Carvers Gap

This is what I look at when I am looking at modeling in the long range... Image 1: Euro Weeklies Control 30d 500map...What could go wrong, but what I don't think will happen. Referring to previous winters and not this set of model runs....the trough tucks out west after several dozen runs on LR ext modeling of it being in the East. There is precedent or that during past winters. Basically, we have followed severe cold for weeks on the weeklies, and at the last minute it dives west of the Rockies. Again, I don't see that right now and the ensemble for the same model doesn't depict that at this time. Image2: Euro Weeklies ensembles 30d 500map....Looks about right. EPO ridge dominates and then retrogrades westward. How far it retrogrades to the West will be a big factor in how long it stays cold here. Image 3: GEFS ext 30d 500map....Please note it doesn't go out as far as the Euro, but still....not bad. Image 4: That is the CFSv2 from this morning for December, January, and March. It probably is dealing with a bit of feedback - meaning keeping the trough in the East too long. However, some of the analogs in my winter forecast have exactly that, so I can't discount that. Big EPO ridge during Dec-Jan. NAO pops in Feb. I noticed Cosgrove mentioned that his winter forecast has been cooled down a bit to reflect the early pattern of winter and more cold intrusions than originally thought. Right now, January is(and has been) a bit of a mystery for me. What we are seeing could just be classic Nina climatology even though we aren't at Nina thresholds. We could still(and I think we are) seeing Nina climatology reflected at the North American surface as evidenced by the warm fall and flip to cold during late November. If the CFSv2 is even half right, we take that and run. If Nina climatology is in play, we should see LR ext modeling warm for much of the rest of winter. Remember, LR ext modeling had December as warm before it flipped cold...Nina climatology won out. That said, and I sound like a broken record, there are two very different paths in analog packages for January. Either fits climatology. That sounds like a cop out, but that is the lay of the land. I still tend to think Jan-Feb are going to be warm. But if you look at my winter forecast ideas, I noted that January is sketchy and that gave me pause for that month. I have two sets of analogs built or that month, and they are very, very different. Even Mark Reynolds on the WJHL11 winter forecast noted that there are two different analog packages for Nina winters. If this goes to a weak La Nina, that is a significant development towards having a colder winter forecast than I have listed. Technically, I can still change my seasonal forecast as it isn't meteorological winter. However, I generally go with the idea that first ideas are often correct, and only change if certain you are wrong. What I think I potentially have correct is that the pattern would flip cold during late November, and that winter starts cold for December.....So, that is tough for me to change since those ideas "seem" correct so far. To be fair, December hasn't occurred, and there are no certainties in weather forecasting at this range. But those cold looks for January could flip warm IF the warm set of analogs turns out to be right. My lean towards a warm Jan-Feb is diminishing though with each passing day. Part of me wonders if the base pattern is the trough in the East??? That said, you can see the SER fight the cold over the southeast, so I think the SER will be a player. More later.

The ensembles have a very cold pattern to start December. We are going to see a lot of variation in modeling. Last night's snow was lost between d7-10, and then very slowly came back on modeling. I don't see a ton of snow on modeling this morning, but let's see how this begins to looks as it gets into range. A rough window is November 30-Dec14. Big questions after that whose answers mighta allow us to squeeze a couple more weeks of less extreme cold out of that pattern. One warning(and I don't see this yet...if anything quite the opposite), sometimes modeling will be too quick in bringing the strongest cold. Right now, ensembles are about as robust as one can get at 500.

The 18z GFS was straight cold. Winter is here. There will be some brief warmer interludes...but looks like it is going to be cold for a bit, especially centered around the first week or two of December.

Pretty steady snow in KPT. Looks like Morristown is getting the best of it. Any reports from down that way?

Snowing at Boones Creek near JC.

