It now appears that the front will stall to our north over the weekend, keeping us in a warm sector. Low pressure disturbances will ride along the front, but the over-running precipitation will be to our north.
So Saturday will have some sun or bright skies in the morning, but clouds will increase by late morning and a cloudy afternoon will be on tap. No rain and temps relatively mild, in the mid 40s.
The same frontal boundary will start drifting towards us on Sunday, with a thicker cloud cover expected, but no precipitation and continued mild temps.
On Monday, the front will make a final push to our south as low pressure forms along it. Much of the day, PHL will remain in the warm sector, but the atmosphere chills late afternoon as the low reaches the coast. All rain for much of the immediate PHL area, but there may be a changeover to light snow very late afternoon, from the northwest into PHL with minimal accumulation.
Tonight will be a good test of the weather models. Both the GFS and the NAM are showing the precipitation associated with an artic front to dissipate before reaching Philadelphia. The GFS cranks out a snow flurry around daybreak with a QPF of 0.01 inches water.
On Sunday, another weather forecasting dilemma presents itself as a stalled front in our area will allow disturbances to develop and move along the front. It’s impossible to know where the front will end up, but recent similar scenarios have the front stalling further south than model predictions. As a result, light snow is seeming more possible than light rain or sleet in PHL. A stronger low pressure system may develop along this front Monday, bringing snow. Amounts not predictable at this time. Stay tuned.