Winter Speculation 17/18 -December Thread

[weathertree4u]

14 hours ago, jaxjagman said:

Clown map of the Control

Wow, looks great, lock it in.

[Carvers Gap]

Great discussion overnight and this AM.  Everything has been pretty much covered so far.  The 6z GFS shows one extreme which is a massive central Apps thumping w some lighter snows to the southwest of that.  Still plenty on the table including a passing wave that goes OTS.  Assuming that we have a storm(and that is still a bit of a reach at d7), here is some "take it w a grain of salt" commentary.  The variables that change w each run are:

1.  How much will the energy diving into the back of the slp impact the deformation band west of the Apps and how much will it deepen the storm?  Basically, how big of a phase (and where) are we talking?

2.  Where is the placement of the slp once energy transfers from the Tennessee Valley?

3.  How much energy goes up west of the Apps?  Are we talking Miller B, hybrid, or a true Miller A?  Leaning towards hybrid right now.

4.  Where is the entry point/angle into our forum area?

5.  How much cold air will be available?

6.  What is the speed of the system once the energy transfers?

As John stated, still a long way out there.  The CMC has shown us during three recent model runs...a Miller A, a cutter, and a "what is all the fuss about?" storm.  There is some potential there for a very big storm for someone in the forum area.   As we have learned this winter, potential does not equal snow.  But, it is there.  We are right on the southwest edge of decent accumulations which means that could change to very good or very bad from run-to-tun.  I am not a big fan of the model runs that cut energy(lots of it too) west of the Apps.  It seems many of the model runs are now showing some variation of this.  Now, big storms usually have some, but the decent amounts modeled punch warm air into the eastern Valley - perhaps all of the forum area.  That said, the comma head(depicted now on several models and model runs) of the storm does work its way across the state and would give us hope of a few inches of snow if it falls at night.  Also, in the eastern Valley we can deal with energy transfer if it transfers into central or southeastern Georgia.  But classic blocking scenario right now being shown in the model.  Another final thought, March storms can be full of surprises even up the last minute.  I would be feeling pretty good right now from say Wise, VA, to New England.  We are at least in the game southwest of that axis.  Again, still want to emphasize that multiple scenarios(prob some not mentioned in this post) will be shown.  Middle TN is not out of this either.  Some model runs push a piece of energy west of the Apps and stall it over TRI if I remember correctly.  Anyway, hopefully some fun tracking ahead.  Hopefully some folks in our forum area see some accumulating snow.

[Carvers Gap]

1 hour ago, Holston_River_Rambler said:

Something else I've been trying to learn more about are the trend maps available on Tropical Tidbits.  I have attached one in hopes that someone can help me if I'm using these incorrectly. This is at 500mb and shows the GEFS 500mb heights as black lines, but also includes Z500 vorticity trends?  If that's the case its interesting that the 500mb trough on the GEFS looks overall more positively tilted, but the 48 hour trend of vorticity looks a little more neutral or even negative as everything rolls from the Mississippi eastward. Again all still a ways off, but thought I'd use this opportunity to try and learn a bit. 

Now that is interesting.  So, the trend is slp placement over the Upstate?  

[Holston_River_Rambler]

53 minutes ago, Carvers Gap said:

Now that is interesting.  So, the trend is slp placement over the Upstate?  

The one posted above is for trends at 500mb so I think (and am not entirely sure) it means lower 500mb heights are trending toward the blue regions.  Here is a similar map, but for MSLP trends.  To be perfectly honest I am not sure I'm using these correctly and am maybe just wishing for a SE trend for the surface low track to avoid a Miller B for MBY. Either way at least something to watch and try to see how things evolve on these trend maps.  

Thought of another thing to add to my earlier (longer) post.  Maybe the stronger this midweek storm for NE trends maybe we can get more confluence to push the later energy more south.  The thing that seems to be giving indications of a Miller B to me (at least for the 2nd piece of energy I mention above) is that this midweek storm for NE does a "Fujiwara dance" (MRX talked about this yesterday AM and am using their language) with a piece of energy from SE Canada and that is great for NE since it makes the storm a little stronger and delays its departure. However, for those of us further south the storm now takes longer to get to a 50/50 position so there's less confluence behind it and a tendency for energy piece 2 to cut up into the midsouth.  So now to the maybe part: If the midweek NE storm gets stronger and even though it may take more time to move out, maybe it makes the 3rd piece (in my above 500 potential vort map) dive more? None of this intended to be more than idle speculation, but just trying to make sense of some of the trends.  

[nrgjeff]

Excellent discussion is in progress. Storm would probably have to manufacture its own cold air, which can and does happen in March.

