December 2025 Short/Medium Range Forecast Thread

[John1122]

I suspect it's going to collapse at some point, but the RAP just gave me 4 inches. Sharp cutoff south of about 15 miles north of 40.

[Carvers Gap]

With the axis of this narrow strip of snow, small upstream changes create HUGE downstream changes.  Think of it like this.  When a hurricane is approaching the coast at an angle, any upstream change drastically changes the landfall location.  This snow axis fluctuates with almost every run.  The current 12z GFS is a good lollipop for TRI.  The 14z HRRR is north of its past run and TRI is blank.  I think time of day is going to be huge.   I think likely that some in the forum area will see a stripe of frozen precip along the northwest boundary of this.  Where?  Your guess is as good as mine.  But a line from Nashville to Abingdon, VA, seems about right.  Anyone 30 miles to the south of that and 150 miles north of that is fair game.

[Carvers Gap]

2 minutes ago, John1122 said:

I suspect it's going to collapse at some point, but the RAP just gave me 4 inches. Sharp cutoff south of about 15 miles north of 40.

FWIW, that axis looks about right w/ TRI maybe being a sloppy mess.  

[Scottie16]

So snow in the tn valley is basically a crapshoot at the moment?
I've been trying to educate myself on what makes this particular area so difficult to forecast, it's really fascinating to me.

What I like to do is look on wunderground at the different weather stations throughout the valley. It usually is a good indicator on where the rain/snow line could setup during nowcasting.


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[John1122]

The 14z HRRR was very similar to the RAP.

[John1122]

The 15z axis is slightly north but bullseyes the Nashville area.