Winter 2013-14 Pattern Discussion II

[dsaur]

 Sun. therapy part 3 (4 for N GA): fwiw, the 12Z GFS is like night and day vs. the prior three runs during the 11-15 in that it is much colder as ridging gets reestablished in the west. Included in this is a big Arctic outbreak that brings 850's down to -16C at RDU and -12 C at ATL on 2/3 with lows of 13 in ATL and RDU on 2/4. Temp.'s never get above 30 on 2/3 at ATL! 

The nice models are trying to be all things to all people.  If you want warm, wait a few runs, and you get torch.  If you want cold, wait a few runs, and it's earth changing cold, lol.  One size models fit all.  Looks to me it the big two ever key on a storm within a few days it might happen.  Short of that, may as well use a magic 8 ball.  I went outside and looked up and it was very cloudy last night late..but no sleet fell.  I'll do the same come Tues, or so, if it clouds up.  Seems the most reliable method for sleet detection at the moment, lol.  T

[Shawn]

The GFS is flip flopping like a fish out of water.  Using anything else than ensembles outside 120 hours is pointless.

 

The 00z Euro isn't too bad for some areas to see a possible dusting, maybe a bit more in a widespread SE  type area.. but as always the WXBell maps seem to include ZR and IP as snowfall.  Not sure there's much of any accumulations outside the mountains.

 

GGEM has really backed off its snow/zr chances on the accumulation maps as of 00z last night.

 

12z GFS did want to bring the cold train back later on in fantasy land.  But that's the problem; fantasy land.

[GaWx]

The GFS is flip flopping like a fish out of water.  Using anything else than ensembles outside 120 hours is pointless.

 

The 00z Euro isn't too bad for some areas to see a possible dusting, maybe a bit more in a widespread SE  type area.. but as always the WXBell maps seem to include ZR and IP as snowfall.  Not sure there's much of any accumulations outside the mountains.

 

GGEM has really backed off its snow/zr chances on the accumulation maps as of 00z last night.

 

12z GFS did want to bring the cold train back later on in fantasy land.  But that's the problem; fantasy land.

 

Shawn,

 Just to clarify and for the model record: Whereas the WxBell clown maps overdo things, the 0Z Euro legitimately gives the Atlanta-Athens corridor 1-1.5" of snow per my much more reliable provider's Euro clown map (and 1.5-2" west of there). It is legit. because the warm biased Euro has 2 meter temp.'s down to near 32 and 850's that drop from +1 C to the -1 C to -2 C range as the snow comes in and causes evap. cooling at 850 mb.

[Cheeznado]

OK, now that several runs in a row of the Euro have the north GA snow threat I will at least pay attention. 12 Z still has about .25 with 850T at or below zero Friday. I hope other models come on board at some point, right now I am very cautiously optimistic.

[FallsLake]

Aren't said readings generated by the GFS Ensembles?

They are but they're many runs that overwhelmingly support the operational model. As stated above they are almost all solidly showing a "bad" pattern. Not a lot of variation to provide a higher doubt. Now as other have stated the whole mathematics, or data modeling, that come to this conclusion may be wrong and the euro will be king. I sure hope it is.

[Snowless in Carrollton]

OK, now that several runs in a row of the Euro have the north GA snow threat I will at least pay attention. 12 Z still has about .25 with 850T at or below zero Friday. I hope other models come on board at some point, right now I ma very cautiously optimistic.

even shows some snow down here in central Georgia ( south of I-20).

[NCSNOW]

Cheez or anyone w/access hows the qpf look east of the apps through the Carolinas Tues night/Wed on 12z euro

[GaWx]

Shawn,

 Just to clarify and for the model record: Whereas the WxBell clown maps overdo things, the 0Z Euro legitimately gives the Atlanta-Athens corridor 1-1.5" of snow per my much more reliable provider's Euro clown map (and 1.5-2" west of there). It is legit. because the warm biased Euro has 2 meter temp.'s down to near 32 and 850's that drop from +1 C to the -1 C to -2 C range as the snow comes in and causes evap. cooling at 850 mb.

