The barometer on my watch is extremely good for localised forecasting - if the pressure drops suddenly or continuously then rain is 95% likely at my current location.
E&M what watch you got have you got a link?
Was looking at some of the digital watches on amazon a few month's back, a bit dear and i remember some of the reviews saying that weather forecasting by air pressure alone wasn't very accurate :

Weather forecasting more than 5 days in advance is total guess work according to met office.
remember hearing that newspaper sales increase by 20% when they headline with the weather i.e
B.B.Q/wet summer......snow ect ect..