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Winter Speculation 17/18 -December Thread


AMZ8990

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9 minutes ago, John1122 said:

I think that'd be snow in Nashville. sub freezing 850 and 35 degrees at the surface with heavy precip falling screams snow to me.

Possibly,it's close.But you can see the warm nose better here

 

GFS 0.5 Degree FORECAST FOR: BNA    LAT=  36.12 LON=  -86.68 ELE=   591

                             00Z JAN31
PRESSURE LEVELS  SFC  1000   975   950   925   900   875   850   825   800      
                 MB    MB     MB    MB    MB    MB    MB    MB    MB    MB      
                (C)   (C)    (C)   (C)   (C)   (C)   (C)   (C)   (C)   (C)      
WED 00Z 31-JAN   -2     1     0    -2    -4    -3          -2          -3       
WED 06Z 31-JAN   -2     0     0     0    -1     0           2           2       
WED 12Z 31-JAN   -1     0     0     1     3     4           4           2       
WED 18Z 31-JAN   11     9     7     5     3     5           6           3       
THU 00Z 01-FEB    5     8     8     7     6     6           6           4       
THU 06Z 01-FEB    5     7     7     6     6     6           3           0       
THU 12Z 01-FEB    6     8     7     5     6     6           3           0       
THU 18Z 01-FEB    8     9     8     6     6     5           3           1       
FRI 00Z 02-FEB    5     5     3     2     0     0          -2          -3       
FRI 06Z 02-FEB   -3    -2    -4    -6    -7    -6          -4          -6       
FRI 12Z 02-FEB   -5    -6    -8   -10   -11    -9          -8          -8       
FRI 18Z 02-FEB    5    -3    -5    -7    -9   -11          -8          -8       
SAT 00Z 03-FEB   -3    -2    -3    -5    -7    -9          -7          -8       
SAT 06Z 03-FEB   -4    -3    -4    -5    -5    -4          -4          -5       
SAT 12Z 03-FEB   -2    -2    -3    -2     0     0          -2          -5       
SAT 18Z 03-FEB    7     4     2     0     0     0          -3          -4       
SUN 00Z 04-FEB    2     4     4     3     2     1          -4          -3       
SUN 06Z 04-FEB    1     3     2     1    -1    -1           0          -1       
SUN 12Z 04-FEB    1     3     2     1     1     1           0          -1       
SUN 18Z 04-FEB    2     3     1     0     0     1           0          -2       
MON 00Z 05-FEB    1     2     0    -1    -2    -2          -3          -2  
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The 0z EPS is either really wrong or the 0z GEFS is really wrong during the 10-15 day range.  Looks to me like Isotherm's concern is legit....that the MJO hits a brick wall, stalls in phase 7, and heads to the COD.  But here is the problems as Jeff and others have noted, the models have not been handling the MJO well.  IMHO, I think the EPS and the GEPS are too warm.  Their operational runs are very reasonable.  Cold pinwheeling down with warm being injected in between shots.  The problem w the EPS is that the shallowness of its troughs has rarely verified this winter.  I really do not like being on the same side as the GEFS which has trended some to the EPS but still shows a reasonable trough given the -EPO.  Speaking of which, if that EPO is that negative... that trough should deepen on the EPS.  Oddly, I do think the Euro operational has handled recent storms well...butthe EPS, which was infallible during early January, is quite human at the moment. So, I think the Euro operational is my money model right now....w the EPS and GEFS given equal weight past d10.  

Definitely still interested in the Sunday/Monday system...

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From MRX this AM.  And I agree...the synoptic set-up is good.  We definitely are marginal on temps, so no false hope.  But I will take that track all day long.  Miller As, especially in NE TN, can create interesting situations as they pull by...

