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March 11th-13th Winter Weather Event. Winter's last gasp?


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13 minutes ago, Silas Lang said:

The latest  6z NAM is on board. Noticed some mixing happening. For some reason there is a strip of sleet and freezing rain. Anyone looked at any soundings? Kind of a random strip, but you can see it on some other snow maps too. Southwest of Anderson County on down. 

nam-218-all-southapps-total_snow_kuchera-7108000.png

nam-218-all-southapps-sleet_total-7108000.png

nam-218-all-southapps-frzr_total-7108000.png

 

The NAM is much warmer than other models and has an unusual warm nose from 700mb down to 850mb that caused the sleet/zr in those areas. 

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For E TN, I am not a huge fan of the micro-northwest jog on the GFS which is causing the slp to creep towards the east slope of the Apps - and that may just be a GFS bias in play.  IDK.  That said, the rule again is those who are closes to heavy rain will see the heaviest snow.  Maybe the one difference(maybe this is hope and not forecasting) is that this low fires earlier than the other lows this winter which have taken similar tracks.  I would be surprised to see things take a long time to change over.  The cold just crashed into the back of this storm on pretty much each model.  Plateau looks like money for a big one.  NE TN is still in question, but latitude will help as the cold front will likely lean northeastward.  MRX does a nice job with this write-up. 

Discussion:

A more active weather pattern returns for the extended with the
potential for wintry weather this weekend. We begin on Thursday
amidst broad southwest upper level flow. High pressure at the
surface will keep things dry Thursday and Thursday night with
temperatures moderating back to above normal. A weak shortwave
progressing through this southwest flow early during the Thursday
period will bring an increase in cloud cover but expect this cloud
cover to quickly decrease by Thursday afternoon leading to clearing
skies. Much of Friday will be quiet in terms of weather as the upper
level begin to amplify in response to phasing out west. This upper
level trough will quickly dig into the plains by late Friday.
Southerly low level flow will not only advect moisture northward,
but also advect warmer temperatures poleward with highs on Friday
approaching the mid to upper 60`s with near 70 certainly possible in
the southern valley.

Friday night a frontal boundary will be draped across the lower
Mississippi River Valley and across much of the Tennessee Valley and
Central Appalachians. High pressure descending from the northern
plains will keep this front moving eastward fairly quickly into
Saturday morning with much colder air in its wake. Aloft, a deep
upper trough will move through the region with height falls
overspreading much of the southeast. An area of low pressure is
forecast to form in response to increasing upper level dynamics and
lift NE along the frontal boundary across the Southern Appalachians
into Saturday morning. It will take some time for the atmosphere to
moisten Friday afternoon and evening but increasing upper level
dynamics will move in sometime around or after 00Z Saturday as a
strong jet impinges on the area. Increased PoPs rather sharply after
00Z Saturday with the highest PoPs highlighted between 06-12Z
Saturday which is supported by NBM/GEFS/EC guidance.

There is rather good agreement on the timing of the aforementioned
front with only the most recent NAM being slightly slower. This
front will be moving through the area between 06 and 12Z Saturday
with much colder air moving in behind it. 850mb temperatures will
crash post fropa with temperatures in the -10 to -15 C range by
Saturday afternoon. All of this to say that precipitation starting
late Friday night as rain will be transitioning to snow. There are
increasing signals for heavier snowfall rates as well with upper
level ascent maximized within favorable lower thermal profiles. Of
course the main question is just how much snow will accumulate and
given it is early/mid March adds increasing uncertainty. Things such
as recent warm weather, warmer soils, and timing of heaviest snow
all will have implications to accumulations. At this point, the
lowest confidence in snowfall exists across the valley locations,
and higher confidence in accumulating snow exists across the higher
terrain.

Precipitation will be moving out of the area late Saturday with only
high elevation snowfall possible Saturday afternoon and evening.
Temperatures on Saturday will be much colder with highs struggling
to get above freezing, and nearly 20-25 degrees below normal.
Saturday night, skies will be clearing with the center of high
pressure situated nearly directly over the area. Light winds, and
clearing skies will bring excellent radiational cooling conditions
for lows to fall into the teens Saturday night. If we do end up with
any snow accumulations then temperatures may even be colder.

The much colder temperatures will be short lived however, as
increasing heights and southerly flow returns for Sunday into
Tuesday. Highs will moderate and by Monday we will be back into the
60`s. Guidance suggests another wave will move into the southern
plains and southeast by mid week which could offer increasing
chances of precipitation to end the extended period.

 

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As noted, I am not a huge fan the 6z GFS for E TN.  It is not a clean pass and involve energy transfer to a secondary/inland runner about 150 miles inside the coast.  The initial rams into the southern spine of the apps in northern Georgia and then transfers.  That is the absolute closest it can get without sending some ghost of a low up the eastern valley.  The ensemble has that, but is much more acceptable....but trends do matter on the operational runs now.  If the trend were to continue, it takes the eastern valley out of play.  If it stops or slightly reverses...big storm possible for many.  Here are some of my favorite looks from the 6z GEFS.  Great looking snow mean and nearly perfect placement of the secondary slp.  This should be a nice winter storm(major) for someone.  

