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Feb. 18-20, 2012 Disco/Analysis


Poimen

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@54 NAM shows two LPs on this system. Have we seen that in any prior runs?

Yes, it's been showing up on almost every run. When the low pressure (in Alabama) heading northeast runs into the confluence that it feels from the 50/50 in place it should almost stall briefly and then hand off it's energy to a coastal low. The dying low will typically decay itself out while the new low on the coast will strenghen.

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Yes, it's been showing up on almost every run. When the low pressure (in Alabama) heading northeast runs into the confluence that it feels from the 50/50 in place it should almost stall briefly and then hand off it's energy to a coastal low. The dying low will typically decay itself out while the new low on the coast will strenghen.

translated......... dry slot in the piedmont!

TW

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What folks in NC really need to see is this second disturbance we've been talking about (seen below on the 12z NAM as it's over MO) to really maintain its strength as do it's magic as it moves through later Sunday. If it were to happen to be able to dig a little more as it moves into our region, some folks would be in business. Going to be tough though.

post-390-0-69765400-1329490397.png

Just basing it off this Jeremy...but deep down I know. I know.

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I'll wait til after all 12z is in, but the agreement among most is pretty good now. The northeast confluence is going to keep this relatively south of the upper MidAtlantic. The additional 5H energy seen around Kansas City tomorrow will either kick the main system or phase into it, it looks like a classic elongated shear axis, where moisture stretches west/SW to east/NE from eastern Arkansas, across TN/KY into the Apps and across Virginia. Southern NC , Upstate and Ga would dryslot fairly quickly. The 850 low really gets going around the foothills of NC early to midday Sunday, and the cold aloft will be pressing on it as it rotates toward northern NC during the day Sunday. So for western and central VA, there will be cold low levels but a slight warm nose so either sleet or ZR will occur in spots, but heavy snow just west of there and changing to snow in most of those areas at some point when the warm nose works east. By then, most of eastern KY will have had a decent snowstorm, same for northeast TN and it looks like most of TN could get atleast some snow, but my favorite areas are northeast and the northern half of the state. Southern and central WVA mountain empire gets clocked good with all snow and no ice issues.

As the storm begins to congeal off OBX , eastern NC and VA will have accumulating period of pretty heavy snow if the system deepens quickly enough , I think it will.

The last place for snow I think would be central Al, most of GA and most of SC, except maybe northeast SC, and southwest south central NC from Charlotte back west to southern foothills region, since strong downsloping will be ongoing at the time the cold enough air is working in. All this is just my early thoughts on the models to this point. If the models miss the speed of the southern system by 6 to 12 hours, then that would allow more damming to occur in NC and change things substantially. Its a pretty tight walk.

Really impressed with the consistency of the 850 low throwing down hard snow rates in central and western VA for a time..Could be some foot totals.

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I'll wait til after all 12z is in, but the agreement among most is pretty good now. The northeast confluence is going to keep this relatively south of the upper MidAtlantic. The additional 5H energy seen around Kansas City tomorrow will either kick the main system or phase into it, it looks like a classic elongated shear axis, where moisture stretches west/SW to east/NE from eastern Arkansas, across TN/KY into the Apps and across Virginia. Southern NC , Upstate and Ga would dryslot fairly quickly. The 850 low really gets going around the foothills of NC early to midday Sunday, and the cold aloft will be pressing on it as it rotates toward northern NC during the day Sunday. So for western and central VA, there will be cold low levels but a slight warm nose so either sleet or ZR will occur in spots, but heavy snow just west of there and changing to snow in most of those areas at some point when the warm nose works east. By then, most of eastern KY will have had a decent snowstorm, same for northeast TN and it looks like most of TN could get atleast some snow, but my favorite areas are northeast and the northern half of the state. Southern and central WVA mountain empire gets clocked good with all snow and no ice issues.

As the storm begins to congeal off OBX , eastern NC and VA will have accumulating period of pretty heavy snow if the system deepens quickly enough , I think it will.

The last place for snow I think would be central Al, most of GA and most of SC, except maybe northeast SC, and southwest south central NC from Charlotte back west to southern foothills region, since strong downsloping will be ongoing at the time the cold enough air is working in. All this is just my early thoughts on the models to this point. If the models miss the speed of the southern system by 6 to 12 hours, then that would allow more damming to occur in NC and change things substantially. Its a pretty tight walk.

