Carvers Gap

John pretty well covered the first potential winter event next weekend which will likely precede an underdetermined period of warmth which follows. The EPS certainly looks like it would kick the trough eastward(if it continue?) late in its run as AN heights move into the GOA. Just to show that we aren't talking out of our minds. This is what the CFSv2 has this morning after a similar set-up (to the EPS) on it. Will be interesting to see which fork in the road modeling eventually takes. I do my best not to talk in absolutes but it can happen. So for now, just presenting two options. The warm option has been well documented. However, I do not think it is a given right now that things turn warm and stay warm through the core of winter. I certainly don't discount that, but certainly can see that the potential for other scenarios exist. Again, my overall winter forecast ideas are warm with January and February being the warmest month. My main contention is that cold(possibly severe at times) will be embedded within those warm means similar to 17-18. IF(stress IF) the AN heights in the Aleutians move into the GOA, this is the potential that exists if that happens. The control is a little later with this evolution, and I think it is certainly possible that the CFS breaks down the eastern ridge too quickly. And again, the CFS is not a model which I trust as it has a cool bias at times. However, with the Euro suite bouncing around about as much as the CFSv2...might as well give it a look.

Thanks, PSU, for the great posts. I eventually made a similar map just with a NH view. It is posted in TN Valley thread. I compared it to the 18z CFSv2. I also have added the analogs for the d8-14 CPC LR forecast. Some famous ones and some infamous ones. Been trying to make sense of the Scandinavian AN heights I am seeing showing up in modeling after d10. It is interesting to see a similar feature showing up(on analog maps) in the Scandinavia and/or Ural regions.

Notice the the three air masses(cold and warm). Actually the December analog package looks similar to our November which we just had. Also, notice the ridge near Scandanavia - as fickle an analog as it may be. Current differences would have nearly opposite 500 features over NA and Greenland. Either we have just left this configuration or we may be headed there. Below is the 18z CFSv2 for the last part of December and first part of January. Not exact but close to the analog maps above.

Here are the December composites of PSU's Nina maps. I haven't taken into account which were second year Ninas.

Here are the d10-14 analog packages. Some interesting ones in there. Beware, this graphic might change with each update. There are extreme winter analogs (warm and cold) in that package. The best and worst winters I have experience are found in that analog package.

I don't think the way to colder weather will be via an SSW though a perturbation of the TPV is probably likely at some point this winter season. Just pointing out that some similar features to those analogs are showing up on current modeling. Pretty cool I think. We will see in time where that leads. I asked in the MA thread if PSU knows how those Decembers looked. I just don't have time to enter those into reanalyses program. If you have time, go for it. Would be interesting to see what a composite of those previous Decembers looked like...

PSU, I wonder what those Decembers looked like?

Take a minute and look at the analog package graphic of the past 30 years of La Nina's. PSU notes there are two different clusters. There is a bit of a misconception the the trough is in the West. Now, also note the ridge just east of Scandinavia and the ridge in the central Pac. Those features are showing up in some variation in LR modeling.

I tend to agree with Jeff on the MJO, though I am less bearish for winter. Jeff pretty much holds court over the IO and western Pacific knowledge. When in doubt, follow his lead on that one. I think we are going to need help in the Atlantic as you note earlier. The CFSv2 is the way out of long term warmth. No idea if it is right. I don't share a foxhole with that model at any point! LOL. OR....in the really unusual circumstance it gets cold during warm phases. For me, just too early to tell. I definitely agree with base-warm for winter. I just think we see some extreme cold embedded. My question is do we get 1 or 2(with the second being after mid-winter) cold intrusions. I do think the ongoing BN precip is likely a more limiting factor for snow. Makes precip so much harder to connect with colder patterns if there is little precip in the pattern. The QBO cycle should produce cold. It is uncanny how well descending QBOs correlate to cold in E TN. So for now, we are looking for windows for potential snow prior to the potential warm-up. I like the idea of an eastern ridge from Dec 15-22 at least. We will see if that continues from that point on. I would lean that the warmth continues, but again, no slam dunk. I do think there is a chance for some cold around Christmas or slightly thereafter. Going to leave you guys to it for a bit. May check back later this evening. TN vs Purdue in the Music City Bowl in Nashville....will be fun to track the wx for that one.