 

Screen_Shot_2022-03-09_at_7.03.32_AM.png
Screen_Shot_2022-03-09_at_7.03.15_AM.png

 

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For E TN, I am not a huge fan of the micro-northwest jog on the GFS which is causing the slp to creep towards the east slope of the Apps - and that may just be a GFS bias in play.  IDK.  That said, the rule again is those who are closes to heavy rain will see the heaviest snow.  Maybe the one difference(maybe this is hope and not forecasting) is that this low fires earlier than the other lows this winter which have taken similar tracks.  I would be surprised to see things take a long time to change over.  The cold just crashed into the back of this storm on pretty much each model.  Plateau looks like money for a big one.  NE TN is still in question, but latitude will help as the cold front will likely lean northeastward.  MRX does a nice job with this write-up. 
Discussion:A more active weather pattern returns for the extended with thepotential for wintry weather this weekend. We begin on Thursdayamidst broad southwest upper level flow. High pressure at thesurface will keep things dry Thursday and Thursday night withtemperatures moderating back to above normal. A weak shortwaveprogressing through this southwest flow early during the Thursdayperiod will bring an increase in cloud cover but expect this cloudcover to quickly decrease by Thursday afternoon leading to clearingskies. Much of Friday will be quiet in terms of weather as the upperlevel begin to amplify in response to phasing out west. This upperlevel trough will quickly dig into the plains by late Friday.Southerly low level flow will not only advect moisture northward,but also advect warmer temperatures poleward with highs on Fridayapproaching the mid to upper 60`s with near 70 certainly possible inthe southern valley.Friday night a frontal boundary will be draped across the lowerMississippi River Valley and across much of the Tennessee Valley andCentral Appalachians. High pressure descending from the northernplains will keep this front moving eastward fairly quickly intoSaturday morning with much colder air in its wake. Aloft, a deepupper trough will move through the region with height fallsoverspreading much of the southeast. An area of low pressure isforecast to form in response to increasing upper level dynamics andlift NE along the frontal boundary across the Southern Appalachiansinto Saturday morning. It will take some time for the atmosphere tomoisten Friday afternoon and evening but increasing upper leveldynamics will move in sometime around or after 00Z Saturday as astrong jet impinges on the area. Increased PoPs rather sharply after00Z Saturday with the highest PoPs highlighted between 06-12ZSaturday which is supported by NBM/GEFS/EC guidance.There is rather good agreement on the timing of the aforementionedfront with only the most recent NAM being slightly slower. Thisfront will be moving through the area between 06 and 12Z Saturdaywith much colder air moving in behind it. 850mb temperatures willcrash post fropa with temperatures in the -10 to -15 C range bySaturday afternoon. All of this to say that precipitation startinglate Friday night as rain will be transitioning to snow. There areincreasing signals for heavier snowfall rates as well with upperlevel ascent maximized within favorable lower thermal profiles. Ofcourse the main question is just how much snow will accumulate andgiven it is early/mid March adds increasing uncertainty. Things suchas recent warm weather, warmer soils, and timing of heaviest snowall will have implications to accumulations. At this point, thelowest confidence in snowfall exists across the valley locations,and higher confidence in accumulating snow exists across the higherterrain.Precipitation will be moving out of the area late Saturday with onlyhigh elevation snowfall possible Saturday afternoon and evening.Temperatures on Saturday will be much colder with highs strugglingto get above freezing, and nearly 20-25 degrees below normal.Saturday night, skies will be clearing with the center of highpressure situated nearly directly over the area. Light winds, andclearing skies will bring excellent radiational cooling conditionsfor lows to fall into the teens Saturday night. If we do end up withany snow accumulations then temperatures may even be colder.The much colder temperatures will be short lived however, asincreasing heights and southerly flow returns for Sunday intoTuesday. Highs will moderate and by Monday we will be back into the60`s. Guidance suggests another wave will move into the southernplains and southeast by mid week which could offer increasingchances of precipitation to end the extended period.

 


What could go wrong they said….


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Not to be a negative Nancy, but I'm not putting much stock in this.  I'll admit I haven't been following along on this system because of other work/life responsiblities, but this year just hasn't worked out very well for my location in Knoxville when compared to the many opportunites for bigger storms.  The main thing that makes me not get excited about this is the transfer of energy off the coast.  I just haven't seen very favorable results in those type scenarios for my location this year.  Plus.....my skin has already felt the warmer temps of impending spring, and I'm done with winter.  So I'll begrudgingly take my four snows of one inch each and call it done.

(I have stated my rant, so lets hope I'm wrong and we all get a big thumping!!!)

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57 minutes ago, Holston_River_Rambler said:

6z Euro (no Kuchera available)

ey6359L.png

That is a good look IMO.  I think it is more related to the sequence of energy transfer. We generally have some type of rain shadow with nearly every event at TRI, the once exception is if the precip originates to our southwest and come up the valley parallel to both mountain chains.  For me, and you have lived this as well, I pretty much know my totals are going to be lower.  That said, a well-placed strong storm will overcome a lot of that.  This is probably the best looking storm on modeling which I have seen for MBY all winter.  It is encouraging to see a solution which is not overly amped.  I would think the GFS amping issue is probably a bigger problem during spring with systems having more energy to draw from.

And for those who are conservative with their expectations...always a wise move.  This should be a storm where folks may be able to easily drive to good totals.  Great to be tracking during March...that doesn’t always happen.

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Just checking the 6z Euro.  It pops a 988mb slp inside Hatteras.  Give me that all day long.  No run is perfect and it is not a clean pass.  I says this often, most good storms for E TN have some energy transfer.  It is very rare to have a clean pass and not have it go too far to our east when that happens.  

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