Carvers Gap

Watching this baby trend south again on the 18z GFS, that makes me happy to be on the Southside of this system for once.

The RGEM has a healthy system, AND it doesn't even have the second NW flow system accounted for in accumulations. That little system is still inbound.

MRX....afternoon disco. Wednesday into Thursday will be the time frame to keep an eye on as the surface low with this system tracks near the Gulf coast, so the southern Appalachian area will be on the cold side of the system with respect to winter precipitation. If the general model consensus pans out and the precipitation moves in during the day on Wednesday the main forecast difficulty will be determining which type of precipitation will fall. Based on forecast soundings the mid to lower levels of the atmosphere will be very cold, being supportive of snow with very cold temps around 850mb. HOWEVER if the snow does occur during the daytime many times in these scenarios the sun is able to offset some of the heavier snow intensities. And at the same time, based on the track of the surface low we`ll likely start seeing downsloping winds coming off of the Appalachians across the eastern side of the Valley. So all of this will combine to make a tricky forecast for snowfall totals, as a slight change of a few degrees anywhere within the bottom few thousand feet of the atmosphere will have dramatic affects on precipitation type and potential snow accumulations. As of right now, probabilistic guidance shows that the valley has the most likely chance to see 0.5- 3 inches of snow, with higher amounts possible along the Cumberland Plateau and in the southern Appalchians. Once this event gets closer and higher resolution models are able to get a hold of this time frame we should be able to narrow down the accumulation window. Thursday will see most of the precipitation clear out of the region with the typical northwest flow light flurries lingering in the area in the very cold temperatures Wednesday night through Thursday night. We`re not expecting really anywhere to climb above freezing for about 36 hours Wednesday night through Friday morning.

The 18z ICON, as John noted looks good. It looks reasonable. It also continued the trend of pushing the heavier snow axis toward the northern TN border.

If it creeps back north, it usually means the high was over modeled(in that particular scenario), OR it verified north of original guidance which I think is the most common problem. Often modeling will overdo how far south the cold air actually gets. Occasionally, it will under model very cold air as Arctic air is nearer the surface, and slides under 500 modeling. And then of course sometimes it is just timing here in the subtropics where the base state mostly rain.

Yes. Modeling has been slowly creeping south during the last 36 hours. We should be locked in by tomorrow morning one way or another.

La Nina's don't offer up many Miller As. During La Ninas, we often depend on NW flow(and sliders) which we didn't get this year during the cold shot. We need a very weak El Nino (without La Nina characteristics like the recent one) for that. We have been in a La Nina base state of late.

I will echo that. Feel better, Matthew. It has been a LONG cold and flu season and flu B is now starting to show up.

I don't see that on any deterministic or ensembles. Maybe TWC is using an in-house model. It could happen as it is still way out there. Right now next weekend looks really cold.

February systems are notorious (infamous?) for under modeling precip amounts. One caveat as maybe Holston mentioned overnight, we are seeing some convection along the GOA. That will cause the spigot to be shut off. I think we are seeing variations of that in modeling. IF that convection wasn't there, we could see much more snow. That might actually be a nowcast once the event starts.

Today or next week?

The 12z GEPS has more snow than its deterministic run. With us still being 3 days out, there is room for this to get stronger - plenty of room

The 12z Euro has less snow accumulation over E TN which has been a trend. Again, I think the Euro has been on the low side of modeling this winter. BTW, the WxBell clown map is in for almost the entire run while the 6 hr precip output map is lagging way behind. Again, I am riding w/ the GFS on this one. It has locked in pretty good.

The 6z Euro AIFS has another slider on Sunday....decently robust.

The GFS has more snow. Given that it is February, that makes more sense. The GDPS is a really a two part event - a slider and then upslope. Both almost get the same point on Kuchera snow maps, but....you gotta include the upslope even that slams into the area on very cold winds. With ratios likely being high for the upslope event...wouldn't surprise me if the upslope produces better than the actual storm.

Significant upticks for NE TN on the 12z GDPS. NE TN, which has been on the short end of the stick for the past few winters, is being depicted with a solid 4-6" of snow. We take that all day long. The 12z GFS is a healthy event.

For E TN, it is REALLY important to get the piece of energy which crashes into the back of this. If you cut off the accumulation maps right after the storm passes, it is missing the northwest flow event which follows immediately after.

12z GFS is a solid 4-6" for NE TN. The NAM is not in range. It is going to be crazy jacked up which is why it has a Miller B. I think the GFS has it in its wheelhouse now. It is not budging from run to run. The Euro has tended to be a bit to weak on precip this winter.

It looks bad. Scannerfood is posting some crazy images on FB. I hate you all are having to deal with this, man. Stay safe.

18z GFS looks good.

TT has rain in E TN but gets the same heavy snowfall maps as WxBell?

Heads up. Pivot/Wx Bell look completely different than Tropical Tidbits......like "not even looking at the same storm" different. The WxBell GFS run looks awesome as does the Pivotal run. But the TT run is a rainer. Head scratcher!

Foothills peeps are gonna like the 12z GFS.

The clown maps on wxbell again do not match the surface maps which precede it. Head scratcher. The surface maps are absolutely ripping.

12z GFS is a pretty big run.