A deepening upper trough over the Plains will result in surface
cyclogenesis over Texas on Saturday night, with the low tracking
along the Gulf Coast on Sunday, then to the Outer Banks region on
Sunday night in a Miller A pattern. Strong isentropic upglide over
the warm front across AL/GA and favorable upper jet positioning for
divergence brings precip into our area starting Saturday night,
during which time temperatures will be in the 30s, so it may begin
as snow before a transition to rain as warm advection increases.
However, there is a lot of uncertainty this far out, so will mention
a rain/snow mix for most of the area, with northern areas having
greater chances of snow. Cold advection behind the system develops
Sunday night, and moisture wrapping around the deepening low, the
snow potential will continue into Sunday night. How much potential
depends on the track and strength of the low, which remains highly
uncertain. The GFS is quite agressive with snow amounts in the
mountains and SW VA, while the ECMWF is lower but still focuses in
on NE TN and SW VA as the areas of greatest accumulation. It is
still too early to project specific amounts, but the potential
exists for a significant snowfall for parts of the area, mainly
northern sections.
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2 minutes ago, Carvers Gap said:

From MRX this AM.  And I agree...the synoptic set-up is good.  We definitely are marginal on temps, so no false hope.  But I will take that track all day long.  Miller As, especially in NE TN, can create interesting situations as they pull by...

A deepening upper trough over the Plains will result in surface
cyclogenesis over Texas on Saturday night, with the low tracking
along the Gulf Coast on Sunday, then to the Outer Banks region on
Sunday night in a Miller A pattern. Strong isentropic upglide over
the warm front across AL/GA and favorable upper jet positioning for
divergence brings precip into our area starting Saturday night,
during which time temperatures will be in the 30s, so it may begin
as snow before a transition to rain as warm advection increases.
However, there is a lot of uncertainty this far out, so will mention
a rain/snow mix for most of the area, with northern areas having
greater chances of snow. Cold advection behind the system develops
Sunday night, and moisture wrapping around the deepening low, the
snow potential will continue into Sunday night. How much potential
depends on the track and strength of the low, which remains highly
uncertain. The GFS is quite agressive with snow amounts in the
mountains and SW VA, while the ECMWF is lower but still focuses in
on NE TN and SW VA as the areas of greatest accumulation. It is
still too early to project specific amounts, but the potential
exists for a significant snowfall for parts of the area, mainly
northern sections.

Love the track depicted for the weekend storm!  Hopefully temps are over modeled warm and we can at least just squeak through for the majority of the forum.  Also while GFS and Euro have went into the toilet a bit the last run, the Canadian is still advertising accumulating snow with both systems.  RGEM doesn't look terrible for the first event.

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11 minutes ago, ShawnEastTN said:

Love the track depicted for the weekend storm!  Hopefully temps are over modeled warm and we can at least just squeak through for the majority of the forum.  Also while GFS and Euro have went into the toilet a bit the last run, the Canadian is still advertising accumulating snow with both systems.  RGEM doesn't look terrible for the first event.

Yeah, temps are marginal so I want to make sure folks know this is a thorny path of sorts.  For NE TN, the mean temps never go above normal for the event.  Looks like mid to upper 30s for the event w some downsloping warming present.  However, temps drop as the slp slides by.  Really, we want this as strong as possible and let the northwest quadrant work its magic.  If it is weak, probably just a mixed bag to rain.  However, it that amps a bit...then we could see a narrow band of heavy wet snow somewhere.

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1 minute ago, Carvers Gap said:

Yeah, temps are marginal so I want to make sure folks know this is a thorny path of sorts.  For NE TN, the mean temps never go above normal for the event.  Looks like mid to upper 30s for the event w some downsloping warming present.  However, temps drop as the slp slides by.  Really, we want this as strong as possible and let the northwest quadrant work its magic.  If it is weak, probably just a mixed bag to rain.  However, it that amps a bit...then we could see a narrow band of heavy wet snow somewhere.

Agree, but I don't like them to amp until turning toward the NE while in southern GA, when they strengthen too soon they amplify WAA into the Eastern Valley, but if they amp after they have passed east of the valley and the winds are no longer coming from the S or SW thats when I like to see them blow up!

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Euro is much warmer for Sunday and would be all rain in all of Tenn. GFS appears to start it as snow along I-40. Euro has more PVA energy north; I figure the GFS has too much south in error. Even on the GFS partial thickness hints at a warm nose, so I will go with the Euro.

