Carvers Gap

Sure looks like the 18z has held back the energy on this run and sped up the energy flowing underneath. It probably won't get to 12z Euro levels, but that is a big step at 500.

@Mr Bob, @PowellVolzis locked out of his account again. If you can give him a hand, it would be hugely appreciated by Powell. Thank you!

MRX from this afternoon.... Ridging builds back in Thursday afternoon with warmer temperatures and quasi-zonal flow in the mid and upper levels of the atmosphere.. A more progressive trough will approach the Mississippi Valley by late Friday with an associated surface low pressure near the Great Lakes. A cold front will move eastward across the forecast area Friday night into Saturday morning with widespread showers and thunderstorms expected. A few rounds of shortwaves will strengthen the upper-level trough across the region Sunday night into Monday. Deterministic and ensemble members are in good agreement even this far out from the weekend. The LREF indicates about a 70+ percent chances of temperatures less than 32 degrees across the valley next Monday night, which is a fairly strong signal this far out for a widespread freeze. With northwest orographic flow and 850mb temperatures below 0C, some light snowfall will be possible for higher elevations above 4000 ft across the mountains. A significant return of cold air appears likely early to mid next week bringing an early taste of winter.

Noticeable trend southward on 12z ensembles. Something to watch, but it is a great example of why looking at 500 maps tells the story. IF(stress IF) that holds, somebody would likely get hammered by that. Definitely will be watching this for a few days. Huge grains of salt as climatology really doesn't support snow this early, but Fountain mentioned a great example above of this actually occurring. It is uncanny how close those maps look. I will be interested to see the trends. Also interesting, 2014-15 turned out to be a great winter. I bet the QBO dipped around then off the top of my head.

Compare that GFS ensemble sigma to the Euro operational at the same range....

@fountainguy97, that is uncanny. The 12z Euro drops 16" over the same high elevations spots as it did in 2014. Good find.

Hmmm. Well....

Looks to me like the GFS and CMC at 12z are quicker w/ the energy over the GL. The Euro slows it down and drops it into the backside of the trough. That might be an error by that model as it tends to hold energy back. I'd feel better if the GFS had it. I need to check the ensembles. But...if that were legit, that is a lot of energy to crank to our SE. The sigma maps on Weatherbell are impressive at 500 for the Euro operational.

Not many other models are showing this much development, but man....that will leave a mark. Partial phase, but doesn't get neutral in time for us. There are some nice upslope snows for those in the best spots.

We really need to start looking at a way to archive these threads and save them as an online library. It would be a huge loss to lose these. This forum is probably the best library of weather events dating back to 2014 for the Tenn Valley.

Fountain, if you go to the Oct 24th or 25th(2014 thread above) post by @tnweathernut, there is some good discussion by John, 1234, and tnweathernut. I have no idea what I was doing during that timeframe! I didn't post until a bit closer to the event which is unusual. Anyway, 1234 posted some maps of the event from about a week out. That was a fun one to track. Pretty sure there was snow in the Williams-Bryce Stadium stands in Columbia, SC, for that game.

Here are our threads: Tennessee fans had trouble getting to the game in South Carolina. This was part of a string of early season snows around that time frame. Pretty sure we were the bullseye, and it shifts SE. There are some good maps and discussion in our threads. The Capitol Weather Gang has some maps as well. Indeed, there are some photos of Erwin in our observations thread. Crazy storm.

https://www.washingtonpost.com/news/capital-weather-gang/wp/2014/11/01/incredible-early-season-snow-slams-the-southeast-impacts-felt-across-eastern-u-s/

Haha, no idea! That's hilarious. I figured it was you.

This is 10mb at the end of the GEFS weeklies. Due to the 2-3 week lag, that would imply that sometime later in December and into January that there is a possibility of very cold air draining into NA provided it doesn't go to Asia which has higher odds.

Of note, the Euro weeklies don't have strat maps, but the GEFS weeklies do. While I am not expert in SSWs or just warmings which cause slight displacements....it sure looks like the SPV slides into Canada w/ some extension into the lower 48.

