The NAM and GFS continue to predict different scenarios for the coastal storm tomorrow, Wednesday.
The NAM predicts amost twice as much precipitation with more falling as snow. The GFS has warmer temperatures at the surface and delays changeover to snow until late in the afternoon, as the amount of precipitation (QPF) winds down.
The NAM has often overstated QPF in past storms. So I’m going with the GFS model, which has a changeover to snow between 2-4 PM and conditions allowing accumulation after 4 PM. Still going with 1-2 inches of snow for Philadelphia and the immediate suburbs. Further NW, greater amounts possible.
The new models come out about 10:30 PM. I’ll update if things look different.
The recent national news has covered the highly amplified upper air configuration that’s bringing below average temperatures to the middle of the US. That deep dip in the jet will slowly advance eastward through Thursday, and temps will fall with highs in the 40s by Friday.
The models have been hinting at a weak coastal low that develops Thursday night as the cold air advances over us. The latest GFS model shows light snow possible for much of South Jersey and around the US 95 corridor late Thursday night into Friday morning. Accumulations will be light, if any.
Several other disturbances ride up the upper trough, both Sunday and next Monday into Tuesday, with chances of precipitation each time. Some of the precip will be in the form of light snow showers (Sunday) and a wet wintery mix Monday night. Stay tuned.