 

 The 12Z Euro is VERY similar to the 0Z Euro but has less precip. in the ATL-AHN corridor during the crucial time of early Saturday morning. Also, it isn't quite as cold at two meters at 7 PM on Friday night. This combo means not quite as cold to start and not as much evap. cooling at 850 to bring it down to the -1 to -2 C like the 0Z Euro had. The 850's instead remain at +1 C, which means no snow for the city southward though the northern burbs likely get some (under 1"). The clown maps agree.

 Regardless, if this ends up playing out similarly, these two Euro runs suggest that it would be a VERY close call between no snow and 1-2" of snow early on 1/25 in the ATL-AHN corridor.

[FallsLake]

OK, now that several runs in a row of the Euro have the north GA snow threat I will at least pay attention. 12 Z still has about .25 with 850T at or below zero Friday. I hope other models come on board at some point, right now I ma very cautiously optimistic.

So what's the big difference? I see the GFS is holding back the system(Texas), what allows the Euro to push the precip east? 

[Marion_NC_WX]

Cheez or anyone w/access hows the qpf look east of the apps through the Carolinas Tues night/Wed on 12z euro

 

 

Its got the usual shadow on the immediate eastern slopes of the Apps, but got a pretty good area of .10 or slightly more east of I-77. Looks decent for your area in particular.

[GaWx]

OK, now that several runs in a row of the Euro have the north GA snow threat I will at least pay attention. 12 Z still has about .25 with 850T at or below zero Friday. I hope other models come on board at some point, right now I am very cautiously optimistic.

 

Cheez,

 That's interesting because my maps show the 850's staying at around +1 C in the city proper on the 12Z Euro run vs. ~-1 to -2 C  on the 0Z Euro.

[Cheeznado]

Cheez,

 That's interesting because my maps show the 850's staying at around +1 C in the city proper on the 12Z Euro run vs. ~-1 to -2 C  on the 0Z Euro.

I was just doing a crude eyeball look, I do not try and get too precise at this time frame, the basic scenario very similar. I do like the fact that the timing is for the precip to begin about 06Z, if it was a mostly daylight event then the chances would be reduced. In this type of situation the evap cooling factor may make the difference with the 850 temps so close to 0.

[Brick Tamland]

just days ago it was looking like historic events would take place toward the end of Jan. and Feb.  lots of cold and

potential for great southern storms.  did it all go poof? 

Looks like the potential is there but the models are going back and forth, especially outside 7 days, and the GFS is really flip flopping. Just can't tell much outside 48 hours. But I will believe a big storm when I see it two days out.

[NCSNOW]

Its got the usual shadow on the immediate eastern slopes of the Apps, but got a pretty good area of .10 or slightly more east of I-77. Looks decent for your area in particular.

Thnx Maion: Trolling through MA thread and saw where the JMA and Ukie where juicer with the qpf. Euro does tend to be drier qpf wise than other models at times leading up to an event. Even though it's splitting hairs the difference between .10 and even .15-.20 are huge as you know. Maybe we can get a car topper out of Tues deal.

[K4CF]

just days ago it was looking like historic events would take place toward the end of Jan. and Feb.  lots of cold and potential for great southern storms.  did it all go poof? 

Not so much poof as OTS 

[GaWx]

I was just doing a crude eyeball look, I do not try and get too precise at this time frame, the basic scenario very similar. I do like the fact that the timing is for the precip to begin about 06Z, if it was a mostly daylight event then the chances would be reduced. In this type of situation the evap cooling factor may make the difference with the 850 temps so close to 0.

 

Even though the 12Z op. GFS has nothing,  the 12Z GEFS mean has some qpf along with temp.'s close to 0Z at 850 in the Atl-Athens corridor for 1/25. It is a bit more robust than most recent runs.

[burgertime]

Even though the 12Z op. GFS has nothing,  the 12Z GEFS mean has some qpf along with temp.'s close to 0Z at 850 in the Atl-Athens corridor for 1/25. It is a bit more robust than most recent runs.

 

Didn't see anyone comment on it but the Canadian also has QPF for the south and ATL on Friday. Puts down around .10...not much but it's a start considering it hasn't been there the last few runs. It wouldn't take much to juice this up into something better. 

[EmersonGA]

If snow does fall early Saturday ground temperature should not be a problem. Next week looks plenty cold before the storm. Having a cold ground is always a plus.

