Carvers Gap

Bout time for a Fall thread. It sure looks like the summer time pattern is starting to break down a bit early compared to recent years. Cold fronts could be getting further south than recent years if modeling is to be believed. And they are lined up one after another. I certainly don't think we have seen the last of the summer heat, but the sustained heat may well be over by Labor Day - ie weeks on end of high temps and humidity.

If you want a really good illustration of what happens when there is no gap in a mountain range, then the Bitterroot Valley is your huckleberry. Take some time and look at the annual snow totals for Hamilton and also at their winter temps. Then, look at Missoula's. Different worlds and only about 30mins apart. We nearly moved here, so I had done a lot of research about the valley. They used to grow apples in that valley. It is a true banana belt. The downlsope winds keep it warm for most of the winter. There are few ways for cold air masses to get south into the valley. Just of this area gets bitterly cold during winter. The eastern TN Valley is similar to this in many ways.

That also means the airport deals with downslope winds that Knoxville and western burbs don't see nearly as much.

I tend to lean towards the idea that AMO cycles flipped around 1990. We are due for it to reverse. As John noted last winter, there is some debate as to whether the AMO actually exists. I think the big change is that we finished a -AMO cycle during the late 1900s, and that greatly changed our weather in E TN. We also really need the -NAO in E TN to have decent shots at Nor'Easters. That is a different answer for the Plateau westward where the PDA/PNA ridge complex matters tremendously. There were some crazy strong El Nino's during the 90s. Right now we are in a pattern of La Ninas which I believe is driving the weather pattern here and placing the default NA trough over the Mountain West during many winters. Eventually, the pattern will change to something entirely different. La Nina is not great for the coast. It is weird, but TRI is kind of linked to DC's pattern. When it is snowy there, it is often snowy here. TRI generally does poorly in La Nada's and moderate to strong La Nina's. Strong El Ninos are torch city as well. We also have a wicked bad rain shadow here. Lately, downsloping over the eastern Foothills has been a problem. We are feast or famine up here. We generally do well w/ inland runners, sliders, NW flow, and a once in a decade setup where a low stalls/forms in the lee of the Apps. But trajectory of each system matters greatly. A slider with nearly perfect east-west trajectory is no good here. We need it to bend NE just a hair. The missing piece during recent winters are Alberta clippers. I believe the lack of clippers is probably directly correlated to the lowering snow totals. Joe Bastardi (who I like when he talks historical weather patterns) says that it snows where it wants to snow. During some winters, it just snows more here regardless of the pattern. He also notes there is a connection between late season cold and late hurricane action. One other JB note is that if a place has a rainy fall, that is generally where cold will try to setup. Those are fairly sound observations which have merit. Also as John notes, we generally hit big winters in cycles.

Oh, man. That isn't good. I have the same recollection of that year.

The PDO is not good. Extremes in, though, weather can wreck havoc. I remember some of those extremely -NAOs turned out to be terrible here. The NAO cycle right now appears to be trending towards more negative episode. I am gonna guess it fires early and holds off/on through January(beginning in late November). We are always fighting something. If it isn't the PDO, it is something else. However, during the last few winters we have found extreme cold making its way into the area despite a multitude of bad teleconnections. Until I see otherwise, I am riding the seasonal trend of cold early to mid winter. One of these days that extreme cold is gonna hit the atmospheric river over the TN Valley. I am gonna be here for that action Lord willing!!!!