Holston is right on about the 500 mb vorticity. If it works out, precip flips over to snow and somebody gets TROWAL'ed. Key is for that back vort max to stay vigorous. GFS has it shear out a bit but not a deal killer. Euro actually makes the back vort max dominant; therefore, the Euro drops more snow. Definitely keep an eye on those 500 mb progs.

Agree with Carvers the cutter solution seems a little out of touch. I could see the back vort max crap out and things gin up for the coast only, just the opposite of a cutter. A dominant back vort max should not cut in the forecast weather pattern. Therefore, I am rooting for the back vort max to be dominant. Long way out though.

Most likely scenario IMHO is a whiff and then coastal situation. Cutter may be least likely. Hope we can split the difference.

[Carvers Gap]

Good call by Jeff.  The 12z operational suite all but removed the western solutions.  If that trend holds, we're are down to two solutions...

1.  Miller A that taps a very warm GOM.

2.  Whiff.

I think both are on the table.  The 12z GFS, Euro, and CMC all trended southeast and less organized.  That has been a trend for several runs, but is more pronounced during this run because it impacts the weather here.  The GEFS has a decent snow mean over our area.  The 12z Euro brings in the northern stream energy, and its snow totals are likely underdone IMO.  The way I see this...the 12z suite was a pretty big change in the slp track.  There is almost no energy going up west of the Apps.   I have no idea if it is done trending, SE but I doubt the storm comes back to the 0z position .  This could trend into a weak slp that goes OTS w light snow here due to the northern stream...or if models are just reconsolidating the track after a big shift, could be a pure Miller A.  The northern GOM is much above normal in terms of water temps.  

[Holston_River_Rambler]

Had to chuckle at the statement that rounded out NWS Blacksburg's AFD for this PM: (not totally banter as the earlier part agrees with Carver's post above)

"The latest ECM and GFS showing more of a Miller A setup which
usually provides us more snow. Still bears watching as it is 6-7
days out, but appears some will see several inches or more of snow
by early next week in the mid-Atlantic and as far south as the
Carolinas.

In addition, the timing of this is the 25th anniversary of the
"Storm of the Century" in 1993. Trends on this system are weaker and
further north than that storm. "

[Carvers Gap]

MRX afternoon disco snippet regarding the weekend system...

A low pressure system then develops over the Great Plains states
Friday afternoon...and approaches the area by the end of the
weekend. A shortwave ahead of this low will bring rain chances
beginning late Friday night through Sunday afternoon. PW values are
around the 75th percentile for this time of year...with limited
instability available. There is decent upper level forcing present
as the area is between two jet streaks Saturday afternoon...but the
chance for thunder appears to be too isolated to include in the
forecast for now.

The low pressure system then moves through the area Sunday and
Sunday night. There is a lot of uncertainty with this system.
Already the models have trended bringing the low pressure into the
area slightly earlier...with the center of the low pressure system
moving farther south than previous runs. Plenty of moisture will be
associated with this system...with moisture in the atmosphere up to -
30 degrees. Snow is anticipated late Sunday night into Monday
morning. Areas north of I40 and especially in SW VA and the higher
elevations in east TN can see several inches. However...right
now...even with the northerly flow...temperatures are expected to
rise to above freezing by Monday afternoon.

[Carvers Gap]

Near term for Tuesday/Wednesday...

.LONG TERM...(Tuesday night through Sunday)...
A low pressure system passing through the Ohio Valley will bring
wrap around moisture and cold air to the area Tuesday night
through Thursday night. Models disagree on amount of moisture
available...with GFS more optimistic on snow and rain accumulation
totals. Most of the forcing and moisture will be in areas north
of I40 through Thursday night...with northwest flow keeping the
highest accumulations in the higher elevations of east TN and SW
VA. Late Tuesday night light snow showers are possible...changing
to rain late Wednesday morning through the afternoon...and back to
snow again Wednesday night before changing to rain Thursday
morning. Thursday night...a few remaining snow showers could cause
an additional couple of tenths of accumulation as dry air quickly
moves into the area. Temperatures through the end of the work
week will be several degrees below freezing...with low
temperatures Wednesday and Thursday night in the 20s.

[Carvers Gap]

The 12z EPS reflects MRX's comments above....

It did not take the southward jog to the extent that the Euro operational did.  It is actually in a good spot for portions of E TN(better the more north that you go) IF IF IF it is done trending.  That is not a given.

[PowellVolz]

The 12z EPS reflects MRX's comments above....
It did not take the southward jog to the extent that the Euro operational did.  It is actually in a good spot for portions of E TN(better the more north that you go) IF IF IF it is done trending.  That is not a given.

