NCEP model guidance for the 2009–0 mid-Atlantic snowfest

The winter of 2009-10 will be remembered for many years in the mid-Atlantic region for the numerous heavy snow events that occurred. The Washington, D.C. to Philadelphia corridor was crippled on three separate occasions (12/19, 2/5-6, and 2/9) with significant impact further north into the New York City metropolitan area as well, and these three events will be the focus of the paper, but other smaller but challenging events such as the Washington, D.C. "surprise" snow of 1/30 will also be examined.

This paper looks back at the performance of National Centers for Environmental Prediction short-range model guidance related to these events. All aspects of the predictions, including location of heaviest snow, amounts, precipitation type, and timing will be examined. This study will of course feature the forecasts from the NAM and GFS models, but it will also examine the Short-Range Ensemble Forecasts (SREF) as well as high-resolution guidance, such as that from the high-resolution (4 km) window runs of the WRF. In all of these cases, the primary synoptic models (NAM, GFS) did a fairly good job identifying the general threat, but the SREF was instrumental in determining the location of the sharp northern edge of the precipitation shield, while the high-resolution guidance helped predict the upper limits of the snow totals.