Winter 2020-21 Medium/Long Range Discussion

[A-L-E-K]

CAD incoming

[Spartman]

 

[A-L-E-K]

scott gonna bust

[OHweather]

The pattern coming up is going to feature plenty of cold / Arctic air over North America to tap, along with a continued tendency for blocking over the Atlantic. 

A Rossby wave making machine will be in place over the western Pacific, encouraging persistent north Pacific blocking and a cross polar flow into Canada. This is occurring while a tendency for high latitude blocking continues across the board for multiple reasons. 

This loop of the GFS helps show the continued cross polar flow into Canada, and how the retrograding -NAO helps shove the tropospheric polar vortex towards the CONUS this weekend and next week, bringing a cold snap to much of the Lower 48. With the Pacific blocking likely continuing for the forseeable future, the model shows Arctic air reloading towards the end of the run in mid-late February. 

One of the reasons we will remain "blocky" for the forseeable future is the continued downwelling of the weakened stratospheric polar vortex into the troposphere, which encourages a -AO and blocking:

 

On top of that, there's been a recent uptick in tropical forcing across the western hemisphere, and western Pacific forcing will continue until further notice:

This deposits momentum in the tropics and subtropics (enhances the sub-tropical jet). Because momentum is a conserved quantity, the increase in momentum in the tropics and subtropics results in a decrease in momentum in the higher-latitudes, which causes a tendency for blocking. The 12z GFS is shown as an example of this, note how the stronger sub-tropical jets over the eastern Pacific and eastern Atlantic occur beneath weaker higher-latitude flow, and how this encourages high latitude blocking:

The persistent western Pacific forcing will keep our Pacific blocking in place for most of February, and the Arctic air dropping into North America will encourage continued cyclogenesis near the east coast, which will help encourage Atlantic blocking as well. 

Basically, the US will lean cold for much of February. There will be a baroclinic zone across the southern / eastern US, though the cold will seep south and east at times given the -NAO and the quality of the cold that will be available. The Arctic air may lead to near to below average precipitation for a lot of the CONUS (save for perhaps the southeast/east coast), but the pattern will stay at least somewhat active given the baroclinic zone and hints of a subtropical jet. The GEFS and EPS weekly forecasts for the next 30 days speak for themselves: 

While suppression and lack of moisture may be a problem at times, we are already in a rather wintry stretch that will probably last through all of February, and perhaps into early March. 

[pondo1000]

7 minutes ago, OHweather said:

The pattern coming up is going to feature plenty of cold / Arctic air over North America to tap, along with a continued tendency for blocking over the Atlantic. 

A Rossby wave making machine will be in place over the western Pacific, encouraging persistent north Pacific blocking and a cross polar flow into Canada. This is occurring while a tendency for high latitude blocking continues across the board for multiple reasons. 

This loop of the GFS helps show the continued cross polar flow into Canada, and how the retrograding -NAO helps shove the tropospheric polar vortex towards the CONUS this weekend and next week, bringing a cold snap to much of the Lower 48. With the Pacific blocking likely continuing for the forseeable future, the model shows Arctic air reloading towards the end of the run in mid-late February. 

One of the reasons we will remain "blocky" for the forseeable future is the continued downwelling of the weakened stratospheric polar vortex into the troposphere, which encourages a -AO and blocking:

 

On top of that, there's been a recent uptick in tropical forcing across the western hemisphere, and western Pacific forcing will continue until further notice:

This deposits momentum in the tropics and subtropics (enhances the sub-tropical jet). Because momentum is a conserved quantity, the increase in momentum in the tropics and subtropics results in a decrease in momentum in the higher-latitudes, which causes a tendency for blocking. The 12z GFS is shown as an example of this, note how the stronger sub-tropical jets over the eastern Pacific and eastern Atlantic occur beneath weaker higher-latitude flow, and how this encourages high latitude blocking:

The persistent western Pacific forcing will keep our Pacific blocking in place for most of February, and the Arctic air dropping into North America will encourage continued cyclogenesis near the east coast, which will help encourage Atlantic blocking as well. 

Basically, the US will lean cold for much of February. There will be a baroclinic zone across the southern / eastern US, though the cold will seep south and east at times given the -NAO and the quality of the cold that will be available. The Arctic air may lead to near to below average precipitation for a lot of the CONUS (save for perhaps the southeast/east coast), but the pattern will stay at least somewhat active given the baroclinic zone and hints of a subtropical jet. The GEFS and EPS weekly forecasts for the next 30 days speak for themselves: 

While suppression and lack of moisture may be a problem at times, we are already in a rather wintry stretch that will probably last through all of February, and perhaps into early March. 