Really impressed with the consistency of the 850 low throwing down hard snow rates in central and western VA for a time..Could be some foot totals.

Are you saying they will be the last ones to get in on the snow or they have the least chances of getting anything?

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Are you saying they will be the last ones to get in on the snow or they have the least chances of getting anything?

I should have worded that better. Thats the least favored areas to see snow. Could be a period of ending snow in northern parts of Ms, Al, GA though. But most of GA and SC is a shutout. Much of NC could get some ending snow, obviously the mountains and the coast will thanks to how this plays out, and probably northern NC, and possibly much of eastern half of NC, but not much chance in southwestern NC east of the mountains thanks to downslope.

The last place for snow I think would be central Al, most of GA and most of SC, except maybe northeast SC, and southwest south central NC from Charlotte back west to southern foothills region, since strong downsloping will be ongoing at the time the cold enough air is working in.

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For us down east it all depends on that backside piece getting in here in time to keep the moisture going as the coastal low departs. This is from the 12z NAM, map 6hrs prior has the sn line along and west of 95 based on thickness, so some of this would like be frozen here, unsure how much but maybe a couple tenths on the high end. Not quite as robust compared to 6z, but a little lower with the thickness plots.

12znamp06thickpmsl_MA066.gif

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I'll wait til after all 12z is in, but the agreement among most is pretty good now. The northeast confluence is going to keep this relatively south of the upper MidAtlantic. The additional 5H energy seen around Kansas City tomorrow will either kick the main system or phase into it, it looks like a classic elongated shear axis, where moisture stretches west/SW to east/NE from eastern Arkansas, across TN/KY into the Apps and across Virginia. Southern NC , Upstate and Ga would dryslot fairly quickly. The 850 low really gets going around the foothills of NC early to midday Sunday, and the cold aloft will be pressing on it as it rotates toward northern NC during the day Sunday. So for western and central VA, there will be cold low levels but a slight warm nose so either sleet or ZR will occur in spots, but heavy snow just west of there and changing to snow in most of those areas at some point when the warm nose works east. By then, most of eastern KY will have had a decent snowstorm, same for northeast TN and it looks like most of TN could get atleast some snow, but my favorite areas are northeast and the northern half of the state. Southern and central WVA mountain empire gets clocked good with all snow and no ice issues.

As the storm begins to congeal off OBX , eastern NC and VA will have accumulating period of pretty heavy snow if the system deepens quickly enough , I think it will.

The last place for snow I think would be central Al, most of GA and most of SC, except maybe northeast SC, and southwest south central NC from Charlotte back west to southern foothills region, since strong downsloping will be ongoing at the time the cold enough air is working in. All this is just my early thoughts on the models to this point. If the models miss the speed of the southern system by 6 to 12 hours, then that would allow more damming to occur in NC and change things substantially. Its a pretty tight walk.

Really impressed with the consistency of the 850 low throwing down hard snow rates in central and western VA for a time..Could be some foot totals.

While I agree with most of what you say, I can not see anyone in Virginia seeing more than 6" from this storm regardless of which model you look at. Yes, there will be a heavy band of snow along and North of the 850 low, however; With recent mild weather and warm surface temperatures leading up to the event it is going to take awhile before you start seeing an accumulation of any significance. Depending on which model you look at, most areas in VA are looking at between 1" and 1.5" of liquid. With a 10:1 ratio on average (It will probably start out a little lower and end up a little higher at the end), some of this will fall as rain before any changeover, and some will be lost before any accumulation will begin. At best 50% of the precipitation that falls will result in accumulating snow. Therefore I would expect the areas in the "bulls eye" to see 4" to 6" at best, with an isolated spot or two seeing 6"+ but not much more than that. I can't see how anyone South of Roanoke to Lynchburg to Petersburg outside of the higher elevations in the West sees more than an inch. And the areas along the NC/VA border will likely see no more than a slushy accumulation on the grassy areas Sunday evening as the precipitation ends. As you mentioned the best area in NC to see any accumulation would be the extreme Northeastern sections since the moisture would linger a little longer. I do think that there is a chance that most people in North Central NC from the Triad to the Triangle stands a decent chance of seeing a change over to wet snow with the current look of the models, but anyone holding out for accumulating snow in those areas are going to be disappointed I'm afraid.

