February/March 2020 Winter's Last Chance Thread

[Carvers Gap]

It has been a busy few days, so just now settling in a bit.  The 12z EPS control had an almost identical run to the 18z GFS.  While I think it is an outside shot...here is what I am seeing on those two runs.  The EPO ridge builds in, kicks the western trough eastward, the EPO ridge retrogrades slightly, trough tucks West, and gets kicked out again.  IMHO, that has a chance at being the pattern which is better than a wall-to-wall ridge.  When this pattern showed up in early December, I felt strongly we were going to be warm for a long time and banged that drum pretty loudly.  I think  this time that ridge tucking West is a lot closer call than what was shown in early December.  That EPO ridge pushing into Alaska will be felt by that trough from time to time.  So, while we are in a base warm pattern in the East this winter...cold fronts can come eastward - especially as wavelengths change-up.

[Holston_River_Rambler]

NAM was optimistic with the 3rd wave deal we've been talking about:

I'll count the Saturday thing as a win if we get NAM'd a couple of times, lol. 

[Kentucky]

29 minutes ago, Holston_River_Rambler said:

Sorry @Kentucky saw you down in the "recently browsing" tab and realized I keep forgetting your area in these:

 

Thanks @Holston_River_Rambler, really appreciate all the maps/insight/models you post.

[Mr. Kevin]

I noticed Allan Huffman pointed out the strong Icelandic low is causing the +ao/nao. Its 926mb. Pretty strong. I still believe we need a pattern reshuffle. Everything is going against us.

[PowellVolz]

Everything is going against us.

.

[John1122]

00z GFS backed down on the heavy snow from 18z but still has some version of it at elevation. NAM is advertising widespread snow showers into Friday morning still.  It was better than other models with the NC snow earlier this past weekend. Maybe it's onto something for Tennessee. 

[Carvers Gap]

Of note, the 0z Euro has the event on the 9th again.  The 6z GFS has the same system.   It a small but powerful vortex diving into the back of the departing trough. 

[weathertree4u]

 

So looks like the latest run of the GFS is not nearly as torchy, especially in the long range

[Holston_River_Rambler]

8 hours ago, PowellVolz said:

 

.

 

[Holston_River_Rambler]

23 minutes ago, Carvers Gap said:

Of note, the 0z Euro has the event on the 9th again.  The 6z GFS has the same system.   It a small but powerful vortex diving into the back of the departing trough. 

I'd be feeling pretty good about that one if I lived on High Knob, Pikeville/ Wise areas. Not that it is out of the question for others, but I think elevation and latitude will win on this one. 

EPS has not really backed off or amped up since yesterday:

Although it does look like it too likes the idea of some flakes behind the 3rd wave we've been talking about, (the one John mentions above)

[Holston_River_Rambler]

7 hours ago, John1122 said:

NAM is advertising widespread snow showers into Friday morning still.

Looks like it even went for a little bit of anafrontal too at 6z:

OH BOY!!! first NAMing in two months!!!!

[Carvers Gap]

Lots of great stuff in here from MRX this morning... @Math/Met, low end mountain wave event?  

Wednesday night into Thursday, the cold front slows down due to the aforementioned strong high east in the Atlantic. This forces the low to take sharp turn north up toward the Great Lakes which orients the cold frontal boundary south-southwest to north-northeast. The atmospheric mean flow will be parallel to this boundary and heavy rainfall will occur along and east of this boundary. So the placement of the boundary will be very important in regards to how much rainfall our area will receive on Thursday. As of now, it looks like the areas that have the greatest chance for seeing heavy rainfall will be east of I-75 and moreso from southwest NC up along the spine of the Appalachians and into northeast TN. The heaviest rain will occur further east just on the other side of the Appalachians. Also during this time, Wednesday night through Thursday afternoon, the 850 mb jet will strengthen to around 50 Kts which will allow the higher elevations to see some gusty winds. There is a brief period Thursday morning where we could see some mountain waves but the winds will be mostly aligned parallel to the terrain through the duration of this event. Rainfall Amounts: Wednesday night through Thursday morning, most areas will see rainfall amounts around 1 inch with up to 2 inches possible across SWNC. On Thursday, areas along the eastern mountains will see up to another inch of rainfall and up to two more inches across SWNC. So from Wednesday through Thursday night, most locations will see rainfall amounts between 1.5 to 2.5 inches. Southwest North Carolina will see amounts between 3 and 4 inches with isolated amounts up to 5 inches. No headlines will be issued during this forecast as the heavy rain doesn`t start until Wednesday night. We will wait and see what the next round of model data shows before any decisions are made on any watch products. The boundary pushes further east Thursday night into Friday with colder air moving in behind the front. Any remaining moisture will change over to snow across the higher elevations with precip ending by early Friday afternoon. Another system moves in Friday night into Saturday as a shortwave trough swings across the area from out of the northwest. This system has the chance to bring more snowfall to the higher elevations but it`s too far out for any specifics regarding snowfall amounts at this time. Conditions clear out Saturday night into Sunday with another system moving in late Monday.