[GaWx]

Didn't see anyone comment on it but the Canadian also has QPF for the south and ATL on Friday. Puts down around .10...not much but it's a start considering it hasn't been there the last few runs. It wouldn't take much to juice this up into something better. 

 

Burger,

 It may be such a delicate balance that more juicing could mean no snow in Atlanta. Right now, the 500 mb flow is westerly on 1/25. A WSW flow would certainly mean more juicy but also could mean a further north track and likely warmer 850's prior to evap. cooling. So, even if there's more evap. cooling from heavier precip., it may not matter in that case. The bottom line as far as I'm concerned for Atlanta is that if I were somehow given a choice between taking the 0Z Euro solution, which produces 1-1.5", and taking a chance on a juicier system, I'd go with the 0Z Euro's very weak system rather than risk getting no wintry precip. Besides, 1-1.5" is just above KATL's ~1" median for the entire winter. In my mind, the max potential snow at ATL from this system within reason is somewhere around 2". There are numerous scenarios that would give ATL nothing. Heck yeah, I'd take 1-1.5" and call it a month!! Then again, I'm talking about ATL, not NC. If I were in NC, I'd probably hope for more WSW flow/a juicier system.

[Pilotwx]

As of now I can see where those east of the apps( foothills, Piedmont region  of both North and South Carolina and part of VA) look to be dry. For the next couple of systems. I think the eastern parts of those states stand a better chance as of right now of some sort of snowfall either a dusting or something more. 

[MillerA]

Gsp disco.

as of 255 PM Sunday...not much change for the NC mountain forecast. However...guidance continues to flip flop on precipitation potential outside of the mountains a strong short wave crosses the area Tuesday pushing an Arctic cold front across as well. Precipitation onset across the mountains has been delayed slightly as moisture...cold air advection and northwest flow do not really crank up until after midnight. Even then...the best moisture...cold air advection and northwest flow not kick in until after daybreak. Therefore...have delayed the likely pop until then as well. Expect snowfall rates to pick up significantly during the day given the high snow to liquid ratio from the strong cold air advection. In addition...low level lapse rates become quite steep leading to some weak instability increasing the convective nature of the snow showers. The snow showers begin to taper off Sat afternoon with the greatest coverage retreating to the Tennessee border. Scattered snow shower will continue through the evening...then taper off quickly after midnight as the flow weakens and moisture becomes very shallow. Advisory level snow looks likely along the Tennessee border...higher amounts possible in the higher elevations...with amounts quickly tapering off to the Blue Ridge. That said...given the convective potential...if areas of heavy snow bands set up...snow would quickly accumulate over those areas. Forecast remains tricky outside of the mountains as all but the European model (ecmwf) have backed off on snow potential over our County warning forecast area. Some do still snow snow showers developing to our east...while the European model (ecmwf) shows snow showers moving out across the NC foothills and Piedmont. The NAM shows areas of low level convergence...increased moisture and low level lift. The NAM and GFS forecast soundings also show weak low level instability with steep low level lapse rates developing. The guidance does not agree on the amount of frontogenesis moving out of the mountains and any coincident negative epv. Given the continued disagreement between models and run to run variability...will continue the dry forecast outside of the mountains still...later shifts will have to keep an eye on this period in case consensus develops. Lows Monday night near to slightly above normal with highs Tuesday 10 to 15 degrees below normal over the mountains and around 5 below normal elsewhere. As the very cold Arctic air mass moves in Wednesday. Lows and highs will be around 15 to as much as 20 degrees below normal all areas. Wind chill values should fall into the advisory range across much of the NC mountains

[jburns]

Gsp disco.

