Winter Speculation 17/18 -December Thread

[jaxjagman]

Nice for Mid Alabama

 

National Weather Service Birmingham AL
533 AM CST Fri Dec 8 2017

.UPDATE...
For 12Z Aviation.

&&

.SHORT TERM...
Today and Tonight.

Southwest to northeast band of precipitation has set up across the
area as expected. Temperatures range from 35-37 in this area.
Already have received reports of snow in Jefferson and Blount
Counties, and WFO MOB recently received a report of 0.5" in
accumulation in Choctaw County, just south of Sumter County. Also
just saw a report of snow covering the ground in St. Clair County.
Expect precipitation to continue to change over to snow over the
next few hours, with the main rain-snow line setting up just north
of I-85 by midday. But areas north of this line could switch back
and forth between rain/snow throughout the day based on
precipitation rates and hourly temperature trends.

Models are in excellent agreement on precipitation trends through
the day today. Confidence in the meteorological conditions for snow
is high, with the main point of uncertainty being somewhat non-
meteorological factors which will determine what happens to the snow
when it comes into contact with the warm ground, roads, etc. Short-
term models have trended cooler with air temperatures near the
surface, and they should be sitting right around 32-34 while the
snow is falling, so there is now increasing concern for travel
impacts especially on bridges and overpasses. Also, precipitation
amounts have trended higher. Forecast soundings generally show
saturated sub-freezing profiles, with mid-level ascent in the
dendritic growth zone. Some ice pellets may mix in at times with an
isothermal 0C layer present at times, but snow should be predominant.
Model consensus has also trended wetter for this afternoon, with
moisture remaining in the area longer as continued synoptic forcing
occurs ahead of the trough. The warm ground temperatures will make
it difficult for accurate snowfall measurements, but WPC snowfall
amounts and SREF mean values now indicate a swatch of 1-2+" across
the area. Really can`t argue with that based on trends, so portions
of the winter weather advisory were upgraded to a winter storm
warning. There could be a relative minimum in the middle of the
warning area along the I-65 corridor where amounts stay just under
the 2" criteria. This would be between relative maxima in the
southwest counties where heavier precipitation is falling now during
the overnight hours, and another relative maxima in the higher
elevations of East Alabama. However, opted to go ahead and fill in
the gap as it will be close. The advisory was also expanded to
include Pickens, Fayette, and Walker Counties based on northward
trends.

Models are suggesting a deformation zone may set up over the
southeast counties later this afternoon and this evening, south of
the current winter weather advisory. Thermal profiles suggest this
will be mainly rain, but it will be borderline. Added in some small
0.1" accumulations southeast of the current advisory, and will
monitor short term model trends to determine if the advisory needs
to be expanded for tonight. Temperatures will fall into the 20s late
tonight across the area, resulting in the potential for black ice to
develop wherever moisture remains on roadways.

[John1122]

Unfortunately the current system is missing 90 percent of the forum and the clipper train now looks to be driving from Minnesota into New York. 

A surprise might gin up between now and then but I figure with the dry pattern it might be a good while before most of us have a good shot at anything. 

The GFS is hinting at a pattern change to warmth for a week or so and a big cutter that should at least break the dry part up for us. Still too far out to tell for sure though.

[tnweathernut]

Hard to tell if the modeled pattern warm up is brief or a fairly quick reload.  Long range indicators are hinting we reload the cold pattern as we head into the last week or so of December.  The brief (if that's what it is) warm up will feel nice!  The extended EPS would indicate the possibility of something to track around Christmas.  Time will tell....

[Carvers Gap]

Tnweathernut hit the nail on the head.  Both the 12z GEFS and EPS depict an increasingly cold pattern from d10-15 than what was modeled a few days ago...even a few runs ago.  The EPS was noticeably colder from d10-15.  Massive PNA ridge.  Seems there is a bit of a battle.  The trough had been modeled to pullback but never completely leave eastern NA.  The problem is it had the warmth to our southwest undercut it.  Now, as tnweathernut stated, it appears a significant reload may take place beginning sometime after d10.  I know many don’t like JB, but he has been all over this.  I personally wait to use him as a source, because some of his forecast can be hype.  So, I wait to see it with my own eyes.  This current cold shot(the one this week) actually moved forward in time quicker than modeled at medium range.  There are some signs the next cold spell may do the same.   The EPS yesterday was very warm d10-15.  Today, there was more back and forth...with the hammer dropping d14.  I wall also add that our own EnergyJeff called the potential Christmas cold shot well before JB.  

[Carvers Gap]

The 18z GFS continues to show a trend towards colder in the 10-15 day forecast...a monster PNA ridge.