I’m game for one more shot before spring gets cranking.


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[Holston_River_Rambler]

I was actually more in the whiff camp last night as the 500mb vort. seemed to trend east yesterday as it dropped in out of Canada, but it is still there on the Euro, GFS, CMC, and ICON as of now. 

The Euro has it, but now is crashing some extra energy out of the southwest and Pacific and the interaction they have as the vort in question drops in over the Rockies (IMO a much better place for it to be heading southeast) is unraveling it. 

The CMC had lost it but now has it back and wrapped up as it drops in with minimal interaction with anything...until it gets where we would want it, south of the TN River, where, for some reason that is above my head, it magically looses all organization and gets stretched out. I suspect the answer here lies in being able to comprehend the new 2 PVU maps on Tropical Tidbits where a starkly different world of pressures and wind lie just south of the Gulf Coast. I'm still not exactly sure how to use those maps, but that seems to be the common denominator for the energy getting sheared out. 

GFS does something interesting in that it dives the vort in further west (EDIT: in the short range as it enters North America and drops down the Canadian coast) than it had yesterday, but then splits it. It's "tail" keeps on trucking and eventually drops in over MN and wraps up as it dives SE and over KY and Middle and east TN.  The vort's "head" interacts with some Pac energy and gets stuck under a ridge in the west. The tail, while it does manage to reorganize as I said above and does produce some snow across the area, seems to have the same problem the CMC had, in that it gets stretched out as it swings through. 

ICON suggests something completely different based on its 0z run.  A powerful 3 contour upper low dives in through MN, but then interacts with what is left of NE's mid week system and rolls through the Great Lakes. 

Overall I would say trends have been further west overnight on the globals with the vort in question, but exactly how the vort and surrounding pattern evolve is still very much in question (it is 6 days out after all). To give you an idea of the uncertainty of the whole shebang, here is a gif of the last 5 runs of the GEFS, set to the 500mb vort 48 hour trends on 6z Monday, March 12th, so this gif is a trend of the trends at 500mb.   

Our vort comes ashore in AK overnight, so may see some changes then.  (Am not trying to start a debate about "off runs" or any satellite data vs soundings, just speculating that things may change for better or for worse). 

[Carvers Gap]

The 0z/6z Operational and the 0z Euro are far, far apart when looking at surface comparisons.  (Holston, this is not in response to your most recent post...I was typing as it rolled in.)  The GFS is now back to the cutter situation again while the Euro is slides everything off to our south harmlessly.  I noticed in the MA, that one of their posters(likely PSU) mentioned that how quick the blocking breaks down is being modeled differently which changes the position of the 50/50 low.  That in turn is changing how far north this can make it.  

[Holston_River_Rambler]

No worries, I was actually just about to add as an overall thought that the Euro and the ICON seem to be the bookends as of this AM in terms of the vorts geographic progression. The ICON says Great Lakes low and the Euro loses it in the Rockies. I've heard the ICON is sort of the Euro's NAM, if so it's interesting that they have such different solutions. 

I think the current system is just a beast and the models seem to be playing catch up with what it can and will do. I think I saw three separate 500mb lows rotating around one another at one point yesterday (fidgit spinner effect takes Fujiwara to a new level)

The positive here may be that if the trend is to underestimate strength prior to a storm we may be in for some fun. On the other hand until this system rolls on out it will be hard to get a good take on what comes after.  

[Holston_River_Rambler]

As an aside more to do with the immediate weather, if you get a chance take a look at the NEXRAD over the upper Midwest. It looks like a weakening tropical storm's precip shield, except it's snow! Hiking up Mt. Cammerer tomorrow and hope this bodes well for chances to see some snow up there. 

[nrgjeff]

Overnight NWP is a debacle. Of course when I say little/no chance of a cutter, GFS shows this. Actually one could argue it is more of a never than a cutter. Fails to dig and just stays north.

Hope springs eternal, on the Euro Ensembles. Several of the members have surface lows stronger than shown on the Op and still tracking south like the Euro Op. Ensemble mean 500 mb is lower than that of the Op. Some 500 mb members are significantly better. Long time readers know I reject cherry picking, but these are majority clusters and actually the entire Euro Ensemble suite mean.

We are at Day 5-6 depending on if one counts today. My head wants to walk away but my heart hopes anything can happen in March. Kind of like basketball, lol!

[Carvers Gap]

40 minutes ago, nrgjeff said:

Overnight NWP is a debacle. Of course when I say little/no chance of a cutter, GFS shows this. Actually one could argue it is more of a never than a cutter. Fails to dig and just stays north.

