February/March 2020 Winter's Last Chance Thread

[John1122]

Almost everything outside of the mid-week light snow shower chance is now based in hoping February's decent ensemble modeling trends aren't the 40th head fake of the winter season. The GEFS snow mean is nice but seemingly meaningless the past few winters, as it has virtually not verified in 48 months when it shows these snowy solutions.  The Euro at D10 looks better than it did at day 10 yesterday, so there's that. Still looks like a robust frontal passage behind a cutter in a fast moving pattern, rather than something that will set up shop and allow for truly cold weather to arrive for any length of time.  

If we get lucky and the Polar Vortex splits but will it help us? It split last year and record breaking cold hit the Midwest but didn't propagate into our back yards. I've not looked but I'd guess there's been very few times when Chicago had highs in the -10 range that it didn't get cold here. Last year that happened and we stayed warm.  It also takes a few weeks for the PV to change weather in the Lower 48 most of the time. That would put us on track for the backside of February into March at best, where even with the aid of the TPV we'd probably be looking at lower elevation cold rain and elevated snow unless we got a bowling ball.

If we are still hoping to reel in something in the D9-16 range in a week or 10 days, winter is likely over until late March or April, where it will invariably turn frigid for 2 weeks with rain or snow showers.

[Carvers Gap]

Thanks for the new thread, @John1122.  Looks like this is pinned to the top, so I will place afternoon ensemble discussion here.  

[Carvers Gap]

12z GFS still on time with a strong cold front and ensuing trough around Feb 5th.  Something to watch, as noted in the previous thread, is whether energy will make a run along the incoming front.  In this case there were 3 waves of precip long the front.  First was rain and the last was snow as the Arctic front passes.  We have scored on those during the past decade, usually 2-4" type snow events.   Obviously at this range, a lot can and will change.  Things to monitor will be whether the cold actually modifies as the event nears or will it maintain that strong frontal passage.  Another thing to watch will be the angle of the front.  If it sort of gets a positive lean to it, that raised the likelihood of something riding the front, especially if the tail is slow to move along in Texas.  In other words, we want it to drape across the SE as a frontal boundary.  Will be interesting to see where the rest of the run leads.

As for this weekend's look, still not sure I buy the suppressed look but certainly looks that way as of right now.  The energy that digs in behind it would likely induce snow shower activity.  

[Carvers Gap]

I think the 12z GFS at least shows why we have been watching this timeframe for seemingly weeks.  Get cold air into the pattern with an STJ and the 12z GFS is a potential option.  There was an additional wave which I think makes four along that front which hugs the coast.  Long way out there, but something to track for now.

[tnweathernut]

Good posts, Carvers.. 

It's definitely cold at day 10, but if the 12z GFS is close to correct at 500 at 240, it would almost be a certainty for FRIGID air to come at us toward day 15.  MJO phase 1-3 FTW?   

Around day 9, the 500 charts are pretty much a "money" look for overrunning to begin almost immediately behind the frontal passage day 9.  Is it right, I don't have that confidence.  Is it inside day 10...............YES!

[weathertree4u]

4 minutes ago, tnweathernut said:

Good posts, Carvers.. 

It's definitely cold at day 10, but if the 12z GFS is close to correct at 500 at 240, it would almost be a certainty for FRIGID air to come at us toward day 15.  MJO phase 1-3 FTW?   

Around day 9, the 500 charts are pretty much a "money" look for overrunning to begin almost immediately behind the frontal passage day 9.  Is it right, I don't have that confidence.  Is it inside day 10...............YES!

Is that -45 just above the Great Lakes?

[tnweathernut]

The wave after day 10, with energy diving in and a storm on the SE coast could be a nice Miller A for our region.  It could also be snow on snow if overrunning sets up somewhere in our region a day or two before.   

If you want snow, you really need to cross your fingers the GFS is onto something.  Most of the time, it's just ON something.  Maybe the other modeling will give us some clarity as we move toward @Carvers Gap period, centered around the 5th of February.  I can't remember the last time I have seen a great Atlantic and Pacific around day 10.  It's usually day 13-15........ Maybe this one isnt a head fake.  (insert Lucy pulling the football from Charlie Brown gif)

[Carvers Gap]

5 minutes ago, weathertree4u said:

Is that -45 just above the Great Lakes?

Yeah, it is cold up there.  Will be interesting to see if that verifies.  The 500 pattern as @tnweathernut mentions would support that type of cold.  However, we had that forecast I think(at LR) last week and Canada ended up with +30 to +40 departures from normal.  LOL.  The good thing about this run is the actual initial front is inside of d10.  Will come into focus here over the next 3-4 days.  

