burgertime Posted February 18, 2012 Share Posted February 18, 2012 12z NAM may be a tad slower out to 12 and just a hair south...but like Matt said the south trends are probably over. It doesn't look any further south to make any kind of difference. Link to comment Share on other sites More sharing options...
Tullioz Posted February 18, 2012 Share Posted February 18, 2012 Been comparing last few runs of RUC to NAM -- don't see major differences with southern S/W or the northern energy. Only difference I can see is the RUC is digging the "Nebraska S/W" more than the NAM. At 3z Sunday, RUC runs has that s/w well down into Kansas -- NAM still has it on Nebraska/KS border. You can clearly see the the shortwave in Nebraska on the water vapor loop, and it is certainly dropping in a little faster than the NAM had shown. Also it appears to be a little West as well. I would not be surprised if the models shift the track of the surface low a little further North with the 12z runs. Link to comment Share on other sites More sharing options...
Lookout Posted February 18, 2012 Share Posted February 18, 2012 As I figured days ago, I have no dog in this fight and this is your typical nc special with ga being completely left out (save the highest elevations but even there I don't expect much). But as depressing as it is to be left out, I'm still rooting for those who could get some snow..which is looking likely right now. I haven't read this thread much and I see jeremy has made a note of it but even though at first glance 850mb temps are low enough to be overcome by appreciable precip rates and forcing, the 06z nam has a strong warm nose centered around 800mb and as high as 750mb. Later on, it cools it to 1c while the rest of the column is subfreezing. (using hky for example) So, depending on where/when the precip falls there could be quite a bit of sleet in some areas, in particular those on the southern end of the cold air. However, the gfs doesn't have this warm nose nearly as warm. The nam does destroy this warm nose eventually and there will be snow but this warm nose, if it is as warm and pronounced as the nam, is likely to have an effect on precip type for a while. One would think such a small warm nose wouldn't have an impact but man I've seen such relatively small warm noses on model soundings really screw people out of snow, including here. Just wanted to point this out since often times many just look at 850mb temps as a guide to precip type when these warm noses can exists above that level, especially in the south. Link to comment Share on other sites More sharing options...
beanskip Posted February 18, 2012 Share Posted February 18, 2012 Yes, I guess if this is an actual trend there are two questions -- how does it affect the southern s/w and does it prolong the backside precip some of us are counting on. You can clearly see the the shortwave in Nebraska on the water vapor loop, and it is certainly dropping in a little faster than the NAM had shown. Also it appears to be a little West as well. I would not be surprised if the models shift the track of the surface low a little further North with the 12z runs. Link to comment Share on other sites More sharing options...
Rankin5150 Posted February 18, 2012 Share Posted February 18, 2012 12z NAM may be a tad slower out to 12 and just a hair south...but like Matt said the south trends are probably over. It doesn't look any further south to make any kind of difference. At some point, we need to look at Radar trends. The question is when? This is a doozy of a system to track, b/c there are so many variables that can change things in the golden hour. What a roller coaster. Link to comment Share on other sites More sharing options...
eyewall Posted February 18, 2012 Share Posted February 18, 2012 I am definitely glad to be in Orange County now instead of Moore and the Southern Pines area . Link to comment Share on other sites More sharing options...
packbacker Posted February 18, 2012 Share Posted February 18, 2012 I am definitely glad to be in Orange County now instead of Moore and the Southern Pines area . HAH, your a snow magnet, you and Widre look to be in a good spot. Link to comment Share on other sites More sharing options...
Cold Rain Posted February 18, 2012 Share Posted February 18, 2012 The new NAM is slightly north and closer to the NC coast with the low. Not sure I'm happy about this sort of trend here at the 11th hour. Link to comment Share on other sites More sharing options...
swva Posted February 18, 2012 Share Posted February 18, 2012 12z Nam is definitely further north Link to comment Share on other sites More sharing options...
HKY_WX Posted February 18, 2012 Share Posted February 18, 2012 I'll make a forecast on my examiner page after i see the euro this afternoon. At this point things look pretty similar to last night. The models have probably shifted a tad north from last night, but at this point it is close to nowcasting. Hoping to see this continue trending slower. IMO that will allow more cold air to work in at the sfc from the high and also will allow a little more phasing at the end to perhaps bring a more significant deformation axis which is what we will be depending on for snow. Link to comment Share on other sites More sharing options...