Hope springs eternal, on the Euro Ensembles. Several of the members have surface lows stronger than shown on the Op and still tracking south like the Euro Op. Ensemble mean 500 mb is lower than that of the Op. Some 500 mb members are significantly better. Long time readers know I reject cherry picking, but these are majority clusters and actually the entire Euro Ensemble suite mean.

We are at Day 5-6 depending on if one counts today. My head wants to walk away but my heart hopes anything can happen in March. Kind of like basketball, lol!

Great assessment.  LOL - just when I think the models are playing fair, the progressive model is west and the model w the westward bias is east.  I think a cutter is highly unlikely as well.  I agree...it is more of a northern latitude slider as depicted on the GFS.  I also agree that the 0z EPS held serve.  Definitely not cherry picking on our part.  And yes, this has the feel of one of those systems that is slipping away mainly because the ridge axis out west is pushing things eastward.  I might add...I say "slipping away" but reality is all that matters.  If it does not snow here, we never had it to begin with.  BUT, it might be fun to see these models work this out.  I am just paying attention, since it is likely this is our last window minus a Hail Mary in the Valleys.  (The Weeklies bring back the cold which might leave the mtns in play into April...no idea if right).  I think the EPS is likely correct w a system that goes south of the forum area.  Now, does it gain latitude and thus pivot the system over our area OR does it just slide by and go OTS. That, I do not know.  March systems can have a ton of surprises.  I do sometimes see these systems get "lost" on modeling for a few days and then they come back.  Tough to know.

Hopefully we see a few flakes of snow tomorrow, and maybe steal a win/storm during the late weekend.  Hated to see the Bucs lose last night.  Tough loss.

[Carvers Gap]

CMC, ICON, and GFS at 12z all have different solutions.  I probably still lean(barely) towards a Miller A hybrid, but the models are all over the place.  No real continuity at the moment w operational solutions ranging hundreds of miles apart due to timing/confluence.  

[John1122]

I don't see the storm cutting, the blocking is still holding just enough at 500 to keep it south and moving W to E. The 12z GFS is about 100 miles further south than 00z but warmer with less energy on the second piece. Models take huge jumps but I don't know if there's enough of a cold press to push it down to the gulf coast.  If we get lucky it may ride closer to I-20 than I-40 or I-64. Strong and along 1-20 may be close enough to pull in more cold and give some of us a chance at some heavy wet snow as the storm passes. The downside is that the bulk of the energy passes during the day during the current run of the GFS.

[tnweathernut]

maybe mid month we can score a small size hail system enough to cover the ground?  If that happened, both severe weather and winter lovers (kind of looks like snow) could be fed.  lol

[Holston_River_Rambler]

Nice snowquall showing up on some of the mesoscale models for Southwest VA overnight tonight. The 18z suite has trended the 500mb low and cold pool a little further south. In fact the 18z NAM 3k rolls it right through SE Kentucky, NE TN, and SW VA.  The 3k NAM while probably not right in the particulars of the location, suggests a swath from near Duffield to Whitetop. If that materializes someone somewhere might pick up a quick inch or two. 

Update for AM 3/7: Looks like my little high decibel return band materialized a little further south over more of the central, eastern Great Valley and plowed on east. Must have been some pretty good rates even in Grainger county since they delayed 2 hours and Scott County, TN closed. Pretty excited to head up to Mt. Cammerer today above 5000 feet!

[Carvers Gap]

6z GFS and 0z CMC are at least interesting.  CMC now has a true Miller A that is slightly too far to the east to help.  The GFS basically pulls the slp east and transfers energy to the Piedmont.  The backside drops snow over NE TN.  The 0z Euro is still a massive "no go."  Although if one was going fishing...it does develop some coastal energy behind the system in yet another possible solution....that is too far to the east.  Models continue to have trouble depicting the energy that dives in the back of the system IMO.  I think chances are diminishing, but I am not sure that we are much closer or further away than we were several days ago as modeling overnight has returned somewhat to the energy transfer solutions w coastal solutions mixed-in.  The CMC does show how we could still get a Miller A....but then we need it west.  Anyway, worth watching but with all caveats applied.  Not trying to provide false hope, but interesting overnight model runs.  

[Holston_River_Rambler]

Overnight Euro still has my little vortex at 500 mb.  This AM at least looks a little more consolidated over Kansas for next Sunday.  I counted around 35 EPS members that had it as well, though some of those were obviously in different places, but most of the placements looked like they would either swing west and south (possibly being sheared) or pass over some folks in the forum area.  The operational Euro shears it out as well as it passes south, but I'd just like to get it into the CONUS, wrapped up, and dropping toward us at this point and see what Hi-Res models do with it.

