Latest GFS has moved more towards a coastal track versus the offshore track it featured yesterday.

Latest GFS (Global Forecast System) Potential Snowfall Accumulation Forecast

Latest NAM (North American Model) Potential Snowfall Forecast: (typically this model has had a cold bias with over-done totals this year). However, the European model seems to agree (next image)

Latest European Forecast Model:  Potential Snowfall Forecast (A Snow Lovers Dream)

The key to the million dollar question of “how much snow will you get in your backyard” weighs heavily on timing the two pieces of energy that will likely phase Wednesday and Thursday.

The problem tonight is that the energy riding the northern branch of the jet stream hasn’t even reached the coast of North America yet and models do not get a good handle on the downstream system (coastal storm) until the northern branch energy reaches land.  Why? Because in the world of weather it’s all about physics and the exact track of this northern system will dictate how close to the coast the main storm system comes. **The data that these forecast models crunch (calculus) will be more accurate when our land based weather stations ingest accurate data (when the system is overhead/overland).**

The next detail to iron out once the track is clearer (tomorrow) will be the temperatures in the mid levels of the atmosphere. How much sleet will mix in along or east of interstate 95? Will sleet mix in at all? Exact track will be key because if this system hugs the coast too much, warm ocean air will be drawn into the system causing snow to change to sleet (frozen rain drops). While sleet can accumulate and cause nightmare road conditions, it also cuts down on snowfall accumulations.

Current thinking of the various main forecast models:

North American Model (NAM) – Currently forecasting a snow lovers dream for the interstate 95 corridor and the immediate eastern suburbs of DC and Baltimore.

European Forecast Model – Currently forecasting a snow lovers dream for the western suburbs & cities with well over a foot of snow.

Global Forecast System (GFS) – Medium impact storm with snow and sleet. Accumulations of 5″ or more.

Details will definitely become clearer tomorrow when the piece of energy over the Pacific makes landfall overnight tonight into Tuesday. Stay Tuned.