After an unseasonably mild winter last year with temperatures 5.2 degrees above average and only 2 inches of snow at Reagan National, 1.8 inches at BWI Marshall and 3.7 inches at Washington Dulles, the area should finally get back on track this winter with more seasonable winter temperatures and snowfall.
- 2012-2013 Winter Outlook
The ABC 7 Storm Team is expecting snowfall and temperatures to be near or slightly below the long term average. With that said, we are calling for the majority of the D.C. Metro area to receive around 10 to 14 inches of snow. The 18 inch amounts, shown above, in the western portion of the area shaded in blue. Lesser amounts are forecast east of D.C. towards the Chesapeake Bay and even less forecast on the Eastern Shore. The highest amounts will be, as usual, across the Blue Ridge (where there has already been measurable snowfall) and through Western Maryland where they typically average over 100 inches along the western slopes of the Appalachians. The average snowfall map for the region is shown below.
- Average D.C. area snowfall (NWS Sterling)
What will steer our winter patterns? Not El Nino or La Nina this winter.. ENSO (El Nino-Southern Oscillation) is nearly in a neutral state right now, with sea surface temperature anomalies in the equatorial Pacific near zero. This leads us to look at other patterns such as the North Atlantic Oscillation and the Arctic Oscillation to play a much bigger role in forecasting regional snowfall.
- November Sea Surface Temperature Anomalies
Above is November SST Anomaly, which is in a weak El Nino to neutral state. Check out last January(shown below). The evident la Nina pattern may have accounted for the meager snowfall.
- January SST Anomalies
Those patterns make the forecast a little easier. Just as with moderate to strong El Nino, the region has the potential for greater than average snowfall and with moderate to strong La Nina, the region has a better chance for below average snowfall.
We must remember, however, that with this kind of season ahead, all it takes is one big snowfall and our forecast is a bust. With the AO and NAO possibly swinging negative again during the winter months, along with ample cold air in place, the potential for heavy snowfall does exist.
- Commutageddon... Let's hope never again..
As far as snowfall variability, in a weak El Nino, for all of the events in the D.C. area, the range of snowfall has been anywhere from 9 inches in a year to 34 inches in a year. Good thing we're not in a weak La Nina, as the snowfall variability is even greater, with the low end at 8 inches and the high end at 48 inches!