Carvers Gap

It is possible we could get downsloped west of 75 and 81. It happens with big coastal storms but the opposite side of the valley. I would be really surprised if anything slowed this front down. I have been monitoring web cams on the front range today. Even the folks in those areas are impressed.

Can anyone tell if there would be lightning w those bands just east of Nashville on the GFS 18z?

Just eyeballing, the Happy Hour run of the GFS looks a bit more robust mid-state.

Wow, that is a big analog. It does look like a reloading pattern. The 12z CFSv2 has that. I really like 10-11 as my analog. If I had a wishful analog....raindance would be it. I was thinking today that maybe this wasn't our only bout of sever cold this winter w/ so much HL blocking showing up. Many forget that some of these really cold winters had very warm interludes.

If many get an inch or two of snow.....you get them both. Honestly, with as wild as this is about to get(tropical storm force winds and sharp temp drop)....the thread will deliver.

12z Euro trended south. Nice hit from the Plateau westward and north of I-40.

Sheridan, WY...I am noticing many roads in Wyoming are getting closed as we speak.

The 12z CMC has the clipper after the front this weekend.

@Holston_River_Rambler @jaxjagman I though this was pretty interesting.

I always forget to look at the SOI. Let us know when the thing drops, especially if sharply...big storm signal if so.

Good point. Yeah, this is tropical storm force winds followed by bitterly cold temps.

Kind of sneaky, but ZR is now showing up for tomorrow AM in eastern Sullivan, Unicoi, eastern Washington, and Johnson counties of TN. SW VA also has some showing up as well. It isn't anything huge, but might be a pain in the you know what to drive on ~0.03 to 0.1. edit: W NC is also showing this and probably has the highest likelihood of problems.

Here is another page from that site. I really hope that data is made a pay site. Easily is my top historical site for climate data. https://psl.noaa.gov/data/usclimdivs/correlation/long.html

The reanalysis page which I use has this message: Default climatology has been changed to 1991-2020 That site might be a good place to start as you can toggle the base period norms: https://psl.noaa.gov/data/usclimdivs/

10-11 was a great winter. This winter is so far running quite parallel to that one.

'14-15 is the snowiest I have ever seen my area of the TRI - and that includes some great winters of the 80s and 90s. From mid January to the end of February it just snowed and snowed. There were school systems with had 10+ days banked which ran out of days, and these weren't systems which just called out at the drop of a hat. I think that is one winter where my area was actually snowier than John's.

Larry Cosgrove has had a pretty hot hand of late...These are his recent comments. He is a great follow on social media. Over the past five days, the various numerical forecast models have gone crazy with predictions of warming across the entire continent. I follow the more conservative GGEM ensemble run, since that is the only series that acknowledges the possible impact of a major storm undercutting a ridge in Nunavut AR. If you accept the idea of the January Thaw coming early, then a harsh winter weather pattern will return in the middle of next month.

I was thinking about this as well. I think the wind chills make this unique and maybe the overall coverage of the cold. We actually have a shot to break some record lows and probably record high mins, especially in Chattanooga and TYS. I think it was 2018(December) when the North Fork of the Holston froze here. Likely, they are talking about the air mass in general as Montana may well set the hp record for North America. But certainly you are correct in saying we have had bouts of severe cold of late, especially December. This "might" be a tier colder though. Excellent catch as usual.

Just a wee bit of variability....6z CFSv2 run on left. I "thin" January starts warm. How long that lasts is TBD. I do hear some chatter that it might have some aspects of November embedded in the pattern. That would mean a period of warmth followed by cold. I am 50/50 on whether this is a 4-6 week complete pattern change(see image on the right) or typical January thaw (end result see image on the left).

The power outage potential due to high winds is concerning. MRX reiterated this on social media a few hours ago.

MRX morning discussion.... Key Messages: 1. Extreme cold that has not been seen in this area for decades will build into the area on Thursday night and continue through Saturday. 2. Expected impacts from this extreme event will be gusty winds that may cause power outages, potentially hazardous road conditions from snow/ice, and dangerous wind chills. The arrival of an extremely cold air mass continues to be the big story for this period. From 00Z Fri to 12Z Fri, most of the area will see around a 30-40 degree drop in temperatures. The cold front will move through quickly, from around midnight to 4 AM, and dry air aloft builds in a few hours after surface fropa. So there will only be a small window when there will be potential for snow accumulation, which appears to be from 06Z to 12Z. For the most part, the SREF and NBM members have mostly settled on snow amounts from about a quarter inch to one inch for the Valley, with up to 2 inches in the higher elevations and SW VA, and the forecast amounts will fall in this range. Outside of some light snow showers or flurries adding a tenth or so in the mountains and SW VA, accumulating snowfall will mostly end by 12Z. As we have been emphasizing the past few days, despite the light snow amounts, travel in the area may be impacted by the rapid drop in temperatures causing any moisture on roads to quickly freeze. Icy road conditions may persist through Friday and potentially through Saturday as well, since max temperatures will be in the teens and 20s. With the frontal passage will come a sharp increase in winds, with sustained winds expected to be in the 15-30 mph range with gusts in the 40s, and near 50 mph in the mountains. A concern with these winds will be the potential for downed trees and power lines leading to power outages when temperatures will be getting extremely cold. Wind chill values on Friday will be below zero for the entire area through Friday and Friday night, and -15 to -25 in the mountains, Cumberland Plateau, and SW VA. Therefore, a Wind Chill Watch will be issued for the entire area from 09Z Fri through 18Z Sat. The TN Valley may end up in a Wind Chill Advisory, but at this point, will have a blanket Watch and let later shifts divide it by topography for an Advisory/Warning. Bottom line, this will be an impactful, extreme cold event that has not been seen in this area for decades. The rest of the forecast period will be dry with a gradual warming trend.

The global ensembles overnight are singing the same song....The Hudson Bay block sags a bit too far south to help at all. At 0z and 6z, I don't see any remarkable cool downs. Again, normal temps will get it done, and it may be a struggle to get those. All of that said, we are ten days from January....LONG way to go.

The 18z GEFS seems to have made a significant move to the 12z CMC at 500mb for the second week of January.

Yeah, it's rare air. I know everyone likes snow, but to get to witness this type of extreme in December is something we don't see every season. I looked at Cut Banks' wind chills and they are showing -50F.

I looked at Sheridan, WY, and they have wind chills head to -40. But -40 on the thermometer w/ wind chills is gonna get crazy.