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Wintry Possible Snow & Ice Threat Nov 14-15

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drfranklin said:
namconus_asnow_seus_29.png
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I will say the nam handles CAD situations better than global models but I’m not sure that’s true out to hr84. Better screenshot this because it’s about to go *poof*
 
Since we’re evaluating the 84hr NAM: it has 850’s as hot as the surface of the sun and temps in the mid to upper 30’s yet the upstate gets crushed by ice? ok
 
That upper level low that develops over the TN valley area could surprise some people in those areas. An inch of snowfall not out of the question for NE MS/NW Alabama northeast through TN and KY Thursday.

As far as the ice in NC/SC, a little more skeptical about that. The high is in a good spot, but I'm not sure there's enough cold air to advect down south to get ice.
 
LovingGulfLows said:
That upper level low that develops over the TN valley area could surprise some people in those areas. An inch of snowfall not out of the question for NE MS/NW Alabama northeast through TN and KY Thursday.

As far as the ice in NC/SC, a little more skeptical about that. The high is in a good spot, but I'm not sure there's enough cold air to advect down south to get ice.
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You don't get a snow event in the Carolinas from that set-up. It will be freezing rain and sleet, if we have any winter weather at all. With that being said, the upper level low can throw a wrench into the works if it tracks farther south, but I am not expecting that at the moment. I also am having a hard time believing that we can get enough cold air this time of year to produce a freezing rain event. The set up is perfect, just too early in the season.
 
The one glaring issue with this setup wrt freezing rain is the intensity of the precipitation and very marginal surface temps which at best will be either near 32F or close to 30F, the precipitation rates will become so intense esp during the heart of the storm that it limits ice accrual in that there will be so much latent heating that the temperatures will quickly warm to freezing and change to cold rain despite the nice overall setup, ice storms are self-limiting. For big ice storms with heavy precip rates you really need to see surface temps in the mid-upper 20s to provide a buffer for latent heating at the surface that takes place under heavy rates. For lighter rates temperatures closer to 30 may suffice but I think we'll be closer to the former.
 
Webberweather53 said:
The one glaring issue with this setup wrt freezing rain is the intensity of the precipitation and very marginal surface temps which at best will be either near 32F or close to 30F, the precipitation rates will become so intense esp during the heart of the storm that it limits ice accrual in that there will be so much latent heating that the temperatures will quickly warm to freezing and change to cold rain despite the nice overall setup, ice storms are self-limiting. For big ice storms with heavy precip rates you really need to see surface temps in the mid-upper 20s to provide a buffer for latent heating at the surface that takes place under heavy rates. For lighter rates temperatures closer to 30 may suffice but I think we'll be closer to the former.
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Yeah to add to this you can see the rates here on the 12km NAM are pretty heavy at hour 75.
namconus_ref_frzn_seus_49.png


Within 3 hours the heating of the day and latent heat release along with warming upper levels shifts this ice zone all the way into VA.
namconus_ref_frzn_seus_50.png


Still it appears that the 12km NAM is advertising a quick hitting period of 2-4 hours of icy conditions before things warm above freezing. Could cause some issues early on. I personally will be waiting for the 3km to get in range as it does a good job picking up on the various temp profiles better than other models including the 12km nam.
 
Tarheel1 said:
View attachment 7326 Somebody just got Godnam’d! Latest run, borrowed from the other board!
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None of that is snow. It is all ice or cold 33F rain. The tidbits maps have some issues with handling the p-type depictions. Pivotal Weather has much better maps when ice is involved. With the marginal temps of 30-32F and latent heat release and heavy rates the actual ice accrual would probably be quite low. Still may cause some issues with the roads early in the morning.
ZR.JPG
 
Euro trended a bit faster and a bit colder. Might be a warm nose higher than 850 but just looking at 850s it could support snow for some.
 
Nomanslandva said:
Euro trended a bit faster and a bit colder. Might be a warm nose higher than 850 but just looking at 850s it could support snow for some.
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A little snow way up in the VA foothills/mountains but for NC it's just ice in the mountains and rain for everyone else.
 
snowlover91 said:
None of that is snow. It is all ice or cold 33F rain. The tidbits maps have some issues with handling the p-type depictions. Pivotal Weather has much better maps when ice is involved. With the marginal temps of 30-32F and latent heat release and heavy rates the actual ice accrual would probably be quite low. Still may cause some issues with the roads early in the morning.
View attachment 7328
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Well, after looking at soundings for my area from the 18z run of the NAM. It has temps below freezing from 850mb all the way to the surface during the early part of the event. There is a pronounced warm nose above 850 which would prevent snow from falling, but just taking this at face value, it is a sleet sounding as temps are as low as -4C at 925mb. This is due to some very dry air in those levels at the onset of the precip with dew points in the -30C range (very dry). That is the difference between the Nam and the other models. It sets up a very cold layer just off the surface which will be dragged down with the precip for a period of time. We will have to monitor this dry air layer in future runs to see if it is valid.
 
We had a little sleet today right at the beginning and that was also because of dew point depressions off the surface. Also, the high was supposed to be 43. The wedge either held or built back in because it was 34 when I got back home at 5 and is still 35. Miserable cold rain but CAD for the win!!!
 
Imagine this week's storm later with alot more snow cover where the hp is placed, would be a major winter storm, just goes to show what this active pattern can offer
 
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