Rumors are swirling about a possible snow storm Friday through Sunday of this upcoming week. Some models dump over 15″ of snow across the entire DC Metro (yes even in the urban heat island of downtown Washington).  But before we get our hopes up, let’s take a closer look at the uncertainty that always exists due to the complexities of the forecast models.

First up is the Global Forecast System Ensembles (images courtesy weatherbell): Here you are looking at just a portion of the ensemble models. An Ensemble model simply put is where you slightly tweak the input data at initialization and then let the model run X hours out (in this case 144 hours out into the future).  What do you get? Rain, Snow, a Mix, no Snow, etc. This is because there is little agreement among each individual ensemble run on where the surface low develops and how strong the area of high pressure hangs in to the north.

Running the same GFS Ensemble for Snowfall Accumulation (image courtesy weatherbell):

As you can see, we have scenarios ranging from nothing (Boo!), to a few inches (I’d take that over nothing),to the heavy, crippling accumulating snow (Please God!) that the ski resorts, kids and snow-loving adults want. If you run into someone who hates snow remind them that they are welcome to “take one for Team-Washington” and move to the South, lessening our traffic problems as well as our affordable  housing crisis. There are in fact places in America where you can swat mosquitos all year round living in an inferno for 9 months out of the year, sweating all over the place.

The European Operational and Control Ensembles do show some blocking (orange colors) over eastern Canada… but will this hold? Will it be enough?  Will there be enough arctic air out ahead of this storm system?

Ensemble Control (image courtesy weatherbell):

Ensemble Mean (image courtesy weatherbell):

And of course here is what the current european operational (caution – this will change and may not be accurate at all) drops on our region late this week: if this panned out, it would be the Megalopolis Snowstorm that the 55 million people from the suburbs of Northern Virginia to the northern suburbs of Boston have been “dying for”.

Pessimism:  Again, the blocking high may slip out, it could snow to our south as it slips out to sea or… or the storm comes north but warm air wins out with cold rain or a mix for us and heavy snow to our north.

Optimism: There is the potential (yet again) for a snow event later this week into the weekend.