as of 255 PM Sunday...not much change for the NC mountain forecast. However...guidance continues to flip flop on precipitation potential outside of the mountains a strong short wave crosses the area Tuesday pushing an Arctic cold front across as well. Precipitation onset across the mountains has been delayed slightly as moisture...cold air advection and northwest flow do not really crank up until after midnight. Even then...the best moisture...cold air advection and northwest flow not kick in until after daybreak. Therefore...have delayed the likely pop until then as well. Expect snowfall rates to pick up significantly during the day given the high snow to liquid ratio from the strong cold air advection. In addition...low level lapse rates become quite steep leading to some weak instability increasing the convective nature of the snow showers. The snow showers begin to taper off Sat afternoon with the greatest coverage retreating to the Tennessee border. Scattered snow shower will continue through the evening...then taper off quickly after midnight as the flow weakens and moisture becomes very shallow. Advisory level snow looks likely along the Tennessee border...higher amounts possible in the higher elevations...with amounts quickly tapering off to the Blue Ridge. That said...given the convective potential...if areas of heavy snow bands set up...snow would quickly accumulate over those areas. Forecast remains tricky outside of the mountains as all but the European model (ecmwf) have backed off on snow potential over our County warning forecast area. Some do still snow snow showers developing to our east...while the European model (ecmwf) shows snow showers moving out across the NC foothills and Piedmont. The NAM shows areas of low level convergence...increased moisture and low level lift. The NAM and GFS forecast soundings also show weak low level instability with steep low level lapse rates developing. The guidance does not agree on the amount of frontogenesis moving out of the mountains and any coincident negative epv. Given the continued disagreement between models and run to run variability...will continue the dry forecast outside of the mountains still...later shifts will have to keep an eye on this period in case consensus develops. Lows Monday night near to slightly above normal with highs Tuesday 10 to 15 degrees below normal over the mountains and around 5 below normal elsewhere. As the very cold Arctic air mass moves in Wednesday. Lows and highs will be around 15 to as much as 20 degrees below normal all areas. Wind chill values should fall into the advisory range across much of the NC mountains

 I know they used paragraphs.  What happened?

[GaffneyPeach]

I know they used paragraphs. What happened?

They used upper and lower case. Can't have everything, Burns.

[GaWx]

 The 12Z Euro ensemble mean is more bullish for SE snowfall for this Saturday, 1/25. Its clown actually has a 1-2" oval shaped area with outer edges being Cumming (GA), GSP, HKY, and the NC/TN line. That's very impressive for a 50+ member ensemble set for five days out! The 0Z Euro ens. mean had no area at 1+".

 

 For the ATL-AHN corridor, the 0C 850 line is in the northern burbs while the surface is ~30 F after the high the prior day of only ~35 F. Simply put, there's not enough time for surface temp.'s to modify much with no sig. warm air advection with a very weak sfc low and this pretty far south sfc low track (Gulf coast). The 0C 850 line is very close. It does look like there could be some sleet, especially in the southern burbs including Tony's place. Mean QPF is a respectable ~0.20".

[WidreMann]

The 12Z Euro ensemble mean is more bullish for SE snowfall for this Saturday, 1/25. Its clown actually has a 1-2" oval shaped area with outer edges being Cumming (GA), GSP, HKY, and the NC/TN line. That's very impressive for a 50+ member ensemble set for five days out! The 0Z Euro ens. mean had no area at 1+".

 

 For the ATL-AHN corridor, the 0C 850 line is in the northern burbs while the surface is ~30 F after the high the prior day of only ~35 F. Simply put, there's not enough time for surface temp.'s to modify much with no sig. warm air advection. The 0C 850 line is very close. It does look like there could be some sleet, especially in the southern burbs including Tony's place. Mean QPF is a respectable ~0.20".

What do the ensembles say for Tuesday?

[GaWx]

What do the ensembles say for Tuesday?

 

Widre,

 The clown shows only 1"+ amounts. For RDU area and all of NC, no 1"+ amounts are shown. There's just under 0.10" of QPF with 850's falling from ~-5 C to -7 C during precip. This suggests to me the potential of 1/2-1" of snow. The model mean may actually be in the 1/2-1" range but that won't show on these maps.

[MillerA]

Check out @RaleighWx's Tweet: https://twitter.com/RaleighWx/status/425012963741691904

From Allan Huffman tweets, 18z Nam more juiced up.

[Marion_NC_WX]

FWIW, 18z GFS still has a suppressed look at 108, snowing lightly in Dallas, mixed precip streaking across Central Louisiana.

 

 

EDIT: Sleet falling just north of New Orleans at 114...

[GaWx]

18z GFS: Based on dry WNW 500 mb flow on 1/24, I'm confident it won't show snow on 1/25.

[Marion_NC_WX]

18z GFS: Based on dry WNW 500 mb flow on 1/24, I'm confident it won't show snow on 1/25.

 

 

Just like everyone says that the trend is our friend, in this case Suppression leads to depression.