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Wintry Dec 8-10th Winter Storm

18z runs in general had a stronger ull which flipped RDU sooner. But good news is most models are showing front end snow. See if 0z continues with stronger ull.
 
SoutheastRidge said:
NWS has 5-11" for Charlotte. I take it some of you think that's too high ? I see Webber has 1-3 for Charlotte LOL. What does Webber see that the NWS doesn't ?
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A 50-60+ KT jet at 700 hPa coupled to large amounts of QPF often leads to the warm nose being stronger than forecast and the heavier precipitation rates can lead to the creation of an in-situ dome (superimposed onto the larger-scale CAD) that accelerates the end of the warm nose aloft in the downwind direction as considerable latent/sensible heating is deposited onto where the warm nose is strongest while cooling occurs below the level of maximum heating aloft. Another obvious caveat with the models is they don't have sufficient vertical resolution, the proper mixing schemes, and pretty crappy convective parameterization schemes to account for all of the above, thus leading to weaker warm noses than forecast (& often the low-level cold dome is weaker than reality in these same models).


This profile on the NAM while taken at face value (bad idea) is all snow near RDU, that's an absurd amount of mid-level veering and warm air advection above the CAD dome. Apart from all of the above, I've been burned many times the last several years figuring the models would have a good handle on this feature, and figured the warm nose wouldn't be that strong, it's usually a good idea to go a few degrees warmer near the height of the warm nose in situations like this and that favors less snow and more mixed phase precipitation in areas like Charlotte and Raleigh, this could end up being a respectable ice storm for someone in/around these areas.
The NWS GSP snow forecast of 5-11" here is likely way out to lunch (shocker) and assumes more of the precipitation will fall of snow here, the main precipitation type is liable to be sleet.

nam_2018120718_042_35.89--78.72.png
 
Fv3 still looks like snow north of 85 to me. In South Carolina if it verifies fv3 will be the go to model. I think nam slows it down way to much
 
So here is an interesting model to pay attention to. New in 2016, was a response for the US to get better numerical modeling after our failure with Sandy in 2011. Just had major upgrades to version 3.0. It's the NBM (National Blend of Models)...very similar to the NWS superblend. It contains input from pretty much everything (ECMWF, GFS, Canadian, NAM12/3k, some WRFs, HRRR, etc). It has a ton of interesting parameters (Unfortunately I haven't been able to create plots for all of them yet), like variable ratio snow accumulation, positive energy of warm nose, negative energy of cold surface layer, line and flat ice accumulation and more. This model cycles every hour, so there are frequent updates. Here is the simulated reflectivity with p-type. While plots here only go to 36 hours, it runs out to 240 hours, although not all parameters are available after a certain number of hours. I'm interested to see how this pans out, it's basically a massive ensemble mean, so probably pretty well.

https://media.giphy.com/media/1zR7XLSCwPbnt3XVrx/giphy.gif
 
scroback said:
So here is an interesting model to pay attention to. New in 2016, was a response for the US to get better numerical modeling after our failure with Sandy in 2011. Just had major upgrades to version 3.0. It's the NBM (National Blend of Models)...very similar to the NWS superblend. It contains input from pretty much everything (ECMWF, GFS, Canadian, NAM12/3k, some WRFs, HRRR, etc). It has a ton of interesting parameters (Unfortunately I haven't been able to create plots for all of them yet), like variable ratio snow accumulation, positive energy of warm nose, negative energy of cold surface layer, line and flat ice accumulation and more. This model cycles every hour, so there are frequent updates. Here is the simulated reflectivity with p-type. While plots here only go to 36 hours, it runs out to 240 hours, although not all parameters are available after a certain number of hours. I'm interested to see how this pans out, it's basically a massive ensemble mean, so probably pretty well.

https://media.giphy.com/media/1zR7XLSCwPbnt3XVrx/giphy.gif
Click to expand...

Here's a still image in case you can't get the giphy link to load1544346000 (1).png
 
FV3 is pretty much the same, its been consistent all week. The backside is pretty much a no go. Every model seems to have trended warm with it today.
 
Just gonna drop this bad boy off here since pivotal isn't finished (although it is truly insane in the snow areas):

fv3p_asnow_eus_17.png


The FV3 is either the new DGEX or the kang.
 
GeorgiaGirl said:
Just gonna drop this bad boy off here since pivotal isn't finished (although it is truly insane in the snow areas):

fv3p_asnow_eus_17.png


The FV3 is either the new DGEX or the kang.
Click to expand...
Look.. if the gfs was any good they wouldn’t replace it with fv3. So considering it’s updated technology. It might be right
 
FV3 finally in the process of caving. Can’t wait to see its Kucharacha map.
 
hikingtheappalachians said:
So the past few days I have been thinking of heading up for a snowy day hike northeast of Cashiers, near Lake Toxaway, tomorrow... (I don't have Sunday available). This dry air modeled by the NAM concerns me a bit. Is there any past history on this? It's only a 7-hour difference, but for me, the difference between snow starting on a hike at 5 PM versus snow starting on a hike at 10 AM would be humongous. It seems like most modeling supports a start around 10 AM (except the 12km NAM), and GSP is similar, having changed the start time of their WSW to noon. How long does dry air take to erode usually in situations like this?
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Anyone?
 
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