The 12z ensembles are still very cold. There are days twenty degrees below normal embedded. No single storm has been zeroed in upon. If anything, modeling is a bit colder and drier today. I have a feeling we see frozen precip though. Patterns looks really good. Lots of virga IMBY at the moment. Wind is cranking and it is appropriately cold for late November unlike the endless summer which has thankfully and abruptly left us until another year!

Probably one more question as the 6z GFS has this scenario... 5. How long (if at all) does the SER keep the extreme cold at bay? This reminds me a lot of the setup which led to the historic middle and west TN (and also MS, western KY, eastern Arkansas, maybe Mizzou?) overrunning event a few years back. I tend to think the cold gets to the East Coast even if a bit modified. The source regions for this cold are cold. This isn't Pacific air. I wouldn't even call it Canadian origin. This is from up top.

The 6z GEFS ensemble is about as cold as one can get at this range. Some questions that I don't have the answer to regarding this cold air intrusion... 1. Duration of the event? Best guess is very late November into mid-December, and maybe right up to the week prior to Christmas. Then we see a thaw o sorts. 2. Does the pattern reload with more than one cold air mass or is this just a 7-10 day cold shot, and then done ? 3. How much frozen precip falls? There is certainly an active precip pattern predicted. I think the risk of an overrunning event for middle and west TN is increasing. However, an ana front like we saw at Christmas(but not Christmas this time) a few years ago is probably also on the table. 4. Does winter return(if it arrives) after December? Big question w/ lots of differing opinions. With the ENSO forecast busting badly, I think that will cause some unseen downstream forecast problems, especially in LR ext modeling(as it continues to change in order to handle the new SST data). The climatology changes IMHO if this is a very weak Nina. My original winter forecast....climatology might not apply. Weak Nina climatology argues for a mid-winter thaw, and then more snow and cold later in January and early Feb. For now, I remain cautiously optimistic(if one can say that given the human suffering left by Helene) that winter is on its way, and that some in the forum area will see wintry precip. This season I do pause a bit with the celebration of the return of winter. I know folks in the mountains are in a tremendously bad spot - roads, homes, heating sources still being put into place. The good thing lately is that it has been dry, but extreme cold would add insult to injury. Hopefully responding agencies are looking at longterm forecasts for December, and are moving heat sources into place. Those warm interludes between cold shots would definitely be helpful. So, if it gets warm at times during the winter....it is probably appreciated by those impacted by Helene. Mountain people are tough though. They have lived through severe cold before. On a final note, I know JB talks a lot about late season hurricanes being correlated to December cold...that looks to possibly verify. Some of the cold showing up on modeling would be cold even in the middle of winter.

Surface pressure (Euro Weeklies ext) is very much EPO driven. Cold goes down the front range and spread quickly eastward. The only thing to watch is if modeling tucks that trough under the EPO ridge into the Mountain West. That means cold would come down the west slopes of the Rockies. However, I feel given the time of year that the cold will drain down the front range and race eastward. This is a cold and storm pattern. Precip is normal to above for the forum area during December. This would allow for a January thaw and potentially winter returning later in January. It is a good thing that we are seeing this in November as the winter will often repeat November patterns. This is a 30 day map! That is Alaska cold with a great mechanism to get it south eastward.

This is pretty cold for a 7-day ensemble at range. That means reality could be much colder. Almost 20 degrees below normal at this range is a big number. Now, this could change, and we have seen these looks evaporate or just be a 7-10 days too early. Something to watch, but super impressive. That is an overrunning look if I have ever seen one. Somewhere between I-40 to the Ohio River looks like it could be the track.

Modeling could be a bit too quick, but they generally are showing a very cold regime Dec 1-7 at least.

Good catch. I was thinking this setup is purely PAC driven. That being crazy cold to this area. The 18z ensembles generally supports that look. Edit: Sorry, I though that was the 18z GFS which John notes (Below) is powerful.

@PowellVolz, all right man. Time to jump in!

The 12z Euro AI is just ridiculously cold for day 10-16.

