 to 3 deg Celsius over Rajasthan and Madhya Pradesh. They dipped to below normal by 1 to 2 deg Celsius over East Uttar Pradesh, Bihar and Gangetic West Bengal. Satellite cloud imagery on Thursday afternoon shows convective clouds over parts of south Andaman Sea.

FRESH WESTERLY

A fresh western disturbance would affect western Himalayan region from Friday onwards.

Global models said that the westerly system would linger over the region during the weekend and late into the next, dictating weather not just over the northwest but also to the east in phases.

Meanwhile, the low-pressure area over south Andaman Sea has weakened into an upper air cyclonic circulation overnight and lain over south Andaman Sea.

A short-term forecast said that fairly widespread rain or thundershowers would occur over the Northeastern States, sub-Himalayan West Bengal and Sikkim.

It would be isolated over Bihar, Jharkhand, Gangetic West Bengal, Coastal Andhra Pradesh and Orissa.

Scattered rain or snow would occur over western Himalayan region from Friday. Isolated dust storm or thunderstorm would occur over Rajasthan, Punjab and Haryana until Friday evening.

Scattered rain or thundershowers would occur over Andaman and Nicobar Islands and isolated over Kerala, south Karnataka and Lakshadweep.

No significant change is expected in maximum and minimum temperatures over northwest and adjoining central India during the next three days.

RAIN FOR NORTHEAST

An extended forecast until Tuesday next (April 5) said that fairly widespread rain or thundershowers would occur over the Northeastern States.