NWC REU 2011
May 23 - July 29



Photo of author

Forecast Validation of Three Sierra Nevada Precipitation Events

Rebekah Banas, and Heather Reeves


What is already known:

  • Atmospheric rivers can result in heavy precipitation, especially in mountainous regions on the US west coast, like the Sierra Nevada Mountains.
  • These rivers vary and so does the resulting precipitation amounts/types.
  • Forecast accuracy for these events is thus very important.

What this study adds:

  • Exploratory look into the NAM forecasts with some preliminary results.
  • Provides basis for more in-depth investigation on the predictability of atmospheric rivers and heavy precipitation in the Sierra Nevadas.


In this paper, three precipitation events which occurred in the Sierra Nevada Mountains are investigated. These three events are all associated with atmospheric rivers, from which the resulting precipitation can be quite heavy. The 24-, 48-, and 72-h NAM model forecasts of temperature, dewpoint, and 24-h accumulated precipitation are analyzed at four Sierra Nevada stations. Temperature and dewpoints errors from the model output show a tendency to overestimate the temperature and underestimate the dewpoint during these three events. For one event, the precipitation was strongly underestimated (by about half). The other two events show no specific trend in either time or space.

Full Paper [PDF]