Ladies and Gentlemen, here we go...from MRX this evening. Modeling nailed this from a ways out. That is good, but modeling has more on the table after this. Key Messages: 1. Gusty winds expected across the higher elevations of the southern Appalachian Mountains Wednesday through Saturday. Gusts from 30 to 40 mph will be common. 2. Breezy winds in the lower elevations across the valley Wednesday through Friday. Gusts from 20 to 30 mph will be common. 3. Wind chills in the 30s and 40s for valley locations Thursday and Friday during the day. Wind chills in the teens for the higher elevations of the southern Appalachian Mountains. 4. Light snow accumulations likely across the northeast TN and southwest VA mountains. Amounts of 1 to 2 inches are expected. Isolated 3"+ amounts are probable.. 5. A return to normal temperatures by Sunday. Discussion: Active weather for the back half of the work week, with a shock to the system as we transition fairly quickly from shorts weather to parka weather. Well see a quick-moving weather system passing through the Ohio River Valley to kick things off. Expect the system will move in Wednesday night into Thursday night, bringing with it a blast of colder air as it moves south. Because of this setup, were looking at some light snowfall in our area from Thursday night through Saturday morning. As the weekend progresses, this system will move out and high pressure will start to build back in, bringing temperatures back to normal by Sunday. Snow: Were in for some of our first snowy weather in our higher elevations, and we might even see a few flakes overnight in the valleys of northeast Tennessee and southwest Virginia. The big question is how much moisture well actually get. Right now, it seems like we can expect around 1 to 2 inches of snow in the mountains of northeast Tennessee and southwest Virginia, with some spots possibly getting up to 3 inches. Theres about a 50-75% chance of seeing those higher amounts in isolated areas when looking at probabilistic guidance. Further south, places like Newfound Gap and Mt Leconte are looking at around 0.5 inches of snow due to less moisture. For now, were sticking with these snowfall estimates, but theres still some uncertainty. The actual snowfall could vary quite a bit, from 3 to 5 inches, depending on how much moisture we end up getting and the exact position and strength of the low pressure system to our northeast. Some of the high resolution models are indicating we could see some enhanced moisture off the Great Lakes, which can really increase snow amounts in a narrow area...But just as likely is the low shifts 30 miles to the north and much of the moisture stays across Kentucky and West Virginia. Also complicating the forecast is how warm the ground will be early this week leading into the snowfall which could melt much of it upon contact. Wind: On Wednesday, were looking at some pretty gusty winds as a weather system moves through. Expect winds of 30 to 40 mph across the higher elevations in eastern TN, southwest NC, and southwest VA. As we move into Wednesday night through Saturday morning, those strong west to northwest winds will stick around, keeping the gusts going at 30 to 40 mph in the mountains, with some spots possibly hitting up to 45 mph. It still appears we will remain below High Wind Warning criteria, but a Wind Advisory is still very much in play. On Thursday and Friday afternoons, as the winds mix down to the surface, we`ll also see breezy conditions in the valley areas, with wind gusts from 20 to 30 mph being pretty common. By Saturday, the winds will start to calm down as the weather system moves out to the east. Temperatures: After the cold front moves through on Thursday and Friday, its going to feel a lot more like January. Daytime highs will be chilly, and with the breezy winds, it`ll feel like its in the low to mid-30s for most of the area. In the higher elevations, wind chills will dip into the teens. Keep in mind, these are daytime wind chills, not overnight temperatures. While these wind chills arent out of the ordinary for us, they`ll definitely be a bit of a shock given the recent warm spell. If youre planning to spend time outside, make sure to dress warmly and be prepared for the cold especially the kiddos waiting for the bus in the morning on Thursday and Friday!

