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Pattern The Great December Dump

Webberweather53 said:
Hard to dislike that configuration going into mid-December where the pattern was leaning mild for a while, perhaps for reasons I noted yesterday the GEFS will beat the EPS to the punch here in the extended. December NINOs that are BN around here usually find a way to produce a substantial winter storm in central NC in Dec, if we keep this up, eventually we may score one.
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Yep, I noticed it this morning, the EPS is not warm, but seems to be coming around to the general idea of the GEFS, just a bit more muted: PV in SE Canada, westernish ridge, just not as tall, and the beginnings of an Aleutian low. Basically our pattern for the last 5 years, but this time in December too. I'm still a bit disappointed our -NAO evaporated (sigh), but having a cool/cold pattern persist this early is encouraging. Hopefully this is the beginning of a long cold winter.

1575384830070.png
 
The bias of the EURO to push the trough into the West and build a ridge in the East is well known. The EURO will likely continue the correction and the trough will end up sliding East on future runs as we have seen it do so far. Nothing is guaranteed in the long term on the models but the pattern is looking much better than last December. If we can get that Western Canada ridge to build stronger and the NAO to go at least neutral, I like the chances for something happening before Christmas in the 40/85 corridor at least
 
MichaelJ said:
The bias of the EURO to push the trough into the West and build a ridge in the East is well known. The EURO will likely continue the correction and the trough will end up sliding East on future runs as we have seen it do so far. Nothing is guaranteed in the long term on the models but the pattern is looking much better than last December. If we can get that Western Canada ridge to build stronger and the NAO to go at least neutral, I like the chances for something happening before Christmas in the 40/85 corridor at least
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Agreed...the only thing I would say here is that the northern plains and east-central US is probably going to be favored for the coldest anomalies, until we get a favorable configuration up in the NAO domain. I would expect negative anomalies to be tempered in the SE with a bit of a gradient pattern through the region. Same with winter storm chances. I'd think northern and western zones are favored, as has been said, rather than threats to the deep SE. But you never know. Anyway, it's a much better boat to be in heading into mid-December than the last few.
 
Based on data today from Maxar, this Atlanta bias analysis is what really makes me wary about the recent trend toward colder in the models:

ATL Bias last 30 days (Negative Model Is Too Cold; Positive Model Is Too Warm)

1-5, 6-10, 11-15

T-AVG

GFS OP
GFS EN
Euro OP
Euro EN

1-5 Day
-2.6
-5.1
-3.6
-3.6

6-10 Day
-3.0
-6.6
-4.7
-4.3

11-15 Day
-1.1
-4.3
N/A
-2.3

This didn’t copy in the right format, but the gist of this is obvious: universal
model cold bias for ATL in 1-5, 6-10, and 11-15 the last 30 days with the GEFS being the worst in all 3 timeframes and even the Euro suite not a whole lot better.​
 
Rain Cold said:
Agreed...the only thing I would say here is that the northern plains and east-central US is probably going to be favored for the coldest anomalies, until we get a favorable configuration up in the NAO domain. I would expect negative anomalies to be tempered in the SE with a bit of a gradient pattern through the region. Same with winter storm chances. I'd think northern and western zones are favored, as has been said, rather than threats to the deep SE. But you never know. Anyway, it's a much better boat to be in heading into mid-December than the last few.
Click to expand...

Yeah, the thing with these -EPO driven cold outbreaks when we do get good cold south, is they tend to be cold and dry for a bit, and by the time a storm comes through it's gone because of the progressive flow. It can be frustrating, but it can work. I'm not looking for storm chances this early anyway. I'll just call a cool December a win if we can get it and hope for a shake up in the NAO domain in January to slow everything down.
 
GaWx said:
Based on data today from Maxar, this Atlanta bias analysis is what really makes me wary about the recent trend toward colder in the models:

ATL Bias last 30 days (Negative Model Is Too Cold; Positive Model Is Too Warm)

1-5, 6-10, 11-15

T-AVG

GFS OP
GFS EN
Euro OP
Euro EN

1-5 Day
-2.6
-5.1
-3.6
-3.6

6-10 Day
-3.0
-6.6
-4.7
-4.3

11-15 Day
-1.1
-4.3
N/A
-2.3

This didn’t copy in the right format, but the gist of this is obvious: universal
model cold bias for ATL in 1-5, 6-10, and 11-15 the last 30 days with the GEFS being the worst in all 3 timeframes and even the Euro suite not a whole lot better.​
Click to expand...
It appears that the GFS Op is not too bad after all. I can understand the GEFS being too cold because, and I may be wrong about this, the individual members are still the old GFS model.
 
GFS (operational) goes sends the upper Midwest into the icebox from around hour 170 til the end of the run..crucial as we don’t want our high pressure moderating as it drops down out of Canada for the next several months
 
I understand the cold bais of the GEFS and the 12z GEFS from D9 till the end of the run looks cold and wet.
b234edc2710e9982f55d0a19742badbf.jpg
5b18b9714c9d52d11e87f871c9456375.jpg



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Some may disagree, but the possibility of a significant snow event is still there for the 10th/11th time frame. I think there will be snow from the Lower Mississippi Valley, Southern parts of TN, through AL, GA and up into the Carolina's. It will most likely be an overrunning event/embedded low.

