December 16th event

[xwx]

Folks, I'm not trying to be the weenie but its so hard to work out of town and try to keep up with so many different versions of posts. I thought we ditched the Thursday event earlier today and were focusing on the weekend. Now it appears we are back in the hunt for Thursday? If so, flying into GSO from Nashville Thursday night is going to be a pleasure........NOT. Somebody give me the best guess please.

Three events pre-Christmas??? Maybe four??? Geesh!

at face value the nam run is a mod event over western central and northern nc on tgnts run ...........There is a sweet spot of 6" over north central nc......verga will be a live and well at 12z thurs....by 15z the omega fields and the 1000-700mb r/s line is running thru the Queen city...........This event is a nc/sc event as far as winter wx.....

xwx

[BullCityWx]

at face value the nam run is a mod event over western central and northern nc on tgnts run ...........There is a sweet spot of 6" over north central nc......verga will be a live and well at 12z thurs....by 15z the omega fields and the 1000-700mb r/s line is running thru the Queen city...........This event is a nc/sc event as far as winter wx.....

xwx

you wouldnt happen to be acweather, would you?

[xwx]

you wouldnt happen to be acweather, would you?

no sir....is that good or bad

xwx

[FoothillsNC]

Posted this in the other thread, but I think it actually fits better here.

Looks like the NAM shows snow quickly turning to sleet and freezing rain for the southern piedmont. It then quickly brings surface temperatures above freezing for everyone south of I-40 by mid morning. However I think places that receive some heavier precipitation will stay right around the freezing mark a little longer than those who only receive light precip. This could make a lot of difference in that freezing rain at 32 degrees with very cold ground temperatures can be much worse then when you have 32 degrees and relatively warm ground temps.

at 60, the sfc freezing runs from SW NC to northern SC to southeast NC, with most of NC 30 or less at the surface. It takes until 66 hour, middle of the day Thursday when the 32 line runs from Mt Airy to Concord to eastern NC around Rocky Mtn, leaving the central and northern piedmont of NC subfreezing, but by then most of the qpf has probably occurred. And by 72 its dropped it back down to south of CLT and I'm sure by then all meaningful precip has ended. Its a wierd look though with the surface winds. They are from the south depending on where you are, but they are very weak, so theres not going to be much advection warming from the southeast coastline like in a normal CAD setup. We hardly ever see this, so I'm not sure what to think. I'd think light precip would hardly warm the atmosphere much, but very heavy precip obviously would.

[xwx]

you wouldnt happen to be acweather, would you?

I had 20 some ppl ask me lastngt who i was....Just enjoying wx and the board....I love raising interesting issues and curious hypotheses that are good at learning wx

xwx

[xwx]

at 60, the sfc freezing runs from SW NC to northern SC to southeast NC, with most of NC 30 or less at the surface. It takes until 66 hour, middle of the day Thursday when the 32 line runs from Mt Airy to Concord to eastern NC around Rocky Mtn, leaving the central and northern piedmont of NC subfreezing, but by then most of the qpf has probably occurred. And by 72 its dropped it back down to south of CLT and I'm sure by then all meaningful precip has ended. Its a wierd look though with the surface winds. They are from the south depending on where you are, but they are very weak, so theres not going to be much advection warming from the southeast coastline like in a normal CAD setup. We hardly ever see this, so I'm not sure what to think. I'd think light precip would hardly warm the atmosphere much, but very heavy precip obviously would.

exactly....upper level forcing and inversion that may include the barrier jet could keep the n/w piedmont under 32

xwx

[BIG FROSTY]

10pm JB update for anyone interested...

Lots of fun and games on modeling the next 10-15 days. Another southern snow slips east Thursday and brings the second snow of the season as far south as NC, with a bigger ticket threat this weekend that may turn northeast far enough for snows in the big cities. This does have potential to be a sizeable storm as it fits the overall pattern and chances are with time, the models that are out at sea will correct west

[FoothillsNC]

.

exactly....upper level forcing and inversion that may include the barrier jet could keep the n/w piedmont under 32

xwx

well you're obviously a met. or atleast read enough intro books. There have been documented cases in the foothills of the barrier jet, and this situation could be one since its an In-situ event. However its always strictly for a narrow sliver of the foothill counties. Although you need to expound on the upper forcing part. All you need is a lack of parent high and light winds, with marginal upper warm advection.