Edit: To echo Carvers who posted precisely when I did, the energy at the end (what I'm keying in on) is tricky and will probably still bounce around as it has been doing for a while. Also this energy is now in NAM range (though this may not be worth much) and the NAM has it dropping in and starting to wrap up over the Dakotas at the end of its run. 

[Carvers Gap]

Interesting 12z suite so far....The 12z GFS continues the trend of the 0z and 6z GFS.  It has 4-6" snows over NE TN.  Has a bit of a front end thump which the CMC and ICON to do as well.  It has trended north(doubt it is done doing so) and is a Miller A(w marginal temps) while the GFS transfers energy to a developing slp over the Upstate of SC.  So, to me it looks like the models are torn between a slider that moves along the northern Gulf states and then bends around the base of the Apps OR a system that barrels across TN and transfers energy to the coast.  The 0z operational Euro continues to be the weakest of the bunch.  It depicts the path to no snow. The GFS does show a path to some accumulating snow if it falls at night.  The ICON(hey...the Germans make good cars, right?) also has an interesting solution.  Honestly, I would have likely just thrown in the towel at lunch...but the GFS/CMC/ICON do show options for accumulating snow especially in the mountains, northern Plateau, and have potential the northern valley.  I am not adding the usual caveats as I think most folks hanging in there already know those and don't need them repeated.  And while the chances are not overly high, for NE TN this probably our best chance for decent snow all winter - I say that only because we have had so few opportunities this winter.  Keep in mind, we have had very little up this way compared to most locals and compared to our normals.  The weaker Euro solution is definitely a concern from 0z.  Right now the timing of the wave diving into the system and the latitude of the slp into the western forum area vary and that is producing sight variations that have big downstream consequences.  House money is always on no snow, especially during March...but right now can't rule out snow either.  March systems are notorious for not behaving, because they have often have quite a bit more energy to pull from.  I felt the 12z models would abandon ship, but not as of yet....though I am not sure I trust the operationals quite yet as they are a bit wonky.  The 12z GFS and 0z Euro seem like reasonable options.

[Carvers Gap]

The 12z UKMET continues w the interesting runs for the lunch time suite.  Storm is to the south(barely) and then turns the corner.  Would be a nice run for middle and west TN...maybe even E TN as it passes.  

[Carvers Gap]

Take into the UKMET has a tendency to be overly wound-up...and that is a decent run for somebody in the forum area.

[Carvers Gap]

For those in NE TN(areas along the I-81 corridor to the mountains and north of I-40), the 12z suite is not benign.  We are likely looking at a situation where the models had the storm, lost it, and have now found it again.  Now, nobody is promising massive amounts of snow.  Any snow in March is classified as bonus snow in my book.  So the 12z Euro, GFS, CMC, and UKMET are not that far apart.  Below is a shot of the Euro at 102.  The red line is the 0z track.  The black line is the 12z track w some energy handoff likely from north Alabama to inland coastal Georgia.  The yellow line would get the aforementioned region in the game.  The yellow dashed line is the backside energy that we want to phase.  Many of the models (Euro and GFS off the top of my head) sped up that energy.  If it dives into the back of the departing energy, it deepens the storm and pulls it back.  That is likely why the 12z run turns the corner a bit more than the 0z run. Interestingly, some convective feedback issues in the GOM around 84 likely delayed the strengthening of the slp during this run.  So, though weak, it actually might have been a bit stronger if the moisture transport from the central GOM had not cut off the inbound precipitation transport.

[John1122]

The GFS is throwing 4 inches of snowfall in my area and even showing a snow depth of 2 inches by Monday morning. I'll be stunned if that happens but I was pretty shocked this morning that there was accumulation. A few nights in the 20s this week did the trick even though it was 59 degrees yesterday evening.

[Carvers Gap]

The 18z GFS is basically a Miller A hybrid.  Give me that look, and I will take my chances here in NE TN.  Leave it right there with a chance to strengthen and come back west.  Not saying that happens.  But at 102 that is about all that you can ask for during March...that and a bit more cold air.  March Madness, people...

[PowellVolz]

The 18z GFS is basically a Miller A hybrid.  Give me that look, and I will take my chances here in NE TN.  Leave it right there with a chance to strengthen and come back west.  Not saying that happens.  But at 102 that is about all that you can ask for during March...that and a bit more cold air.  March Madness, people...

That’s a cold rain for everyone outside the areas where a few hundred feet in elevation can make a huge difference.


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