Which model to trust

Every storm in the catalog, scored at DCA, IAD and BWI. One "case" is one storm at one station: the model's storm-total forecast at a given lead time, compared with what the airport measured.

forecast–observation pairs from storms. Liquid is the fairer test: most models' snowfall is derived at about 7:1 from frozen precipitation, so a snow score mixes precipitation skill with a snow-ratio guess.

How far off, on average

Average absolute miss of the storm total, by lead time. Lower is better. Points with fewer than 6 cases are left out. Hover for every model's value at a lead time.

Too high or too low?

The average signed error. A model can have a small bias but a large average miss if it errs both ways.

Rankings

With storms, most of them minor, these rankings are suggestive rather than settled. Each new storm this winter adds three cases per model and lead time.