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I'll wait til after all 12z is in, but the agreement among most is pretty good now. The northeast confluence is going to keep this relatively south of the upper MidAtlantic. The additional 5H energy seen around Kansas City tomorrow will either kick the main system or phase into it, it looks like a classic elongated shear axis, where moisture stretches west/SW to east/NE from eastern Arkansas, across TN/KY into the Apps and across Virginia. Southern NC , Upstate and Ga would dryslot fairly quickly. The 850 low really gets going around the foothills of NC early to midday Sunday, and the cold aloft will be pressing on it as it rotates toward northern NC during the day Sunday. So for western and central VA, there will be cold low levels but a slight warm nose so either sleet or ZR will occur in spots, but heavy snow just west of there and changing to snow in most of those areas at some point when the warm nose works east. By then, most of eastern KY will have had a decent snowstorm, same for northeast TN and it looks like most of TN could get atleast some snow, but my favorite areas are northeast and the northern half of the state. Southern and central WVA mountain empire gets clocked good with all snow and no ice issues.

As the storm begins to congeal off OBX , eastern NC and VA will have accumulating period of pretty heavy snow if the system deepens quickly enough , I think it will.

The last place for snow I think would be central Al, most of GA and most of SC, except maybe northeast SC, and southwest south central NC from Charlotte back west to southern foothills region, since strong downsloping will be ongoing at the time the cold enough air is working in. All this is just my early thoughts on the models to this point. If the models miss the speed of the southern system by 6 to 12 hours, then that would allow more damming to occur in NC and change things substantially. Its a pretty tight walk.

Really impressed with the consistency of the 850 low throwing down hard snow rates in central and western VA for a time..Could be some foot totals.

Hope you're right, Foothills. Morristown is playing it conservative. I'm in the northern half of East TN (in Oak Ridge) and they are calling for all rain. Would be nice to be surprised with snow.

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While I agree with most of what you say, I can not see anyone in Virginia seeing more than 6" from this storm regardless of which model you look at. Yes, there will be a heavy band of snow along and North of the 850 low, however; With recent mild weather and warm surface temperatures leading up to the event it is going to take awhile before you start seeing an accumulation of any significance. Depending on which model you look at, most areas in VA are looking at between 1" and 1.5" of liquid. With a 10:1 ratio on average (It will probably start out a little lower and end up a little higher at the end), some of this will fall as rain before any changeover, and some will be lost before any accumulation will begin. At best 50% of the precipitation that falls will result in accumulating snow. Therefore I would expect the areas in the "bulls eye" to see 4" to 6" at best, with an isolated spot or two seeing 6"+ but not much more than that. I can't see how anyone South of Roanoke to Lynchburg to Petersburg outside of the higher elevations in the West sees more than an inch. And the areas along the NC/VA border will likely see no more than a slushy accumulation on the grassy areas Sunday evening as the precipitation ends. As you mentioned the best area in NC to see any accumulation would be the extreme Northeastern sections since the moisture would linger a little longer. I do think that there is a chance that most people in North Central NC from the Triad to the Triangle stands a decent chance of seeing a change over to wet snow with the current look of the models, but anyone holding out for accumulating snow in those areas are going to be disappointed I'm afraid.

Agree as well but holding out hope. The NAM did have surface temps getting to freezing or just below with some precip still falling. Would be nice to see at least some snow or ice in the trees on Monday morning.

tw

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While I agree with most of what you say, I can not see anyone in Virginia seeing more than 6" from this storm regardless of which model you look at. Yes, there will be a heavy band of snow along and North of the 850 low, however; With recent mild weather and warm surface temperatures leading up to the event it is going to take awhile before you start seeing an accumulation of any significance. Depending on which model you look at, most areas in VA are looking at between 1" and 1.5" of liquid. With a 10:1 ratio on average (It will probably start out a little lower and end up a little higher at the end), some of this will fall as rain before any changeover, and some will be lost before any accumulation will begin. At best 50% of the precipitation that falls will result in accumulating snow. Therefore I would expect the areas in the "bulls eye" to see 4" to 6" at best, with an isolated spot or two seeing 6"+ but not much more than that. I can't see how anyone South of Roanoke to Lynchburg to Petersburg outside of the higher elevations in the West sees more than an inch. And the areas along the NC/VA border will likely see no more than a slushy accumulation on the grassy areas Sunday evening as the precipitation ends. As you mentioned the best area in NC to see any accumulation would be the extreme Northeastern sections since the moisture would linger a little longer. I do think that there is a chance that most people in North Central NC from the Triad to the Triangle stands a decent chance of seeing a change over to wet snow with the current look of the models, but anyone holding out for accumulating snow in those areas are going to be disappointed I'm afraid.