[Carvers Gap]

17 minutes ago, Holston_River_Rambler said:

I'd be feeling pretty good about that one if I lived on High Knob, Pikeville/ Wise areas. Not that it is out of the question for others, but I think elevation and latitude will win on this one. 

EPS has not really backed off or amped up since yesterday:

Although it does look like it too likes the idea of some flakes behind the 3rd wave we've been talking about, (the one John mentions above)

Regarding the even on the 9th(edit), the Euro looked really good for the Plateau w snow amounts of around 6".  I think getting some lift on that backside wave will help with marginal temps might produce enough precip to cool the air column.  Looks like it also falls at night.    I am not convinced that it doesn't trend north, but it at least gives us something else to track in addition to the wrap-around stuff on wave 3.   I would think areas along the TN/KY border and NE TN / SW VA have a shot at both.  For those new to the forum...yes, we all know these are not slam dunks.  

[Holston_River_Rambler]

It's going to be interesting to see how the precip. maps come out for the 6z Euro, at least for the 7th event that has NAM'd us. It looks similar at 500 mb to the NAM, but is a little further west with its surface low. 

[Carvers Gap]

41 minutes ago, weathertree4u said:

 

So looks like the latest run of the GFS is not nearly as torchy, especially in the long range

GFS at 6z looks pretty warm to me after the 10th.  That said, modeling has periodically been picking up on a brief cool down sometime between the 16th-19th.  Again, I am not super convinced of what is being shown after the 15th.  We will keep watching the MJO...rally cap folks probably need to just pull for that model to hold the MJO in the COD.  

[Carvers Gap]

Just now, Holston_River_Rambler said:

It's going to be interesting to see how the precip. maps come out for the 6z Euro, at least for the 7th event that has NAM'd us. It looks similar at 500 mb to the NAM, but is a little further west with its surface low. 

6z Euro snow accums looks slim for the 7th, but it might not be picking up those well.  Looks like there is a brief period of snow showers modeled for the eastern half of the state though, so it does have that.

[Holston_River_Rambler]

5 minutes ago, Carvers Gap said:

6z Euro snow accums looks slim for the 7th,

Thanks. For some reason every other variable populates on weathermodels for the 6z Euro before precip. The NAM is popping a surface low stronger, earlier, and further east, so probably why it gives us that little stripe of anafrontal snow. 

IMO that could be something the NAM would pick up on first, or could be overamping due to convection. 

[Holston_River_Rambler]

I always forget to look at the UKMET, lol. It gives a different evolution for the 9th:

[PowellVolz]

Looks like it even went for a little bit of anafrontal too at 6z:

OH BOY!!! first NAMing in two months!!!!

It’s a sad day when an 1.5” is getting NAM’ed.



.

[Holston_River_Rambler]

9 minutes ago, PowellVolz said:

It’s a sad day when an 1.5” is getting NAM’ed.

I almost extrapolated it's energy at hour 84 too, lol. It was further south and west than the Euro with it driving down the Rockies and probably would have given us a proper NAMing for the 9th storm. 

[Carvers Gap]

1 hour ago, PowellVolz said:

 

It’s a sad day when an 1.5” is getting NAM’ed.



.

 

Gonna need a bigger glass if you go look at the GEFS MJO.  Seriously, not sure I have seen this much spread on the MJO in a long time.  The EMON takes it a low amplitude into 5/6 for just a few days and then heads to the COD like the BOMM.  The GEFS goes almost off the charts into phase 6 with no COD.  The BOMM from a few days ago is more like the EMON, so I cautiously roll with those two.  But there is basically a vastly different MJO solution for each model.  The CFSv2 even goes into phase 7 after its COD.   With the MJO driving the bus, having wildly different solutions may very well cause some modeling issues after say the 14th.

[Carvers Gap]

...and one last note.  The above figures are used as examples of where the pattern could go and are not intended to be gospel.  When looking at medium and LR patterns, it is understood that modeling can and will likely change.  So, looking at trends, similarities, and differences can give us some idea of the most likely path(s) that the weather might take.  So, view those comments as general observations and kicking around potential.  As much as modeling has bounced around during the past 2-3 weeks...that also has to be kept in mind.

[snowmaker]

40 minutes ago, Carvers Gap said:

...and one last note.  The above figures are used as examples of where the pattern could go and are not intended to be gospel.  When looking at medium and LR patterns, it is understood that modeling can and will likely change.  So, looking at trends, similarities, and differences can give us some idea of the most likely path(s) that the weather might take.  So, view those comments as general observations and kicking around potential.  As much as modeling has bounced around during the past 2-3 weeks...that also has to be kept in mind.