 

[Carvers Gap]

7 minutes ago, tnweathernut said:

The wave after day 10, with energy diving in and a storm on the SE coast could be a nice Miller A for our region.  It could also be snow on snow if overrunning sets up somewhere in our region a day or two before.   

If you want snow, you really need to cross your fingers the GFS is onto something.  Most of the time, it's just ON something.  Maybe the other modeling will give us some clarity as we move toward @Carvers Gap period, centered around the 5th of February.  I can't remember the last time I have seen a great Atlantic and Pacific around day 10.  It's usually day 13-15........ Maybe this one isnt a head fake.  (insert Lucy pulling the football from Charlie Brown gif)

Looks an awful lot like what led to the November pattern....this entire step-down the past few weeks feels like the October(January style) that led to November.  The extreme stuff broke shortly after mid month, then a cool down, warmed up, then another cool down, etc.  Also, the changing wave lengths likely won't hurt either.   We will see where it heads, but the similarities are interesting. 

[Carvers Gap]

The CMC at 12z is a great example of how the angle of that front on the leading edge of the trough makes a big difference.  It doesn't dig quite as much and everything slides OTS.  Ironically, we probably need a little of the Euro "digging into the Southwest" mojo if we want to see an overrunning event.  

[tnweathernut]

15 minutes ago, weathertree4u said:

Is that -45 just above the Great Lakes?

The 12z GFS sent the brutal cold sliding across southern Canada, and largely kept it out of the lower 48, except for brief incursions into the upper Midwest and Great Lakes area.  It's still cold here. 

[tnweathernut]

The 12z GEFS seems to really agree with the OP.  This is smoothed of course, so it won't match exactly but it checks almost all the boxes for winter in the SE/Mid-South.

1.  -NAO, west based

2.  50/50

3.  PV in the Great Lakes

4.  Southern Stream energy off the CA coast

5.  Hints of a - EPO and -AO

6.  Aleutian Low

Some of these points could be consider marginal or not perfectly placed, but all in all one of the better looking maps you will see at day 8.

[Daniel Boone]

1 minute ago, tnweathernut said:

The 12z GEFS seems to really agree with the OP.  This is smoothed of course, so it won't match exactly but it checks almost all the boxes for winter in the SE/Mid-South.

1.  -NAO, west based

2.  50/50

3.  PV in the Great Lakes

4.  Southern Stream energy off the CA coast

5.  Hints of a - EPO and -AO

6.  Aleutian Low

Some of these points could be consider marginal or not perfectly placed, but all in all one of the better looking maps you will see at day 8.

Actually looks good there. Not the best possible look but, good. Wouldn't take alot to become great.

[Carvers Gap]

12z Euro is much different(from its previous run) for the third straight run.  This time it has BN heights in AK and has dampened the eastern Pacific trough.  Not really a break in continuity, but more like very little continuity.  Trough is still there, but the AK BN heights are going to create problems.  Can't find another model doing that right now, even its previous run.  Model mayhem continues.

[Carvers Gap]

12z Euro:  Trough still goes in the East.  Has energy riding the Arctic front like the GFS.  Might be a 3-6 hours slower, but with a stronger trough that digs more(that is why it is slower).  What it is doing over Alaska looks new and might even be a random hiccup.  The Euro does weird stuff sometimes that turns out to be true.  So, I have learned over time not to discount oddities.  However, unless it shows me something on subsequent runs...going to file that as a hiccup.  And before folks think...oh no, here we go again.  The hiccup is not really a problem by 10.  That is a super, super cold look.  Virtually all of NA is in the trough, and it really doesn't roll the western ridge forward like 0z.  So, good run...but wonky as all get out.

[Holston_River_Rambler]

Weeklies for thy perusal:

[Holston_River_Rambler]

850 temps:

[PowellVolz]

850 temps:

.

[Carvers Gap]

Digging through the Euro Weeklies.  They are a bit washed out IMHO.  I don't use 2m temps verbatim when looking at them, because they have a notorious warm bias.  So, a little trick I have learned is to look at 850s.  One can see fronts pass through with those.  Keeping that in mind...First trough rolls through around the 5th.  Warmth builds for a day or two and the next cold front rolls through.  About every week we get a shot of cold for 2-3 days followed by an equivalent warm-up.  Surface temps are basically average out as normal from Feb 5-28.  Looks to me like the cold builds in the front range and presses eastward.  That looks explains why modeling is bouncing around with the SER - i.e. Is the SER real, and if so, how strong after the 10th?  Basically troughs plow through, the SER bounces back to varying degrees, and then the cold builds into the region again.  Looks to me like cold is about to be injected periodically into an active STJ pattern.  It is a progressive pattern that wiill depend on timing, but w AN precip/normal temps.  Of note, Alaska is AN or normal after Feb 10th until almost the end of the run.  Basically, it looks like February climatology.  Might even have some sever wx mid-month.  Not a sever guy, but if we go phase 6 during February and that gets hit by well BN temps...look out.