I don't think most people are expecting much (even here in N. NC). With the past couple of months, a dusting to a half inch (from 12z NAM) would be a victory. There's not much to be be disappointed here.

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I should have worded that better. Thats the least favored areas to see snow. Could be a period of ending snow in northern parts of Ms, Al, GA though. But most of GA and SC is a shutout. Much of NC could get some ending snow, obviously the mountains and the coast will thanks to how this plays out, and probably northern NC, and possibly much of eastern half of NC, but not much chance in southwestern NC east of the mountains thanks to downslope.

The last place for snow I think would be central Al, most of GA and most of SC, except maybe northeast SC, and southwest south central NC from Charlotte back west to southern foothills region, since strong downsloping will be ongoing at the time the cold enough air is working in.

Yes, the dreaded downslope that is all too familiar to this region. I think Hickory is most likely going to fall in this area of limited-to-no snow, as well. (Hey, where's my optimism?) Good ol' Grandfather Mountain just loves to wring the moisture out of the sky instead of letting it make its way down to us poor souls.

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I'm hoping we can eek out a slushy accumulation/dusting here, and I think that is the high end of our expectations for us folks imediatley north and east of RDU. Alas, I admit I'll be happy if we can just get a period of snow falling from the sky. That in itself will be a victory in this winter.

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While I agree with most of what you say, I can not see anyone in Virginia seeing more than 6" from this storm regardless of which model you look at. Yes, there will be a heavy band of snow along and North of the 850 low, however; With recent mild weather and warm surface temperatures leading up to the event it is going to take awhile before you start seeing an accumulation of any significance. Depending on which model you look at, most areas in VA are looking at between 1" and 1.5" of liquid. With a 10:1 ratio on average (It will probably start out a little lower and end up a little higher at the end), some of this will fall as rain before any changeover, and some will be lost before any accumulation will begin. At best 50% of the precipitation that falls will result in accumulating snow. Therefore I would expect the areas in the "bulls eye" to see 4" to 6" at best, with an isolated spot or two seeing 6"+ but not much more than that. I can't see how anyone South of Roanoke to Lynchburg to Petersburg outside of the higher elevations in the West sees more than an inch. And the areas along the NC/VA border will likely see no more than a slushy accumulation on the grassy areas Sunday evening as the precipitation ends. As you mentioned the best area in NC to see any accumulation would be the extreme Northeastern sections since the moisture would linger a little longer. I do think that there is a chance that most people in North Central NC from the Triad to the Triangle stands a decent chance of seeing a change over to wet snow with the current look of the models, but anyone holding out for accumulating snow in those areas are going to be disappointed I'm afraid.

The whole "it's been warm" is bull****. If it's below freezing, the snow will accumulate just fine.

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If the GFS were to tick 20-50 miles south we would have something to work with, still some northern NC looks to do OK, triangle probably sees a dusting at best. I think this is probably as far south as it can go, hopefully it holds.

I may be wrong, but it seems like any model could easily be 20-50 miles off on any given run. Since this appears to be so close for us in northern NC, that amount of difference could be huge.

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The whole "it's been warm" is bull****. If it's below freezing, the snow will accumulate just fine.

Good luck getting the accumulations the maps show after a inch of rain and days of 55-60+ degree weather. It will have to come down hard and hope for at least half of whatever falls stays.

NWS Raleigh

Any wintry precipitation should be of limited duration and impact given the preceding warm ground temperatures...

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I may be wrong, but it seems like any model could easily be 20-50 miles off on any given run. Since this appears to be so close for us in northern NC, that amount of difference could be huge.

The track alone is not the only problem. Even if it took a perfect track there still isn't much in the way of cold air to work with. It would be better if the high was a bit stronger as a 1020/1024 just isn't going to do it. You can always count on dynamics to cool the atmosphere, but unless you have heavy precipitation rates you will still end up with rain. Once the rates lighten up you will end up with nothing more than light rain or drizzle.

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