Welcome aboard. I lived in Knoxville during all of the 70s. I had no idea how good that decade was at the time. During the 70s it often started snowing during late December and usually lasted into February quite consistently. Snow droughts weren't even really anything I thought about, though there were certainly some mild winters embedded during that decade. I also lived there during the 93 blizzard, the 93-94 winter, and 95-96 winter. The 90s did feature some snowless winters or nearly snowless in Knoxville. Those are easily the worst winters of my lifetime, but again, with some great winters embedded. Knoxville has done really well recently(2020s to clarify), even better than TRI during many winters. I do think that notch along the Plateau funnels precip into the Knoxville area - someone (maybe @TellicoWx) had a great post last winter about it. At TRI, we have no such relief...just a solid Plateau wall to our West. At first I was a bit skeptical that the Knoxville notch helped. But when out West, you can see where openings in the mountain ranges (which lie west to east) have higher snow totals. For example, Alpine(WY) is much snowier than Jackson(WY), but Alpine is at a lower elevation. However, Alpine sits right in one of those notches if you look on Google Earth. Places in Star Valley to the south have less say in Afton. Afton is at higher elevation - but no opening in the mountain for snow to reach it easily. So, long story short. I think Knoxville does really well during certain NW flow events(almost wnw flow events), during snow storms where the fetch is from the SE(but limited warm nose), and they do incredibly well with sliders. Sliders seem to be our best snow makers these days, and that would also explain TRI getting less snow during recent winters. I would say "for now" that 4-6" is about right for Knoxville, BUT recent trends definitely have Knoxville trending better. I would guess there are places in the Knoxville which are averaging 10+" during good winters recently. At one point during the 2010s and 2000s, I can remember on this forum where Knoxville would get very little compared to TRI. Recently, Knoxville has had two really big snows. I do think the sliders in conjunction w/ that notch where I-40 comes into town is the big contributor. Even during those 197-s winters as a kid, I knew the best snows usually went from Memphis to Knoxville. Still true today. I also think the 2020s and late 2010s cold shots, though short lived, have produced an environment where Knoxville kind of is in the sweet spot. Gulf moisture interact w/ the cold air from the North at about Knoxville's latitude. South of that, no luck. North of that, too cold. Again 4-6" is probably right as a generality, but I wouldn't be surprised for Knoxville to surpass that average during some(not all) of the upcoming winters if trends persist. I think this winter has a chance to be good for TYS. Here is a TRI note....The early 2000s didn't have a tone of snow here. As this century has progressed, small snows have become more frequent as have some the frequency of short-lived, brutal cold snaps. Big snows have been less. Why? I suspect moderate to strong La Ninas are the likely cause along w the aforementioned PDO by met85. We have had a load of La Ninas since 2016 or so. In NE TN we really need a weak ENSO state but not neutral and definitely not moderate to strong. As John notes, that is less a player as you head west and has less correlation from the Plateau westward. Though, I could make a pretty good case that middle and western Tenn have done decently well w/ the La Nina pattern. Interestingly, east Knoxville and the Foothills are probably is in the same boat as TRI. TYS during good winters: 8-10" (frequency of that about 1 out of every 2-3 years currently) w/ higher lollipops depending on local TYS during lousy winters 2-4" It just seems to want to snow in Knoxville of late. That is weird to say from a scientific standpoint, bit it is kinda true.

I have been sucked-in by La Nada before which is what the SSTs kind of look like. La Nada often looks great at the start, but lots and lots of swings and misses. That said, I have a hard time seeing lots of. misses w/ the Dec-Jan setup as depicted on this month's seasonal Euro. That is about as good as it gets. The fly in the ointment would be cold source and a ridge bellying underneath across the South. The Great Lakes region looks primed for cold. Can it get south of the Ohio River? We will see. I do agree the QBO should be good for this winter - such an odd metric to be so accurate. Honestly, it is a weak Nina in the eastern Pac and a weak Nino in the western Pac -> maybe that is the ticket which is the best of both worlds. That warmer western Pac might be enough to get convection into phase 8-1 during mid winter. It may well be that we see the NAO fire again as recent winters have seen it much more active in a good way. John might have better information about Nada's w his personal records in conjunction w/ the QBO. His data set is the only data set I truly trust for this region.

The Euro seasonal SST anomalies don't really line-up w the NA pattern. AN SSTs in the centiral IO imply convection which spreads into the Maritime Continent. @nrgjeff@Daniel Boone@Met1985@John1122@GaWx@Math/Met what is causing those big blocks over NA w/ the Pac and IO basins being meh? If I didn't tag you, please don't be offended. Feel free to jump right in. I know some folks from other forums might also have some input. If you don't have access to SST maps, I can post those.