@GaWx, one thing I did notice regarding the SSW discussion you all are having. Anytime we see an EC ridge hook into AN heights over Greenland, I have observed the stratosphere get hammered. I actually tried looking at the Weeklies for strat anomalies, but wxbell doesn't have it I don't "think." I tried looking due to the ridge that is forecast to roll through mid November. If it connects into those heights in Greenland....that is when I notice SSWs occur. I notice it also when a WAR does the same. That would completely shakeup up LR ext modeling if it occurs partially or in full. Great disco. I will drop a link below. Great discussion... @Daniel Boone

@GaWxgot a mention on JB's blog today. Awesome stuff. It is regarding the 50mb PV displacement which is much earlier than normal.

The interesting thing is that JB's analogs show a warm December and a cold last 1/3 of winter. The CFSv2, which changes daily, shows the same thing this morning and has waffled between a cold Dec and Feb since I posted the above. I lean towards a cold start to December, but how long that cold lasts in December is up for grabs. The Euro weeklies, if they can be trusted during shoulder season, show a retrograding PNA/EPO ridge which (by the end of the run) is trying to get into the Aleutians. Looks like we have a window of about 1-2 weeks to start winter, and then TBD.

Just looking at this afternoon's Euro Weeklies.... 1. Still looks like a warm up mid month followed by winter after Thanksgiving. December 1-15 looks like a good window for cold. 2. Fly in the ointment is a little belly ridge over Texas which might try to shunt systems to our north. 3. The control run is very aggressive. 4. The Euro will often(sometimes woefully) under model eastern cold at range. It is shoulder season, and it could still be badly wrong. 5. American LR ext modeling (Euro Weeklies equivalent) will be cold on some runs for December and at other times....hook a mid continent trough into the NAO. We really might not want a -NAO in December. Still too early in the season to be a true playa IMHO. 6. Overall, I still like a cold start to December which is followed by a warm-up. That fits the pattern of recent winters. Cosgrove's "late start" to winter idea is supported by this morning's GFS seasonals. I still think it gets cold early, warms, and then is a crap shoot. I tend to favor a return to winter after mid-late January. That second cold shot often favors western areas of our forum. This year, due to the QBO, I think the cold manages to get to the spine of the Apps.

Haha. Wow. Yeah, that definitely looks like a default mode on the model. Nearly identical. It may be right, and we are due El Nino conditions...but that looks identical to a level that if two middle schoolers both had that on a test which required prediction, they would be busted for cheating. Good catch.

Computer modeling is so good right now that I almost feel more confident in the weeklies 500 pattern between weeks 3-4 than the detailed look at d7-12 on operationals. Long wave pattern modeling has gotten really good. But that said, I have been burned more times than I can count by a shoulder season 500 look at range! BTW, I don't want people thinking I am walking things back this morning. I have only looked at 6z operationals...no seasonals or LR ext stuff. LOL

WAAAY out there, the new CANSIPS also has next summer at norma tempsl which implies an El Nino ENSO setup. MA mentioned a Modokai. I honestly didn't look at SSTs, but the NA weather pattern looks like it. Fall "should" be cool next year if so. I would call for a backloaded winter next winter as well if so....way too early to tell. Cansips evidently put out the exact same map (from last year at this time) for next fall. Kind of an embarrassed for that group. Don't think so? Go look at the post in the MA forum with the maps side by side. Completely disregard the above.

New CANSIPS is out on Tropical Tidbits(courtesy MA forum): https://www.tropicaltidbits.com/analysis/models/?model=cansips&region=namer&pkg=T2ma&runtime=2025110100&fh=2 Some decent changes. Also, check out the MA forum for Webbers comments about winter. Good stuff in their winter forum.

Absolutely take it. We are gonna get a thaw which lasts 3-4 weeks. Anytime we can grab 8 weeks of winter, we take it...even during our best winters IMBY. Plateau folks have longer stretches!