Saddle up! Here we go!!! The Weeklies ext(Euro) have the Christmas warm-up, but then they move back to seasonal which is plenty good during early January. I lean warm for winter overall with a cold start. That said, the weaker this ENSO gets....the more we are dealing with an SST forecasting bust which is in progress. If this goes Nada...probably still warm. But....... a weak La Nina has to be accounted for in terms of cold intrusions. It also brings a new set of analogs into play if one uses analogs. I guess what I am saying is that my original forecast is probably busted right now as we speak. If it was Monopoly, I would say, "Bank error in your favor. Go collect $200." This first cold shot could be a one-off. That has certainly been the case for the last few Nina winters....cold until Christmas and then torch. However, in middle and western areas of the forum, winter returned during a couple of winters to historic levels. What I like looking at LR forecasting: -Sometimes we can't get it to snow at all when the cold comes around. In LR modeling, snow is accompanying the cold at varying latitudes east of the MS. -The late landfalling hurricanes do have some correlation to wild winters here. -We haven't had any early season snowfalls...seems to be the kiss of death for bad winters IMBY. -There is cold in North America.\ -I tend to think the EPO is going to be the driver through the first half of winter w/ warm (maybe very warm) interludes. I did NOT think that several weeks ago. However, I think winter is showing a bit of its hand. -If I was going to re-write my winter forecast, it would be similar. HOWEVER, I think winter returns during January. -I have been super uneasy(and have stated that) about this winter. We may struggle to get to La Nina status. Why is that important here? The SER will have trouble holding all winter IMHO. A moderate or strong La Nina? Get out the Bermuda shorts and don't put away the lawn mower. A weak La Nina? Wicked cold to the Apps and beyond w/ maybe even some Piedmont ice/snow. -Bottom line....climatology for weak La Ninas in this area is IMHO the best, single predictor of cold winters here. I will take that ENSO state over all others. And that gives me great, great pause. I still lean warm for winter, but Mother Nature could yank that carpet out at any time. What I don't like: PDO MJO tendencies towards warm phases(but this winter could be one of those that bucks the trend....if my suspicion about the EPO as the driver is correct....the EPO trumps the entire pattern) The cold is just a bit early. I like cold to show up just before or after Christmas. Analog in play: 95-96....Cold came in waves, and snow moved along that boundary at times during the winter. Today's 8-14 analogs: John and Boone can fish the info out of these. I think there are some decent ones in there... 19891217 19561202 19511211 19551214 19761203 20081205 19631213 19611210 19641121 20001207 One last note: The ingredients are there for an early season snowstorm, and maybe more than one. No guarantees, but that is wild given how warm it has been.

Yeah, man! I had it in the queue for you or John or holston. AMZ definitely brings the cold when he starts a thread. December is gonna be a cold thread. Take it to the bank now.

I just want summer to be over before met winter starts!!! LOL.

I was thinking that looked like the strat was getting hammered pretty good. Two lobes at 30mb and 50mb around this timeframe. I don't know if I would call it a split, but definitely looks dislodged. Reading in the MA....I would add to their discussion and say that active Pac jet may be the cause of it.

This is what I am looking at. It was there at 12z, but not this crazy. The 18z GEFS has it as well. The GFS has an uncanny ability of spotting early season cold. I am NOT saying this is going to happen, but it is worth noting even at this range. Just a few snippets from 18z.

That high gets to 1065 I think near the Yukon.

The thing I like, and it is in fantasy land...is that big 1055 high late in the run. When we see those in December, that is a good sign if it verifies. Big highs in Montana will often find their way here as long as they are on the east slopes.

Happy hour, baby!!!!

Flow is fast, but we can score with that setup on the 12z GFS and CMC. I am not talking about one particular event, just the general setup. That is a good setup for John and folks in NE TN, SE KY, and SW VA. I am halfway eyeballing a weak overrunning event as well, especially for middle and western areas. That look is a shallow trough with the area of confluence around the KY/TN border....and kind of offset eastward just a bit. That allows for the low left section of the trough to be attacked by return flow. Potential is there. 12z GFS is honking later in that run.