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December/January 2019/20 Winter Speculation Thread

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I just noticed how especially cruel to Knox County specifically that it is. 

That said, I would have to think we would do a little better outside elevated areas with that kind of monster taking that path East of the Apps. 

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1 hour ago, John1122 said:

I just noticed how especially cruel to Knox County specifically that it is. 

That said, I would have to think we would do a little better outside elevated areas with that kind of monster taking that path West of the Apps. 

Middle TN gets the shaft on that run also, what else is new? Too bad it will not be a totally different solution the next time the model runs!

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2 minutes ago, weathertree4u said:

Middle TN gets the shaft on that run also, what else is new? Too bad it will not be a totally different solution the next time the model runs!

It's very likely we don't see anything close to it again. It's one of the few paths towards snow for any of us with the marginal cold. Normally that storm in January or February would be golden.  But the models are throwing out these storms and the results are what you'd normally seen in March or even April with great tracks  but cold rain and elevated snow. 

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Just now, John1122 said:

It's very likely we don't see anything close to it again. It's one of the few paths towards snow for any of us with the marginal cold. Normally that storm in January or February would be golden.  But the models are throwing out these storms and the results are what you'd normally seen in March or even April with great tracks  but cold rain and elevated snow. 

Yep, seems like last year it was similar in a way in that the real cold was locked into the upper midwest, this year, just cannot get cold to amount to anything to come down for any length of time into the continental us or at least it seems.

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10 hours ago, Carvers Gap said:

I knew you were.  I was just playing along.   It means that he reverse mojo'd it.  He took back his call and then the EPS found the AN heights over Greenland again.  I was just tagging on to what you were saying.  It would have sounded better if in person...

Glad someone got my attempt at humor.  Haha

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If any one lives in the E. mts or SW VA, here's the monster John was talking about, not sure I've ever sen those colors on the Euro snow maps over anything near our area, lol:

Like John said: 500mb low passes southeast of us

giphy.gif

What  gives valley and southern folks the extra screw is the phasing at 850mb. I'm guessing that upper low over Iowa and Illinois messes with the dynamic cooling of the southern low.  

giphy.gif

Still....

 

giphy.gif

 

giphy.gif

 

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Even the new, magical, CMC has the idea. I would say some sort of a big Gulf low is a guarantee, details TBD, since models have been honking on it for a while and have been as consistent as they can be, but we see how that's worked out the past two years. 

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Some fairly big changes and model swings in the MJO regions.  Yesterday was about as inconsistent as I have seen all winter.  CPC has not updated of the MJO reading for the 23rd.  Really interested to see where that goes.  The RMM1GEFS loops and heads towards 3 fairly quickly.  At this point, I don't think it is looping back into the warm phases as there is a lot of subsidence over many of the warm regions forecast, but like I said, nothing is super consistent.  The good thing is that we have storms to track or at least a reason to watch modeling under 10 days.  At this point, the Hudson Bay block is doing its dirty work.  The AK vortex is keeping Arctic cold from entering that pattern.   That said, it is winter and a proper Miller A can do the job.    We have been patient all winter to get to the point where we can track individual systems, so enjoy.  

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From MRX...(I normally don't post the entire disco, but worth a read)

.Long Term...(Saturday through Thursday)...
The medium range forecast period kicks off on Saturday morning as a
closed H5 cyclone rotates atop the OH/TN valley region, driving a
surface cold front through the southern Appalachians.  PVA
associated with shortwave activity rotating through the upper low
will traverse the region keeping rain chances elevated at fcst
initialization atop the region of caa. With that, thermal profiles
atop the higher peaks/ridges of the southern Appalachians (including
the High Knob area in southwest VA) will favor a transition from
rain to snow, while a few flurries will also be possible across the
northern plateau with all rain in the valley.  From that point
forward through Saturday, the upper low will slowly transition
eastward favoring more NVA into the area Saturday night. Likewise,
H85 flow will veer more nwly as well therefore supporting at least
some minimal orographically forced snowfall across the mountains
through Sunday morning.

Meanwhile another shortwave will slide southeast through the
Cornbelt across the MS river and into the OH/TN valley by Sunday
evening.  Surface cyclogenesis beneath this wave across western
KY/TN will support weak moisture advection atop the OH/TN valley
region Sunday night as thermal profiles cool.  On that note, for
early Monday morning, critical thicknesses look to support snow for
elevations above 2.5-3kft (including the plateau), with a rain/snow
mix in the valley generally south of I40, and all snow in the valley
north of I40.  Fortunately at this point this system does look
somewhat moisture starved (despite weak advection), and it`s also a
fast mover.  Therefore, for now accumulations look low, generally
around an inch over the high terrain and a trace to half inch max
north of I40.  All that said, much could still change so stay tuned,
especially considering this will be ahead of or during the Monday
morning rush hour.

Beyond that into midweek, the operational guidance favors another
southern stream H5 low moving across the Deep South with a region of
surface cyclogenesis over the northern GOM. Previously there was
some disagreement between the GFS/ECMWF, however they both now tend
to open up the H5 low and dive it southeast across the GOM only to
be replaced with flat ridging over the southeast CONUS.  Therefore
pops are kept low given range and model uncertainty.  Overall,
temperatures through the period will be near or slightly above
normal.
 

 

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East Tennessean’s could be in worse places than the northwest quadrant of a bombing low, especially in early Feb (speaking of the 0z Euro). Even with a lack of cold air at the surface and razor thin 850’s.  Probably silly to even look at details (although it can be fun), but if you want to have a chance that’s where you’d want to be.

Just having multiple models spit out sizable storms should give decent confidence for a big storm somewhere in the southeast down the line.  
 

