A slow moving front will today finally bring much needed rain to the West Coast.

MetService has issued a severe weather watch with forecasters expecting an active trough to move slowly across the northern half of the South Island this evening and Thursday.  

They predict the heavy rain will be preceded by a moist northerly flow, which is expected to bring further rain with a few heavy falls to the Westland ranges north of about Franz Josef Glacier through to the early hours of Thursday, and to the ranges of Buller and northwest Nelson during Wednesday evening and Thursday morning.

MetService says at this stage rainfall amounts are unlikely to reach warning criteria, except possibly in a few isolated pockets. However, a watch will be maintained in the meantime.

The rain is going to be welcomed by west coasters who have seen little rain fall over the region in recent weeks along with temperatures over the 30s for a number of days.