Like the CANSIPS seasonals which were just released, the Euro seasonals show decent signals for HL blocking for Dec-Jan. That would fit nicely with a weak La Nina. No, I haven't checked SSTs yet for the Euro.

Wait, there is more....that would be a double block. Some zonal underneath, but that would very likely get the job done.

Yep. That will do it.

Record high min at TRI yesterday. One thing I have noticed is that the point-and-click forecasts have been way too high all summer(at range) for MBY. I had mid-upper 90s forecast for much of last week(early and middle). If I remember correctly, 93 was as high as it got. The Apple wx app has been more accurate.

A steady light rain is falling. Temps are cool. It is so surreal. It is like someone flipped a switch. Very thankful for the blessing of cooler weather.

Man, it feels freaking awesome outside. After weeks and weeks of serious humidity, it feels like fall out there. Winds are out of the north and it feels glorious.

The August CANSIPS is out. Normal to BN temps through December. AN temps Dec/Jan w/ a gradient type of cold centered over the Great Lakes. Feb is BN. There is definitely room for cold intrusions w/ most of the intense warmth centered out West through Feb. The ridge will slide eastward at times, but the key feature is a trough over the EC. I still have my doubts as endless summer seems to be a recent and nasty weather trend during fall. The CANSIPS seems to imply that the worst of summer is behind us with the exception of a 2-3 weeks of near certain return of summer temps. Is it right, IDK but the CFSv2 seems in agreement about normal to BN temps over the forum area for Fall.

***Update***Almost 4” of rain in less than an hour. Flooding has been significant and impressive. Scannerfood has a ton of photos from the region. Only in Florida have I seen it rain that long and with that intensity. I was using a snow shovel and a squeegee to push water out of my garage - losing battle! I will try to upload some photos later.

Always good to see cold fronts pressing south of the Canadian border during early August. Nice little aforementioned(by TV crew) summer relief incoming later this week. I haven't feel like this summer has been overly hot, but it has for sure been overly humid. We got a nice thunderstorm mid-day today w/ some much needed rain. Kingsport tends to do what Chattanooga does during many events....we get the rain shadow from 500 different directions. To my surprise, my run was in light run early this morning.

He is gonna be missed greatly.

The lightning in these storms around TRI has been insane. We have definitely been catching a break with more rain than we have been getting. TRI seems to dry out during July-October...so we take what we can get. What Helene did was super similar to what happened in the Smokies many years ago when the road between the Y and Gatlinburg was wiped out. I am beginning to think these events are slightly more common than once thought. Buffalo Mountain had a catastrophic flood just out of the blue several years ago.

Glacier NP is expecting snow above 8000' tomorrow. So, is that a "last snow of the season" or the "first snow of the season?" It is kind of crazy, but it really hasn't quit snowing in the West this year. I saw it with my own eyes. For places above 10,000', fall begins and ends during September.

It amazes me more and more with each passing each year how much PAC and IO ocean SSTs impact the eastern half of NA. Now, I gotta remember to factor in the North Atlantic? LOL

Both the CANSIPS and Euro Seasonals have the coastal BN SSTs in the NE Pac basin subsiding. So, no bueno on those. Still plenty of warmth where we need to be cool west of that. The CFS seasonal today has a complete flip of the PDO to a more favorable conditions by October, though I have my doubts as it doesn't have support from other models. It looks like a weak La Nina(fall and winter) from say just west of the dateline to South America - and I mean weak. Some might even call that a La Nada, but that setup would allow for the jet to buckle in the East IMHO by late fall. Even just getting those NE Pac coastal temps to neutral would help as it would prevent the trough from locking into the West.

What did the July 1 seasonals show for winter in that area in regards to GOA SSTs? It seems like the June 1 CANSIPS had it easing up a bit. I need to look more closely at July1.

I managed to find my way to Mammoth Lakes last week and part of this week. We saw it snow at 10k’ as a thunderstorm complex dropped temps like a rock while we were hiking. We had temps in the low 40s. The mountain range to our east had new snowfall the next morning. Crazy how the weather behaves at high elevation.