A low-pressure area has been prowling the waters of southwest Bay of Bengal over the past couple of days, but it is initially seen as propelling itself towards eastern Sri Lanka coast.
Dry winds
Forecast analysis shows the winds over the southern peninsular India would be drier and colder northwesterly-to-northerlies blowing in from the plains of the north and west.
The wind pattern is forecast to shift to being rain-friendly easterlies only from the weekend, with scattered rains dropping over southern coastal Tamil Nadu.
This might translate into isolated showers over the interior parts of the State as well as the adjoining southern Kerala, even as the core of the erstwhile ‘low' wallows in the southern Arabian Sea.
India Meteorological Department (IMD) has said in its outlook bulletin that isolated rain or thundershowers may occur over extreme south peninsular India on Wednesday and Thursday but scale up thereafter.
MERCURY CLIMB
Meanwhile, the weather over northwest India might turn a shade for the better with the arrival of a western disturbance marked by rising motion of air upfront, convection, build-up of clouds and snow and rainfall.
Growing cloudiness will cause minimum and maximum temperatures to rise by 2 to 3 degree Celsius over parts of northwest and central India.
Cold wave
This would in turn lead to abatement of cold wave conditions over some parts of these regions.
But fog to shallow fog would envelop parts of Uttar Pradesh, Bihar and some parts of sub-Himalayan West Bengal and Sikkim. This may progressively extend over Assam and Meghalaya also.
Forecast valid until Friday said scattered rain or snowfall would occur over Jammu and Kashmir, while it would be isolated over Himachal Pradesh and Uttarakhand.
Rain likely
Isolated rain or thundershowers are likely to unfold over the plains of northwest India from Thursday.
The European Centre for Medium-Range Weather Forecasts says the core of the westerly system would drift in across the northwest border around Friday, but the warming impact is expected to unfold from Wednesday.
An IMD outlook said the western disturbance would affect weather over the western Himalayan region during the rest of the week starting Wednesday.
The impact would be felt over the adjoining plains of northwest India from Thursday.
Meanwhile, international weather models see no big churn in the weather over northwest India after the westerly system passes.
There is no big follow-up westerly system seen anytime until January 21, which would clear up the air for cold to colder northwesterly winds to blow into the plains.
Relatively colder conditions are being forecast for even the southern peninsula, with only the fringes of the west and southwest coasts being the exception.