Winter Speculation 17/18 -December Thread

[Carvers Gap]

As for the LR, the EPS consistently shows the 500 heights dropping in the West around d13/Jan 17.  The ridge gets pumped in the East.  The control is maybe a day faster.   The torch is not as bad in the SE as some cooler air gets trapped under the rising heights.  What is interesting is that the control almost looks like(d15-16) it will pop a -NAO when the big area of BN heights reach the West coast.  Sends those AN heights pushing into northeast Canada.  And then it appears to want to reset the current pattern if one dares extrapolate past d15.  The mean plops the trough in the West coast and slowly moves it.   Looks locked in place.  The 6z GEFS/0z GEPS look very similar as well at 500. 2m temps on the non-Euro ensembles are not overly warm....40s for highs.  But at that range, those could easily verify warmer due to being washed out.

[John1122]

12z GFS shifted about 1000 miles south and east with it's track for Monday. Still too warm for anything but rain as all cold air quickly leaves the entire country. Crazy how much it's bouncing around and within 5 days. I don't see any point in trusting anything it throw out there. Canadian looks like it will be consistent with it's track. Not that it seems to matter much, one thing they are consistent with is that the cold will retreat very fast and allow everything to quickly change to rain.

[ShawnEastTN]

I see a large difference this run over the last on the GFS in how it depicts cold after the second "Cutter".  This run looks like it wants to bring a deep trough back after the second cutter. 

[Carvers Gap]

The storm behind the first one is interesting...JB brought that up, and I see it as well.  See the 12z CMC for slp placement.  I am not worried about snow maps.  Give me that second storm low placement on the CMC, and let's play ball.  The 12z GFS is not quite sure what to do IMO.  Check it out at the 500vort maps...drops one positively tilted vort after another. The CMC does the same as well.  IMO, I would not call that a loaded pattern...but the amount of energy rounding that trough is interesting.  Three pieces of energy on both...need a tad more separation.

[nrgjeff]

Clippers seem to be running into upper level confluence this year. Yes, one would expect a phantom clipper or two within 36 hours a couple times. This year they are getting rejected like a blocked basketball shot right under the rim.

Mid-January pattern looks pretty awful at the moment. Previous forecast of occasional blocking is gone, and heights are still AN over the Lower 48. Models are struggling with the MJO, and therefore the Alaska forecast. Glimmer of hope is the Northeast Asia trough remains. It's been a fixture this winter to-date. Need it to stay on the Euro tonight.

Looking farther out, either way I'm confident in more cold periods this winter. QBO remains negative. Alone it is a weak correlation down here. With everything that's transpired I think it's helping cold this year. AK ridge is stubborn and West ridging fits La Nina. 

[ShawnEastTN]

14 minutes ago, Carvers Gap said:

The storm behind the first one is interesting...JB brought that up, and I see it as well.  See the 12z CMC for slp placement.  I am not worried about snow maps.  Give me that second storm low placement on the CMC, and let's play ball.  The 12z GFS is not quite sure what to do IMO.  Check it out at the 500vort maps...drops one positively tilted vort after another. The CMC does the same as well.  IMO, I would not call that a loaded pattern...but the amount of energy rounding that trough is interesting.  Three pieces of energy on both...need a tad more separation.

Yeah the CMC's depiction of that second one is interesting nice high to the north with low south of us....  Would be a setup I would normally like to see all things considered.  

[Carvers Gap]

5 minutes ago, ShawnEastTN said:

Yeah the CMC's depiction of that second one is interesting nice high to the north with low south of us....  Would be a setup I would normally like to see all things considered.  

To echo what Jeff said..warm-up highly likely in mid-Jan.  It is not uncommon for cold patterns though to end w a big storm or even a couple.  I was thinking maybe the current system was that pattern changer.  Looks like we have 10-12 more days in the current pattern, and then the trough goes west or we go zonal...either scenario we are warm.  Back to the day1-12.... though temps are marginal, a well placed slp in January can be good.  Was actually surprised at the amount of energy in the pattern from d5-12ish.   Something to watch.  Still a couple of days from getting that in better focus.  Best I can say right now is that it is interesting and has potential.