Rest of next week is not inspiring. GFS spits out some (likely) false alarms based on its track record this winter. Euro denies the action and regular readers know I go with the Euro.

The GFS forecasts 9 out of every 1 storm - Mike Smith originally about hurricanes. 

So my hopes are on that week of February 12 now. Seems the flow may not be totally buried after all. Flow could be anywhere from just right to drifting too far north. Euro and GFS diverge sharply. I might have to say Canadian Ensembles offer a good compromise. I only say Canadian once in a blue moon. You bet the pun is intended, lol! 

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Excited about possibilities for NETN on Sunday. I've had 4 dustings so far - just NW of Johnson City. So MRX saying potential significant snowfall for northern sections is the best news I've heard in a while. Maps have different signs but only the good Lord knows how much falls from the sky and how much eventually accumulates. Hoping for 4 or more!!!

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I don't like the trends. Looks to be a cold rain for most of the forum area at this point for Thursday night and Sunday. Still some time for the Sunday system to come back, but I'm betting on cold rain and hoping to get surprised at this point.

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Right now the trend is an inland runner, Miller A.   We have had several of those rain on us...but that 12z GFS run in the NE Valley keeps us in the mid 30s for the event.  The CMC looks good, but it has been off all winter.  I can't remember the last time it has been right.  But...both the GFS and CMC at 12z have Miller As.  Now, the GFS is further north and west.  That will take us out of the game quickly if that continues....but even at this (increasingly closer) range that run can move all over the place.  The ensembles do need to be considered.  As Jeff mentioned, temps are not great.  As I said earlier, this is a thorny trail.  But I am going to be most interested in this...the Euro has shifted systems southeast time and time again this winter because it misjudged the boundary of the cold air.  This system will be following on the heels of the system Friday morning.  This is fresh, cold air that will have to be scoured out....not stale.  I think the mountains get hammered on this above 3,500'.  The NE Valley is in the game IMHO.  That is a decent track.  I take track over all other cards.  It is my Draw Four.  I learned a long time ago not to ignore inland runners in NE TN an SW VA.  Probably a 65% chance this falls as mix to rain...but the track is the key.  

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The ICON, CMC, and GFS all have an inland runner, Miller A solution for the 12z suite.  The have different outcomes because at this range (to steal a line from the MA forum) they are very much like just one of the members of the ensemble.  Need to the trend NW to stop...otherwise 18z will put us out of our misery.  Still...interesting to finally see an inland runner on the models.

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What is really crazy is if I only saw the feature placements on this map with being middle of winter I would say dang, about to get walloped!  Nice big strong High in the plains SLP going up through SC to Hatteras, looks beautiful on paper.   I definitely wouldn't be thinking its raining all the way to the Ohio River.

SLP.PNG

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12 minutes ago, ShawnEastTN said:

What is really crazy is if I only saw the feature placements on this map with being middle of winter I would say dang, about to get walloped!  Nice big strong High in the plains SLP going up through SC to Hatteras, looks beautiful on paper.   I definitely wouldn't be thinking its raining all the way to the Ohio River.

SLP.PNG

Just speculating and not meaning to give false hope....But those highs have tended to press more than modeled all winter to the point that systems would start over the TN Valley and go to New Orleans.  Off the top of my head, the northwest extent of the Euro is getting pressed on the 12z run.  Also, the Euro has a more defined slp which means it is stronger relatively for a weak slp...but it is not much warmer(if any) here...I would have expected it to be warmer.  

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At 102, the slp is getting "kicked" by the incoming cold.  As Bob Chill stated in the MA, we need the hp over the top of the storm.  But the slp at 12z definitely is being influenced by the cold. Great slp placement....I never rule out snow when I see a slp in that spot(slp to the Piedmont to Hatteras).   Like I said....thorny path, but since there is nothing else to watch, I am watching this.

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Indeed the slp is south and west of the placement on 0z.  That high pressure is doing its work.   Heck, it may get suppressed.  Look at the difference in the hp as Shawn noted.  Good catch.  The slide before this is even more impressive.  There is a reflection of the storm at 0z un Upstate, SC.  At 12z, it is an inland runner closer to the coast.