Poimen Posted February 18, 2012 Author Share Posted February 18, 2012 The new NAM is slightly north and closer to the NC coast with the low. Not sure I'm happy about this sort of trend here at the 11th hour. I'm not sure it really makes a difference for us. Our snow is coming on the back end with the deformation band overnight Sunday/Monday morning, assuming it happens of course. Through 36 hours, it looks like the NAM will still have this feature pivot across the state. Link to comment Share on other sites More sharing options...
Isopycnic Posted February 18, 2012 Share Posted February 18, 2012 HAH, your a snow magnet, you and Widre look to be in a good spot. Indeed. Link to comment Share on other sites More sharing options...
Brick Tamland Posted February 18, 2012 Share Posted February 18, 2012 I'll make a forecast on my examiner page after i see the euro this afternoon. At this point things look pretty similar to last night. The models have probably shifted a tad north from last night, but at this point it is close to nowcasting. Hoping to see this continue trending slower. IMO that will allow more cold air to work in at the sfc from the high and also will allow a little more phasing at the end to perhaps bring a more significant deformation axis which is what we will be depending on for snow. Yes, I want to see what the Euro says. It seems it and the Canadian picked up on this sooner than the other models. I'm not so much worried about the NAM showing it a bit north now. I think the better trend is it is slowing down and allowing the cold air to get here sooner. If that keeps up, I think that trumps the little jog north. I doubt it will go even further north. Link to comment Share on other sites More sharing options...
Cold Rain Posted February 18, 2012 Share Posted February 18, 2012 I'm not sure it really makes a difference for us. Our snow is coming on the back end with the deformation band overnight Sunday/Monday morning, assuming it happens of course. Through 36 hours, it looks like the NAM will still have this feature pivot across the state. What I'm wondering is if the initial system is more north, does that have any affect on where the best precip axis sets up when the backside energy comes through, assuming it doesn't move farther north too? Link to comment Share on other sites More sharing options...
beanskip Posted February 18, 2012 Share Posted February 18, 2012 Not sure I see the north trend others are -- comparing to 6z NAM, main 12z trend is SLOWER and the southern s/w digs a bit more. Link to comment Share on other sites More sharing options...
metwannabe Posted February 18, 2012 Share Posted February 18, 2012 I'm not sure it really makes a difference for us. Our snow is coming on the back end with the deformation band overnight Sunday/Monday morning, assuming it happens of course. Through 36 hours, it looks like the NAM will still have this feature pivot across the state. Agree, however at one point yesterday (may have been 18z nam) it had this almost starting as snow right along the border, so if it could have trended just a tad more south could have been significant. With that said, @42 on 12z nam 850's coming down and the deform band appears to have shifted tad north as well, along Va/NC border. Link to comment Share on other sites More sharing options...
tarheelwx Posted February 18, 2012 Share Posted February 18, 2012 What I'm wondering is if the initial system is more north, does that have any affect on where the best precip axis sets up when the backside energy comes through, assuming it doesn't move farther north too? Yes. Looks ot me that the 12z nam puts the deformation band further north over southern VA and border counties. Not as much for n NC. TW Link to comment Share on other sites More sharing options...
beanskip Posted February 18, 2012 Share Posted February 18, 2012 Comparing 500 mb maps of 12 NAM at 39 hours to 6z at 45, I'm surprised this run didn't come in colder than it did -- s/w and the 552 line significantly SW of 6z position. Link to comment Share on other sites More sharing options...
Poimen Posted February 18, 2012 Author Share Posted February 18, 2012 What I'm wondering is if the initial system is more north, does that have any affect on where the best precip axis sets up when the backside energy comes through, assuming it doesn't move farther north too? gotcha. At 42 hours the NAM does have the highest axis of qpf further north, compared to its earlier run. So perhaps you are on to something. Then again, I don't think we will really know up until kick-off. Obviously, the farther north one is in NC the better chance he/she will have to see accumulating snow. Link to comment Share on other sites More sharing options...
swva Posted February 18, 2012 Share Posted February 18, 2012 much wetter this run. things look pretty good up here in ROA. Link to comment Share on other sites More sharing options...
HKY_WX Posted February 18, 2012 Share Posted February 18, 2012 Roanoke get's destroyed on this one. GSO get's a nice little storm if it's right. I am agreeing with lookout though, with this slp track, sleet will be an issue in a lot areas. SLP i just too far north if the NAM is right. If it's more towards southern Al/GA then it's less of an issue. Link to comment Share on other sites More sharing options...