[Carvers Gap]

Just a thought.  One thing that continues to catch my eye are the heights around the Davis Straits late in the global operational and ensemble runs.  The MJO would argue for a trough to lock in the West(see Jeff's comments above about the MJO).  But I want to play the flip side of the warm argument (I am in the warm camp for mid-Jan to early Feb).  Never bad to see what could change that.  The WAR ridge is raging by the end of the GFS run.  Now, it is unlikely that is exactly right, but just looking at the overall picture.  The trough(think I mentioned thus above) in the West kicks those heights northeast towards the Davis Straits just West if Greenland.  If that area has above normal heights, a sort of feaux -NAO pops.  And that potential  makes me wonder if the seeds for the next round of cold are being planted.  I could envision AN heights forming over the top of a trough(in the eastern PAC near AK) and then kicking one of those troughs East.  That in turn gets filled w cold by the forced NAO.  Might not last long, but it might create a window for a storm and an earlier redevelopment of the eastern trough.  Thus, the warmth would be shortened.  I noticed the same thing on the Euro control from last night.   As for the Weeklies, it will be interesting if they redevelop the cold in Feb like the last run...but really we are getting to the point where they matter less to the winter forecast.  Once, we hit February their skill will likely drop due to the changing seasons getting set to begin.  They have been decent up to this point inside of four weeks.  All right...enough on my part.  Only so much one can say with any accuracy regarding a pattern change back to cold four to five weeks away....obvious warm-up on the way.  Just looking to see what could flip it(to cold)earlier.

[Carvers Gap]

12z Euro definitely moved to is 0z EPS ensemble w suppression...but it is warm.  That puzzles me to see a system be so suppressed during a warm-up.  Normally systems are suppressed by cold HP.  Now, the 500vort map for the first system indicates a much stronger system at the surface and detached from the northern stream.  That may account for the warm-up in front of the storm.  But precip(liquid) totals are not good.

 

edit: very strange look for a strong vort that would normally want to gain latitude and not lose it to Miami?   

[Carvers Gap]

Kind of a strange run of the 12z Euro.  Will need the EPS to sort out the cutoff that wonders...trust me.  You need to see if for yourself. Go to the 500vort maps and look.  The second storm is an Apps runner. I am not even sure I can adequately describe what happens at d8.5.  Systems goes negative tilt to our south.  Looks good.  Another piece of energy dives into the back of it and pulls it straight north as an Apps runner. Then, it does some sort of fujiwhara dance with the incoming energy.  So...my take.  Decent chance at that time frame.  If that shifts even 50-75 miles east and consolidates the slp...that is a big storm.

[Carvers Gap]

The 0z EPS sniffed out the big operational changes at 12z.  Will be interesting to see where it goes.  IMO, it has been pretty decent with finding and placing storms....maybe not exact details, but the general idea.  The 12z operational Euro was close to being an inland runner.

[John1122]

We will see where it goes, but MRX is getting really bullish for an extremely wintry Sunday night here. 70 percent chance of sleet/snow/freezing rain with a low of 29. We will see how much moisture can catch the cold.

[tnweathernut]

15 minutes ago, John1122 said:

We will see where it goes, but MRX is getting really bullish for an extremely wintry Sunday night here. 70 percent chance of sleet/snow/freezing rain with a low of 29. We will see how much moisture can catch the cold.

Per their hazardous weather outlook:

Hazardous Weather Outlook
National Weather Service Morristown TN
229 PM EST Thu Jan 4 2018

NCZ060-061-TNZ012>018-035>047-067>074-081>087-098>102-VAZ001-002-
005-006-008-051930-
Cherokee-Clay-Scott TN-Campbell-Claiborne-Hancock-Hawkins-
Sullivan-Johnson-Morgan-Anderson-Union-Grainger-Hamblen-
Northwest Cocke-Cocke Smoky Mountains-Northwest Greene-
Southeast Greene-Washington TN-Unicoi-Northwest Carter-
Southeast Carter-Roane-Loudon-Knox-Jefferson-NW Blount-
Blount Smoky Mountains-North Sevier-Sevier Smoky Mountains-
Sequatchie-Bledsoe-Rhea-Meigs-McMinn-Northwest Monroe-
Southeast Monroe-Marion-Hamilton-Bradley-West Polk-East Polk-Lee-
Wise-Scott-Russell-Washington-
229 PM EST Thu Jan 4 2018 /129 PM CST Thu Jan 4 2018/

This Hazardous Weather Outlook is for portions of Southwest North
Carolina...East Tennessee and Southwest Virginia.

.DAY ONE...Tonight

Wind chill readings late tonight will be colder than 5 degrees
area wide, with higher elevations getting wind chill readings down
to the minus 5 to minus 15 degree range.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

Very cold temperatures and wind chills will persist into Friday
morning.

