We’re not going to win any awards for our forecast for yesterday’s snowstorm. In some areas it was right on, in others it was a bust on the low side. But, grading on the curve, our forecast was satisfactory.

We forecast 5-9″ for most of the region, with a small bulls-eye of 7-11″ in our southern areas.

In reality, most areas got 4-6″, around the low-end of our range. Our idea of a 7-11″ bulls-eye in our southern areas did not work out for the most part although there was a small zone of 6-8 inches from around Leesburg to Culpeper.

Our forecast erred a bit on the high side because we relied on the model consensus which generally suggested a little more snow than fell, especially south of the District. Models often have a hard time pinpointing where the heaviest precipitation will occur and this storm was no different.

What we did well

  • Accurately characterized the storm impacts: that mixed frozen precipitation would change to snow and that this would turn into a frozen mess on the roads.
  • Generally captured the timing of the “high impact” storm conditions, which were between 4 a.m. and noon Monday, as forecast
  • Correctly stated that, despite warming into the 50s during the day Sunday, temperatures Sunday night and Monday would crash through the 30s and 20s.
  • Did not buy into “outlier” high-end model forecasters of 10-14 inches or more.  Several local forecasters did this; even the National Weather Service issued a forecast for 10-14 inches at one point before back tracking to 6-8 inches.

Where we struggled

  • The transition from rain to sleet to snow occurred roughly one to two hours later than we thought…closer to 4 a.m. rather than 2-3 a.m. in the immediate metro region (and even later towards Fredericksburg and southern Maryland, 5-7 a.m.)
  • Nowcasting the storm became tricky mid-to-late Monday morning.  As dry air started to push into our northwest suburbs and snow started to shutoff north of the Beltway, I thought the accumulating snow was perhaps ending prematurely.  But after that, as some more moisture surged northward, it overcame the dry air and another band of accumulating snow set up from around Leesburg to Baltimore that produced more accumulating snow across the area.  Determining exactly where the northern edge of accumulating snow would set start and stop turned into a challenging issue both before and during the storm.

Overall, I’d give us a grade of B for this storm (although I understand if those of you who live around Fredericksburg and Charlottesville – which got 4″ rather than 7-11″ would give us a D).  We told a consistent story without wavering, correctly characterized the storm impacts, and for the immediate D.C. area (our primary forecast area) were in the ballpark in terms of forecast accumulations.

What do you think?