[Carvers Gap]

Look for a lot of flopping around on the GFS from d10-15 as it appears some pretty cold air will try to make into NA.  The wild changes can be a sign of very cold air.  The 0z GFS was dealing w a SER while the 6z sends cold air into the East.  Even as we are in our current cold shot, it appears a second is on the horizon...but where does it go and how far does it get?  The EPS after its “flip” back to colder during d13-15 still maintains that at 0z. It is not a true flip becaus the pattern never really changes during the warm-up.  The trough just pulls back north and reloads.  The one note on the EPS is how dry things get while it is cold.

edit:  The 0z Euro operational is beginning to mute the duration of the warm-up late in its run.  Also, the precip in this pattern seems to originate from the northern stream which is why it is dry.  We either need split flow w some systems undercutting the western ridge or we need the trough to tap the GOM.  A -NAO would work to slow things down so that we could get a storm.  So even though we have cold, there are some other things that need to fall in place as well.  

[John1122]

39 minutes ago, Carvers Gap said:

Look for a lot of flopping around on the GFS from d10-15 as it appears some pretty cold air will try to make into NA.  The wild changes can be a sign of very cold air.  The 0z GFS was dealing w a SER while the 6z sends cold air into the East.  Even as we are in our current cold shot, it appears a second is on the horizon...but where does it go and how far does it get?  The EPS after its “flip” back to colder during d13-15 still maintains that at 0z. It is not a true flip becaus the pattern never really changes during the warm-up.  The trough just pulls back north and reloads.  The one note on the EPS is how dry things get while it is cold.

edit:  The 0z Euro operational is beginning to mute the duration of the warm-up late in its run.  Also, the precip in this pattern seems to originate from the northern stream which is why it is dry.  We either need split flow w some systems undercutting the western ridge or we need the trough to tap the GOM.  A -NAO would work to slow things down so that we could get a storm.  So even though we have cold, there are some other things that need to fall in place as well.  

There's a few surface similarities to 1989. '89 had some warmth early. 89 had waves of cold with brief warm ups inbetween. 89 had a very deep south unusual snow event and 89 was very dry here.  .75 or so for the month if I remember correctly. 

[weathertree4u]

49 minutes ago, John1122 said:

There's a few surface similarities to 1989. '89 had some warmth early. 89 had waves of cold with brief warm ups inbetween. 89 had a very deep south unusual snow event and 89 was very dry here.  .75 or so for the month if I remember correctly. 

December '89 was the same way in the Nashville area and essentially, Winter was done at that point that year. January and February were essentially no-shows

[AMZ8990]

3 hours ago, Carvers Gap said:

Look for a lot of flopping around on the GFS from d10-15 as it appears some pretty cold air will try to make into NA.  The wild changes can be a sign of very cold air.  The 0z GFS was dealing w a SER while the 6z sends cold air into the East.  Even as we are in our current cold shot, it appears a second is on the horizon...but where does it go and how far does it get?  The EPS after its “flip” back to colder during d13-15 still maintains that at 0z. It is not a true flip becaus the pattern never really changes during the warm-up.  The trough just pulls back north and reloads.  The one note on the EPS is how dry things get while it is cold.

edit:  The 0z Euro operational is beginning to mute the duration of the warm-up late in its run.  Also, the precip in this pattern seems to originate from the northern stream which is why it is dry.  We either need split flow w some systems undercutting the western ridge or we need the trough to tap the GOM.  A -NAO would work to slow things down so that we could get a storm.  So even though we have cold, there are some other things that need to fall in place as well.  

What do you think about the precipitation we could possibly get around d12-d14?  Models are hinting at a possibility of something around that time frame.

[Carvers Gap]

