How much snow could Philadelphia get this weekend? Totals depend on storm's track

A significant winter storm could be on its way to the Philadelphia area this weekend.

Looking ahead to Sunday and Monday, there are several factors that are still coming into focus. Here's what we know right now.

Cold air moves in

We are highly confident the air will be cold enough with an Arctic airmass in place and daytime highs all weekend in the teens and low 20s. The overnight lows will be in the single digits and teens.

It will be the coldest air of the season yet, and any snow will be at a high ratio due to the cold. In other words, the colder the air, the more snow is squeezed out. A 20:1 snow ratio means 20 inches of snow would be produced from 1 inch of water. In comparison, so far this season, we have seen wet snow with ratios of 6:1 and 8:1. 

We will be in a cold, dry atmosphere with a 20:1 ratio for light, fluffy snow. If there is 1/2 inch of water, we will see 10 inches of snow; if there is 1/4 inch of water, we will get 5 inches of snow; and if there is 3/4 inch of water, we will see 15 inches of snow.

When will snow start in Philadelphia?

We are highly confident in the timeline for the storm. Here's the timeline:

Snow begins Sunday morning. 

• In the European model (ECMWF), snow begins between midnight and 6 a.m. and lasts through pre-dawn Monday morning with light snow showers through the morning.
• In the American model (GFS), snow begins between 6 and 10 a.m. Sunday and lasts through noon Monday with light snow showers into the afternoon.

There will be some blowing and drifting snow throughout the day on Monday, complicating travel and snow removal.

How much snow will Philadelphia get?

We are moderately certain about the storm track. That will be the biggest factor in how much snow we receive.

Both long-range models currently show the storm center sliding from Texas across the Deep South, through the Carolinas and northeast into the Atlantic.

Here in Philadelphia, we will be on the northwestern edge of the storm. The question is how far north and west the storm tracks.

Just 50-100 miles can mean the difference between 6 inches of snow with sleet and 12 or more inches of snow.

We are moderately certain regarding snow totals. The models are coming into agreement with 6-12 inches or more possible across the area.

Again, the amount of snow is all about location. Someone in the mid-Atlantic will likely see monster snow numbers. Will it be us?

6-8 inches: Snow ending with sleet in Philly if the storm tracks farther north or closer to the coast.

8-12 inches or more: All snow in Philly if the storm stays on current track, which is slightly south and farther offshore of the area.

There may be pockets of snow higher than 12 inches if the storm intensifies rapidly while passing Philadelphia.

• The last time Philadelphia saw 6 inches or more of snowfall in Philadelphia was 7.5 inches on Jan. 29, 2022.
• The last time Philadelphia saw 12 inches or more was 19.4 inches on Jan. 23, 2016.
• The last time Philadelphia saw more than 24 inches of snow was 28.5 inches on Feb. 5-6, 2010.

The best advice is to stay with the NEXT Weather Team for frequent updates each day to plan and prepare for the weekend. Have the shovels and ice melt ready. This could be the heaviest snow of the season.

What's NEXT?

Depending on the timing and track between Saturday night and Monday, there may also be school delays or closings on Monday, Jan. 26.

Temperatures will plummet Monday through the middle of next week with highs in the low 20s and overnight lows dipping to single digits and below zero. So, plan on this snow sticking around through the end of the month.