Snow will develop across the Washington Region during the morning hours on Sunday continuing through the late afternoon with a widespread 3 to 5″ of accumulation expected.
Snow may mix with Sleet during the evening hours and then potentially taper off to Freezing Drizzle during the overnight hours.
A glaze of ice from freezing rain is expected for locations east of interstate 81 and south of interstate 70.
On Monday a secondary storm will deepen off of the Del-Mar-Va coast line and slowly move northeast allowing for any Sleet and or Freezing Rain to change back to Snow.
The Snow will likely pick up in intensity on Monday afternoon through the evening with low visibility and treacherous travel conditions. Snow will taper off to flurries on Tuesday morning before ending around noon. This will be a major winter storm with widespread travel disruptions.
The latest forecast models continue to show some differences in how far north the wintry mix makes it on Sunday evening, and how far south the wrap-around heavy snow falls on Monday afternoon through Monday night. My snow map took the middle ground (a blend of the GFS and European models).
All of the forecast models below (courtesy WxBell) start at 4AM Sunday and continue through 7pm Tuesday
First up is the European model. Blue/purple colors represents Snow, orange represents Sleet, pink represents Freezing Rain and green represents plain Rain.
European Snowfall Forecast:
GFS (American model):
GFS Snowfall Forecast:
Canadian Forecast Model:
I think that there is a very high probability of National Airport (DCA) picking up at least 6″ of snow with Dulles (IAD) and Baltimore-Washington International airport (BWI) picking up at least 8-10″ (storm total).
Could totals go up? Yes and will depend on the exact track and how quickly the coastal storm strengthens on Monday.
Could snow totals go down? Yes, if warmer air intrudes the mid-levels of the atmosphere over the metro area sooner than expected on Sunday afternoon, sleet/freezing rain could bring totals down. Also if for some reason the coastal storm on Monday is much weaker than forecast and moves away more rapidly, then snowfall totals across the northern half of the forecast area could come down as well (see my storm total map at the top of this post).