Winter 2013-14 Pattern Discussion

[FLweather]

We shouldn't forget the "possible" minor event for early next week. northeast NC currently showing close to 1 inch of snow.

 

12z GFS snow cover at 120 hours:

http://www.twisterdata.com/index.php?prog=forecast&model=GFS&grid=3&model_yyyy=2013&model_mm=12&model_dd=26&model_init_hh=12&fhour=120&parameter=SNOWIN&level=SURFACE&unit=none&maximize=n&mode=singlemap&sounding=n&output=image&view=large&archive=false

 

Agree FL.

 

Really considering its about 5 days out I'd say the GFS,GGEM,Euro today are all in remarkable agreement about bringing light snow potential to portions of SC,NC,VA. Will be interesting to see how this upper level s/w actually plays out of the next couple to few days.

[FallsLake]

Agree FL.

 

Really considering its about 5 days out I'd say the GFS,GGEM,Euro today are all in remarkable agreement about bringing light snow potential to portions of SC,NC,VA. Will be interesting to see how this upper level s/w actually plays out of the next couple to few days.

RAH did mention this in the afternoon discussion; stating possibilities of sprinkles or flurries. **so basically at this point they're not taking this too seriously but they are keeping an eye on it.

 

RIGHT NOW THE LOW IS PROGGED TO EXIT TO OUR NE BY SUNDAY EVENING...

WITH COOLING/DRYING IN ITS WAKE FOR SUNDAY NIGHT. BOTH THE GFS AND

ECMWF DEPICT A TRAILING SHORT WAVE AND SECONDARY COLD FRONT MOVING

ACROSS OUR AREA MONDAY AND MONDAY NIGHT.  ECMWF IS DRYER...BUT GFS

HAS ENOUGH MOISTURE FOR A FEW SPRINKLES OR FLURRIES LATE ON MONDAY

OR MONDAY NIGHT WITH THE PASSAGE OF THE TROUGH AXIS.

[GaWx]

Folks,

 For those rooting for there to actually be a 1/2 SE wintry event, there's some decent news regarding the 12z Euro ensemble vs. the 12Z Euro op. run. Per the ~50 member mean, the 48 hour QPF for the period 12Z on 1/1 to 12Z on 1/3 is 0.25" at  Jackson, MS, ~0.20" at BHM, and 0.15-.25" in all of GA/SC/NC. This compares to virtually no QPF on the 12Z op. Euro. Many/most runs appear to have little to no precip. So, that means that some must have pretty ample precip. to allow 0.15-0.25" average amounts over 50 members. The track of the precip. is suggestive of mainly a Miller A for those runs that generate precip. Also, the ensemble mean flow at 500 mb is W vs. the op.'s drier WNW. The mean flow actually has a few members with moist WSW flow. These are undoubtedly the ones generating decent precip. and with a Miller A. At 850, it is slightly colder on the ensemble mean during the crucial 1/2 period vs. the op. run with the 0C line from the N burbs of ATL to Columbia to Wilmington and the -4C line from Asheville to RDU vs. the op.'s 0C line being from Chat. to Charlotte to Wilmington and its -4C line near the NC/Va border. The 0Z Euro ensemble was actually similar but slightly wetter/warmer vs. the 12Z Euro ensemble mean and much wetter than the 0Z Euro op.'s very dry run.

 

 So, in summary, the 0Z and 12Z Euro ensemble runs suggest to continue watching the period around 1/2 for some potential SE wintry magic since several members do suggest a GOM low with cold enough air to threaten wintry precip.

[tnweathernut]

I think you guys have something to follow with regards to the follower after this weekends rain event.  Looks a little sharper at 500 and the 18z initiates some heavier precip in central NC at 114.  Good luck to you guys, hope it trends into something better from here on out

[franklin NCwx]

Gfs sharpens the trough much sooner at 18z.

[GaWx]

18Z gfs:

 

1) 2-3" S RDU area on 12/31 per clown! Brick gonna go apesh*t!

 

2) Map  as of 6Z on 1/1 tells me not looking good for 1/2.

[Poimen]

Happy Hour GFS in the house. I don't care if it's only a few flakes...at this point I'm in favor of seeing some snow.

 

With that said...120 hours is still a long ways away.

[SnowNiner]

18Z gfs:

 

1) 2-3" S RDU area on 12/31 per clown! Brick gonna go apesh*t!

 

2) Map  as of 6Z on 1/1 tells me not looking good for 1/2.

 

Yeah, it's like the 1/2 storm has become the 12/31 storm.  ???? I think I liked the 1/2 storm cause it was colder, or am I not reading it right.

 

[GaWx]

Yeah, it's like the 1/2 storm has become the 12/31 storm.  ???? I think I liked the 1/2 storm cause it was colder, or am I not reading it right.

 

 

 These are two different systems though they likely affect each other in some indirect way (butterfly effect). 1/2 showed up as colder on some runs. The 12/31 one on the 18Z GFS gives much of N NC 1-3" with heaviest centered near Brick's abode...at least that's what the clown said. Please don't tell him. He'll be out of control with excitement when it is far from a definite.

