Argentinean Patagonia presents a large potential for wind energy generation. Currently, despite of several projects being developed, there is no installed wind power at Río Negro province. In the present paper, we perform an assessment of the wind energy resource in the province, using wind data derived from MERRA (Modern Era Retrospective Analysis for Research and Applications) reanalysis. We compared time series, histograms and wind roses between wind data derived from MERRA and wind data observed at several meteorological stations finding, in general, good agreement between them. We fitted the hourly wind data to a Weibull distribution for each grid point of the MERRA dataset, and mapped the mean annual wind speed and Weibull k factor. We then computed the capacity factors for different wind generators. We have identified several different spots with optimal parameters and closeness to existing infrastructure (power lines and roads).