Analysis of Forecast Performance for Hit, Miss, and False Alarm Thundersnow Events during ROCS

With this study, daily outlooks of thundersnow from the Research on Convective Snow (ROCS) project are analyzed to determine the causes of forecast success and failure, the latter category encompassing both missed forecasts (no forecast of thundersnow where it did occur) and false alarms (forecasts of thundersnow where it did not occur). At the time of each forecast, forecast discussions were composed daily (October-April) by various project members, wherein they detailed their rationale for issuance/non-issuance of a thundersnow outlook. Six events are chosen from the archives of recent winter seasons (2006-07 and 2007-08) for analysis: two successful forecasts; two missed events; two false alarms. In each instance, a detailed synoptic analysis has been completed, with an assessment of forcing for ascent, moisture, and temperature profiles. Each case displayed the necessary ingredients for snow production, but mid-level stability appears not to have been consistent in all cases. Sounding and cross section analyses are underway as of this writing which detail the time changes of stability predicted by operational models in each case and compare them to the actual observed (when available) and RUC initial field soundings.