 As I suspected, 1/2 has nothing on the 18Z GFS. Also, there's nothing exciting on the rest of the run wintry precipwise though there is some really nice dry cold 1/2-3. So, the highlight is 12/31 (for mainly NC).

[NCCatawba]

I think you guys have something to follow with regards to the follower after this weekends rain event.  Looks a little sharper at 500 and the 18z initiates some heavier precip in central NC at 114.  Good luck to you guys, hope it trends into something better from here on out

 

Monitoring a few tenths of an inch of precip as we get hit by heavy rain this weekend will be fun. Mood swings with every run going up or down .1 or .05 for another 5 days. I feel like we have been down this road before.

[CAD_Wedge_NC]

Monitoring a few tenths of an inch of precip as we get hit by heavy rain this weekend will be fun. Mood swings with every run going up or down .1 or .05 for another 5 days. I feel like we have been down this road before.

 

Go back and re-read the Christmas storm threads. I remember the GFS had some runs where it looked eerily similar to what's being shown this evening. Yes, there will be mood swings, but that's all a part of tracking these events. Right now, it's just casual conversation.

[superjames1992]

I'm much more interested in the system on New Year's Eve than the early January storm at this point.

 

However, I see no reason to throw in the towel with the January 2nd-3rd system yet.  As CAD_Wedge_NC pointed out, the Christmas 2010 Storm looked like it was going to go wide right just 48-72 hours before many of us got hammered.  That doesn't mean it is going to happen again, but it could.

[BullCityWx]

The system on New Year's Eve looks way too warm at the surface for the immediate CLT metro.

[BullCityWx]

Actually, it appears to be way too warm for even Hickory.

[Tacoma]

The system on New Year's Eve looks way too warm at the surface for the immediate CLT metro.

what about the mountains. been hearing for two weeks about all the cold air, where is it when the moisture is coming?

[Cold Rain]

The Christmas storm was a just-in-time phase kinda deal. I can't see the 18z right now. Is that what we're talking about here? Or is it just a potent southern stream vort?

[griteater]

The Christmas storm was a just-in-time phase kinda deal. I can't see the 18z right now. Is that what we're talking about here? Or is it just a potent southern stream vort?

Definitely not a potent southern stream vort. These are northern stream shortwaves diving into an eastern trough. The ones that sharpen at the base have the ability to generate precip.

[BullCityWx]

looks like there's a NE wind at the surface that cools off areas that see snow

[Cold Rain]

Definitely not a potent southern stream vort. These are northern stream shortwaves diving into an eastern trough. The ones that sharpen at the base have the ability to generate precip.

Gotcha. Thanks sir! Not sure why I even care about the 18z GFS for a 5 day out storm anyway.

[griteater]

Gotcha. Thanks sir! Not sure why I even care about the 18z GFS for a 5 day out storm anyway.

Cause sadly it's all we got...it's all we got, lol

[NCCatawba]

Warm as in mid to upper 30s. It's workable 5 days out if we can trend things cooler. EURO/NAM is better IMO for profile temp but we are too far out to see/bother at this stage.

[Bsudweather]

Here in the upstate if the upper levels is cold enough we can see our better snows with sfc temps in the mid 30s

[CAD_Wedge_NC]

Actually, it appears to be way too warm for even Hickory.

 

As modeled, the freezing level only gets down to 925mb. Everything above that level is <0C. So, it does look like the surface temps will be a problem. It's never easy to get accumulating snow outside of the mtns. However, there is plenty of time to watch this one unfold.

[superjames1992]

It looks like the 18z GFS keeps GSO in the mid-30s for most of the precipitation.  I'm not overly worried about that at this point, but I've seen us get screwed over by warm BL temperatures before, so it shouldn't be overlooked if the models continue to show warm BL temperatures.  Verbatim, it looks like "white rain", perhaps.

[FLweather]

looks like there's a NE wind at the surface that cools off areas that see snow

Thats a good sign really... shows that the greatest pressure gradient and surface cyclogenesis will be immediately along the coast. Which would also suggest the deepest 500 mb vorticity will be along the gulf coast states through southern GA.

 

As modeled, the freezing level only gets down to 925mb. Everything above that level is <0C. So, it does look like the surface temps will be a problem. It's never easy to get accumulating snow outside of the mtns. However, there is plenty of time to watch this one unfold.

Surface would be 33-35 with snow then.  But I guess still too early to get into major details but since its a cold pocket aloft surface temps shouldn't be a issue really. If anything will be an issue is how much moisture.

 

But we have about 84-96 hours before seeing the effects... could change better or worse. I hope better.

[CAD_Wedge_NC]

The Christmas storm was a just-in-time phase kinda deal. I can't see the 18z right now. Is that what we're talking about here? Or is it just a potent southern stream vort?

 

Energy dives down on the east side of the Rockies and rounds the base of the trough in LA and heads ENE OTS. the trough never goes negative tilt, but still puts down roughly .25" of total precip with the passing energy to our south. Thicknesses are sub 540 out this way during the event, but as mentioned before the surface temps (as modeled) are a little too warm for accumulations.