[POWERSTROKE]

10pm JB update for anyone interested...

Lots of fun and games on modeling the next 10-15 days. Another southern snow slips east Thursday and brings the second snow of the season as far south as NC, with a bigger ticket threat this weekend that may turn northeast far enough for snows in the big cities. This does have potential to be a sizeable storm as it fits the overall pattern and chances are with time, the models that are out at sea will correct west

yeah buddy

[FoothillsNC]

The GFS is out to 48 hour and has precip already right at Southwest NC Tenn border. Ice in n. Al and Ga.

[UNCCmetgrad]

at 60, the sfc freezing runs from SW NC to northern SC to southeast NC, with most of NC 30 or less at the surface. It takes until 66 hour, middle of the day Thursday when the 32 line runs from Mt Airy to Concord to eastern NC around Rocky Mtn, leaving the central and northern piedmont of NC subfreezing, but by then most of the qpf has probably occurred. And by 72 its dropped it back down to south of CLT and I'm sure by then all meaningful precip has ended. Its a wierd look though with the surface winds. They are from the south depending on where you are, but they are very weak, so theres not going to be much advection warming from the southeast coastline like in a normal CAD setup. We hardly ever see this, so I'm not sure what to think. I'd think light precip would hardly warm the atmosphere much, but very heavy precip obviously would.

I was thinking that heavier precip would offset any heating due to insolation, and allow temperatures to reach wet-bulb, but I see where your going in that heavier freezing rain would heat the atmosphere due to latent heat release. Interestingly enough the NAM has wet-bulbs around 27 degrees around the southern peidmont just before precipitation begins and keeps them below freezing throughout most of North Carolina and some of northern South Carolina throughout the day on Thursday.

[FoothillsNC]

by 54 hours the freezing aloft (snow) runs from just west of CLT to AVL to Ne TN and central KY. QPF looks to have increased in eastern TN and w. NC by that hour. The surface freezing is still in N. GA from Lake lanier to south central TN.

[POWERSTROKE]

The GFS is out to 48 hour and has precip already right at Southwest NC Tenn border. Ice in n. Al and Ga.

Come on buddy! I need to get rid of some salt and ice melt!

[xwx]

.

well you're obviously a met. or atleast read enough intro books. There have been documented cases in the foothills of the barrier jet, and this situation could be one since its an In-situ event. However its always strictly for a narrow sliver of the foothill counties. Although you need to expound on the upper forcing part. All you need is a lack of parent high and light winds, with marginal upper warm advection.

strong vertical motion with CAA will create the rn over to sn part.........Insitu damming event is from pcp falling and its a ground event or typically in the lowest 1km of the atomosphere..............

xwx

[jrips27]

DT cracks me up!

[FoothillsNC]

by 60 hours, all of TEnn atleast east half has .25" and a little more around Cookesville, and NE tenn is still subreezing at the surface so they've iced over decently after some accum. snow probably. The surface freezing line runs down into the Upstate of SC and all of NC is in precip. About .10" or more By 66 hour the freezing line has retreated to Va border. This run did trend a little colder and wetter for NC.

[FoothillsNC]

strong vertical motion with CAA will create the rn over to sn part.........Insitu damming event is from pcp falling and its a ground event or typically in the lowest 1km of the atomosphere..............

xwx

I change my mind , theres no CAA with this that I can find.

Anyway this run is colder and by 72 hours the subfreezing line is back into northern NC but by then most of the precip is done. Over a .10" to some spots more than .25" around GSO to RDU it looked like. I still think northern NC has the most impact from this event, with the best chance at staying subfreezing for most of the event, as well as nw NC. Also ne TN probably gets a good bit of ice and snow as well as sw Va.

[UNCCmetgrad]

Looking at BUFKIT profiles for CLT actually looks like a decent little event for the Charlotte area. Gives us just under an inch of snow before transitioning to ice pellets to freezing rain. About a third of an inch of precipitation falls as freezing rain before changing to all rain around noon. Still a very interesting setup as winds stay light out of the south and never really swing around to the northeast as you see so many times with in situ situation. As was discussed a few days ago looks like moisture overrunning a retreating arctic air mass.

