Snow is still in the forecast but the system has slowed down and the models are still not certain about the position of the system. I guess before we talk about the amount of snow, I should give you a basic understanding of the information that the GFS and European models are all about.
The Global Forecast System (GFS) is a global numerical weather prediction computer model run by NOAA. This mathematical model is run four times a day and produces forecasts up to 16 days in advance, but with decreasing spatial and temporal resolution over time. It is widely accepted that beyond 7 days the forecast is very general and not very accurate, and most nongovernmental agencies rarely use any of the model’s results beyond 10 days (mainly due to the fact that there is no other 16-day model with which to compare). Along with the ECMWF’s Integrated Forecast System, which runs out 10 days, it is one of the two predominant synoptic scale medium-range models in general use.
The Integrated Forecast System (IFS) is an operational global meteorological forecasting model. IFS is developed and maintained by the European Centre for Medium-Range Weather Forecasts (ECMWF) based in Reading, England. Because of its source, it is often known as the “ECMWF” or the “European model” in North America, to distinguish it from the American Global Forecast System (GFS).
The IFS is a global model that runs every twelve hours. Its output runs out to ten days, with a temporal resolution of one day (24 hours). The operational model runs both in a deterministic forecast mode and as a 51-member ensemble. The deterministic mode has twice the horizontal resolution of the ensemble, and one and a half times the vertical resolution (60 layers in the deterministic compared to 40 in the ensemble); both modes’ vertical layers follow terrain at low levels. The IFS, like the GFS, uses spectral representation rather than a grid-based system.
With that basic understanding this is what those two models are saying. The GFS has the system moving along the Gulf of Mexico and then tracking up the East coast but pushing farther off the coast and we would only see around 1 to 3 inches on Sunday. The GFS has not changed much over the last 72 hours of the track of the system but the model is never that solid to forecast with. The ECMWF has been tracking the system along the Gulf of Mexico but then tracking right along the East coast and bombing out over North Carolina and Virginia, dumping around 1 to 2 feet of snow. This model is one that is used to forecast around the three day mark of the forecast. Nothing has changed with the track of this model over the last 72 hours.
With all that in mind why has nobody really forecast anything? The system we are tracking is just now dumping tons of rain on the coast of California, so there is nothing we could really look at to track this system across the country. This should all change by the end of the day and should have a better understanding of the amount of snow. I am still sticking with my forecast of about 1 to 2 inches of snow for Chesterfield County.