As far as snow, with a lack of cold air in place at the surface, and no real chance for cold coming into any developing Miller A........  it would require serious luck to score anything other than rain outside of the higher elevations.  We are probably talking about a dumb and dumber type “so you’re telling me there’s a chance” of luck.  The upcoming patter reminds me of springtime, not mid winter.

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45 minutes ago, Carvers Gap said:

12z GFS with some wildness.  LOL.  New storm on Wednesday.  Crusher for M TN after that.  Something for everyone.  

Gets even better out in fantasy land with a Deep South slider and an end of run arctic blast that provides a state wide snowfall. If only.......

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19 minutes ago, weathertree4u said:

Great thanks! 

Basically, the EPS strengthens BN heights over the eastern US and weakens the BN heights in AK.  That is very important.  If the heights in AK are strongly negative and plunge southward, they could dig the trough into the western US.  If the BN heights in the East are deeper, that likely means that ridging is strong to our west and east.  That might force that cold into the Plains which would then spread East.  The 12z GEPS on TropicalTidbits shows the option where a stronger AK vortex plunges West and digs the trough further West.  The EPS shows how to potentially keep the trough in the East longer.  I don't think we are necessarily in a pattern where the trough stays in the East, but we if we could get the trough to hold for 3-5 days then we might be in business.  The equatorial rainfall west of the dateline continues to brew over a strong ENSO 4 region.  That is phase 6 of the MJO.  Phases 1 and 2 are firing just east of Africa.  As JB noted, those have strengthened in modeling over the past day or two.  They might strengthen enough to mute phase 6.  I think that is why we see modeling tease the phase 6 jaunt again only to pull that away.  So, the EPS shows a more prolonged presence of the trough in the East.  Now, if one wants to see our pattern just burn in flames...the 12z CFSv2 is the one.  Thankfully, it is almost never right.  That said, both the GEFS and GEPS  at 12z showed the trough dig into the West while holding eastern heights BN.  It might be that those ensembles are actually showing two solutions and can't choose.  The EPS, which is handling the MJO better, is still steady.  I expect plenty of fluidity and unpredictability in February.  Lastly, the EPS continues to show at least a temporary wave of AN heights in the Davis Straits region.  Probably is just a mirage, but interesting as that feature strengthened at 12z.  

I see @Holston_River_Rambler is on it.  I like those gifs because you can see the pattern evolve.  If you look at ensembles right now, watch AK at the end of those runs on the 500 anomaly map.  You will see the cold form AK begin to head south.  I talked a little about that being a fork in the road in the pattern.  If that cold hits the front range and spreads east...money.  If it digs into the West...big SER.  The Weeklies yesterday showed a SER of varying strength yesterday, but manageable.   The 12z CFS, unlike the cold 6z CFS, depicts an unworkable SER.   The key to this will be for the Eastern NA cold anomaly to be strong and the PNA to be strong as well.  

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As a follow-up, I would not be surprised in the least if the trough that forms is a Rockies to Apps trough w the EC has to deal with warm temps east of the Apps...just based on today's trends.

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1 minute ago, Carvers Gap said:

As a follow-up, I would not be surprised in the least if the trough that forms is a Rockies to Apps trough w the EC has to deal with warm temps east of the Apps...just based on today's trends.

At the least it is different from last years endless warm. I am sure next year will be different too!

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Several MJO forecasts are starting to see 8-1-2-3 in the COD as possibilities. GaWx pointed out that Atlanta was an average of 3 degrees colder when the MJO went through these phases in the COD vs at higher amplitude. 

The Australian model that runs through March 1st sends the MJO into the COD on the 8-1-2-3 area and stops it just before 4 and loops it back into 3. The GEFS goes 1-2-3 in the COD. When February 2015 turned brutally cold, especially for the 2nd half of the month through March 7th or so, the MJO was in the COD in those areas or in the very center.

combined_image.png

 

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MRX actually mentions this Sunday night as being conducive to snow north of I-40 but with limited precip.  If someone wants to post the disco...have at it.  

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55 minutes ago, Carvers Gap said:

MRX actually mentions this Sunday night as being conducive to snow north of I-40 but with limited precip.  If someone wants to post the disco...have at it.  

From the MRX disco on Sunday night's event:

 

A brief break from rain chances on Sunday ahead of our next fast
moving system, a shortwave moving out of the southern plains Sunday
night into Monday. Model soundings are showing profiles conducive to
snow, especially north of I-40 and along the Cumberland Plateau.
This means that we could see a quick shot of snow as the system
moves through. Models continue paint this system as being relatively
moisture starved and fast moving, so accumulations look to be pretty
limited at this time, remaining below Advisory Criteria. Biggest
concern with this system will be the timing of the snow with light
snow possibly beginning to accumulate ahead of the Monday morning
commute, so while a low end event looks likely as of now, it may
cause degraded driving conditions.
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1 minute ago, Runman292 said:

From the MRX disco on Sunday night's event:

 

A brief break from rain chances on Sunday ahead of our next fast
moving system, a shortwave moving out of the southern plains Sunday
night into Monday. Model soundings are showing profiles conducive to
snow, especially north of I-40 and along the Cumberland Plateau.
This means that we could see a quick shot of snow as the system
moves through. Models continue paint this system as being relatively
moisture starved and fast moving, so accumulations look to be pretty
limited at this time, remaining below Advisory Criteria. Biggest
concern with this system will be the timing of the snow with light
snow possibly beginning to accumulate ahead of the Monday morning
commute, so while a low end event looks likely as of now, it may
cause degraded driving conditions.

Read that earlier. Things may get interesting up in the mountains early Monday morning. Hoping the elevation will give me a nice surprise. Also got my eyes on next weekend!

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