Sunday Update on Potential Midweek Major Winter Storm

“Tim, your weather post yesterday was very scientific can you just get to the point and tell me how much snow is going to fall in my backyard on Wednesday?! ” – anonymous friend of mine in Arlington.

For those of you who are looking at your weather apps on your smart phones and have noticed that the snowfall forecast for Wednesday keeps fluctuating it is because those apps are averaging all of the ensembles from all of the various forecast models.

Yesterday I showed you the various ensembles of potential solutions within the Canadian (GEM), GFS (American) and European forecast models. Today I will show you the average of the ensembles from the American Global Forecast System (GFS) and the European models.

The GFS (image below courtesy tropical tidbits) currently tracks the storm further off the Mid-Atlantic coast, keeping colder air locked along the 95 corridor and dumping a lot more snow in the metropolitan area.

Latest GFS Ensemble model average showing potential snowfall accumulation:

The European Ensemble model (image below courtesy WxBell)  has shifted the track of the coastal storm closer to the coast which would allow for warmer air to move into the 95 corridor changing snow back over to sleet and or rain, before ending as snow and cutting down snowfall accumulation east of the Blue Ridge mountains

Latest European Ensemble model average showing potential snowfall accumulation:

Averaging models doesn’t provide an accurate forecast because the exact track (not an average track) of a storm determines how much snow will fall in a given area.

For those of you that live along and west of the Blue Ridge you have the best chance of seeing all snow with hefty accumulations. For those of you that live between the blue ridge and interstate 95 the forecast is much more uncertain because snowfall totals here are highly dependent on just how close to the coast this system tracks. Those of you east of interstate 95 have the best chance of starting as snow before changing back to rain/sleet cutting way down on accumulations. 

The shortwave responsible for the evolution of the coastal storm will reach the northwest coast of the United States this afternoon.  I suspect that the forecast models will begin to merge on a solution as they receive more accurate input data from the ground stations across the western United States. Stay Tuned.