A very large nor’easter (surprisingly, our first nor’easter of the winter) will affect the Northeastern United States late tonight into tomorrow. Even though the forecast models are still not completely in consensus about the location of the rain/snow line, I am confident enough to make an official forecast for this upcoming system.

Part 1: The Forecast

My forecast is based on a combination of the European and NAM model solutions. The NAM tends to really amplify the precipitation tomorrow morning, while the European has a more realistic precipitation field. The problem that many forecasters are faced with right now is whether a changeover to mix/rain will occur sometime tomorrow. While I believe that sleet could fall for a time around Philadelphia and its immediate suburbs tomorrow, I do not think it will last long. If the snow continues to fall heavily tomorrow morning, dynamic cooling will occur and keep the precipitation type all snow. If a lull in intensity occurs, a changeover could occur as warm air from the ocean comes in aloft. Either scenario, I believe that this will be a significant snowstorm with drastic effects on people’s lives tomorrow and Friday.

Part 2: The Map

My snow-map below shows the most snow falling north of the immediate Philadelphia area and into Northern NJ and Maryland. It is in these areas where the precipitation will likely stay as all snow and be very intense for most of the morning tomorrow. I am calling a general 11-15 inches for this area. For people living along I-95, a general 7-11 inches is expected with the snow changing to sleet, then back to snow by tomorrow midday. In south jersey and along the coast, totals will really be held down by mixing and rain.

Part 3: Timing and Intensity

This storm will not be a short one. A full 24 hours of precipitation will fall from early Thursday morning to early Friday morning.

1 AM Thursday-4 AM: Light snow starts from South to North

4 AM- 2PM: Peak of snow, could change to sleet in southern part of the region

2 PM-5 PM: Possible lull in precipitation (changeover likely to sleet over I-95)

5 PM-11 PM: 2nd round of moderate snow for most of the region

11 PM-3 AM: Friday: Ending South to North

Morning and evening rush hour on Thursday will be treacherous. Morning rush hour on Friday will also be extremely slick. The winds will also be high during this storm, which means for possible power outages during the height of the storm on Thursday. If you really have to drive tomorrow or Friday morning, make sure to take it slow. Schools will be closed on Thursday and possibly Friday depending on final totals.

Luckily, we are looking at a substantial warmup next week with temperatures possibly getting into the 50s, which will help us with melting some of this snow!

Enjoy the storm!