Great post as usual. Any chance of a real clipper type pattern developing and not these Pacific Northwest impulses? 

[OHweather]

2 minutes ago, pondo1000 said:

Great post as usual. Any chance of a real clipper type pattern developing and not these Pacific Northwest impulses? 

After the PV starts lifting out next week, there may be an opportunity for clippers if heights can rise on the west coast around mid February. 

[Malacka11]

It may not be a real clipper train, but damn is there a rumbling round the bend. RC was right, looking at the ensembles makes it look literally like a week straight of snow chances. Hopefully a few of them actually do okay. 

[madwx]

man the 0z GFS gets weird in the extended.  By next weekend it basically sets up very little flow over the entire lower 48.  the 850 mb level just stagnates and the cold air just sits over the entire country.  Then afterwards we get a major chinook event and warm air floods in from the pacific

[A-L-E-K]

where did all the snow go

 

[Chicago Storm]

gonna be up a lot by Wed.

the rebound continues.


.

[Malacka11]

Can anything decent happen with that supressed south mess or

[WaryWarren]

Looks like Malacka answered his own question mid-post.

[janetjanet998]

Models hinting at another nickel and dime event 11-12th instead of cold blast

so Sat is system 1.......

Monday/Tuesday is system 2 (or is 2 and 3 in there combined)?

next is thursday/friday no thread yet) 

 

[StormfanaticInd]

Spring is going to be delayed again. Have to wonder if indeed another mini ice age is starting lol

[Baum]

^ it ain't 1976-1980 by a long shot.

[Malacka11]

Not sure there's a proper thread, but some interesting trenderonies on the GFS regarding the later week system

[janetjanet998]

00z GFS interesting for the 11-12th 

windy too

even has a lake connection for NE IL at times

 

[hawkeye_wx]

Brutal cold behind the system, too.

[StormfanaticInd]

For the love of God!!! 

[StormfanaticInd]

There is some serious potential of a major winterstorm late next week

[WHEATCENT]

these models are ridiculous 6 days ago it was suppose to be below 0 starting tomorrow here in ohio sunday-tuesday the last 2 days it was suppose to be pushed back to next thursday and friday, now well i guess not. 

[StormfanaticInd]

15 minutes ago, WHEATCENT said:

these models are ridiculous 6 days ago it was suppose to be below 0 starting tomorrow here in ohio sunday-tuesday the last 2 days it was suppose to be pushed back to next thursday and friday, now well i guess not. 

Oh its coming. 

[madwx]

Lol lots of anxiety posting here.  Above average temps after February 24.  You heard it here first 

[Scorpion]

It’s already too damn cold to do anything outside can’t believe it’s just gonna get worse.

[Snownado]

1 hour ago, madwx said:

Lol lots of anxiety posting here.  Above average temps after February 24.  You heard it here first 

I don't know. I'm starting to believe that we are entering the next ice age.

[RobertSul]

19 minutes ago, Snownado said:

I don't know. I'm starting to believe that we are entering the next ice age.

Alaska was glacier free during the last ice age and roughly averaged two degrees WARMER than today. I guess even in extreme long term patterns, a warmer Alaska meant a colder CONUS. 

[purduewx80]

3 hours ago, RobertSul said:

Alaska was glacier free during the last ice age and roughly averaged two degrees WARMER than today. I guess even in extreme long term patterns, a warmer Alaska meant a colder CONUS. 

Alaska was most definitely not ice-free. The mountains were glaciated, while the interior was ice-free because it was a desert. Moisture sources were farther removed due to much lower sea levels. 

[RobertSul]

1 hour ago, purduewx80 said:

Alaska was most definitely not ice-free. The mountains were glaciated, while the interior was ice-free because it was a desert. Moisture sources were farther removed due to much lower sea levels. 

You’re right, I should’ve said /largely/ glacier free, especially in contrast to mid-latitude regions.

[Powerball]

I'm almost tempted to make a thread, as February 12th - 13th seems to have good potential for a significant winter storm across the region. The GFS has been showing it for the past couple of runs, and there's good ensemble support. 

The setup has some similarities to the PV Blizzard back on 1/6/14.

That said, I would like to see some more agreement from the EURO and GGEM first.

[michsnowfreak]

20 minutes ago, Powerball said:

I'm almost tempted to make a thread, as February 12th - 13th seems to have good potential for a significant winter storm across the region. The GFS has been showing it for the past couple of runs, and there's good ensemble support. 

The setup has some similarities to the PV Blizzard back on 1/6/14.

That said, I would like to see some more agreement from the EURO and GGEM first.

Before you know it were going to be worse than the Eastern subs when it comes to making storm threads lol. I do like the potential tho