That was never in question.

Euro monthlies are warm, but when aren't they for winter? Maybe a few examples, but wicked warm bias in general. As for Hugo, just thought his information was interesting. I generally buy into the idea that it is going to be difficult for the MJO to work into 8, but who knows. I generally try to look at both sides of the coin. The CFSv2, which I scorn regularly, is not base warm from Christmas week onward. Again, it is December 5th. Not unusual for winters to start warm and return to cold, especially after cold Novembers. It is not out of the realm of possibility that the winter will remain AN either. There are precedents for both. I am certainly not going to hang my hat on a wx model which has a know warm bias or a known cold bias. We will know soon enough. Winter forecasting can be humbling for us all...and if it hasn't been yet, it will be.

Actually that is not true IMHO. -3F for November. While that is not a winter month, fits Nina climatology to the T. Warm start to fall followed by a quick flip to cold late in fall. Textbook front loaded cold...problem for us is the front load came during a time when we really don't get a ton of snow historically.

I think Jeff summed-up Bam's track record of late. IMO, more of an SST problem where the cooler temps in areas where 8-2-1 reside won't allow impulses to propagate into favorable phases. That said, we are not really into longer wavelengths associated with winter yet - meaning wavelengths are still changing. Until those really set-up, not sure where those "standing waves" set-up over the US as well. SER is definitely favored at times but not guaranteed. Right now we are seeing three pools of BN heights and three pools of AN heights in the northern hemisphere. That is extremely stable. However, I suspect we move to four of each by mid-winter. See if you can dig up some articles about teleconnections of Scandinavian ridging and/or Ural ridging in relation to patterns over NA during winter. Might also see if that Scandinavian ridge is a prelude to high latitude blocking setting up(potentially due to an SSW). Also, some really good information is what John posted earlier about La Nina winters for this area. I trust his information above all other sources.

Interesting. Found this on the MA forum.

I can say this much, I am not losing a second of sleep about modeled warm weather patterns on December 5th. LONG way to go. Could it be a non-winter? Sure. But could it be a winter with a memorable cold snap? Sure. Saw where JB is worried about the late 90s non-winters as a possibility. Thing is, that is always a possibility but is about as unlikely as a severely cold winter. But one look at the CFSv2, and the long term continuation of a warm pattern is no slam dunk - reference MA forum discussion. We have just come off a November at TRI which was -3F. So, we already have had a front end cold snap of sorts - the weather doesn't adhere to manmade calendars. We aren't going to stay below normal forever. We are right on time for a switch in patterns. The positive is that we know there is a decent correlation between cold Novembers and winters which are BN. While there are a few clusters of analogs that produce warm, nearly snowless winters....most second year La Nina winters have some winter. Many of those winters have extreme cold. While last year was not a second year Nina, it did produce a memorable period of winter for those in western TN and Texas. That is the calling card of La Nina.

Interesting to see the 12z GEFS begin to allow the eastern ridge complex to decay/retrograde west. Don't think so? Switch your model over to surface temp anomalies and let it loop. Moves east, and then slips back into the West again. The deep trough which was forecast to go into the West is nothing more than a blip. Hate that for the ski slopes there as they are suffering now.

Yeah, I don't see cold locking in before Christmas for more than a day or two. Think our best chance for snow next weekend is for the cold to crash into the back of the system while a slp or wave buckles it, thus slowing it down. Long shot, but not impossible at all. Tough to know as modeling was nearly blind to the amplification.

Hurricane force winds and snow. Somebody's dream scenario somewhere. LOL - not mine. I definitely could enjoy a blizzard, but not touching 125mph winds!

Yeah, that was a good look, John. Looks like we have two timeframes to watch....Wednesday and next Sunday. Wednesday looks marginal, but it is there on modeling. Maybe a dusting for some areas? Next Sunday is one to watch. Long way to go, but this appears to be a low that cuts followed by a potential second low. Just how far that boundary gets south is going to be key. In the LR, the CFSv2(notable cold bias) seems to like some cold around the Christmas timeframe, another warm-up, and then much colder. I would not disagree. Base warm for the next few weeks as others have noted with cold interludes. However, I suspect that we see a more prolonged cold pattern(2-3 weeks) at some point this winter.

