griteater

We say "it's a tough call" a lot, but the HRRR and latest NAMs suggest that this is a tough call for the GSP to CLT corridor. Conservative forecast would be to go with rain, with a chance for snow to mix in. The soundings suggest that when the precip is heavy, it could very well flip to snow (I looked at Simpsonville). There is a lot of discussion about the warm nose...but I wanted to point out that the warm bubble east of Atlanta over into the upstate is where there is a pocket of above freezing air in the lower levels of the atmosphere (cold air having a tough time moving in over the mtns). As precip falls and we go toward morning, the sounding shows cooling of this lower level warmth, down to where it could be cold enough for snow. This is different from what is traditionally referred to as a warm nose where warm air is pouring in aloft from the southeast at the 850-750mb levels. In that case, the sounding shows the warmth aloft 'nosing' above freezing as opposed to lower level warmth above freezing. Bottom line: having the above freezing warm layer closer to the ground is easier to overcome than warm air pouring in aloft from the southeast. The text below is the scenario we are looking for here. That is, the 850mb low isn't closed and strong with our storm tomorrow and the warm advection aloft is staying closer to the SE coast than it is pouring inland (source - http://www.wxonline.info/topics/preciptype.html ) "Melting of Snow to Rain" "Melting snow to rain requires latent heat. This heat is taken from the surrounding air. In order to obtain substantial temperature change due to melting, it is necessary to have rather heavy amounts of precipitation falling with little or no warm advection. If this occurs, you can have heavy rain turn to heavy snow as the freezing level sinks downward due to cooling by latent heat absorption. Although this situation can occur, cases of substantial lowering of the freezing level due to melting are relatively rare because the combination of heavy precicpitation without warm air advection is rare."

Birmingham is an area that struggles to get good setups for snow. Good chance IMO that you see some with this system with some light accumulations

I tell you what, my confidence is fairly high that Lake Toxaway is going to see a good wallop of snow from this....hoist the Winter Storm Warnings there Isohume!

You had it correct though...that's the 12z RGEM thru hr 48, then it kicks in with the CMC Global after 48hr

This is like an exact climo southeast snowstorm...why do we need to spend 80 hours a day looking at this stuff

You can throw the SC mtns in there with NC and GA mtns, ha...Caesar's Head

The Euro just locks the 35-37 degree type temperatures and dewpoints for the entire storm east of Atlanta to upstate to southern foothills to southern piedmont.....doesn't budge a millimeter

My own analysis of where the Euro is supportive of snow (without regard for the snow map or precip type algorithm on the model): 1AM Fri: Snow in GA and NC Mtns, and northern NC foothills 7 AM Fri: Snow just N and NW of ATL into SE TN, GA and NC Mtns, northern NC foothills 1PM Fri: Snow NW side of ATL metro into NW and N Central GA into SE TN, GA and NC Mtns, northern NC foothills 7PM Fri: Snow NW side of ATL metro, GA and NC Mtns, northern foothills, NW Triad 1AM Sat: Snow NW side of ATL metro, GA and NC Mtns, northern foothills, Hickory to NW Triad 7AM Sat: Snow N side of CLT to Hickory to Triad Just S and E of these areas, there could be some snow where precip bursts and cools the column...or rain/snow mix Having said all of that, I wouldn't be surprised to see the Euro a little warmer than this on the 00z run

For your area it has decent precip into Sat AM, winding down late morning / lunch

The Euro moved NW with precip...it now has 0.5-0.6 along the eastern Blue Ridge escarpment.

Here are the Charlotte surface observations from the Nov 2000 storm. It probably won't be this cold, but similar setup relying on precip to cool the lowest warm layer in the atmosphere http://mp1.met.psu.edu/~fxg1/NARR/2000/us1119.php

Looking at the isobars there, you can see how Alabama and Georgia have more northerly wind component trying to feed in cold air...whereas SC and central NC are struggling in that department

It looks a whole lot like tonight's CMC and GFS based on the early maps...more detailed maps come out later

As long as the system doesn't just collapse on the models, yeah, it usually nudges NW at the end. Had weaker model runs this aftn and evening, but we still have a storm

Well, this may put more folks east of the mtns in play for some flakes if temps cooperate (a big if)...regardless, there is usually a little NW nudge with these systems before go time

New UKMet looks like GFS/CMC

Storm wise, the CMC was very much in the GFS/Euro camp this run

GFS is actually a little flatter than 18z at 500mb

GFS out to 21 and I don't think it's going to budge....height field across the SE is an exact match and little change out west

ha, never sweat the NAM run...gotta see the globals

NAM out to 22 looks closer to 18z than the big 12z run

Thoughts: 1. My forecast map is based on where I think the models will end up, not where they necessarily are now. 2. I like a more amped up solution closer to the UKMet and CMC. Warmer. More precip back to the west, even more than shown - models are notorious for being skimpy with precip on the NW side with Miller A's. Also, jet structure (right entrance region of strong jet) is excellent for building precip back west. 3. I was mainly focused on NE GA / SC / NC on the map...didn't look hard at N GA into Bama or other states.

I dusted off the model performance thread to capture the difference here with GFS/Euro vs. CMC/UKMet https://www.americanwx.com/bb/topic/49398-southeast-winter-storm-threats-model-performance/?do=findComment&comment=4682114

It's kind of amazing how the Euro has fallen from how it used to be regarded

Euro is taking a baby step, but not a big one