The South Trend is On
I mentioned yesterday that the timing of the cold front swinging through the area was going to be huge in determining who saw how much snow. The early Saturday morning model runs have really sped up the surge of cold air coming into the region Monday morning. Below shows how drastic this change has been. Both of the images are the 2 meter temperatures for Monday morning at 7am. On the left is the early 6z run from Friday morning of the gfs, while the right is the early Saturday morning 00z gfs run.
You can see the 32 degree surface temperature line is a good 100 miles further south on the latest run than what we were seeing earlier on Friday. It looks like the models are picking up that the arctic air mass moving in behind the front is going to be stronger. With a more vigorous high pressure pushing into the upper midwest, the front is forces to sink further south quicker. To varying degrees, most other model guidance (euro, euro ensemble mean, gfs ensemble mean, canadian, ukmet) are all also on board with this. The two exceptions have been the NAM and SREF, but we're still outside their good ranges (inside 48 hours). Without focusing on exact numbers (I do think these are overdone), check out the snowfall maps below from the Euro 2 days ago on the left vs the current Euro run on the right. The axis of heaviest snow has shifted a good 150-200 miles because of how south the cold front gets.
The keys here will be:1) how quickly the cold front pushes through
2) how much moisture is leftover behind the front
Saturday mid-day 12z models continued the colder trend, with the NAM finally joining the party. Below is my 2nd Call Map. I believe the Euro/Nam totals are a bit too high and are struggling with how fast the change over to snow occurs. Leaning more towards a Canadian/British model blend. Final Call will be out Sunday afternoon.
It's also worth noting that after the front clears the area and this storm moves out, temperatures Monday night are going to get very cold. We may break some daily record lows in some areas. Here's the gfs (left) and nam (right) temperatures for 7am Tuesday morning. It's looking like we'll see widespread teens and single digits, with some higher elevations likely going below zero.