Wintry precipitation will be possible Sunday night through
Tuesday. Please continue to follow the forecast closely through
the weekend.

 

[ShawnEastTN]

With this beginning after dark for the eastern forum on Sunday I really begin to think back to other scenarios where WAA was forecast to be quite strong and it didn't fully pan out and switch over never occurred, or occurred only at the very end of precip.  Even if it switches over around daybreak which the Euro shows, it could end up being 5 or 6 hours of frozen precip before switching could be a really messy Monday Morning Commute.

[ShawnEastTN]

MRX afternoon Disco, mention same conditions from today potentially repeating tomorrow with our clipper, and the Sunday/Monday storm:

Quote

Area Forecast Discussion
National Weather Service Morristown TN
305 PM EST Thu Jan 4 2018

.SHORT TERM (Tonight and Friday)...Some breaks in the clouds are
finally allowing the sun to shine through in many locations this
afternoon. Radar is still showing there may be some very light
bands of snow still present as moisture is squeezed out of the
atmosphere along the Southern Appalachian Mountains, but very
little accumulations are likely the rest of today and would most
likely only occur in the highest terrain. 700mb jet out of the
northwest will continue tonight along tightening pressure
gradients leading to continued breezy conditions. This wind
combined with temperatures around 20 degrees below normal will
lead to another night of low wind chill values. Locations in the
Valley will likely see wind chill values in the single digits
while places in the higher terrain will reach near zero, and
coldest of all will be the mountains of Southern Appalachia. Many
locations in the mountains will see wind chills around -10 to down
to -15 degrees overnight. With these conditions expected there is
a wind chill advisory in effect tonight in the mountainous areas
of SW Virginia, E Tennessee, and SW North Carolina.

Similar conditions to what we saw today are expected again tomorrow.
There will be some mid/low level moisture moving in tomorrow morning
which could get squeezed out along the terrain of the area. Will
have mention of light snow flurries for overnight into tomorrow for
some locations even though models are not depicting any QPF at this
time (mostly because of how poorly they handled this mornings
atmospheric conditions).

.LONG TERM (Friday night through Wednesday)...The Eastern U.S.
upper level trough and arctic surface high will be gradually
shifting east away from the forecast area through the first half
of the weekend. High temperatures will still be below the freezing
mark on Saturday but should be rising back into the middle and
upper 30s on Sunday as the low level flow becomes southwesterly
ahead of an approaching short wave. Surface low pressure
associated with the feature will be shifting east across the Mid
South on Monday, with a warmer and moist southerly flow preceding
the surface system later Sunday night into Monday. Surface
temperatures will probably drop back below freezing during this
period and with the moisture building in over the top of this sub-
freezing airmass, precipitation would begin as a light wintery
mix of snow, sleet, and some freezing rain. Will await later model
runs to see what the eventual impacts will be with this system as
some changes are likely to occur with low pressure center timing,
track, and associated temperature and moisture profile. It
appears that enough warming will occur later in the day Monday for
the precipitation to become entirely rain; even across Northeast
Tennessee and Southwest Virginia. There will be a chance for the
rain to mix with some snow as the system makes it`s exit Monday
night into Tuesday morning. The forecast area will enjoy another
dry period Tuesday afternoon through Wednesday night; possibly
into Thursday. However, another upper trough will be on the
approach on Thursday with a slight chance of rain during the day
and a better chance for rain showers Thursday night.

 

[ShawnEastTN]

Clipper looks fairly healthy I'm sure a good portion is virga, but still none-the-less doesn't look too ragged.  With the extreme cold we may get some snow showers out of this late tonight/tomorrow.

 

[John1122]

The 18z NAM at 84 is about 150 miles further south with the LP leaving Texas than the 12Z GFS.  Sub freezing temps more widespread in Middle Tennessee on the NAM than the GFS as well.

[ShawnEastTN]

From OHX Afternoon disco concerning Sunday/Monday Storm:

Quote

On Sunday, south winds and warm advection will increase, but
clouds will thicken and some light precipitation will begin to
develop in the afternoon. This will result in a complex forecast
scenario, with the potential for mixed precipitation. If clouds
thicken quickly or precip develops more quickly than expected,
temperatures will be colder than indicated by models. Cold and
dry low level profiles along with frozen ground could lead to
travel problems with snow, sleet, or freezing rain at the onset of
precipitation. If clouds are thin and precip holds off until
Sunday evening, then air temps will likely warm well above
freezing, but we will still be dealing with very cold road and
ground temperatures.