[FoothillsNC]

by 18z Sat. our gulf low is now in central Ga, YIKES. Its a little too warm for snow except on the backside in western Tn and Arkansas and its ending for them. Looks like DC may get this one after all.

[xwx]

I change my mind , theres no CAA with this that I can find.

Anyway this run is colder and by 72 hours the subfreezing line is back into northern NC but by then most of the precip is done. Over a .10" to some spots more than .25" around GSO to RDU it looked like. I still think northern NC has the most impact from this event, with the best chance at staying subfreezing for most of the event, as well as nw NC. Also ne TN probably gets a good bit of ice and snow as well as sw Va.

in the lowest levels 940-945 u can have Caa with no anticyclone located to the north.....hp will be to far south......in the 850 layer is were the warm layer comes in on ssw winds........hope this helps

xwx

[HKY_WX]

by 18z Sat. our gulf low is now in central Ga, YIKES. Its a little too warm for snow except on the backside in western Tn and Arkansas and its ending for them. Looks like DC may get this one after all.

looks like it changes over to snow by 00z sun. obviously this will change about 100 times b/n now and then, but at least it looks like it is on the map now.

[superjames1992]

by 18z Sat. our gulf low is now in central Ga, YIKES. Its a little too warm for snow except on the backside in western Tn and Arkansas and its ending for them. Looks like DC may get this one after all.

Looks like Big Frosty would do well. I'm very borderline here.

BTW, is this board getting really slow for anyone else?

[POWERSTROKE]

we will all be fine guys. It is still 6 days away. I will be looking for more plows!

[FoothillsNC]

Looking at BUFKIT profiles for CLT actually looks like a decent little event for the Charlotte area. Gives us just under an inch of snow before transitioning to ice pellets to freezing rain. About a third of an inch of precipitation falls as freezing rain before changing to all rain around noon. Still a very interesting setup as winds stay light out of the south and never really swing around to the northeast as you see so many times with in situ situation. As was discussed a few days ago looks like moisture overrunning a retreating arctic air mass.

yeah, i agree. Good little event for much of NC, and I'm very curious how it works out. I really don't know what to think with temps at the surface. At the start, you can see plenty of dry air up and down the east coast east of the Apps, and acutally drier in SC and GA and n. Florida, than here , maybe because we've saturated by that time but the winds are light. On the high. res. of NAM theres almost zero wind in NW NC, so I'm about positive they never get to Zero. The models are gong to have a problem with the this, but the trend tonight is colder and more precip in NC and earlier. I think its still on the table for sure. We keep getting unusual events, the prefrontal snow in the mountains and now whatever this is, ZR with southerly winds. I don't think the winds will be any more than 3 to 5 knots in the piedmonth and you can see some ne winds in the upstate bending around the southern Mtns for a time.

Not sure if I should mention the next storm in this thread, but it has the 850 low right over CLT at 120 hours, with snow obviously on the nw shield so that would once again place w. and NW NC is bonus heavy snow with that track. Later on goes to make it snow everywher in the northern piedmont, pretty good at that. I'm right on the line. I never like the cold coming in to meet the moisture, but we're having all these oddball events, maybe therees a first for eveything.

[NCSNOW]

by 18z Sat. our gulf low is now in central Ga, YIKES. Its a little too warm for snow except on the backside in western Tn and Arkansas and its ending for them. Looks like DC may get this one after all.

Whats even scarier to my untrained eye, if you look at the last frame of the Nam/ hr84, looks like our low is begining to amplify way out SW, which means it could close off by the Mississippi, which = App/GL path as an old rule of thumb. Am I seeing this correctly on the 84 hour Nam. Not that the Nam means anything at this range, just looking for clues/trends to unfold over the next couple days in model world like everyone else.

[FoothillsNC]

looks like it changes over to snow by 00z sun. obviously this will change about 100 times b/n now and then, but at least it looks like it is on the map now.

yep. I spoke too soon. It gets nw NC and nothern NC good with the 850 low track. Obviously many changes ahead.

Whats even scarier to my untrained eye, if you look at the last frame of the Nam/ hr84, looks like our low is begining to amplify way out SW, which means it could close off by the Mississippi, which = App/GL path as an old rule of thumb. Am I seeing this correctly on the 84 hour Nam. Not that the Nam means anything at this range, just looking for clues/trends to unfold over the next couple days in model world like everyone else.

it also amps up on the GFS over the Carolinas.

