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Jan 25th Winter Weather Discussion Thread


Marion_NC_WX

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That's part of the fun though, the excitement of tracking a storm, not knowing what will happen, the ups and downs of the emotions... this is great! :snowing:

Even though in terms of temps this winter is just as warm as last winter, this winter has been a little more exciting in terms of wintry weather threats.

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I wouldn't classify this as a typical clipper.  The trajectory of the weak wave / vort max is Oregon>Nebraska>Kentucky, as opposed to a diver out of southwest/south central Canada...but nevertheless, it's a weak system.  I like the idea of this being a light-moderate precip event for N Georgia / TN / NC mountains, and light east of the mountains in Carolina.

 

The warm air advection / overrunning / isentropic upglide (all the same thing, with different names...lol), isn't shabby.  You can see the 40-50 knot wind max here at 850mb in N AL / N GA / E TN (1st image).  The 2nd image shows the 850mb temperatures.  So at hr54 here, you've got warm air in the low levels originating from the Arklatex overrunning colder air to the northeast, creating the lift and precipitation.  The stronger the wind and the stronger the temperature gradient, the stronger the lift.

 

The third image shows the freezing temperatures trapped at the surface in NE TN / western and central NC / NE GA / SC Upstate.

 

I also looked at the 200-500mb levels, and I really don't see anything in the way of jet level support for lift.  As a matter of fact, you can see in the 4th image that the southeast is located in the right exit region of a jet streak over the Ohio Valley.  The right exit region of an upper level jet is subject to upper level convergence (not supportive of rising motion).  So, this combined with the weak vorticity advection associated with the weak 500mb vort max adds little to the precipitation processes.  It's also likely the culprit for lower relative humidity numbers in the mid-levels associated with the snow growth zone.

 

All this to say that we have a decent low-level overrunning type precipitation event here...but not a deep, moist column, or a prolonged event supportive of heavier precip amounts.  Again, I like the idea of this being a light-moderate precip event for N Georgia / TN / NC mountains, and light east of the mountains in Carolina.

 

850i.png
850mbt.png
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300cd.png
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the dewpoints are so low that when the precip starts the temp is going to come on down until the dewpoint comes up.  maybe winter storm watches will come out later today.  we're getting to around 36 -48 hours for the event to start.  I think they like to put out the watches 30 to 36 hours ahead of time.

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Allan Huffman's thoughts.

 

 

Right now I would go with perhaps an inch of snow for the RDU area changing to sleet and perhaps some light freezing rain before ending. IF this is true, travel during the Friday rush hour and through Saturday morning will likely be treacherous.

 

http://www.examiner.com/article/snow-possible-friday-warm-up-next-week

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the dewpoints are so low that when the precip starts the temp is going to come on down until the dewpoint comes up.  maybe winter storm watches will come out later today.  we're getting to around 36 -48 hours for the event to start.  I think they like to put out the watches 30 to 36 hours ahead of time.

Just not sure they'll do that with the precip amounts, and types, still in question. If we "assume" that an area gets .25 liquid, to get to Warning criteria would almost require that the winter weather type stay all one type (all snow or all freezing rain). Otherwise you only meet Advisory critera with a mix.  

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Even though in terms of temps this winter is just as warm as last winter, this winter has been a little more exciting in terms of wintry weather threats.

 

But even that is way more particular in where it has been this year.  I haven't been close to being as warm overall, however ENC and much of GA certainly have been.

 

Definitely more to look at this year though.

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Sounds like the smart approach since we really don't know what will happen yet. When will the models get to sample that shortwave?

 

I don't look for much at all.  A moisture starved system moving into dry air is not a recipe for a decent event.

 

Brick, you have to learn how to do your own analysis. So here is your very own shortwave to sample.

 

i-ChxFNpD-L.jpg

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Hopefully this is ok to post since it is an old map. This was the hi-res snow map 12 hours before Friday's event. It certainly was correct for MBY and not too bad up north...I do think given this setup the solution today is certainly possible....but of course as we learned with the last storm you wanna see more models coming to a consensus. 