For Sunday night, mixed precipitation, including pockets of
freezing rain, could continue to be a problem, mainly for areas
east of I-65. It looks like the precipitation will be all liquid
by daybreak Monday morning, but we are concerned that stubborn
pockets of low level cold air will continue to create travel
problems for the Upper Cumberland into Monday morning.

Again, this is a complex scenario with a lot of uncertainties.
The main thing to know is that travel problems with a wintry mix
of precipitation are possible Sunday afternoon and evening,
especially for the Upper Cumberland. Hopefully the warmer model
solutions with temps in the upper 40s Sunday will prove correct,
and we will not have to deal with widespread problems.

As the low pressure system crosses the region Monday, rain
showers will continue. Around 1 inch of liquid is expected with
this system, and with quick runoff on frozen soil, there could be
some problems with standing water and street flooding. The system
will exit Monday night with a few snowflakes possible along the
back edge of the moisture. Residual icy spots from refreezing of
moisture will be a concern for Monday night.

 

[John1122]

It will forever haunt the snow lover in me how often we can be extremely frigid for long periods of time only to warm to 33 and rain. That's where we will be too, we will not warm to 38 with heavy precip falling on Monday. Usually in this scenario I sit at 33.2 or so once I get above freezing, until the precip stops. 

[Carvers Gap]

3 hours ago, *Flash* said:

I don't think that's far-fetched at all. My gut the past week has been our forum area will score in the midst of a pattern shift (i.e. as the atmospheric deck is shuffled, not the same as transient pattern). D8-9 could very well line up. We'll see. Euro tends to show decent flashes of what could happen around this time frame, even if it loses footing in the mid-range.

To clarify...I think the synoptic pieces of that particular run got very squirrelly.   The first system was suppressed...no problem there. Then, it wondered around as a cutoff for much of the run.  That is on no other model.  Highly unlikely that is correct, but that energy can IMO cause issues upstream.  Now, I have said for a few days that the second piece of energy needed to be watched...even making sure we don't miss anything on the first one that precedes it.  So, the idea that a storm would be there is not far fetched at all...I have been quoting JB on this for a while.  But the operational IMO was not realistic in how it developed.  Now, the 18z GFS looks more reasonable, even the 12z CMC.  Unlikely there is an Apps runner right down the spine like the 18z.  Most systems go to one side or the other.  My guess is that this goes east of the Apps through the Piedmont.  Still many variations to go before the final solution for sure.  But with suppression as a factor, who knows?  I would suggest that the WAR will turn this up the coast and act as a pseudo -NAO.   Not too many moving pieces on this one.  So, should be an easier forecast as we get closer.  All models have multiple vortices that are involved that are spaced a day or so apart.  It may be a case of them trying to decipher which ones will impact sensible weather.  I commented to someone after the 12z Euro, that was very close to being a big storm.  But the big pieces are there...just have to sort through the static.

[Carvers Gap]

...to add, the 18z came very close to hammering middle TN w the second system.  I suspect that it continues to correct eastward, but the storm was there on this one.

[Carvers Gap]

Here is the 500vort map from the 12z Euro.  The vortex over Florida is the energy for this Sunday night that gets shunted south and just wonders around until d8.  It is not on the previous run and not on the 18z GFS.  You can see it interacting with the second piece of energy and fouls up the run IMO.  Now, it could happen that way...but just seemed like an unlikely wrinkle and an outlier.

[Carvers Gap]

I should also add...this system is still at d8. Much disappointment has been had tracking systems at this range.  Still, as Flash and I discussed, a storm in that time frame fits the pattern.  The 18z GFS, 12z Euro, and 12z CMC all have storms in a similar time frame w similar mechanics in producing the storm....meaning it is not a rabbit out of the hat model run.  The pic below is right before the slp in Mobile(edit) comes north.  Great setup.   This will undoubtedly change/vary over the next few days...but something to watch.

[John1122]

I can't see how that LP tracks so steeply NNE with that set up. Big high to its NW and a LP close to the 50/50 area. Storm shouldn't cut up the Apps. 