 

Edit: 1000-500 thicknesses start out at 538 and drop to 532 by the end of the event. As a rule of thumb, but not always, the 540 thickness line is a good rain/snow demarcation boundary.

[GaWx]

 These are two different systems though they likely affect each other in some indirect way (butterfly effect). 1/2 showed up as colder on some runs. The 12/31 one on the 18Z GFS gives much of N NC 1-3" with heaviest centered near Brick's abode...at least that's what the clown said. Please don't tell him. He'll be out of control with excitement when it is far from a definite.

 As I suspected, 1/2 has nothing on the 18Z GFS. Also, there's nothing exciting on the rest of the run wintry precipwise though there is some really nice dry cold 1/2-3. So, the highlight is 12/31 (for mainly NC).

 

 Interesting turn of events on the 18Z GFS ensemble:

 

1) Very little support for the 12/31 NC snow. There's only ~.02-.03" of qpf on the mean. So, the 18Z GFs op. is a wet outlier vs. its ensemble members as it has ~.30" of qpf in the bullseye near RDU.

 

2) OTOH, the 1/2ish SE wintry event has much more support from the ensemble members than the 18Z op. GFS, which had virtually no qpf. The 18Z ensemble mean is the wettest of the last four GFS ensemble means with 0.25-0.50" of qpf over all of GA/SC/NC for the period 12Z on 1/1 to 12Z on 1/3! The average qpf is a very respectable ~0.35" and is suggestive of a classic Miller A track for several members. Compare that average to only 0.20-0.25" on the 12Z and 6Z means and ~0.20" on the 0Z mean! There are several members with moist WSW flow, which is consistent with a classic, weak Miller A track. There is very cold Arctic air centered to the north providing for plenty of low level cold air for wintry precip., largely snow.

[CAD_Wedge_NC]

 Interesting turn of events on the 18Z GFS ensemble:

 

1) Very little support for the 12/31 NC snow. There's only ~.02-.03" of qpf on the mean. So, the 18Z GFs op. is a wet outlier vs. its ensemble members as it has ~.30" of qpf in the bullseye near RDU.

 

2) OTOH, the 1/2ish SE wintry event has much more support from the ensemble members than the 18Z op. GFS, which had virtually no qpf. The 18Z ensemble mean is the wettest of the last four GFS ensemble means with 0.25-0.50" of qpf over all of GA/SC/NC for the period 12Z on 1/1 to 12Z on 1/3! The average qpf is a very respectable ~0.35" and is suggestive of a classic Miller A track for several members. Compare that average to only 0.20-0.25" on the 12Z and 6Z means and ~0.20" on the 0Z mean! There are several members with moist WSW flow, which is consistent with a classic, weak Miller A track.

 

Good information...... How do the temps look on the ensembles for the 1/2 event? I would assume, with that track, it would be cold enough for wintry precip.

[GaWx]

Good information...... How do the temps look on the ensembles for the 1/2 event? I would assume, with that track, it would be cold enough for wintry precip.

 

 Thanks. IF there is an actual suppressed, weak Miller A and pretty steady precip., it very likely would be cold enough over most of NC, N SC and far N GA for mostly snow with 850's below 0C per the 18Z GFS ensemble. Two meter highs would be in the 30's with lows in the mid to upper 20's suggesting mainly snow in these areas. Places like ATL, AHN, Augusta, Columbia, and Florence would probably not be all wintry (as usual) though some of those cites could easily be mostly wintry. Cities like Columbus and Macon could easily get some wintry.

 Overall, the wintry looks like mainly snow with no real CAD situation though I suppose there would be some IP in some areas.

[WeatherNC]

The Christmas storm was a just-in-time phase kinda deal. I can't see the 18z right now. Is that what we're talking about here? Or is it just a potent southern stream vort?

 

I still have the RUC image somewhere in archives, never forget that HPC model disco where "all models appear to be suffering from feedback."  Classic example of not knowing it was gonna happen for sure till about 18 hours out, it was honestly that close, with the phase occurring over the eastern Gulf coast.

 

18z GFS implies phasing, albeit, these are weak parcels in the northern and southern streams.  A strong shortwave which is coming into the Pac NW in the next 24 hours rides down ivo the 4 corners around day 3, some northern junk in the trunk enters CONUS near Glacier National Park same period.  @96 there is energy in the northern Plains and the southern piece moving east out of Central TX, keep in mind, none of the vorts are strong, these are pretty weak parcels, and the 18z GFS times them almost perfect 4+ days out, but given the lack of potent vorticity contained at the base even with interaction, trough axis is still pos well east of the MS.

 

Quick look at the 18z ens mems, several still have the 1/2-1/3 system, a couple which show a weak slp developing off the VA Capes 12/31 still show another stronger system 1/3  A and B types.  We need to start keeping an eye on what the guidance is showing near the Great Lakes, 12/31 and 1/3, I am seeing lots of evidence indicating a clipper type during both periods.