One final note, just glancing at MJO....Overall,  my guess would by moderate MJO phase 1and 2 and 3 during the first 10 days of Feb.  Then it progress through low amplitude 4-5, a higher amplitude 6 from Feb 10-20.  Then, it looks like 7, 1, and 2 fire during the last ten days.   Convection west of the dateline is just going to be a pain the rest of the winter.  The good thing is changing wavelengths will help.  

Honestly, it looks very much like the d10-15 of the EPS from this morning continued throughout the run.  Really is a shame it didn't run from the afternoon run which had a stronger -NAO and centered the LR trough in the continent's mid section.

There you go... a much too long diagnosis of a model run that is already behind its 12z run.  

 

[Carvers Gap]

28 minutes ago, Holston_River_Rambler said:

Weeklies for thy perusal:

Interestingly, those weeklies don't look like the WxBell version of March.  LOL.  Heights are normal to below for 500 anomalies on it, excluding the first four days.  February looks about right.  

[Carvers Gap]

26 minutes ago, PowellVolz said:

 

.

 

Nah, man.  The run didn't actually look that bad.  Temps are normal(edit...excluding first four days roughly of Feb...I was looking at daily maps which average out about normal) and precip AN for February.  Now, that doesn't mean much as they have been terrible...but seriously, not a bad run.  

[Carvers Gap]

35 minutes ago, Holston_River_Rambler said:

850 temps:

Man, that looks way different than what I am looking at.  

[Carvers Gap]

Ah sorry, I see...5 day increments on those gifs.  One day, @Holston_River_Rambler, you will need bifocals like me and understand.  The single day increments actually show the frontal passages.  Everything on the gif is about five days late and washes out the strength of the troughs and fronts.  But overall same idea.  Here is Feb 6 at 850.  And thanks for the gifs!

[Carvers Gap]

One thing to note, troughs on Weeklies are notoriously not deep enough.  They have correct deeper most of the time this winter.  We just didn't have many troughs until mid Jan.

[Carvers Gap]

Switching gears back to this weekend.  I still think NE TN needs to keep an eye on the wx.  The 18z GFS has a strong coastal low with decent snow in the mountains.  It would not take much of a westward shift and a slightly stronger storm to change the narrative at TRI over the weekend.  The open wave or weak slp has trended a good bit stronger at 18z.  Just toggle back a few runs and look at how much stronger it is.  Here is the zoomed in version:

 

[Carvers Gap]

As @tnweathernutnoted earlier today, the cold behind that front is bitterly cold.  Seeing some lower single digits after 240 - so take with a huge grain but shows the potential.  That air mass, if it verified, would be the coldest of the season.  Still a long ways to go, but interesting to look at.  And the trough still seems to be on time.  We knew we had trouble earlier this winter when fronts would get pushed back...As of now still Feb 5th.  

[Holston_River_Rambler]

16 minutes ago, Carvers Gap said:

One thing to note, troughs on Weeklies are notoriously not deep enough.

Yeah, I had heard someone saying they looked bleak so that's why I went and looked, but I thought it wasn't that bad with the overall pattern.

Unfortunately weathermodels only has the 5 day increments. 

[Carvers Gap]

Just now, Holston_River_Rambler said:

Yeah, I had heard someone saying they looked bleak si that's why I went and looked, but I thought it wasn't that bad with the overall pattern.

Unfortunately weathermodels only has the 5 day increments. 

They look better than Thursday.  LOL.  And the 12z EPS looks even better.  Not saying it is going to be a cakewalk as I noted some phase 6 MJO tendencies mid month.  But looks like we will have 2-3 windows during February.  First window looks like Feb 5-10 roughly.  Weeklies weren't exactly a fan of spring either - we all knew that was coming!

[Carvers Gap]

2 hours ago, PowellVolz said:

 

.

 

But save that gif though, cause at some point sooner or later...we are going to need it!

[Carvers Gap]

I also should have noted that the Euro Weeklies and CFSv2 imply that we will have a restocked Canada in terms of cold.  I am a little gun shy as they have done that once recently.  Both of those LR models have another trough amplification around Feb19-20.  Take that with a huge grain of salt.  Both models portray periodic intrusions of quite cold air into the East during February.  May be right and may be wrong, but that is what is on modeling this evening.