5a72169a80e60_ScreenShot2018-01-31at2_17_55PM.png.39c7aa99d8ad4fe475e383d540919f07.png

5a72169befe8e_ScreenShot2018-01-31at2_18_09PM.png.42f745e8952dc31da5c3790ccacaba9b.png

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SREFs seem to be giving a little love back or the Friday system

TYS: Avg 1.6", 1 big dog at 6", 7 in the 2-3" range

CHA: Avg 0.07" (dont sneeze)... 

TRI: Avg 1.9. 1 big dog at 4", 11 in the 2-4" range

 

Weather south has a nice right up (albeit from yesterday evening). He is cautiously beating the drum on a substantial wet snowfall somehwere around 40 near the apps

From his paid blog... doubt I should be posting this

 

"As mentioned about the warming 850 temps, the surface high on Saturday is heading out to sea quickly, but the warming aloft isn’t all that dramatic, thanks to incoming height falls overall. (neutral to iso environment of upper temps). Despite strong warm advection at 850, bringing in copious moisture, the offsetting factor could be rates of fall and the lowering of the 5H height field in TN to NC especially at the base of the jet stream and most divergence region. This always means a super tricky environment for rain versus snow. So, the jury is out on exactly how much snow falls in places like Knoxville, Asheville and Roanoke to Winston Salem, but first guess is that it will be substantial, unless this low pulls much further north. And we know from past experience that lows shown this far out, can pull north. Most models are atleast in decent agreement on the low track from Louisiana to offshore NC then up the East Coast but just barely off the coast.    Once the upper system gets sampled very good in say 2 more days, we’ll know much more on exact tracks. The trend this Winter has been colder and wetter to win out, when youre near a threshold environment though. The difference on this system could be that it is a very wet system overall with excellent jet dynamics involved aloft. I won’t be suprised to see this trend earlier on start times in the Tennessee Valley to western Carolinas.  If so–expect more snow than models advertise right now. No guarantees though. It may well “amplify” a lot more as well , pushing the snow line completely to the Kentucky and WV , VA border, and bring a heavy wet snow strictly for part of Kentucky and West Virginia only basically. We’ll see how this trends."

 

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1 hour ago, Knoxtron said:

SREFs seem to be giving a little love back or the Friday system

TYS: Avg 1.6", 1 big dog at 6", 7 in the 2-3" range

CHA: Avg 0.07" (dont sneeze)... 

TRI: Avg 1.9. 1 big dog at 4", 11 in the 2-4" range

 

Weather south has a nice right up (albeit from yesterday evening). He is cautiously beating the drum on a substantial wet snowfall somehwere around 40 near the apps

From his paid blog... doubt I should be posting this

 

"As mentioned about the warming 850 temps, the surface high on Saturday is heading out to sea quickly, but the warming aloft isn’t all that dramatic, thanks to incoming height falls overall. (neutral to iso environment of upper temps). Despite strong warm advection at 850, bringing in copious moisture, the offsetting factor could be rates of fall and the lowering of the 5H height field in TN to NC especially at the base of the jet stream and most divergence region. This always means a super tricky environment for rain versus snow. So, the jury is out on exactly how much snow falls in places like Knoxville, Asheville and Roanoke to Winston Salem, but first guess is that it will be substantial, unless this low pulls much further north. And we know from past experience that lows shown this far out, can pull north. Most models are atleast in decent agreement on the low track from Louisiana to offshore NC then up the East Coast but just barely off the coast.    Once the upper system gets sampled very good in say 2 more days, we’ll know much more on exact tracks. The trend this Winter has been colder and wetter to win out, when youre near a threshold environment though. The difference on this system could be that it is a very wet system overall with excellent jet dynamics involved aloft. I won’t be suprised to see this trend earlier on start times in the Tennessee Valley to western Carolinas.  If so–expect more snow than models advertise right now. No guarantees though. It may well “amplify” a lot more as well , pushing the snow line completely to the Kentucky and WV , VA border, and bring a heavy wet snow strictly for part of Kentucky and West Virginia only basically. We’ll see how this trends."

 

He may be right.  18Z NAM showing east TN some love.  

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