Thanks for the updates, I am just focusing in on the weekend. As dull as this winter has been this is the first system since November for us in west and most of middle tn this is the first system to even track in a while. No matter how small the system, something is better than nothing. At least starting tomorrow there will be something to track back into Texas. Hopefully all of Tennessee can at least get a little snow before spring, but it won't surprise me if we don't. Last year, we got a little ice In November and this year we got a dusting in November of 1/4 inch. We have had stretches like this before, at some point we will get ours. Just hope we don't have to wait for another year. Neverless, I enjoy coming over here and listening to all weather talk it is educational and fun.

[Carvers Gap]

Want to see some wild differences...take a look at the 12z GFS and the 12z GEFS regarding surface temp anomalies after d10.  It should be noted that they are basically different models as the GFS has the update and the GFS operational is at range.  It may very well be that both models are in error.  The 12z GFS MSLP anomaly is hilariously cold after d10.  The 12z GEFS is a mega torch which may or may not be based on an erroneous MJO(see above post).  Both extremes may very well be incorrect, but at least American modeling has covered the ranges of possibilities for this time frame.  The only thing I find even remotely interesting is that the CMC has a similar MSLP(to the GFS) anomaly as its runs ends.  Other than that...very warm vs very cold.  What could go wrong?  

[nrgjeff]

Weekend snow north of I-40 (and perhaps along parts of I-40) looks decent this morning. Euro remains on board, and even ticked south overnight. Still awaiting 12Z Euro.

I still think snow will not make it south to the 540 thickness line / 0C at 850 line. Low levels look warm and much of the event is Saturday daytime. 500/700 mb vort max still along/north of I-40. Finally, who believes Chattanooga will get snow? Shows 540/0C over town, but nah.

OK, serious again, the more reliable output still keeps snow an elevation event for the Plateau and Mountains. However snow levels are a touch lower, and accumulation at elevation a bit higher. Surface HP comes in behind the system. Might get some cold enough air for BNA/TYS/MRX but it's tough w/o HP already in place and/or dropping from the N/NE. Tri Cities has a slightly better shot at snow, esp if some wrap-around.

While it's a little early to drill down partial thicknesses, they are not as bullish as the total 1,000-500 mb thickness. They are almost as far south, but not quite. The 1,000-850 mb hints at warm boundary layer. The 850-700 mb hints at the vort max a bit north. Again it's early for that tool, and I only have it on the GFS. 

Looking ahead. Carvers offers a path to a nice encore. It could happen given IO Pac convection. Some is in a decent spot. However the IO is firing too. Depends when/how long that meanders over warmer phases of Indonesia. Also if any northern stream TPV energy fails to catch the West trough, SER will be stubborn. Euro is with Carvers. Fingers crossed.

[John1122]

It's probably safe to assume the GEFS is way overamped on the MJO. It tends to try and do that and to have it so high it enters phases it never actually reaches because it verifies much lower than predicted. 

I would have also in the past went on a sled run with the Euro joining a party inside 5 days that shows me with 8 inches of snow. But these days the Euro is only to be used within 24 hours on snow events in our region. It's excellent at other regions though. It's been all over the Texas/Oklahoma event for a week + and it's probably going to get it almost exact. The GFS had the event but was too far South and East with it. 

The snow event in NC last week, the Euro didn't catch on until the 12z run the day it happened. Not sure why our region is so tough compared to all the others around the country.

[Holston_River_Rambler]

Looking at the GFS satellite predictions, I think one thing the GFS is doing with the MJO is popping some cyclones in the south Pac ITCZ. We started with some good convection in the 7/8 regions, but all of it got eaten up in TC Tino, and that led to the +AAM, westerly wind burst, and big run through 6 earlier. 

Euro still has convection in those areas, but maybe not as active with TCs (sorry for the bouncies)

 

 

[Carvers Gap]

8 minutes ago, Holston_River_Rambler said:

Looking at the GFS satellite predictions, I think one thing the GFS is doing with the MJO is popping some cyclones in the south Pac ITCZ. We started with some good convection in the 7/8 regions, but all of it got eaten up in TC Tino, and that led to the +AAM, westerly wind burst, and big run through 6 earlier. 

Euro still has convection in those areas, but maybe not as active with TCs (sorry for the bouncies)

 

 

See, I think it is not an actual null phase.  I think it is 2/3 canceling out 6.  That has not worked well for us this winter as 6 usually has usually won that battle.  

[John1122]

Euro came in much better for non-elevated areas from Northern Middle all the way to the Eastern Mountains this run. Not quite as heavy at elevated areas but still plenty of 3 inch totals or more for a lot of the eastern half of the valley.

[Holston_River_Rambler]

4 minutes ago, Carvers Gap said:

I think it is 2/3 canceling out 6.

I agree, it's everywhere right now and that's why we have the COD. I just think the GFS goes a little bonkers with cyclones in 6, so it amps it up too high. But TCs are hard to predict, so I guess it is a wait and see game for that one as of now. 

In brighter news the Euro looks to come in good this PM for the 3rd wave thingy and Saturday.