Hey everyone. My first semester in college is complete and the weather pattern is starting to heat up. We are looking at a very active week weather-wise. First, a clipper system will affect the area Christmas eve into Christmas day. This storm could drop 2-4 inches of snow by Christmas morning. The second storm will hit a couple of days later. This system will be much larger than the clipper and has the potential to drop over 6 inches of snow over parts of the Northeast.

Storm 1: Christmas Eve Clipper

A weak low pressure system will form over the midwest and skirt to the south of our region on Monday night. Cold air will be first rushed in from the northwest, then transition to the northeast. As a result, precipitation will likely fall as snow. With any clipper, however, the amount of moisture associated with the storm is a concern. If there is enough moisture in the atmosphere and the storm starts to interact with it, snow will fall. The latest GFS forecast model run shows this scenario.:

The NAM forecast model suppresses the moisture, which would lower any snow totals significantly.

In terms of snow totals, if the GFS scenario is correct, 3-4 inches of snow will be on the ground by Christmas morning. I know many kids will be ecstatic when they see a few fresh inches of snow Christmas morning. If the NAM is correct, then a general 1-2 inches could fall.

Storm 2: The Nor’easter? December 26th-27th

Storm 2 is a much, much harder forecast. In terms of teleconnections, we are dealing with a positive NAO and a negative AO, usually not the best signs for large big city nor’easter.  Nonetheless, the forecast models have been showing a possible major storm next Thursday. There are multiple scenarios that the models are projecting for this storm.

Scenario 1: Nor’easter; Mix to snow in Philadelphia, all snow N&W of the city

This scenario is what the latest GFS run has shown. The storm digs the jet and rides the coast bringing in enough cold air to support heavy snow. The heaviest snow would occur Wednesday night into Thursday morning. From this solution, a general 8-12 inches would be expected for areas north of city. Because we are still a little less than a week out, it is very hard to determine if this is likely or not.

Scenario 2: Apps Cutter

Scenario 2 is supported by the European model. This would bring the storm up the Appalachians and push warm air into the Philadelphia region. The form of precipitation with this storm would be mostly rain, with some snow on the backside of the storm. Throughout this past week, this scenario was looking as the more likely solution, but many forecast models have started to back away. Over the next few days, the legitimacy of this scenario will be tested. By Sunday, I should have a better idea for this storm and the path it will take.

It is going to be a busy week for many forecasters across the Northeast; stay with Philaburbia for updates and snow maps for the upcoming storms.