Rankin5150 Posted February 18, 2012 Share Posted February 18, 2012 Not sure I see the north trend others are -- comparing to 6z NAM, main 12z trend is SLOWER and the southern s/w digs a bit more. Hey there stranger! Hope u r well! I was thinking the same thing. These are the kinds of systems that have more times than not surprised us with more wintry weather than initially thought. I wonder about the chance for partial phasing, along with the system slowing down? Thoughts? Link to comment Share on other sites More sharing options...
BullCityWx Posted February 18, 2012 Share Posted February 18, 2012 Roanoke get's destroyed on this one. GSO get's a nice little storm if it's right. I am agreeing with lookout though, with this slp track, sleet will be an issue in a lot areas. SLP i just too far north if the NAM is right. If it's more towards southern Al/GA then it's less of an issue. I mentioned this last night. Someone in the western piedmont/catawba valley is going to see accumulating sleet from this if the NAM holds up. Link to comment Share on other sites More sharing options...
tarheelwx Posted February 18, 2012 Share Posted February 18, 2012 Roanoke get's destroyed on this one. GSO get's a nice little storm if it's right. I am agreeing with lookout though, with this slp track, sleet will be an issue in a lot areas. SLP i just too far north if the NAM is right. If it's more towards southern Al/GA then it's less of an issue. Last night's 00z showed 4.1" for GSO. I don't think this run will be as good. TW Link to comment Share on other sites More sharing options...
tarheelwx Posted February 18, 2012 Share Posted February 18, 2012 One thing I remember from years past when models trend in a certain direction, it is very common for them to reverse course just a little just before the storm hits. Doesn't always happen, but It would be common to see a storm which trended 100 miles south to correct back 25 miles north at the end. That may be what we are seeing here. Also, it appears to me that the hp is just a tad weaker this run. TW Link to comment Share on other sites More sharing options...
Tullioz Posted February 18, 2012 Share Posted February 18, 2012 Last night's 00z showed 4.1" for GSO. I don't think this run will be as good. TW Just because a model shows that much snow, it doesn't mean that is what will actually accumulate. It is not factoring in the warm soil temperatures which would take a very heavy rate of snow to over come that. You would have to have a prolonged period of snow at 1"+ per hour rates to see accumulations in the Piedmont, neither of which look likely. Link to comment Share on other sites More sharing options...
WilkesboroDude Posted February 18, 2012 Share Posted February 18, 2012 Is it true models are not as good within 24hours? Or is that just weenie talk? Link to comment Share on other sites More sharing options...
metwannabe Posted February 18, 2012 Share Posted February 18, 2012 I mentioned this last night. Someone in the western piedmont/catawba valley is going to see accumulating sleet from this if the NAM holds up. Been plenty of talk about soil temps..... Now looks like decent shot of goof amount of sleet in some areas with this, maybe it's just me but seems to me sleet always appeared to cool road surfaces, soil temps a tad quicker than snow....anything to that or just my mind playing tricks on me? Link to comment Share on other sites More sharing options...
tarheelwx Posted February 18, 2012 Share Posted February 18, 2012 Just because a model shows that much snow, it doesn't mean that is what will actually accumulate. It is not factoring in the warm soil temperatures which would take a very heavy rate of snow to over come that. You would have to have a prolonged period of snow at 1"+ per hour rates to see accumulations in the Piedmont, neither of which look likely. Totally agree. However, I could see decks, cars, trees, etc. holding much of what falls since the surface temps will get aob freezing around the time a changeover occurs. Since those surfaces cool very fast, I think those spots would hold most of what falls. So if there are 4" on cars/decks etc. but 1" on the ground, how much snow accumulated? TW Link to comment Share on other sites More sharing options...
tarheelwx Posted February 18, 2012 Share Posted February 18, 2012 Been plenty of talk about soil temps..... Now looks like decent shot of goof amount of sleet in some areas with this, maybe it's just me but seems to me sleet always appeared to cool road surfaces, soil temps a tad quicker than snow....anything to that or just my mind playing tricks on me? .25 qpf falling as sleet vs snow? I would think the impact on surface temps would be similar. In the same manor, rain and mid 30's before the snow begins will have an impact as well. TW Link to comment Share on other sites More sharing options...
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