1989 was the beginning of a time of very warm winters(specifically the heart of winter).  We had seen many cold winters prior to that.  I was at UT during that timeframe.   It was not until '93 that I would see snow while I was on campus.  Is this '89?  Maybe, maybe not.  Good question.  Cold Decembers always remind me of that time...and what would follow.  1989 was super cold followed by the earliest spring I have ever seen.  We missed a big storm that December.  Bastardi is saying that the second half of winter will be warm.  I simply do not know.  I think the solar min will help.  I think the -QBO will help.  How strong does this Nina get?...will matter.  I have read some comparisons to 95-96.  There is a chance for a major cold outbreak after this next warm-up.   Could we make a break for spring like '89?  Sure.  But we could also be in for a prolonged winter of seasonal cold and snow.  I think a January thaw will happen, because at this latitude it is almost a guarantee.  I think the current winter pattern is what we saw in November - just translated to colder months.  Cold builds in the northern Plains, and then it releases southeast.  During November, the residual warmth from summer could fight the new, cold air masses.  Now, the days are shorter, the cold air masses more intense, and less heat in the southwest to fight.  So, the cold can stay longer.  But basically, we are still in that pattern, and it has been a stubborn one to move.  I do think that this Nina will make it dry.  It is dry now.  In my area, moderate to strong Ninas are usually dry.  Look at last fall...bone dry.   I could probably make a case that this last wave event resembled the overrunning events of 95-96 just displaced a bit SE.  The one positive from the models that I have seen up to this point is that warmth in the LR has been short lived.  November ended up warm here, but we had several more days of BN than AN for the month.  95-96 had some warmth embedded during a snowy time.   The past few winters seem to be writing their own analogs.  The persistent feature in short to medium range(even long range) modeling is a monster PNA ridge.  The models will try to break it down and/or displace it...but it returns during subsequent runs.  I suspect that feature will be here for a good part of the winter.  What will be fun is if the SER pops just enough on the eastern side of a trough.

Some interesting model notes and unconnected thoughts....I told a friend that this pattern has ice storm written all over it.  Cold air retreating slowly northward as it is attacked from the southwest.  This cold air, once in place, just does not want to move quickly.  Some years it is in and out in 48-72 hours.   This year, the cold is stubborn.  The 12z GFS late in its run has a cold boundary that stalls and warm air overruns if.  The 12z also has a 1048 high in the northern Plains late in the run.  The 6z GFS had -54F cold over Greenland.  The control for 0z Euro and the 6z and 12z GFS are showing potential for a very cold shot right around Christmas.  Too far out there to say if accurate....but the possibility is there.

[Carvers Gap]

1 minute ago, AMZ8990 said:

What do you think about the precipitation we could possibly get around d12-d14?  Models are hinting at a possibility of something around that time frame.

IMO,  I think we will see some rain ahead of the next cold shot...but if the models speed up the cold that could change.   Looks like the trough pulls north and allows for rain to slide under it.  Again, the pattern is basically the same,  the trough just pulls north.  

[AMZ8990]

3 minutes ago, Carvers Gap said:

IMO,  I think we will see some rain ahead of the next cold shot...but if the models speed up the cold that could change.   Looks like the trough pulls north and allows for rain to slide under it.  Again, the pattern is basically the same,  the trough just pulls north.  

Well if anything, we definitely need some rain.  It's been awful dry to say the least!

[Carvers Gap]

Just now, AMZ8990 said:

Well if anything, we definitely need some rain.  It's been awful dry to say the least!

Yeah, for sure.  When I use the riding mower to collect the last of the leaves...it is a cloud of dust.  Like tnweathenrut, I am encouraged to see a storm with GOM influence this early.  

[AMZ8990]

15 minutes ago, Carvers Gap said:

Yeah, for sure.  When I use the riding mower to collect the last of the leaves...it is a cloud of dust.  Like tnweathenrut, I am encouraged to see a storm with GOM influence this early.  

I know what you mean.  We've been dealing with leaves on the course for the past month,  It's been pretty miserable!

[PowellVolz]

I know what you mean.  We've been dealing with leaves on the course for the past month,  It's been pretty miserable!

What course?


.

[AMZ8990]

1 minute ago, PowellVolz said:

What course?


.

Memphis National,  We've got 2 separate 18 hole courses.

[jaxjagman]

Man,this would be pretty sweet (GOES)

[John1122]

23 minutes ago, jaxjagman said:

Man,this would be pretty sweet (GOES)

That's definitely about as good as it could possibly get as a potential scenario forum wide.

[Carvers Gap]

Not great runs(for those who like snow) of the operational or ensemble models last night for the medium and LR.  The EPS had a modifying trend for d10-15.  The 6z GEFS flattens out the cold and at times looks lost.   That can happen and is not the first instance that the model has shown this.  It has a healthy SER.  The 0z EPS, while modified, keeps the cold pool over the East w little to no SER.  My money is on the Euro.  Now, for a second, let us assume the GEFS is correct.  It stalls a cold front in the nation's mid-section.  If that happens, western areas of the forum would potentially see some frozen precip or a very cold rain.  The eastern areas would be AN.  The 0z EPS and 6z GEFS are night and day at the surface from day 10-15.  Right now, both show an NAO that is a problem for the eastern US.  The GFS does pick up on some frozen precip around d5.  The Euro had it yesterday, and it is gone today.

