Only a day after posting that the deterministic GFS and NAM models have the snow well to our east missing us, today’s models GFS and NAM have jumped onto the snow bandwagon with the statistical models with the light snow occurring before daybreak on Saturday and continuing during the daytime hours. Currently the NAM is showing 2-3 inches in PHL!
The statistical models have been consistently predicting light snow in NJ and extreme SE Pennsylvania for several days. Interestingly, the statistical models have reduce the probability just as the GFS and NAM show increased amounts of snow.
It now appears that the coastal low pressure system will intensify enough to throw snow back into our area through the day Saturday; the snow will be light in PHL with somewhat heavier accumulations in NJ. The NAM now shows 2-3 inches in PHL. The GFS shows 3-4 inches with heavier amounts in NJ! I expect the predicted amounts to change by Saturday.
The newer statistical models are showing an increased signal for the possibility of light snow Friday evening into early Saturday morning as a coastal low off the coast brushes our area. Because the precipitation arrives at night, temperatures will likely be cold enough for snow accumulation. Current predictions are a coating to 3 inches, more in NJ than extreme southeastern PA . I’ve noticed the new statistical models have been pretty good in forecasting precipitation in recent months.
The latest deterministic models (GFS, NAM) aren’t so sure about this, keeping the snow off the coast.
By the way, the NWS will be unveiling a new statistical forecast system sometime this month called the “National Blend of Models”. The NBM promises to provide increased forecast accuracy.
The first amplification of the jet stream this season occurs the end of this week, with high pressure diving down into the central part of the US.
Along the frontal boundary that will be right off of the coast, a low pressure system is expected to develop and move up, somewhat off the coastline. At this time, it might affect NJ and southeastern PA with light snow Friday night. Of course, if the upper trough sharpens and deepens, more of our area will be affected. If the trough becomes broader, we’ll miss the snow.
The statistical models now show something possible, but precip will be light and low probability.
This scenario has been suggested by the long range models for several days; the latest GFS run suggests greater intensification allowing light snow to reach westward into NJ and SE PA.
Stay tuned. (The models didn’t get the cloud cover correct for today; not sure we can trust them with 5 days in the future.)