 

Yes, It did good here also, I only had a dusting...

Keep the faith. I beleive we are in one of those patterns where we get winter threats on the same day of the week for consecutive weeks. GFS yesterday and today is throwing out the idea of something for next Friday. It's big synoptic event. Ofcourse without te euro hinting at it the next few days I ain't buying it, just yet.

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Just not sure they'll do that with the precip amounts, and types, still in question. If we "assume" that an area gets .25 liquid, to get to Warning criteria would almost require that the winter weather type stay all one type (all snow or all freezing rain). Otherwise you only meet Advisory critera with a mix.  

 

Agreed.  48 hours is too far out for any kind of winter weather "watch."  Based on the questionable QPF from the models (wet to dry, now back to wetter), there's just too much uncertainty to issue any kind of product or raise headlines.

 

Even if the .4" of QPF were to verify, it's gonna be a snow to freezing rain mix for AVL and surrounding mountain counties, so likely a Winter Weather Advisory.  IMHO, of course.  :)

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Agreed completely. This is nice to look at it but I really want to see other models have this much precip. Taken at face value though this is a nice little winter storm for most. Given the very cold temps at the surface combined with a deep cold layer (much colder than usual in fact and given how light the precip starts at, such cold temps and the depth will help areas dealing with the warm nose to probably start as sleet.

Looking at charlotte's sounding, for example, it looks to start as snow, then it loos like sleet for several hours as the warm layer is rather cool and with a subfreezing layer from 900mb to the surface and as cold as around 20 at 950mb, certainly supports that. Areas with appreciable amounts of sleet which then turns over to freezing rain will really have a mess on the bridges and roads for sure, even if it's half of what the nam is showing.

The boundary layer temps are very impressive, especially around 900 to 950mb..so it will be a battle between the warm nose aloft to the south and those temps. I didn't think we would see much sleet in ga and we have a much deeper and warmer warm nose aloft but the precip starts off rather light, so that gives it more chances for it to freeze going through a boundary layer that has temps in the low 20s down into northeast ga

The carolinas are really impressive. HKY has a 900mb of 14 at hour 51 (which is snow) and gsp (which looks like sleet) has a 950mb temp of 18 at with precip falling. Places like gainesville, hartwell, etc have a min boundary layer temp of around 21 on this run around that time.

Temps do not rise above freezing in ne ga along the 85 corridor and probably a little south of that.

That said, the gfs is a little slower and further north with the precip. Temps start off very cold, upper 20s with dewpoints in the upper single digits/around 10. When precip really gets going, 18z or after temps still around 29/30 and wetbulbs around 26 for ne ga.

IF the precip shield is further north, some slight warming can be expected but I still don't see most places rising above freezing here in NE ga. But it would be better if the precip shield was a bit further south. On the gfs/nam the best areas for significant accumulations are at and above i-85. The favored areas of from gainesville up toward toccoa, look to be in the bullseye (mountains will be warmer due to waa aloft).

Looks like favored areas of the western carolinas, hky, etc, will have several hours of snow before going to sleet.

Will be interesting to see if precip streaks ahead of model predictions, as if often the case.

You are looking good at the moment for sure. In fact, you are going to be very cold for a wedge, low to mid 20s per both models.

I'm just happy to have a damn wedge with precip to follow. I know it's not a huge event but it is rather unique in how cold the boundary layer temps are, especially initially.

Me too that's for sure! Been a long time since ne ha has been in the running for a minor ice event. Hopefully we will have some interesting wx and jobs to track.

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 Today's 6Z and 12Z GFS runs clearly aren't as good for the Atlanta-Athens corridor in terms of verbatim ZR amounts vs. the prior three runs. So, this is not a good trend if you want to see sig. ZR in those areas. However, it is about the same for areas like Gainseville, where it is still ~0.25". During the prior three GFS runs, much of the northern half of the ATL-AHN corridor was getting ~0.25". Now it is just a small fraction of that in much of the ATL-AHN corridor.