[Carvers Gap]

Last post for a bit...Weeklies update.  I can’t see too many specifics as the run is not complete.  But I can see the northern hemisphere 500 pattern.  Trough goes into the NW during week 3 as expected.  By late in week 4 the EPO ridge is trying to get back in there.   That fits the reload look that some recent control runs have hinted at as part of the ensemble runs of the global.  The 2m temps are warm after week 2 pretty much wall-to-wall on the Euro M climate model.  The Euro does its usual deal of trying to put a trough under a ridge...if that corrects, temps will correct as well.  I have little worry that a Feb pattern w an AK ridge will have more energy than the current one.

***will update this post as the rest of the Weeklies roll so as not to take up the entire thread***

update 1:  The temp mean(there are two different sets...the first mentioned above factors in multiple times including past runs and climo...this is just the straight mean) actuall looks pretty favorable w the next wave of cold moving eastward during the first week of February and that fits the global pattern mentioned above.  Some of you will be glad to know that,verbatim, the trough is centered east of center.  Now, that likely corrects more eastward.

update 2:  850s warm around d13 and remain that way until d30.  Looks like roughly a 2.5 wk warm up.  And it is a thaw on this model and not an end of winter.

update 3:  Canada is emptied of cold and then reloads after a couple of weeks.  A cold Canada is a mainstay of this run.

last update:  Overall a nice look to February which gets progressively colder against the norms as the month progresses.  SER is present but manageable.  Prob a product of the Weeklies hanging back west a bit much.

[PowellVolz]

I can't see how that LP tracks so steeply NNE with that set up. Big high to its NW and a LP close to the 50/50 area. Storm shouldn't cut up the Apps. 

This has been the theme in the 7-10 day mods this year. It’s crazy cause almost all the mods have done it this year.


.

[John1122]

NAM has the low moving from Texas SSE into Louisiana where it hits a wall and starts to move north. It then seems to dry the precip out a great deal. Freezing rain begins to develop in Middle TN overnight Sunday into Monday morning then things go kaput.  It may get going after this but no precip overnight will allow warming and take away most frozen for the area. 

[John1122]

GFS was meh on system 1. Pushed system 2 a little more south and east. Possibly some undercutting cold that would charge through the precip and change types to frozen west to east and north to south. Wouldn't get everyone though. Heavy ice possible in west and middle areas, heavy snow in KY.  Still a long way out with a major system in between. 

[John1122]

A couple of very cold snaps in December and the first 8 days of January below freezing and we have this to show for it, and I'll honestly be surprised if it closes up any before February. 

[Carvers Gap]

I like the system at day 8.  Have for a few days.  Why?  Mainly a storm should be there....it is the end of a pattern, but more importantly, the WAR(or what becomes the western Atlantic ridge) “should” force the storm to the NE.  Literally, on the 0z GFS and Euro, the storm runs into the base of the retreating eastern NA ridge and is basically forced due north.  The ridge in front forces it north, but allows it to dig in combination with the ridge that will follow it.  That second ridge is likely to be the ridge that evolves to form our thaw.   Not sure what the trends are on retreating highs...but how quickly that high slides north eastward will decide IMO where that storm turns.  IMO, this is a bowling ball low.  So, it is questionable how much interaction it has w the northern stream...but as of 0z the point of confluence is decent for someone in our area depending on which side of the Apps this takes.  Again, I suspect it trends SE as the ridge speeds up in front of it and due to the first system being pushed SE.  And there is another point of question...the GFS sends the first vort OTS and it is gone.  The Euro sends it into the GOM where it stews. (toggle to 500vort on TT) The previous run had it on the EC of Florida.  Now, I don’t believe the Euro...but if true, that is significant.  Go back and look at what just happened w the EC blizzard.  Similar setup but further West.   SLP stalls over FL and the next system catches it, etc. DT used to always say be careful of wx models that try to repeat the setup of a big storm w subsequent energy.  That rarely happens and is often a model bias to repeat a storm. I think that is true here.  Some of those ideas come from JB...many are my own.  He has had a hot hand this winter and has had much less hype...like the old days.  But wanted to put credit where credit is due.  He called this storm several days ago.  Obviously, he is pulling for it to be more on the EC...Anyway, still a long way to go, but there is a window now for a storm.  Also keep in mind that storms can be lost during the upcoming time frame and then found during later runs.  Best guess is that we have roughly 14 more runs of the Euro and 28 of the GFS before any potential impacts. So, a lot can and will change.  The details are far from certain(options including cutters, sliders, coastals, inland runners, or nothing)....I want to see if the models continue to show this storm for the next couple of days.  In other words, need to get the storm inside of day five where the Euro has it in its wheelhouse.  Sorry...post was too long.