[Carvers Gap]

12z GFS and GEFS cleaned up the odd cold front that was draped over the US.  The operational is more aggressive which is to be expected.  As Jeff stated in another thread...the SER will be stubborn.  It is a product of where the trough is placed.  Further into the Plains, the bigger the SER...further east, the less of a SER we get.  The trough has been too far to the East recently.  I will take my chances with the cold(big highs at that) crashing into the Plains and spreading east.  The precip will ride that boundary.  Would be a really good set-up potentially for some areas of the forum.  IMO, be glad we are on this side of the Apps.  We will have a 4-7 day break as Jeff stated, and even the duration of that is in question.  A little bit of a ridge is a good thing.  But like Jeff said, we need the NAO to be negative to slow things down.

[nrgjeff]

Agree with Carvers, all posts including that long one. KCMO set its all-time record low of -23F two nights in a row in December 1989. Then spring started on New Years Eve. I'm going to go out on a limb.. throw out 1989 despite the +PNA. Actually I am starting to like 2010-2011 going forward, but it could be nostalgia for my first winter here. Note Dec. '17 is not cold enough, so I'm just talking Jan/Feb.  If it were to verify, I'd have to change my slight mild January to slight cold. Continue mild February forecast.

Here is the problem with 2010-2011 though. It had a big -NAO. This year we have seen it at times, but the persistent pattern is the +PNA. If the source region gets cold, the Plains could have a wonderful winter. Here, we need to get back to that hybrid that includes -NAO. Interesting January 1996 has a feel not too unlike recent CFS runs, broad trough over central US (Rockies to Mid-South). I was going to wait for the Euro weeklies, but they would not change the comparison years discussion too much.

[AMZ8990]

29 minutes ago, nrgjeff said:

Agree with Carvers, all posts including that long one. KCMO set its all-time record low of -23F two nights in a row in December 1989. Then spring started on New Years Eve. I'm going to go out on a limb.. throw out 1989 despite the +PNA. Actually I am starting to like 2010-2011 going forward, but it could be nostalgia for my first winter here. Note Dec. '17 is not cold enough, so I'm just talking Jan/Feb.  If it were to verify, I'd have to change my slight mild January to slight cold. Continue mild February forecast.

Here is the problem with 2010-2011 though. It had a big -NAO. This year we have seen it at times, but the persistent pattern is the +PNA. If the source region gets cold, the Plains could have a wonderful winter. Here, we need to get back to that hybrid that includes -NAO. Interesting January 1996 has a feel not too unlike recent CFS runs, broad trough over central US (Rockies to Mid-South). I was going to wait for the Euro weeklies, but they would not change the comparison years discussion too much.

Jeff and Carver-  Thanks for those breakdowns, I really enjoy reading yall's input.  

[Carvers Gap]

12z EPS caved to the GEFS.....w regards to the placement of the NA temps d10-15.  The western forum area will now be coldest if today's run is correct.  The PNA ridge is sharp.  Cold arrives in the Plains and SLOWLY oozes east.  Also of note, the cold did not move forward in time on this run.  It was actually delayed until Christmas Day (or even the day after) for the western 2/3 of the forum area.  The EPS was very dry w less than 1" total for several events.  Both the GEFS and EPS are both rightly or wrongly leaving energy in the southwest.  If that comes out...look out.  The trough east of HI argues that the EPS should be centered a bit more east w cold temps.  The NAO is deeply positive.  Features 1 and 2 teleconnect to a trough in the East.  3 is the energy buried in the SW.  5 is the SER.  4 is the NAO that teleconnects to a storm pattern that is fast.  This is an odd set-up as normally one sees symmetric regions of cold (generalized comment) around the planet.  I would argue that the atmospheres in the NH is in transition.  That elongated area if cold is an odd configuration (not unheard of though).  One would think a ridge would pop over the north Atlantic.

[Carvers Gap]

Monday Weeklies Update.  Short and sweet.  The Euro is colder during the first four weeks than the last run and returns to its former cold self for those weeks....excluding week 2.  That is referring to eastern NA as a whole.  There are hints at a broad eastern NA trough during weeks 2-3.  Week 4 is a transition week to the mid-NA trough and then quickly by week 7 to AK.  The forum area is close to normal for precip.  The trough drops into western NA during wk5, and I am like...there is the new pattern.  Nope.  Then all of NA warms...but the unicorn of the -NAO tries to appear.  Could it be that we lose the +PNA in early Jan and then have a few periods of -NAO after the trough swings back West for a thaw? The EPS is rekmonwed for warming the entire NH late in these Weeklies runs which it does for this one excluding North Africa, some hyperbole there but some truth.  That is why the cold Weeklies were so bizarre.  Normally this model is warm.  Error...this is wrong-->(The snow mean has been cut in half.)  Overall, a very Weeklies forum for winter.  Will add more later as I get time to look...those are my initial thoughts and some of those thoughts are definitely open to debate(maybe all of it).  Still, that is a pretty cold run for the Weeklies if one takes into context how they look most winters.  