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And the 12Z suite rescues the storm from overnight disaster. Could be a lovely ice job from eastern Tennessee into west-central NC, and upstate SC to ne GA. Snow Tri Cities into NC high country. If you believe the WRF/NAM, snow will fall in parts of the Piedmont (north) due to colder air at all levels. And the ski areas will get a blanket of fresh snow. I’m going to punt dissecting models and throw out a comparison.

 

Remember the snow event last year over Martin Luther King Day weekend? Earlier that week in 2012 a rain to snow system moved across. Then it turned cold for a few days. On Saturday of the 2012 MLK Day weekend a clipper type system brought nice fluffy all snow to the high country. FF to this year. This time the rain to snow was on MLK weekend. We’re having some cold days. We have a system coming in from the west-northwest. Not quite a clipper, as noted, which is of some concern regarding the warm layer. Will it surprise to the upside like last year? Believe last year was an emotional model roller coaster as well.

 

Bottom line: We are in a cold pattern that features winter precip. In the South we normally get 2-3 events in quick order before the cold pattern breaks and winter is over. Right now we are in our 2-3 weeks of winter. I like chances of all snow in the high country. Maybe even some Piedmont. Enjoy! :ski:

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Thanks for your IMHO sir :)

 

 

Agreed.  48 hours is too far out for any kind of winter weather "watch."  Based on the questionable QPF from the models (wet to dry, now back to wetter), there's just too much uncertainty to issue any kind of product or raise headlines.

 

Even if the .4" of QPF were to verify, it's gonna be a snow to freezing rain mix for AVL and surrounding mountain counties, so likely a Winter Weather Advisory.  IMHO, of course.   :)

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Agreed.  48 hours is too far out for any kind of winter weather "watch."  Based on the questionable QPF from the models (wet to dry, now back to wetter), there's just too much uncertainty to issue any kind of product or raise headlines.

 

Even if the .4" of QPF were to verify, it's gonna be a snow to freezing rain mix for AVL and surrounding mountain counties, so likely a Winter Weather Advisory.  IMHO, of course.   :)

 

What's your thoughts on the freezing rain end of this for the Mnts? It seems like CAD events have a hard time with zr once you get away from the escarpment.

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 Today's 6Z and 12Z GFS runs clearly aren't as good for the Atlanta-Athens corridor in terms of verbatim ZR amounts vs. the prior three runs. So, this is not a good trend if you want to see sig. ZR in those areas. However, it is about the same for areas like Gainseville.

 

Dang it Larry... don't bust my bubble yet!

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The great thing about getting accumulating snow, then freezing rain or sleet is that stuff is very enduring, harder to melt. I have seen that stuff stay on the ground in north-facing shaded areas after many days over 50.

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Me too that's for sure! Been a long time since ne ha has been in the running for a minor ice event. Hopefully we will have some interesting wx and jobs to track.

Catbird seat!  You always have that priviledge :)

I'm kind of tickled that Ptree City has an hour by hour scenario for an event several days off.  From 9 to 10 I get my sleet, but then a mix, and then rain, then zrain, lol.  If any of it happens, it will be a plus, but with low amounts still, I'll be lucky to see just rain.  I still have my sights set on the week around the end of the month into Feb.  Get a split flow, with an upper low ejecting into it, and a big high coming down....I like them apples...especially if we could get a 50/50 low....ah, fantasy land...such a happy place, lol.

  Not  just some sleet from 9 to 10 on Friday, lol.....though I'll sure be happy to take it, if it happens.  Goofy gives me .15 into 40's and 50's via Meteostar so who knows what happens in two days :)  T

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@60 Euro has light ZR south of I-40 down to the SC/NC state line with snow I-40 points north.  850 line runs roughly from HKY to GSO to RDU...though RDU looks like mainly IP. QPF is going be around .10 - .20...probably falling closer to .10 for most of NC

Well I guess the NWS can issue a heavy frost advisory instead of wsw> :whistle:

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