The UAC mentioned earlier in the South, is set to enter TN on schedule by 28th. From this upper air system, already embedded in the trough, rains along the TN coast can be expected next 2 days from Friday. 

Chennai can get some showers, with gusty winds from the NE. Friday,Saturday,Sunday, i would expect cumulative of around 25 mms in Chenai.

as I expect the system to now move N/NW. Somewhat along the coast. maybe upto Bengal by the 31st...but this to be observed.

AS this moves, rainfall mov along interior Karnataka and into S. Mah by the 30th.

N.I. Karnataka can get showers on the 29th,and Bangallore a day earlier, as mentioned before.

More on vagaries

W.D is affecting Kashmir. Cloudy night ahead for Punjab, Kashmir and Himachal. Rain / snow expected in these zones during next 24hrs.

10pm, Showers seen along S,S-E,central.Tamilnadu coast... http://ow.ly/i/1iJOv

Showers may reach N.Tamilnadu coast and #chennai by early morning !!

7:30pm, Moderate showers are pushing into S,S-E.Tamilnadu and even into central Tamilnadu coast ... http://ow.ly/i/1iGIM 

Cold claims 13 lives in North India ... http://ow.ly/gnA4Q

Cold wave sweeps North India, 30 deaths in UP ... http://ow.ly/gnA8V 

RT @senthilvijay: @weatherofindia Good rain here in #munchirai #marthandam #kanyakumari district. Tamilnadu (4:45pm)

A moderate W.D is almost at the doors of Kashmir and N-N-W India.. Rain / snow expected to start from midnight today.. http://ow.ly/i/1iEzz 

Due to the W.D,  the Minimum temperatures would rise by 2 to 3 °C over northwest India during next 2 / 3 days.

Due to W.D, Rain / Snow is expected for Kashmir, Himachal and isolated over some parts of N-W.India till 29-Dec.

The medium level circulation & a trough of present W.D is expected to continue over N-W India even till 31-Dec.. http://ow.ly/i/1iECq

This circulation & trough is expected to drift E-S-E into N,N-central India, some showers expected to break over central,E.India on 31-Dec

Lowest Maximum temperature of 10.8°C was recorded at Najibabad (Uttar Pradesh)

Till 8:30am, Rainfall over S,S-E,Central Tamilnadu coast..

Colachel (Kanyakumari Dist) 3 CM, 
Vedaranyam and Rameswaram (Ramanathapuram Dist) 2 CM, 

Nagapattinam (Nagapattinam Dist), Tondi (Ramanathapuram Dist), Pamban (Ramanathapuram Dist), Kovilpatti (Toothukudi Dist), Kalugumalai (Toothukudi Dist), Muthupet (Tiruvarur Dist) 1 CM.

#chennai - Morning temp. was 23.6 C and cloudy, Around noon good low cloud formation seen, threatened to drizzle, nothing materialized.