Holston_River_Rambler

Key parts of their rationale for accums: If this precipitation moves in earlier in the morning we`ll likely see more accumulating snow before sunrise, but if it holds off even just a couple of hours and doesn`t start to precipitate in the southern Appalachians until after sunrise, then chances for accumulating snow really decreases. Once the sun comes up and starts to impact the cloud layer history indicates that snow occurring during the daytime, in the later parts of winter with the higher sun angle, and when temperatures are around or just above freezing... It can lead to much slower snow accumulations. In addition there could possibly be some downsloping flow which warms up the atmosphere and eats into the QPF totals. With temperatures expected to slowly climb through the day to above freezing for most of the Valley locations any precipitation that lasts into the afternoon hours will have a decent chance of flipping over to cold rain, which would also help wash away some of the snow that might have accumulated earlier in the day. At this time the most likely scenario is to see advisory level snowfall for much of the Valley locations, with the lowest amounts in the south and along the foothills of the Appalachians. We could see 4+ inches in the higher elevations of the northern Cumberland Plateau and over into far southwest Virginia on Wednesday as they`ll have the snow begin the earliest and the coldest temperatures throughout the day.

Euro upped .qpf a tick again at 12z. Looked RGEMish.

But it is the NAM, so let's see how the rest of the runs go this PM.

Oh yeah, if we got a line of storms pumping moisture N/NE through the deep south rather than parallel to the coast that should help.

I liked that NAM run. It got the heavier precip further north from the Gulf: 12z. vs 6z

I think the hi resolution of the Euro is seeing (rightly or wrongly) more convection in the Gulf. The above is a gif of lightning flash density according to the 6z Euro. It's maxed out just south of Louisiana and the convection is parallel to the coast. The whole complex just pushes SE further into the Gulf. Like Carvers said I think this is kind of a watch and see radar deal now. I wish the RGEM had a similar parameter on weatherbell for comparison. Also, I think the convection is a nail in the coffin for anything more than a widespread 1-3" or 2-4", not necessarily a nail in the coffin for the whole event.

RGEM really likes the upper low/ TPV swinging in. It even has some FGEN over east TN: I wonder if that might turn into something like an arctic front with 20:1 ratios?

I think maybe if we just pretend this is and old fashioned I-40, 2-4" clipper, just forget the precip. to our south, we might not be too far off.

The more I looked at the 500-700mb relative humidity depicted on the Euro, I actually got a little bit more optimistic.

MRX notes the main mechanism for lift is being in the right entrance region of a jet and that looks pretty well set: The lagging jet initially over Montana and Wyoming in the gif above tries to help buckle it But there has to be some precipitable water/ relative humidity to lift. Most of our deeper, mid level moisture is west Pac moisture Some gulf moisture gets involved late, and I think there is some room for the Euro to improve here, but not much.

6z Euro looked a little less dry, but not by much. 4 run qpf trend

12z NAM goes full on Miller B with bit of lp running up through the foothills of the Apps.

AAAnnnddd it's snowing a little bit here now.

I think western areas probably are looking better than eastern ones.

Can't believe I'm saying this, but Im actually rooting for the NBM of the models I posted above.

Here are most of the 6z accumulation maps:

6z Euro looks like it might have some of the parallel convection too:

One thing I noticed with the 6z RGEM was convection parallel to the Gulf Coast. That's a fail mode we haven't dealt with in a while, so something to watch out for. I also think there is a bit of a transfer (like y'all mentioned overnight) in those frames too from FL panhandle to GA coast.

How's everybody holding up? We didn't have it to bad in my part of Morgan County, but I can definitely tell with daylight that there was some minor flooding near me last night, more than we had with any other part of the event.

rgem at the end of its run

This morning's WPC depiction has a low over New Orleans and a 1052 high in western ND near the Canadian border: you'd think that would work out pretty well.

Euro def seemed to tick colder with its 12z solution, from 6z. Just based on eyeballing thicknesses and precip types on weatherbell.

Even the NAVGEM jumped north. Usually it is the most suppressed.

6z Euro: Maybe a touch warmer with thermals than 0z 6z GFS: As noted overnight GFS doesn't have as much influence from the northern upper low. But the 6z seemed like it had a touch more.