[NCSNOW]

yep. I spoke too soon. It gets nw NC and nothern NC good with the 850 low track. Obviously many changes ahead.

it also amps up on the GFS over the Carolinas.

your right, at 126 on gfs it gets neutral and almost looks like it could go negative with a phase , but then just chugs OTS. Ive listened enough and tried to watch over the years to know that when models are trying to forecast a phase of northern stream and southern stream energy, it's highly unlikely until inside 36-24 hours before you can trust them with specifics and even then I'd say your still dealing with a higher level of margin error then if just one stream is involved. By the way thanks for dissecting all these model runs for us.

[WeatherNC]

Don't know what to think looking over the 0z guidance regarding this event, the differences in thermal profile between the american models leads to a lower than avg forecast going forward. It is somewhat intriguing that both models have trended south with the QPF shield, and colder aloft as a result of the warm front shifting south, similar to the trends we saw with the clipper type system a week ago. I would not be surprised, to see the surface wave track just to the south of the NC boarder at this point, putting the 40 corridor into a mod-impact winter weather event, especially when considering ground and road temps Thursday morning. These are the soundings for PGV at 60 hrs from the 0z GFS and NAM, not even close to agreement in terms of saturation aloft...

[HKY18]

Don't know what to think looking over the 0z guidance regarding this event, the differences in thermal profile between the american models leads to a lower than avg forecast going forward. It is somewhat intriguing that both models have trended south with the QPF shield, and colder aloft as a result of the warm front shifting south, similar to the trends we saw with the clipper type system a week ago. I would not be surprised, to see the surface wave track just to the south of the NC boarder at this point, putting the 40 corridor into a mod-impact winter weather event, especially when considering ground and road temps Thursday morning. These are the soundings for PGV at 60 hrs from the 0z GFS and NAM, not even close to agreement in terms of saturation aloft...

yeah i could see northern portions of nc getting close to warning criteria if this thing tracks further south?

[WeatherNC]

yeah i could see northern portions of nc getting close to warning criteria if this thing tracks further south?

Please don't quote images, it adds to the length of pages unnecessarily, delete the image links when replying in quote. I don't know what RAH's WSW criteria is for ZR, but a quarter inch on top of a little SN and IP would yield very hazardous road conditions, especially for the Thursday pm commute. With a more southern track though, ZR would be shifted south, maybe even south of 40, leaving the triangle mostly SN and IP, before ending as some freezing drizzle as the moisture exits. QPF amounts and thickness profiles are the flavor going forward. Any areas that see 3-4 tenths of an inch liquid, and surface temps below freezing for the duration are likely to be a mess in terms of travel, as folks around here do not know how to drive with conditions as such!

MODEL DIAGNOSTIC DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD

1219 AM EST TUE DEC 14 2010

VALID DEC 14/0000 UTC THRU DEC 17/1200 UTC

...SEE NOUS42 KWNO ADMNFD FOR THE STATUS OF THE UPPER AIR INGEST...

00Z NAM/GFS EVALUATION INCLUDING THE NEW UKMET/CANADIAN AND

PREFERENCES

...LOW PRESSURE FORMING OVER THE S. PLAINS/GULF COAST/CAROLINAS

WED-THU...

PREFERENCE: GFS

THE ECMWF SHOWS A GREATER DEGREE OF PHASING OF SHORTWAVE TROUGHS

EXTENDING FROM THE UPPER MIDWEST INTO TEXAS WHICH CONTRIBUTES TO

STRONGER/MORE NORTHWARD SURFACE LOW DEVELOPMENT AND GREATER LOW

LEVEL BAROCLINICITY ACCOMPANYING ITS FRONTAL BOUNDARY THAN BOTH

THE NAM AND GFS. MEANWHILE...THE NAM IS CONSIDERABLY MORE

AGGRESSIVE WITH THE FRONT DROPPING SOUTHWARD ACROSS THE CAROLINAS

ON DAY 3...WHICH IS A RESULT OF ITS GREATER TROUGH AMPLIFICATION

OVER THE WESTERN ATLANTIC AND CURRENTLY DISCOUNTED DUE TO WORSE

INITIALIZATION. THUS...THROUGH A PROCESS OF ELIMINATION RECOMMEND

THE GFS.