Tonight Snow showers likely. The snow could be heavy at times. Some thunder is also possible. Cloudy, with a low around 24. Wind chill values as low as -2. Strong and damaging winds, with a southwest wind 95 to 100 mph, with gusts as high as 125 mph. Chance of precipitation is 60%. Total nighttime snow accumulation of 2 to 4 inches possible. Sunday Occasional snow showers. The snow could be heavy at times. Some thunder is also possible. High near 40. Wind chill values as low as zero. Strong and damaging winds, with a south southwest wind 65 to 75 mph decreasing to 47 to 57 mph in the afternoon. Winds could gust as high as 90 mph. Chance of precipitation is 80%. New snow accumulation of 1 to 3 inches possible. Sunday Night Occasional snow showers. The snow could be heavy at times. Some thunder is also possible. Low around 31. Strong and damaging winds, with a south southwest wind 40 to 47 mph, with gusts as high as 55 mph. Chance of precipitation is 80%. New snow accumulation of 1 to 3 inches possible. Monday Occasional snow showers. The snow could be heavy at times. Some thunder is also possible. High near 40. Strong and damaging winds, with a south southeast wind 37 to 47 mph decreasing to 24 to 34 mph in the afternoon. Winds could gust as high as 55 mph. Chance of precipitation is 80%. New snow accumulation of 1 to 3 inches possible. Monday Night Snow showers likely before 8pm, then scattered rain showers. The rain and snow could be heavy at times. Cloudy, with a low around 28. Strong and damaging winds, with a south southwest wind 24 to 29 mph increasing to 35 to 40 mph in the evening. Winds could gust as high as 49 mph. Chance of precipitation is 60%. New snow accumulation of around an inch possible. Tuesday Scattered rain showers before 2pm, then scattered rain and snow showers. The rain and snow could be heavy at times. Mostly cloudy, with a high near 41. Very windy, with a south wind 30 to 33 mph, with gusts as high as 40 mph. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible. Tuesday Night Scattered rain and snow showers before 2am, then scattered rain showers. The rain and snow could be heavy at times. Mostly cloudy, with a low around 32. Very windy, with a south southeast wind 26 to 31 mph decreasing to 20 to 25 mph after midnight. Winds could gust as high as 38 mph. Chance of precipitation is 30%. Wednesday Scattered showers. Mostly cloudy, with a high near 44. Windy, with an east southeast wind 20 to 30 mph, with gusts as high as 37 mph. Chance of precipitation is 30%. Wednesday Night Scattered showers before 8pm. Clear, with a low around 33. Windy, with an east southeast wind 21 to 30 mph, with gusts as high as 37 mph. Chance of precipitation is 30%.

Blizzard warnings for the higher elevations of Hawaii right now. Let that sink in for a minute. Someone wake-up Jim Cantore. Incredible forecast. See below...

The 18z GFS is very close to a major winter storm next weekend. It is similar to the CMC. Ways out there, and everyone should now the drill.

@nrgjeff, been digging on this and can't find it. I am seeing substantial heights build over Scandinavia and the Urals on the EPS. Seems like that is a precursor to cold here or maybe a strat warm. I can't remember if either is true. Right now I see roughly three pools of warm and three cold, tri-pole right? Maybe that configuration is muting that ridge's influence here?

Ya'll, I am actually thankful for the break in the cold from the last month. @Holston_River_Rambler, check out the 12z GEFS. See that trough develop(retrogrades west) just east of Hawaii late in the run? Probably have to use the northern hemisphere view to see it. That argues for a big ridge out west. Also notice the AN heights rotate out of Europe into Scandanavia. Roll the forward about 48 hours and the trough reforms in the East. There is an argument there for the eastern ridge to break down. It is not out of the realm of possibility that the ridge only lasts for a week and a half.

That would be accumulating snowfall on the 12z CMC about 7 days out. The GFS also loses the eternal ridge. Cold air attacks it over and over.