From today's 12z GFS run, it's still showing a convergence with the polar jet and subtropical jet (big factor for a snow event.)
gfs_uv250_us_32.png
Using today's 12z CMC surface map, it makes more since, moisture re-developing after main frontal passage. Moisture re-develops due to the jets convergence. The 10th/11th time frame is 7-8 days away, so we'll start to see a much more improvement on the models.

gem_mslp_pcpn_frzn_us_32.png


We'll see what today's 12z Euro shows.
 
WxWatch said:
Some may disagree, but the possibility of a significant snow event is still there for the 10th/11th time frame. I think there will be snow from the Lower Mississippi Valley, Southern parts of TN, through AL, GA and up into the Carolina's. It will most likely be an overrunning event/embedded low.

From today's 12z GFS run, it's still showing a convergence with the polar jet and subtropical jet (big factor for a snow event.)
View attachment 26894
Using today's 12z CMC surface map, it makes more since, moisture re-developing after main frontal passage. Moisture re-develops due to the jets convergence. The 10th/11th time frame is 7-8 days away, so we'll start to see a much more improvement on the models.

View attachment 26895


We'll see what today's 12z Euro shows.
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I still disagree as does the Euro. Nothing to see here IMO.
 
Figured that the EPO ridge would make or break our winter. Didn't expect it to be in this position in December thought it would be more of a January/feb thing. Can't be mad about where the 12z gfs/gefs/euro are

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packfan98 said:
CAD storm setup on the Euro:
prateptype_cat_ecmwf.conus.png

prateptype_cat_ecmwf.conus.png
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That one may have big legs on it.

Firstly, western ridge is being under played so far this winter.

Secondly, the big low over the NE is always too fast exiting stage right in modeling. I expect it to trend westward. This wave will likely either hit the jackpot or be crushed. I don’t think we get any sort of cutter with that setup.
 
I really love when patterns w/ a -EPO/+TNH & an active southern stream come calling because that's the general recipe you want to see for a southern slider. However timing is everything & even more paramount in a pattern like this. It can make the difference between being in the 70s and hitting the links vs having tons of white gold in your backyard.

This pattern almost always comes w/ a "side" of SE US/West Atlantic ridge, too much (or even too little) of a good thing can come back to bite you.

gfs-ens_z500a_namer_28.png

Fwiw, here's the pattern about 2-3 days before the Jan 1988 event got going over the southern plains.
compday.rKYL7eqEDj.gif
 
I’ll take E5 please! That Euro 9 1/2 day out storm looks amazing on paper! 1043 high in NY, precip coming in, don’t like the low in TN, but not worried about details! Now we’re cooking with an air fryer, at best!FFC29576-5962-4186-A4C1-4B361F8B4C0B.png
 
For those interested, DTs winter outlook is out on FB, havnt read it yet
 
I don't mind the euro's output, but I'm not a big fan, in comparison to the GEFS with the lack of heights around BC. Though neutral heights are better than negative heights.
gfs-ensemble-all-avg-nhemi-z500_anom-6324800.pngecmwf-ensemble-avg-nhemi-z500_anom-6324800.png
 
ForsythSnow said:
I still disagree as does the Euro. Nothing to see here IMO.
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I understand that you disagree, everyone has their different views. But considering the polar and STJ convergence, there's no doubt that something wintry is bound to happen. It could be minimal, but a quick shot at some heavy snow on the back side of the moisture is possible. Or it could be something significant, a wide coverage of a long duration of heavy snowfall. I do think that strong storm signal around the 15th or so may come up on the tail end of the boundary. We'll see how things shape up, still to early to "iron" out anything.

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Last edited:
FWIW, we're nearing our prime climo for Colder temps.
In GSO
Today's Average temp equivalent; 44.4 degrees which translate to February 26th
December 15th's Average is 41.2 degrees; the equivalent is on February 9th
 
Ollie Williams said:
I don't mind the euro's output, but I'm not a big fan, in comparison to the GEFS with the lack of heights around BC. Though neutral heights are better than negative heights.
View attachment 26914View attachment 26915
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This look on the EPS favors a lakes cutter and severe weather over the SE US, the GEFS obviously tends to wintry weather. I’ll be content with either
 
Webberweather53 said:
This look on the EPS favors a lakes cutter and severe weather over the SE US, the GEFS obviously tends to wintry weather. I’ll be content with either
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You know this ends up meeting in the middle. Decaying arctic air mass with the parent high going ots means a few people start as a few sleet pellets or snow flakes and go to rain quickly. That initial band of iso precip locks in the wedge, the tmb gets stuck east of 95 and most of nc is locked in at 34-40 with 850s of +10 so we get an elevated band of storms rolling through with areas SE of RDU making a last second push to 55-60

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