Addendum 1: Upon further inspection the trough retrogrades from eastern NA, to the West, and then AK during the last two weeks of Jan.

Addendum 2:  During wks 5-7, we lose the trough east of HI.  The Pacific will be of no help then.  It would seem the second half winter will hinge upon whether we can get a -NAO.  The -QBO might mean we have a chance.  A cold AK often means a warm eastern NA.  Other than that....the cold of winter wrecks havoc on the Weeklies.  It is often blind to severe cold outbreaks.  Definitely a thaw during the last half of Jan as modeled.  Then, who knows?  The very last week the cold then seems to make a slightmove to progress eastward out of AK. At that point...it is so far out there...who knows?  

[Carvers Gap]

Good words from Bob Chill in the MA forum.  Click to read the entire post.

 

[Carvers Gap]

Grabbed this from the MA forum as well.

 

 

[Carvers Gap]

Here are Weekly snow means since I was wrong above.  If I missed your city, note it and will look it up or a city near your location.  Earlier, I looked at the 32 day mean.   Here is the 46 day mean.  Impressive that the mean is similar to TR’s after the storm.  Looks like an uptick in snow right around Christmas or right thereafter.  Another two during the first and second weeks of January.  The snow means are a crap shoot, but a healthy mean is a good sign.  Interestingly, the uptick in snow is when the pattern flips warm.  The Plains show an understandable increase which is a good sign for folks in the western areas of our forum.

Bristol: 10”

Elizabethton:  12”

Knoxville:  5.5”

Nashville:  4”

Chattanooga:  3.75”

Bolivar:  2.75”

Memphis:  2.5”

Huntsville, AL:  2.5”

Olive Branch, MS: 2”

[nrgjeff]

Indeed the European weeks 3-4 are colder, Christmas and New Year's weeks. One can infer that cold air undercuts the 500 mb pattern a little bit. Actually the 500 mb heights are lower week 3, which helps with cold. As Carver writes, week 4 the US tough retrogrades west. Still the 500 mb normal line goes through our region.

Next week still looks milder despite Alaska-Russia ridging. Week 3 shows impressive ridging from Russia to Alaska, and colder than normal temps here. Week 4 the US trough shifts a bit west, but Greenland heights go AN. Southeast Coast is shown mild but cold air lurks in the Mid-South. Here in between temps are shown near normal week 4. 

[AMZ8990]

47 minutes ago, Carvers Gap said:

Here are Weekly snow means since I was wrong above.  If I missed your city, note it and will look it up or a city near your location.  Earlier, I looked at the 32 day mean.   Here is the 46 day mean.  Impressive that the mean is similar to TR’s after the storm.  Looks like an uptick in snow right around Christmas or right thereafter.  Another two during the first and second weeks of January.  The snow means are a crap shoot, but a healthy mean is a good sign.  Interestingly, the uptick in snow is when the pattern flips warm.  The Plains show an understandable increase which is a good sign for folks in the western areas of our forum.

Bristol: 10”

Elizabethton:  12”

Knoxville:  5.5”

Nashville:  4”

Chattanooga:  3.75”

Bolivar:  2.75”

Memphis:  2.5”

Huntsville, AL:  2.5”

Olive Branch, MS: 2”

I'm definitely keeping up with how things are looking for Christmas.  I've seen snow on New Years once here when I was a kid but I've never seen snow at or right around Christmas 

[Carvers Gap]

Big changes overnight in a 0z EPS model guidance.  The d10-15 has flipped. Big SER, which is new, during its entirety(d10-15).  Cold for the eastern forum area is totally gone on the EPS during this time frame.  The cold dumps into the mid-section of the country and barely moves.  If it verifies, this would be a very warm pattern for eastern areas and a potentially big temperature gradient from west to east w Memphis being the coldest.  The elongated, stalled cold front is back.  The Euro EPS has caved to the GFS it appears(as was noted yesterday at 12z).  Looks like the snow and ice storm that the GFS/GEFS has hinted at is possible for western areas depending on just how far the cold makes it.  I knew when the cold was pushed back yesterday that something was up.  That is a red flag always.  Now, it does a appear that the cold will try to press eastward which fits the Weeklies.  The 6z GEFS, a model which sniffed this potential change out first, had a SER and does not move it.  Would imply very warm temps for eastern areas for Christmas.  Hope it is wrong regarding eastern forum area temps.